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CephalopodaAn overview

ContentsArticlesCephalopods 1

Cephalopod 1Octopus 22Squid 33Cuttlefish 40Nautiloid 46Nautilus 51Ammonite 58Belemnoidea 67Argonaut 71

Anatomy and behaviour 78

Cephalopod intelligence 78Cephalopod size 81Cephalopod ink 89Ink sac 91Cephalopod arm 91Hectocotylus 93Tentacle 94Dactylus 97Cephalopod eye 97Chromatophore 99Mantle 107Nidamental gland 110Siphon 110Squid giant axon 116

Cephalopod shells 117

Cuttlebone 117Septum 118Aptychus 119Orthocone 120Phragmocone 120

Siphuncle 121Body chamber 122

ReferencesArticle Sources and Contributors 123Image Sources, Licenses and Contributors 126

Article LicensesLicense 130

1

Cephalopods

Cephalopod

Cephalopods

Bigfin reef squid (Sepioteuthislessoniana)

Scientific classification [ e ]

Kingdom: Animalia

Phylum: Mollusca

Class: CephalopodaCuvier, 1797

Subclasses and orders

A cephalopod is any member of the molluscan class Cephalopoda (Greek plural Κεφαλόποδα (kephalópoda);"head-feet"). These exclusively marine animals are characterized by bilateral body symmetry, a prominent head, anda set of arms or tentacles (muscular hydrostats) modified from the primitive molluscan foot. Fishermen sometimescall them inkfish, referring to their common ability to squirt ink. The study of cephalopods is a branch ofmalacology known as teuthology.Cephalopods became dominant during the Ordovician period, represented by primitive nautiloids. The class nowcontains two, only distantly related, extant subclasses: Coleoidea, which includes octopuses, squid, and cuttlefish;and Nautiloidea, represented by Nautilus and Allonautilus. In the Coleoidea the molluscan shell has been internalizedor is absent, whereas in the Nautiloidea the external shell remains. About 800 living species of cephalopods havebeen identified. Two important extinct taxa are the Ammonoidea (ammonites) and Belemnoidea (belemnites).

Cephalopod 2

Distribution

There are around 800 extant species of cephalopod,[1] although new species continue to be described. It is estimatedthat around 11,000 extinct taxa have been described, although the soft-bodied nature of cephalopods means that theyare not easily fossilised.[2]

Cephalopods are found in all the oceans of Earth. None of them can tolerate freshwater, but the brief squid,Lolliguncula brevis, found in Chesapeake Bay may be a notable exception in that it tolerates brackish water whichhas a low salinity.[3]

Cephalopods occupy most of the depth of the ocean, from the abyssal plane to the sea surface. Their diversity isgreatest near the equator (~40 species retrieved in nets at 11°N by a diversity study) and decreases towards the poles(~5 species captured at 60°N).[4]

Nervous system and behaviour

Cephalopods are widely regarded as the most intelligent of the invertebrates and have well developed senses andlarge brains; larger than the brains of gastropods. The nervous system of cephalopods is the most complex of theinvertebrates,[5] and their brain to body mass ratio falls between that of warm and cold blooded vertebrates.[4] :14 Thegiant nerve fibers of the cephalopod mantle have frequently been used as an experimental material ofneurophysiologists for many years; their large diameter (due to lack of myelination) makes them easier to study.[6]

Cephalopods are social creatures; when isolated from their own kind, they will take to shoaling with fish.[7]

Cephalopod 3

Some cephalopods are able to fly distances up to 50 m. While the organisms are not particularly aerodynamic, theyachieve these rather impressive ranges by use of jet-propulsion; water continues to be expelled from the funnel whilethe organism is in flight.[8]

SensesCephalopods have advanced vision, can detect gravity with statocysts, and have a variety of chemical senseorgans.[4] :34 Octopuses use their tentacles to explore their environment and can use them for depth perception.[4]

The primitive nautilus eye functions similarly to apinhole camera.

Vision

Most cephalopods rely on vision to detect predators and prey, and tocommunicate with one another.[9] Consequently, cephalopod vision isacute: training experiments have shown that the Common Octopus candistinguish the brightness, size, shape, and horizontal or verticalorientation of objects. The morphological construction givescephalopod eyes the same performance as sharks'; however, theirconstruction differs as cephalopods lack a cornea, and have an evertedretina.[9] Cephalopods' eyes are also sensitive to the plane ofpolarization of light. Surprisingly—given their ability to change

color—all octopuses[10] and most cephalopods[11] are color blind. When camouflaging themselves, they use theirchromatophores to change brightness and pattern according to the background they see, but their ability to match thespecific color of a background may come from cells such as iridophores and leucophores that reflect light from theenvironment.[12] They also produce visual pigments throughout their body, and may sense light levels directly fromtheir body.[13] Evidence of color vision has been found in the Sparkling Enope Squid (Watasenia scintillans),[11] [14]

which achieves color vision by the use of three distinct retinal molecules (A1, sensitive to red; A2, to purple, and A4,to yellow?) which bind to its opsin.[15]

Unlike many other cephalopods, nautiluses do not have good vision; their eye structure is highly developed but lacksa solid lens. They have a simple "pinhole" eye through which water can pass. Instead of vision, the animal is thoughtto use olfaction as the primary sense for foraging, as well as locating or identifying potential mates.

Cephalopod 4

HearingCephalopods can use their statocyst to detect sound.[16]

Use of light

This Broadclub Cuttlefish (Sepia latimanus) cango from camouflage tans and browns (top) to

yellow with dark highlights (bottom) in less thana second.

Most cephalopods possess chromatophores - that is, coloured pigments- which they can use in a startling array of fashions.[4] As well asproviding camouflage with their background, some cephalopodsbioluminesce, shining light downwards to disguise their shadows fromany predators that may lurk below.[4] The bioluminescence is producedby bacterial symbionts; the host cephalopod is able to detect the lightproduced by these organisms.[17] Bioluminescence may also be used toentice prey, and some species use colourful displays to impress mates,startle predators, or even communicate with one another.[4] It is notcertain whether bioluminescence is actually of epithelial origin or if itis a bacterial production.[18]

Colouration

Colouration can be changed in milliseconds as they adapt to theirenvironment,[4] and the pigment cells are expandable by muscularcontraction.[18] Colouration is typically more pronounced in near-shorespecies than those living in the open ocean, whose functions tend to berestricted to camouflage by breaking their outline.[4] :2

Evidence of original colouration has been detected in cephalopodfossils dating as far back as the Silurian; these orthoconic individualsbore concentric stripes, which are thought to have served as camouflage.[19] Devonian cephalopods bear morecomplex colour patterns, whose function may be more complex.[20]

InkWith the exception of the Nautilidae and the species of octopus belonging to the suborder Cirrina,[21] all knowncephalopods have an ink sac, which can be used to expel a cloud of dark ink to confuse predators.[10] This sac is amuscular bag which originated as an extension of the hind gut. It lies beneath the gut and opens into the anus, intowhich its contents – almost pure melanin – can be squirted; its proximity to the base of the funnel means that the inkcan be distributed by ejected water as the cephalopod uses its jet propulsion.[10] The ejected cloud of melanin isusually mixed, upon expulsion, with mucus, produced elsewhere in the mantle, and therefore forms a thick cloud,resulting in visual (and possibly chemosensory) impairment of the predator, like a smokescreen. However, a moresophisticated behaviour has been observed, in which the cephalopod releases a cloud, with a greater mucus content,that approximately resembles the cephalopod that released it (this decoy is referred to as a pseudomorph). Thisstrategy often results in the predator attacking the pseudomorph, rather than its rapidly departing prey.[10] For moreinformation, see Inking behaviors.The inking behaviour of cephalopods has led to a common name of "inkfish", primarily used in fisheries science andthe fishing industry, paralleling the terms white fish, oily fish, and shellfish.

[[file:Chtenopteryxsicula2.jpg|thumb|left

Viscera of Chtenopteryx sicula]][[file:Ocythoe tuberculataviscera.jpg|thumb|left

Viscera of Ocythoetuberculata]]

Cephalopod 5

Circulatory systemCephalopods are the only mollusks with a closed circulatory system. Coleoids have two gill hearts (also known asbranchial hearts) that move blood through the capillaries of the gills. A single systemic heart then pumps theoxygenated blood through the rest of the body.[22]

Like most molluscs, cephalopods use hemocyanin, a copper-containing protein, rather than hemoglobin to transportoxygen. As a result, their blood is colorless when deoxygenated and turns blue when exposed to air.[23]

RespirationCephalopods exchange gasses with the seawater by forcing water through their gills, which are attached to the roofof the organism.[24] :488[25] Water enters the mantle cavity on the outside of the gills, and the entrance of the mantlecavity closes. When the mantle contracts, water is forced through the gills, which lie between the mantle cavity andthe funnel. The water's expulsion through the funnel can be used to power jet propulsion. The gills, which are muchmore efficient than those of other molluscs, are attached to the ventral surface of the mantle cavity.[25] There is atrade-off with gill size regarding lifestyle. To achieve fast speeds, gills need to be small - water will be passedthrough them quickly when energy is needed, compensating for their small size. However, organisms which spendmost of their time moving slowly along the bottom do not naturally pass much water through their cavity forlocomotion; thus they have larger gills, along with complex systems to ensure that water is constantly washingthrough their gills, even when the organism is stationary.[24] The water flow is controlled by contractions of theradial and circular mantle cavity muscles.[26]

The gills of cephalopods are supported by a skeleton of robust fibrous proteins; the lack of mucopolysaccharidesdistinguishes this matrix from cartilage.[27] [28] The gills are also thought to be involved in excretion, with NH4

+

being swapped with K+ from the seawater.[25]

Locomotion and buoyancy

Octopuses swim headfirst, with arms trailingbehind

While all cephalopods can move by jet propulsion, this is a veryenergy-consuming way to travel compared to the tail propulsion usedby fish.[29] The relative efficiency of jet propulsion decreases further asanimal size increases; paralarvae are far more efficient than juvenileand adult individuals.[30] Since the Paleozoic era, as competition withfish produced an environment where efficient motion was crucial tosurvival, jet propulsion has taken a back role, with fins and tentaclesused to maintain a steady velocity.[2] Whilst jet propulsion is never thesole mode of locomotion,[2] :208 the stop-start motion provided by thejets continues to be useful for providing bursts of high speed - not leastwhen capturing prey or avoiding predators.[2] Indeed, it makescephalopods the fastest marine invertebrates,[4] :Preface and they canout-accelerate most fish.[24] The jet is supplemented with fin motion; in the squid, the fins flap each time that a jet isreleased, amplifying the thrust; they are then extended between jets (presumably to avoid sinking).[31] Oxygenatedwater is taken into the mantle cavity to the gills and through muscular contraction of this cavity, the spent water isexpelled through the hyponome, created by a fold in the mantle. The size difference between the posterior andanterior ends of this organ control the speed of the jet the organism can produce.[32] The velocity of the organism canbe accurately predicted for a given mass and morhpology of animal.[33] Motion of the cephalopods is usuallybackward as water is forced out anteriorly through the hyponome, but direction can be controlled somewhat bypointing it in different directions.[34] Some cephalopods accompany this expulsion of water with a gunshot-likepopping noise, thought to function to frighten away potential predators.[35]

Cephalopod 6

Nautilus belauensis seen from the front, showingthe opening of the hyponome

Early cephalopods are thought to have produced jets by drawing theirbody into their shells, as Nautilus does today.[36] Nautilus is alsocapable of creating a jet by undulations of its funnel; this slower flowof water is more suited to the extraction of oxygen from the water.[36]

The jet velocity in Nautilus is much slower than in coleoids, but lessmusculature and energy is involved in its production.[37] Jet thrust incephalopods is controlled primarily by the maximum diameter of thefunnel orifice (or, perhaps, the average diameter of the funnel)[38] :440

and the diameter of the mantle cavity.[39] Changes in the size of theorifice are used most at intermediate velocities.[38] The absolutevelocity achieved is limited by the cephalopod's requirement to inhalewater for expulsion; this intake limits the maximum velocity to eight

body-lengths per second, a speed which most cephalopods can attain after two funnel-blows.[38] Water refills thecavity by entering not only through the orifices, but also though the funnel.[38] To accommodate the rapid changes inwater intake and expulsion, the orifices are highly flexible and can change their size by a factor of twenty; the funnelradius, conversely, changes only by a factor of around 1.5.[38]

Some octopus species are also able to walk along the sea bed. Squids and cuttlefish can move short distances in anydirection by rippling of a flap of muscle around the mantle.While most cephalopods float (i.e. are neutrally buoyant or nearly so; in fact most cephalopods are about 2-3%denser than seawater[7] ), they achieve this in different ways.[29] Some, such as Nautilus, allow gas to diffuse into thegap between the mantle and the shell; others allow purer water to ooze from their kidneys, forcing out denser saltwater from the body cavity;[29] others, like some fish, accumulate oils in the liver;[29] and some octopuses have agelatinous body with lighter chlorine ions replacing sulfate in the body chemistry.[29]

Shell

[[file:Spirulaspirula.jpg|thumb|right

Cross section of Spirula spirula, showing the positionof the shell inside the mantle]][[file:Herklots 1859 I 2Sepia officinalis - schelp.jpg|thumb|right

Cuttlebone of Sepiaofficinalis]][[file:Sepioteuthis lessonianagladius.jpg|thumb|right

Gladius ofSepioteuthislessoniana]]

Nautiluses are the only extant cephalopods with an external shell. However, all molluscan shells are formed from theectoderm (outer layer of the embryo); in cuttlefish (Sepia spp.), for example, an invagination of the ectoderm formsduring the embryonic period, resulting in a shell that is internal in the adult.[40] The same is true of the chitinousgladius of squid[40] and octopus.[41] Cirrate octopuses have cartilaginous fin supports,[42] which are sometimesreferred to as a "shell vestige" or "gladius".[43] : The Incirrina have no vestige of an internal shell, and some squidalso lack a gladius.[44] Interestingly, the shelled coleoids do not form a clade or even a paraphyletic group.[45] TheSpirula shell begins as an organic structure, and is then very rapidly mineralized.[46] Shells that are "lost" may be lostby resorption of the calcium carbonate component.[47]

Females of the octopus genus Argonauta secrete a specialised paper-thin eggcase in which they reside, and this ispopularly regarded as a "shell", although it is not attached to the body of the animal.The largest group of shelled cephalopods, the ammonites, are extinct, but their shells are very common as fossils.The deposition of carbonate, leading to a mineralized shell, appears to be related to the acidity of the organic shellmatrix (see Mollusc shell); shell-forming cephalopods have an acidic matrix, whereas the gladius of squid has abasic matrix.[48]

Cephalopod 7

Head appendagesCuttlefish and squid have five pairs of muscular appendages surrounding their mouths. The longer two, termedtentacles, are actively involved in capturing prey;[49] :225 they can lengthen rapidly (in as little as 15 milliseconds[49]

:225). In giant squid they may reach a length of 8 metres. They may terminate by broadening into a sucker-coatedclub.[49] :225 The shorter four pairs are termed arms, and are involved in holding and manipulating the capturedorganism.[49] :225 They too have suckers, on the side closest to the mouth; these help to hold onto the prey.[49] :226

The tentacle consists of a thick central nerve cord (which must be thick to allow each sucker to be controlledindependently)[50] surrounded by circular and radial muscles. Because the volume of the tentacle remains constant,contracting the circular muscles decreases the radius and permits the rapid increase in length. Typically a 70%lengthening is achieved by decreasing the width by 23%.[49] :227

The size of the tentacle is related to the size of the buccal cavity; larger, stronger tentacles can hold prey as smallbites are taken from it; with more numerous, smaller tentacles, prey is swallowed whole, so the mouth cavity must belarger.[51]

Feeding

The two-part beak of the giant squid, Architeuthissp.

All living cephalopods have a two-part beak;[4] :7 most have a radula,although it is reduced in most octopus and absent altogether inSpirula.[4] :7[52] :110 They feed by capturing prey with their tentacles,drawing it in to their mouth and taking bites from it.[10] They have amixture of toxic digestive juices, some of which are manufactured bysymbiotic algae, which they eject from their salivary glands onto theircaptured prey held in their mouth. These juices separate the flesh oftheir prey from the bone or shell.[10] The salivary gland has a smalltooth at its end which can be poked into an organism to digest it fromwithin.[10]

The digestive gland itself is rather short.[10] It has four elements, with food passing through the crop, stomach and caecum before entering the intestine. Most digestion, as well as the absorption of nutrients, occurs in the digestive gland, sometimes called the liver. Nutrients and waste materials are exchanged between the gut and the digestive

Cephalopod 8

gland through a pair of connections linking the gland to the junction of the stomach and caecum.[10] Cells in thedigestive gland directly release pigmented excretory chemicals into the lumen of the gut, which are then bound withmucus passed through the anus as long dark strings, ejected with the aid of exhaled water from the funnel.[10]

Radula

Amphioctopus marginatus eating a crab

The cephalopod radula consists of multiple symmetrical rows of up tonine teeth[53] – thirteen in fossil classes.[54] The organ is reduced oreven vestigial in certain octopus species and is absent in Spirula.[54]

The teeth may be homodont (i.e. similar in form across a row),heterodont (otherwise), or ctenodont (comb-like).[54] Their height,width and number of cusps is variable between species.[54] The patternof teeth repeats, but each row may not be identical to the last; in theoctopus, for instance, the sequence repeats every five rows.[54] :79

Cephalopod radulae are known from fossil deposits dating back to theSilurian.[54] They are usually preserved within the cephalopod's bodychamber, commonly in conjunction with the mandibles; but this need not always be the case;[55] many radulae arepreserved in a range of settings in the Mason Creek.[56] Radulae are usually difficult to detect, even when they arepreserved in fossils, as the rock must weather and crack in exactly the right fashion to expose them; for instance,radulae have only been found in nine of the 43 ammonite genera.[57]

Excretory systemMost cephalopods possess a single pair of large nephridia. Filtered nitrogenous waste is produced in the pericardialcavity of the branchial hearts, each of which is connected to a nephridium by a narrow canal. The canal delivers theexcreta to a bladder-like renal sac, and also resorbs excess water from the filtrate. Several outgrowths of the lateralvena cava project into the renal sac, continuously inflating and deflating as the branchial hearts beat. This actionhelps to pump the secreted waste into the sacs, to be released into the mantle cavity through a pore.[58]

Nautilus, unusually, possesses four nephridia, none of which are connected to the pericardial cavities.

AmmoniumThe handling of ammonia is thought to be important in shell formation in terrestrial molluscs, and in othernon-molluscan lineages.[59]

Because protein (i.e. flesh) is a major constituent of the cephalopod diet, large amounts of ammonium are producedas waste. The main organs involved with the release of this excess ammonium are the gills.[60]

The rate of this release is the lowest in the shelled cephalopods Nautilus and Sepia, probably as a result of their useof nitrogen to fill their shells with gas, in order to produce buoyancy.[60] Other cephalopods use ammonium in asimilar way, storing the ions (as ammonium chloride) themselves in order to reduce their overall density and thusbecome more buoyant.[60]

Cephalopod 9

Reproduction and life cycle

[[file:Papierboot Argonauta200705181139.jpg|thumb|right

Female Argonauta argo with eggcase and eggs]][[file:Ocythoetuberculata hectocotylus.jpg|thumb|right

Detail of the hectocotylus ofOcythoe tuberculata]]

[[file:Onykia ingens withnon-erect penis.jpg|thumb|right

A dissected male specimen of Onykia ingens, showing a non-erect penis (thewhite tubular structure located below most of the otherorgans)]][[file:Onykia ingens with erect penis.jpg|thumb|right

A specimen of the same speciesexhibiting elongation of the penisto 67 cm in length]]

With a few exceptions, Coleoidea live short lives with rapid growth. Most of the energy extracted from their food isused for growing. The penis in most male Coleoidea is a long and muscular end of the gonoduct used to transferspermatophores to a modified arm called a hectocotylus. That in turn is used to transfer the spermatophores to thefemale. In species where the hectocotylus is missing, the penis is long and able to extend beyond the mantle cavityand transfers the spermatophores directly to the female. Deep water squid have the greatest known penis lengthrelative to body size of all mobile animals, second in the entire animal kingdom only to certain sessile barnacles.[61]

Penis elongation in Onykia ingens may result in a penis that is as long as the mantle, head and arms combined.[61]

[62]

Most cephalopods tend towards a semelparous reproduction strategy; they lay many small eggs in one batch and dieafterwards. The Nautiloidea, on the other hand, stick to iteroparity; they produce a few large eggs in each batch andlive for a long time.External sexual characteristics are lacking in cephalopods, so cephalopods use colour communication. A courtingmale will approach a likely looking opposite number flashing his brightest colours, often in rippling displays. If theother cephalopod is female and receptive, her skin will change colour to become pale, and mating will occur. If theother cephalopod remains brightly coloured, it is taken as a warning.[63]

The male has a sperm-carrying arm, known as the hectocotylous arm, with which to impregnate the female. In manycephalopods, mating occurs head to head and the male may simply transfer sperm to the female. Others may detachthe sperm-carrying arm and leave it attached to the female. In the paper nautilus, this arm remains active andwriggling for some time, prompting the zoologists who discovered it to conclude it was some sort of worm-likeparasite. It was duly given a genus name Hectocotylus, which held for some time until the mistake wasdiscovered.[63] :227

The eggs may be brooded: female paper nautilus construct a shelter for the young, while Gonatiid squid carry alarva-laden membrane from the hooks on their arms.[64] Other cephalopods deposit their young under rocks andaerate them with their tentacles hatching. Often, though, the eggs are left to their own devices; many squid laysausage-like bunches of eggs in crevices or occasionally on the sea floor. Cuttlefish lay their eggs separately in casesand attach them to coral or algal fronds.[65] Fossilised egg clutches show that ammonites also laid clutches ofeggs.[66]

Cephalopods are occasionally long-lived, especially in the deep water or polar forms, but most of the group live fastand die young, maturing rapidly to their adult size. Some may gain as much as 12% of their body mass each day.[10]

Most live for one to two years,[10] reproducing and then dying shortly thereafter.[67]

In order to free up resources for reproduction, many squid are known to resorb the muscle tissue of their mantle andtentacles, breaking down the tissue and using the energy contained therein to produce more gametes.[68]

Cephalopod 10

Egg cases laid by a female squid

Embryology

Unlike most other molluscs, cephalopods do not have a distinct larvalstage. The fertilised ovum initially divides to produce a disc ofgerminal cells at one pole, with the yolk remaining at the oppositepole. The germinal disc grows to envelop and eventually absorb theyolk, forming the embryo. The tentacles and arms first appear at thehind part of the body, where the foot would be in other molluscs, andonly later migrate towards the head.[58] [69]

The funnel of cephalopods develops on the top of their head, whereasthe mouth develops on the opposite surface.[70] :86 The early

embryological stages are reminiscent of ancestral gastropods and extant Monoplacophora.[69]

The shells develop from the ectoderm as an organic framework which is subsequently mineralised.[40] In Sepia,which has an internal shell, the ectoderm forms an invagination whose pore is sealed off before this organicframework is deposited.[40]

The gene engrailed is expressed first in the arms, funnel and optic vesicles, and is only later present in the tentaclesand eyelids.[40] It is expressed in embryonic stages 17–19 in all arm buds, and subsequently in the future-tentacles instages 24–5, suggesting that it may serve a role in the differential development of tentacles. Sequential expression ofHox genes is also observed in cephalopod arms.[40]

Development

Chtenopteryx sicula paralarvae. Left: Two very young paralarvae. The circular tentacularclubs bear approximately 20 irregularly arranged suckers. Two chromatophores arepresent on each side of the mantle. Centre: Ventral, dorsal and side views of a more

advanced paralarva. An equatorial circulet of seven large yellow-brown chromatophoresis present on the mantle. Posteriorly the expanded vanes of the gladius are visible in the

dorsal view. Right: Ventral and dorsal views of a very advanced paralarva.

Cephalopod 11

Cephalopod eggs span a large range of sizes, from 1 to 30 mm in diameter.[71] The length of time before hatching ishighly variable; smaller eggs in warmer waters are the fastest to hatch, and newborns can emerge after as little as afew days. Larger eggs in colder waters can develop for over a year before hatching.[71]

The process from spawning to hatching follows a similar trajectory in all species, the main variable being the amountof yolk available to the young and when it is absorbed by the embryo.[71]

Young do not pass through a larval stage sensu stricto (in the narrowest sense). They quickly learn how to hunt,using encounters with prey to refine their strategies.[71]

Growth in juveniles is usually allometric, whilst adult growth is isometric.[72]

EvolutionThe traditional view of cephalopod evolution holds that they evolved in the Late Cambrian from amonoplacophoran-like ancestor[73] with a curved, tapering shell,[74] which was closely related to the gastropods(snails).[75] The similarity of the early shelled cephalopod Plectronoceras to some gastropods was used in support ofthis view. The development of a siphuncle would have allowed the shells of these early forms to become gas-filled(thus buoyant) in order to support them and keep the shells upright while the animal crawled along the floor, andseparated the true cephalopods from putative ancestors such as Knightoconus, which lacked a siphuncle.[75] Neutralor positive buoyancy (i.e. the ability to float) would have come later, followed by swimming in the Plectronoceridaand eventually jet propulsion in more derived cephalopods.[76]

However, some morphological evidence is difficult to reconcile with this view, and the re-description of Nectocarispteryx, which did not have a shell and appeared to possess jet propulsion in the manner of "derived" cephalopods,complicated the question of the order in which cephalopod features developed – provided Nectocaris is a cephalopodat all.[77] Their position within the Mollusca is currently wide open to interpretation - see Mollusca#Phylogeny.Early cephalopods were likely predators near the top of the food chain.[10] They underwent pulses of diversificationduring the Ordovician period[78] to become diverse and dominant in the Paleozoic and Mesozoic seas.[79] In theEarly Palaeozoic, their range was far more restricted than today; they were mainly constrained to sub-littoral regionsof shallow shelves of the low latitudes, and usually occur in association with thrombolites.[80] A more pelagic habitwas gradually adopted as the Ordovician progressed.[80] Deep-water cephalopods, whilst rare, have been found in theLower Ordovician - but only in high-latitude waters.[80] The mid Ordovician saw the first cephalopods with septastrong enough to cope with the pressures associated with deeper water, and could inhabit depths greater than100–200 m.[78] The direction of shell coiling would prove to be crucial to the future success of the lineages;endogastric coiling would only permit large size to be attained with a straight shell, whereas exogastric coiling -initially rather rare - permitted the spirals familiar from the fossil record to develop, with their corresponding largesize and diversity.[81] (Endogastric mean the shell is curved so as the ventral or lower side is longitudinally concave(belly in); exogastric means the shell is curve so as the ventral side is longitudinally convex (belly out) allowing thefunnel to be pointed backwards beneath the shell.)[81]

Cephalopod 12

An ammonitic ammonoid with the body chamber missing, showingthe septal surface (especially at right) with its undulating lobes and

saddles.

The ancestors of coleoids (including most moderncephalopods) and the ancestors of the modern nautilus,had diverged by the Floian Age of the Early OrdovicianPeriod, over 470 million years ago.[80] [82] It is widelyheld that the Bactritida, an Silurian–Triassic group oforthocones, are paraphyletic to the coleoids andammonoids – that is, the latter groups arose fromwithin the Bactritida.[83] :393 An increase in thediversity of the coleoids and ammonoids is observedaround the start of the Devonian period, and

corresponds with a profound increase in fish diversity. This could represent the origin of the two derived groups.[83]

Unlike most modern cephalopods, most ancient varieties had protective shells. These shells at first were conical butlater developed into curved nautiloid shapes seen in modern nautilus species. It is thought that competitive pressurefrom fish forced the shelled forms into deeper water, which provided an evolutionary pressure towards shell loss andgave rise to the modern coleoids, a change which led to greater metabolic costs associated with the loss of buoyancy,but which allowed them to recolonise shallow waters.[75] :36 However, some of the straight-shelled nautiloidsevolved into belemnites, out of which some evolved into squid and cuttlefish. The loss of the shell may also haveresulted from evolutionary pressure to increase manoeuvrability, resulting in a more fish-like habit.[49] :289

Phylogeny

Cephalopod phylogeny

Nautiloids Nautilus

Coleoids

Basal Octopods (e.g. Argonauta)

Vampyroteuthis

Heteroteuthis (bobtail squid)

*

Sepia (cuttlefish)

Idiosepius

Sepioteuthis

Spirula

* Certain squid (e.g. Bathyteuthis)

Cephalopod 13

Approximate consensus of extant cephalopod phylogeny, after Strugnell et al. 2007[45] Mineralized taxa are in bold. Theattachment of the clade including Sepia and Spirula is unclear; either of the points marked with an asterisk may represent the rootof this clade.

The internal phylogeny of the cephalopods is difficult to constrain; many molecular techniques have been adopted,but the results produced are conflicting.[45] [84] Nautilus tends to be considered an outgroup, with Vampyroteuthisforming an outgroup to other squid; however in one analysis the nautiloids, octopus and teuthids plot as apolytomy.[45] Some molecular phylogenies do not recover the mineralized coleoids (Spirula, Sepia, and Metasepia)as a clade; however, others do recover this more parsimonious-seeming clade, with Spirula as a sister group to Sepiaand Metasepia in a clade that had probably diverged before the end of the Triassic.[85] [86]

Molecular estimates for clade divergence vary. One 'statistically robust' estimate has Nautilus diverging fromOctopus at 415 [87] ± 24 million years ago.[88]

Taxonomy

Chambered Nautilus (Nautilus pompilius)

Common Cuttlefish (Sepia officinalis)

The classification presented here, for recent cephalopods,follows largely from Current Classification of RecentCephalopoda [89] (May 2001), for fossil cephalopods takesfrom Arkell et al. 1957, Teichert and Moore 1964, Teichert1988, and others. The three subclasses are traditional,corresponding to the three orders of cephalopods recognizedby Bather.[90]

Class Cephalopoda († indicates extinct groups)• Subclass Nautiloidea: Fundamental ectocochliate

cephalopods that provided the source for theAmmonoidea and Coleoidea.

• Order † Plectronocerida: the ancestral cephalopodsfrom the Cambrian Period

• Order † Ellesmerocerida (500 to 470.0 [91] Ma)• Order † Endocerida (485 to 430 [92] Ma)• Order † Actinocerida (480 to 312 [93] Ma)• Order † Discosorida (482.0 to 392 [94] Ma)• Order † Pseudorthocerida (432 to 272 [95] Ma)• Order † Tarphycerida (485 to 386 [96] Ma)• Order † Oncocerida (478.5 to 324 [97] Ma)• Order Nautilida (extant; 410.5 to 0 [98] Ma)• Order † Orthocerida (482.5 to 211.5 [99] Ma)• Order † Ascocerida (478.0 to 412 [100] Ma)• Order † Bactritida (418.1 to 260.5 [101] Ma)

• Subclass † Ammonoidea: Ammonites (479 to 65 [102]

Ma)

• Order † Goniatitida (388.5 to 252 [103] Ma)• Order † Ceratitida (254 to 200 [104] Ma)• Order † Ammonitida (215 to 66 [105] Ma)

• Subclass Coleoidea (410.0 Ma-Rec)• Cohort † Belemnoidea: Belemnites and kin

Cephalopod 14

Atlantic Bobtail (Sepiola atlantica)

European Squid (Loligo vulgaris)

Common Octopus (Octopus vulgaris)

• Genus † Jeletzkya• Order † Aulacocerida (265 to 183 [106] Ma)• Order † Phragmoteuthida (189.6 to 183 [107] Ma)• Order † Hematitida (339.4 to 318.1 [108] Ma)• Order † Belemnitida (339.4 to 65.5 [109] Ma)• Genus † Belemnoteuthis (189.6 to 183 [107] Ma)

• Cohort Neocoleoidea• Superorder Decapodiformes (also known as

Decabrachia or Decembranchiata)

• ?Order † Boletzkyida• Order Spirulida: Ram's Horn Squid• Order Sepiida: cuttlefish• Order Sepiolida: pygmy, bobtail and bottletail

squid• Order Teuthida: squid

• Superorder Octopodiformes (also known asVampyropoda)

• Family † Trachyteuthididae• Order Vampyromorphida: Vampire Squid• Order Octopoda: octopus

Other classifications differ, primarily in how the variousdecapod orders are related, and whether they should beorders or families.

Suprafamilial classification of the Treatise

This is the older classification that combines those found inparts K and L of the Treatise on Invertebrate Paleontology,which forms the basis for and is retained in large part byclassifications that have come later.Nautiloids in general, (Teichert and Moore 1964) Sequenceas given.

Subclass † Endoceratoidea. Not used by Flower, e.g.Flower and Kummel 1950, interjocerids included inthe Endocerida.

Order † EndoceridaOrder † Intejocerida

Subclass † Actinoceratoidea Not used by Flower, ibidOrder † Actinocerida

Subclass † Nautiloidea Nautiloidea in the restricted sense.Order † Ellesmerocerida Plectronocerida subsequently split off as separate order.Order † Orthocerida Includes orthocerids and pseudorthoceridsOrder † AscoceridaOrder † Oncocerida

Cephalopod 15

Order † DiscosoridaOrder † TarphyceridaOrder † Barrandeocerida A polyphyletic group now included in the TarphyceridaOrder Nautilida

Subclass † BactritoideaOrder † Bactritida

Paleozoic Ammonoidea ( Miller, Furnish, and Schindewolf, 1957)Suborder † AnarcestinaSuborder † ClymeniinaSuborder † GoniatitinaSuborder † Prolecanitina

Mesozoic Ammonoidea (Arkel et al., 1957)Suborder † CeratitinaSuborder † PhylloceratinaSuborder † LytoceratinaSuborder † Ammonitina

Subsequent revisions include the establishment of three Upper Cambrian orders, the Plectronocerida,Protactinocerida and Yanhecerida; separation of the pseudorthocerids as the Pseudorthocerida, and elevatingorthoceritoids as the Subclass Orthoceratoidea.

Shevyrev classificationShevyrev (2005) suggested a division into eight subclasses, mostly comprising the more diverse and numerous fossilforms,[110] [111] although this classification has been criticized as arbitrary.[112]

Various species of ammonites

Class Cephalopoda

• Subclass † Ellesmeroceratoidea• Order † Plectronocerida (501 to 490.0 [113] Ma)• Order † Protactinocerida• Order † Yanhecerida• Order † Ellesmerocerida (500 to 470.0 [91] Ma)

• Subclass † Endoceratoidea (485 to 430 [92] Ma)• Order † Endocerida (485 to 430 [92] Ma)• Order † Intejocerida (485 to 480 [114] Ma)

• Subclass † Actinoceratoidea• Order † Actinocerida (480 to 312 [93] Ma)

• Subclass Nautiloidea (490.0 Ma- Rec)• Order † Basslerocerida (490.0 to 480 [115] Ma)• Order † Tarphycerida (485 to 386 [96] Ma)• Order † Lituitida (485 to 480 [114] Ma)• Order † Discosorida (482.0 to 392 [94] Ma)• Order † Oncocerida (478.5 to 324 [97] Ma)• Order Nautilida (410.5 Ma-Rec)

• Subclass † Orthoceratoidea (482.5 to 211.5 [99] Ma)

Cephalopod 16

Holotype of Ostenoteuthis siroi from familyOstenoteuthidae.

A fossilised belemnite

• Order † Orthocerida (482.5 to 211.5 [99] Ma)• Order † Ascocerida (478.0 to 412 [100] Ma)• Order † Dissidocerida (479 to 457.5 [116] Ma)• Order † Bajkalocerida

• Subclass † Bactritoidea (422 to 252 [117] Ma)• Subclass † Ammonoidea (410 to 66 [118] Ma)• Subclass Coleoidea (410.0 Ma-rec)[119]

Cladistic classification

Pyritized fossil of Vampyronassa rhodanica, a vampyromorphidfrom the Lower Callovian (unknown operator: u'callovianround'

[120] million years ago)

Another recent system divides all cephalopods into twoclades. One includes nautilus and most fossilnautiloids. The other clade (Neocephalopoda orAngusteradulata) is closer to modern coleoids, andincludes belemnoids, ammonoids, and many orthoceridfamilies. There are also stem group cephalopods of thetraditional Ellesmerocerida that belong to neitherclade.[121] [122]

Monophyly of coeloids

The coeloids have been thought to possibly represent apolyphyletic group,[49] :289 although this has not beensupported by the rising body of molecular data.[123]

Post-mortem decay

After death, if undisturbed, cephalopods[124] decay relatively quickly. Their muscle softens within a couple of days,and may swell; egg sacs can swell so much that they rip through the mantle. Subsequently, the organs shrink again;at this point the organism may start to break up into fragments. The eyes retain their size while the head shrinksaround them. The gills may remain swollen at this point. After around a week, the carcass collapses in on itself andbegins to disintegrate. The ink sac solidifies around this point. After a fortnight little is left but a blob with eyes,arms and ink sac visible. After a couple of months, these are only recognisable as flattened dark stains - although insome cases the eye lenses can remain intact for up to a year.[68]

Cephalopod 17

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[81] Holland, C. H. (1987). "The nautiloid cephalopods: a strange success: President's anniversary address 1986". Journal of the GeologicalSociety 144: 1–0. doi:10.1144/gsjgs.144.1.0001.

[82] Kröger, Björn (2006). "Early growth-stages and classification of orthoceridan Cephalopods of the Darriwillian (Middle Ordovician) ofBaltoscandia" (http:/ / www3. interscience. wiley. com/ journal/ 119918421/ abstract). Lethaia 39 (2): 129–139.doi:10.1080/00241160600623749. .

[83] Young, R.E.; Vecchione, M.; Donovan, D.T.. "The evolution of coleoid cephalopods and their present biodivesity and ecology". In Payne,AIL; Lipin'ski, M.R.; Clarke, M.R.; Roeleveld, M.A.C. Cephalopod biodiversity, ecology & evolution. South Afriocan journal of MarineSciences. 20. pp. 393–420.

[84] Strugnell, J.; Norman, M.; Jackson, J.; Drummond, A.; Cooper, A. (2005). "Molecular phylogeny of coleoid cephalopods (Mollusca:Cephalopoda) using a multigene approach; the effect of data partitioning on resolving phylogenies in a Bayesian framework". Molecularphylogenetics and evolution 37 (2): 426–441. doi:10.1016/j.ympev.2005.03.020. PMID 15935706.

[85] Strugnell, J.; Jackson, J.; Drummond, A. J.; Cooper, A. (2006). "Divergence time estimates for major cephalopod groups: evidence frommultiple genes". Cladistics 22: 89–96. doi:10.1111/j.1096-0031.2006.00086.x.

Cephalopod 20

[86] Carlini, DB; Reece, KS; Graves, JE (2000). "Actin gene family evolution and the phylogeny of coleoid cephalopods (Mollusca:Cephalopoda)". Molecular biology and evolution 17 (9): 1353–70. PMID 10958852.

[87] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=415[88] Bergmann, S.; Lieb, B.; Ruth, P.; Markl, J. (2006). "The hemocyanin from a living fossil, the cephalopod Nautilus pompilius: protein

structure, gene organization, and evolution". Journal of molecular evolution 62 (3): 362–374. doi:10.1007/s00239-005-0160-x.PMID 16501879.

[89] http:/ / www. mnh. si. edu/ cephs/ newclass. pdf[90] Bather, F.A. (1888b). "Professor Blake and Shell-Growth in Cephalopoda.". Annals and Magazine of Natural History Series 6, Vol. 1:

421–426.[91] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=500–470[92] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=485–430[93] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=480–312[94] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=482–392[95] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=432–272[96] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=485–386[97] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=478. 5–324. 0[98] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=410. 5–0[99] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=482. 5–211. 5[100] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=478–412[101] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=418. 1–260. 5[102] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=479–65[103] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=388. 5–252. 0[104] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=254–200[105] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=215–66[106] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=265–183[107] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=189. 6–183. 0[108] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=339. 4–318. 1[109] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=339. 4–65. 5[110] Shevyrev, A.A. (2005). "The Cephalopod Macrosystem: A Historical Review, the Present State of Knowledge, and Unsolved Problems: 1.

Major Features and Overall Classification of Cephalopod Mollusks.". 'Paleontological Journal 39 (6): 606–614. "Translated fromPaleontologicheskii Zhurnal No. 6, 2005, 33-42.".

[111] Shevyrev, A. A. (2006). "The cephalopod macrosystem; a historical review, the present state of knowledge, and unsolved problems; 2,Classification of nautiloid cephalopods". Paleontological Journal 40 (1): 46–54. doi:10.1134/S0031030106010059.

[112] Kroger, B.. "Peer review in the Russian “Paleontological Journal”" (http:/ / www. tiefes-leben. de/ 2009/ 03/peer-review-in-the-russian-paleontological-journal). .

[113] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=501–490[114] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=485–480[115] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=490–480[116] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=479. 0–457. 5[117] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=422–252[118] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=410–66[119] Bather, F.A. (1888a). "Shell-growth in Cephalopoda (Siphonopoda).". Annals and Magazine of Natural History Series 6, Vol. 1: 298–310.[120] http:/ / toolserver. org/ ~verisimilus/ Timeline/ Timeline. php?Ma=Callovian[121] Berthold, Thomas, & Engeser, Theo (1987). "Phylogenetic analysis and systematization of the Cephalopoda (Mollusca)". Verhandlungen

Naturwissenschaftlichen Vereins in Hamburg. (NF) 29: 187–220.[122] Engeser (1997). "Fossil Nautiloidea Page" (http:/ / web. archive. org/ web/ 20060925110442/ http:/ / userpage. fu-berlin. de/ ~palaeont/

fossilnautiloidea/ fossnautcontent. htm). Archived from the original (http:/ / userpage. fu-berlin. de/ ~palaeont/ fossilnautiloidea/fossnautcontent. htm) on 2006-09-25. .

[123] Lindgren, A. R.; Giribet, G.; Nishiguchi, M. K. (2004). "A combined approach to the phylogeny of Cephalopoda (Mollusca)". Cladistics20: 454. doi:10.1111/j.1096-0031.2004.00032.x.

[124] Experiments were performed on a variety of squid

Cephalopod 21

References

Further reading• Barskov, I.S., M.S. Boiko, V.A. Konovalova, T.B. Leonova & S.V. Nikolaeva (2008). "Cephalopods in the

marine ecosystems of the Paleozoic". Paleontological Journal 42: 1167–1284. doi:10.1134/S0031030108110014.A comprehensive overview of Paleozoic cephalopods.

• Campbell, Neil A., Reece, Jane B., and Mitchell, Lawrence G.: Biology, fifth edition. Addison Wesley Longman,Inc. Menlo Park, California. 1999. ISBN 0-8053-6566-4.

• Felley, J., Vecchione, M., Roper, C. F. E., Sweeney, M. & Christensen, T., 2001-2003: Current Classification ofRecent Cephalopoda. Internet: National Museum of Natural History: Department of Systematic Biology:Invertebrate Zoology: http:/ / www. mnh. si. edu/ cephs/

External links• CephBase - cephalopod database (http:/ / www. cephbase. utmb. edu/ )• TONMO.COM - The Octopus News Magazine Online - cephalopod articles and discussion (http:/ / www. tonmo.

com/ )• Tree of Life Web Project - Cephalopoda (http:/ / tolweb. org/ Cephalopoda)• Mikko's Phylogeny Tree (http:/ / www. fmnh. helsinki. fi/ users/ haaramo/ Metazoa/ Protostoma/ Mollusca/

Cephalopoda/ Coleoidea. htm)• Fish vs. Cephalopods (http:/ / www. cco. caltech. edu/ ~brokawc/ Bi11/ cephalopods. html)• Will Fast Growing Squid Replace Slow Growing Fish? (http:/ / www. atse. org. au/ index. php?sectionid=329)• Biomineralisation in modern and fossil cephalopods (http:/ / biomin. geol. u-psud. fr/ ydweb/ cephalo/ index. htm)• Scientific American: Can a Squid Fly Out of the Water? (http:/ / www. scientificamerican. com/ article.

cfm?id=can-squid-fly)

Octopus 22

Octopus

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The Common Octopus, Octopusvulgaris.

Scientific classification [ e ]

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Superorder: Octopodiformes

Order: OctopodaLeach, 1818[1]

Suborders

• Cirrina• Incirrina

Synonyms

• OctopoidaLeach, 1817[2]

The octopus is a cephalopod mollusc of the order Octopoda. Octopuses have two eyes and four pairs of arms, andlike other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center pointof the arms. Octopuses have no internal or external skeleton (although some species have a vestigial remnant of ashell inside their mantle), allowing them to squeeze through tight places. Octopuses are among the most intelligentand behaviorally flexible of all invertebrates.The octopus inhabits many diverse regions of the ocean, including coral reefs, pelagic waters, and the ocean floor.They have numerous strategies for defending themselves against predators, including the expulsion of ink, the use ofcamouflage and deimatic displays, their ability to jet quickly through the water, and their ability to hide. An octopustrails its eight arms behind it as it swims. All octopuses are venomous, but only one group, the blue-ringedoctopuses, is known to be deadly to humans.[3]

In the larger sense, there are around 300 recognized octopus species, which is over one-third of the total number ofknown cephalopod species. The term octopus may also be used to refer only to those creatures in the genus Octopus.

Octopus 23

BiologyOctopuses are characterized by their eight arms, usually bearing suction cups. The arms of octopuses are oftendistinguished from the pair of feeding tentacles found in squid and cuttlefish.[4] Both types of limbs are muscularhydrostats. Unlike most other cephalopods, the majority of octopuses – those in the suborder most commonlyknown, Incirrina – have almost entirely soft bodies with no internal skeleton. They have neither a protective outershell like the nautilus, nor any vestige of an internal shell or bones, like cuttlefish or squid. A beak, similar in shapeto a parrot's beak, is the only hard part of their body. This enables them to squeeze through very narrow slits betweenunderwater rocks, which is very helpful when they are fleeing from morays or other predatory fish. The octopuses inthe less familiar Cirrina suborder have two fins and an internal shell, generally reducing their ability to squeeze intosmall spaces. These cirrate species are often free-swimming and live in deep-water habitats, while incirrate octopusspecies are found in reefs and other shallower seafloor habitats.

An octopus moving between tide pools duringlow tide

Octopuses have a relatively short life expectancy, and some specieslive for as little as six months. Larger species, such as the North PacificGiant Octopus, may live for up to five years under suitablecircumstances. However, reproduction is a cause of death: males canonly live for a few months after mating, and females die shortly aftertheir eggs hatch. They neglect to eat during the (roughly) one monthperiod spent taking care of their unhatched eggs, but they do not die ofstarvation. Endocrine secretions from the two optic glands are thecause of genetically programmed death (and if these glands aresurgically removed, the octopus may live many months beyondreproduction, until she finally starves).

Grimpoteuthis discoveryi, a finned octopus of thesuborder Cirrina

Octopuses have three hearts. Two branchial hearts pump blood througheach of the two gills, while the third pumps blood through the body.Octopus blood contains the copper-rich protein hemocyanin fortransporting oxygen. Although less efficient under normal conditionsthan the iron-rich hemoglobin of vertebrates, in cold conditions withlow oxygen pressure, hemocyanin oxygen transportation is moreefficient than hemoglobin oxygen transportation. The hemocyanin isdissolved in the plasma instead of being carried within red blood cellsand gives the blood a bluish color. Octopuses draw water into theirmantle cavity where it passes through its gills. As mollusks, octopuseshave gills that are finely divided and vascularized outgrowths of eitherthe outer or the inner body surface.

Intelligence

Octopuses are highly intelligent, likely more so than any other order of invertebrates. The exact extent of theirintelligence and learning capability is much debated among biologists,[5] [6] [7] [8] but maze and problem-solvingexperiments have shown that they show evidence of a memory system that can store both short- and long-termmemory. It is not known precisely what contribution learning makes to adult octopus behavior. Young octopuseslearn almost no behaviors from their parents, with whom they have very little contact.

Octopus 24

An octopus opening a container with a screw cap

An octopus has a highly complex nervous system, only part of which islocalized in its brain. Two-thirds of an octopus's neurons are found inthe nerve cords of its arms, which have limited functional autonomy.Octopus arms show a variety of complex reflex actions that persisteven when they have no input from the brain.[9] Unlike vertebrates, thecomplex motor skills of octopuses are not organized in their brainusing an internal somatotopic map of its body, as is the motor systemin vertebrates[10] Some octopuses, such as the mimic octopus, willmove their arms in ways that emulate the movements of other seacreatures.

In laboratory experiments, octopuses can be readily trained todistinguish between different shapes and patterns. They have beenreported to practice observational learning,[11] although the validity ofthese findings is widely contested on a number of grounds.[5] [6]

Octopuses have also been observed in what some have described asplay: repeatedly releasing bottles or toys into a circular current in theiraquariums and then catching them.[12] Octopuses often break out oftheir aquariums and sometimes into others in search of food. They

have even boarded fishing boats and opened holds to eat crabs.[7]

In some countries, octopuses are on the list of experimental animals on which surgery may not be performed withoutanesthesia. In the UK, cephalopods such as octopuses are regarded as honorary vertebrates under the Animals(Scientific Procedures) Act 1986 and other cruelty to animals legislation, extending to them protections not normallyafforded to invertebrates.[13]

The octopus is the only invertebrate which has been shown to use tools. At least four specimens of the VeinedOctopus (Amphioctopus marginatus) have been witnessed retrieving discarded coconut shells, manipulating them,and then reassembling them to use as shelter. This discovery was documented in the journal Current Biology and hasalso been caught on video.[14] [15]

Octopus 25

Defense

Greater Blue-ringed Octopus (Hapalochlaenalunulata)

An octopus's main (primary) defense is to hide, either not to be seen atall, or not to be detected as an octopus.[16] Octopuses have severalsecondary defenses (defenses they use once they have been seen by apredator). The most common secondary defense is fast escape. Otherdefenses include the use of ink sacs, camouflage, and autotomisinglimbs.

Most octopuses can eject a thick blackish ink in a large cloud to aid inescaping from predators. The main coloring agent of the ink ismelanin, which is the same chemical that gives humans their hair andskin color. This ink cloud is thought to reduce the efficiency ofolfactory organs, which would aid an octopus's evasion from predatorsthat employ smell for hunting, such as sharks. Ink clouds of somespecies might serve as pseudomorphs, or decoys that the predatorattacks instead.[17]

Amphioctopus marginatus travels with shells ithas collected for protection

An octopus's camouflage is aided by certain specialized skin cellswhich can change the apparent color, opacity, and reflectiveness of theepidermis. Chromatophores contain yellow, orange, red, brown, orblack pigments; most species have three of these colors, while somehave two or four. Other color-changing cells are reflective iridophores,and leucophores (white).[18] This color-changing ability can also beused to communicate with or warn other octopuses. The veryvenomous blue-ringed octopus becomes bright yellow with blue ringswhen it is provoked. Octopuses can use muscles in the skin to changethe texture of their mantle to achieve a greater camouflage. In somespecies the mantle can take on the spiky appearance of seaweed, or thescraggly, bumpy texture of a rock, among other disguises. However in

some species skin anatomy is limited to relatively patternless shades of one color, and limited skin texture. It isthought that octopuses that are day-active and/or live in complex habitats such as coral reefs have evolved morecomplex skin than their nocturnal and/or sand-dwelling relatives.[16]

When under attack, some octopuses can perform arm autotomy, in a similar manner to the way skinks and otherlizards detach their tails. The crawling arm serves as a distraction to would-be predators.A few species, such as the Mimic Octopus, have a fourth defense mechanism. They can combine their highly flexiblebodies with their color changing ability to accurately mimic other, more dangerous animals such as lionfish, seasnakes, and eels.[19] [20]

ReproductionWhen octopuses reproduce, males use a specialized arm called a hectocotylus to insert spermatophores (packets of sperm) into the female's mantle cavity. The hectocotylus in benthic octopuses is usually the third right arm. Males die within a few months of mating. In some species, the female octopus can keep the sperm alive inside her for weeks until her eggs are mature. After they have been fertilized, the female lays about 200,000 eggs (this figure dramatically varies between families, genera, species and also individuals). The female hangs these eggs in strings

Octopus 26

from the ceiling of her lair, or individually attaches them to the substrate depending on the species. The female caresfor the eggs, guarding them against predators, and gently blowing currents of water over them so that they getenough oxygen. The female does not hunt during the roughly one-month period spent taking care of the unhatchedeggs and may ingest some of her own arms for sustenance. At around the time the eggs hatch, the mother leaves thelair and is too weak to defend herself from predators like cod, often succumbing to their attacks. The young larvaloctopuses spend a period of time drifting in clouds of plankton, where they feed on copepods, larval crabs and larvalstarfish until they are ready to descend to the ocean bottom, where the cycle repeats. This is a dangerous time for thelarval octopuses; in the plankton cloud they are vulnerable to plankton eaters. In some deeper dwelling species, theyoung do not go through this period.

Sensation

Eye of Octopus vulgaris

Octopuses have keen eyesight. Octopuses, like other cephalopods, candistinguish the polarization of light. Color vision appears to vary fromspecies to species, being present in Octopus aegina but absent inOctopus vulgaris.[21] Attached to the brain are two special organs,called statocysts, that allow the octopus to sense the orientation of itsbody relative to horizontal. An autonomic response keeps the octopus'seyes oriented so that the pupil slit is always horizontal.

Octopuses also have an excellent sense of touch. An octopus's suctioncups are equipped with chemoreceptors so that the octopus can tastewhat it is touching. The arms contain tension sensors so that theoctopus knows whether its arms are stretched out. However, the octopus has a very poor proprioceptive sense. Thetension receptors are not sufficient for the octopus brain to determine the position of the octopus's body or arms. (It isnot clear that the octopus brain would be capable of processing the large amount of information that this wouldrequire; the flexibility of an octopus's arms is much greater than that of the limbs of vertebrates, which devote largeareas of cerebral cortex to the processing of proprioceptive inputs.) As a result, the octopus does not possessstereognosis; that is, it does not form a mental image of the overall shape of the object it is handling. It can detectlocal texture variations, but cannot integrate the information into a larger picture.[22]

The neurological autonomy of the arms means that the octopus has great difficulty learning about the detailed effectsof its motions. The brain may issue a high-level command to the arms, but the nerve cords in the arms execute thedetails. There is no neurological path for the brain to receive feedback about just how its command was executed bythe arms; the only way it knows just what motions were made is by observing the arms visually.[22]

Octopuses appear to have limited hearing.[23]

Octopuses swim headfirst, with arms trailingbehind

Octopus 27

Locomotion

Video of an octopus in its natural habitat

Octopuses move about by crawling or swimming. Theirmain means of slow travel is crawling, with someswimming. Jet propulsion is their fastest means oflocomotion, followed by swimming and walking.[24]

They crawl by walking on their arms, usually on many atonce, on both solid and soft surfaces, while supported inwater. In 2005 it was reported that some octopuses(Adopus aculeatus and Amphioctopus marginatus undercurrent taxonomy) can walk on two arms, while at thesame time resembling plant matter.[25] This form oflocomotion allows these octopuses to move quickly awayfrom a potential predator while possibly not triggeringthat predator's search image for octopus (food).[24]

Octopuses swim by expelling a jet of water from a contractile mantle, and aiming it via a muscular siphon.

Size

An adult North Pacific Giant Octopus,Enteroctopus dofleini

The North Pacific Giant Octopus, Enteroctopus dofleini, is often citedas the largest octopus species. Adults usually weigh around 15 kg(33 lb), with an arm span of up to 4.3 m (14 ft).[26] The largestspecimen of this species to be scientifically documented was an animalwith a live mass of 71 kg (156.5 lb).[27] The alternative contender is theSeven-arm Octopus, Haliphron atlanticus, based on a 61 kg (134 lb)carcass estimated to have a live mass of 75 kg (165 lb).[28] [29]

However, there are a number of questionable size records that wouldsuggest E. dofleini is the largest of all octopus species by aconsiderable margin;[30] one such record is of a specimen weighing272 kg (600 lb) and having an arm span of 9 m (30 ft).[31]

TerminologyThe term octopus, pronounced /ˈɒktəpʊs/, is from Greek ὀκτάπους (oktapous), "eight-footed",[32] [33] with pluralforms: octopuses /ˈɒktəpʊsɪz/, octopi /ˈɒktəpaɪ/, or octopodes /ɒkˈtɒpədiːz/. Currently, octopuses is the mostcommon form in both the US and the UK; octopodes is rare, and octopi is often objectionable.[34]

The plural form octopi is often described as a hypercorrection. The Oxford English Dictionary (2008 DraftRevision)[35] lists octopuses, octopi and octopodes (in that order); it labels octopodes "rare", although the correctGreek plural form, and notes that octopi derives from the "apprehension" that octōpūs is a second declension Latinnoun, though it is not. It is a Latinization of Greek third-declension masculine oktṓpous (ὀκτώπους, 'eight-foot'),plural oktṓpodes (ὀκτώποδες). If the word were native to Latin, it would be octōpēs, plural octōpedes, after thepattern of pēs ('foot'), plural pedēs, analogous to "centipede".[36] The actual Latin word for octopus and other similarspecies is polypus, from Greek polýpous (πολύπους, 'many-foot'); usually the inaccurate plural polypī is used insteadof polypodēs.In modern Greek, the word is khtapódi (χταπόδι), plural khtapódia (χταπόδια), from Medieval oktapódion(ὀκταπόδιον), equivalent to Classical oktápous (ὀκτάπους), variant of oktṓpous.

Octopus 28

Chambers 21st Century Dictionary[37] and the Compact Oxford Dictionary[38] list only octopuses, although the latternotes that octopodes is "still occasionally used"; the British National Corpus has 29 instances of octopuses, 11 ofoctopi and 4 of octopodes. Merriam-Webster 11th Collegiate Dictionary lists octopuses and octopi, in that order;Webster's New World College Dictionary lists octopuses, octopi and octopodes (in that order).Fowler's Modern English Usage states that "the only acceptable plural in English is octopuses," and that octopi ismisconceived and octopodes pedantic.The term octopod (plural octopods or octopodes) is taken from the taxonomic order Octopoda but has no classicalequivalent. The collective form octopus is usually reserved for animals consumed for food.

Relationship to humans

Ancient peoples of the Mediterranean were aware of the octopus, as evidenced by certain artworks and designs ofprehistory. For example, a stone carving found in the archaeological recovery from Bronze Age Minoan Crete atKnossos has a depiction of a fisherman carrying an octopus.[39]

Octopuses were often depicted in the art of the Moche people of ancient Peru, who worshipped the sea and itsanimals.[40]

Octopus 29

In mythologyThe Hawaiian creation myth relates that the present cosmos is only the last of a series, having arisen in stages fromthe wreck of the previous universe. In this account, the octopus is the lone survivor of the previous, alienuniverse.[41]

In literatureThe octopus has a significant role in Victor Hugo's book Travailleurs de la mer (Toilers of the Sea).[42]

Octopus at Tsukiji fish market

As food

Humans eat octopus in many cultures. The arms and sometimes otherbody parts are prepared in various ways, often varying by species.Octopus is a common ingredient in Japanese cuisine, including sushi,takoyaki, and Akashiyaki. Some small species are sometimes eatenalive as a novelty food. Similarly, a live octopus may be sliced up andthe legs eaten while still squirming, which continues for some minutes.

Octopuses are "tickled" out of theirholes‎ in the Hawaiian Islands with

3-pronged polespears

Octopus is eaten regularly in Hawaii, since many popular dishes are Asian inorigin. Locally known by their Hawaiian or Japanese names ("he'e" and "tako"respectively), octopus is also a popular fish bait.

Octopus is a common food in Mediterranean cuisine and Portuguese cuisine. InGalicia, polbo á feira (market fair style octopus) is a local delicacy. Restaurantswhich specialize or serve this dish are known as pulperías. On the Tunisianisland of Djerba, local people catch octopuses by taking advantage of theanimals' habit of hiding in safe places during the night. In the evening they putgrey ceramic pots on the sea bed. The morning of the following day they checkthem for octopuses that sheltered there. A common scene in the Greek islands isoctopuses hanging in the sunlight from a rope, just like laundry from aclothesline. They are often caught by spear fishing close to the shore. Thefisherman brings his prey to land and tenderizes the flesh by pounding the carcass against a stone surface. Thustreated they are hung out to dry, and later will be served grilled either hot, or chilled in a salad. They are considered asuperb meze, especially alongside ouzo.

According to the USDA Nutrient Database (2007), cooked octopus contains approximately 139 calories per threeounce portion, and is a source of vitamin B3, B12, potassium, phosphorus, and selenium.[43]

Care must be taken to boil the octopus properly, to rid it of slime, smell, and residual ink.

Octopus 30

As petsThough octopuses can be difficult to keep in captivity, some people keep them as pets. Octopuses often escape evenfrom supposedly secure tanks, due to their problem-solving skills, mobility and lack of rigid structure.The variation in size and life span among octopus species makes it difficult to know how long a new specimen cannaturally be expected to live. That is, a small octopus may be just born or may be an adult, depending on its species.By selecting a well-known species, such as the California Two-spot Octopus, one can choose a small octopus(around the size of a tennis ball) and be confident that it is young with a full life ahead of it.Octopuses are also quite strong for their size. Octopuses kept as pets have been known to open the covers of theiraquariums and survive for a time in the air in order to get to a nearby feeder tank and gorge themselves on the fishthere. Large octopuses have also been known to catch and kill some species of sharks.[44]

Classification

Cirrothauma murrayi

Amphitretus pelagicus

• Class CEPHALOPODA• Subclass Nautiloidea: nautilus• Subclass Coleoidea

• Superorder Decapodiformes: squid, cuttlefish• Superorder Octopodiformes

• Family †Trachyteuthididae (incertae sedis)

• Order Vampyromorphida: Vampire Squid• Order Octopoda

• Genus †Keuppia (incertae sedis)

• Genus †Palaeoctopus (incertae sedis)

• Genus †Paleocirroteuthis (incertae sedis)

• Genus †Pohlsepia (incertae sedis)

• Genus †Proteroctopus (incertae sedis)

• Genus †Styletoctopus (incertae sedis)

• Suborder Cirrina: finned deep-sea octopus• Family Opisthoteuthidae: umbrella octopus• Family Cirroteuthidae• Family Stauroteuthidae

• Suborder Incirrina• Family Amphitretidae: telescope octopus• Family Bolitaenidae: gelatinous octopus• Family Octopodidae: benthic octopus• Family Vitreledonellidae: Glass Octopus• Superfamily Argonautoida

• Family Alloposidae: Seven-arm Octopus• Family Argonautidae: argonauts• Family Ocythoidae: Tuberculate Pelagic Octopus• Family Tremoctopodidae: blanket octopus

Octopus 31

See also• Octopus wrestling• Legend of the Octopus• Henry the Hexapus, a six-armed octopus• Paul the Octopus, an octopus famous for predicting Germany national football team results

References[1] ITIS Report: Octopoda Leach, 1818 (http:/ / www. itis. gov/ servlet/ SingleRpt/ SingleRpt?search_topic=TSN& search_value=82589)[2] Helsinki.fi (http:/ / www. helsinki. fi/ ~mhaaramo/ metazoa/ protostoma/ mollusca/ Cephalopoda/ Coleoidea. htm), Mikko's Phylogeny

Archive: Coleoidea – Recent cephalopods[3] Unimelb.edu.au (http:/ / uninews. unimelb. edu. au/ view. php?articleID=5755), Tentacles of venom: new study reveals all octopuses are

venomous, University of Melbourne, Media Release, Wednesday 15 April 2009[4] Norman, M. 2000. Cephalopods: A World Guide. ConchBooks, Hackenheim. p. 15. "There is some confusion around the terms arms versus

tentacles. The numerous limbs of nautiluses are called tentacles. The ring of eight limbs around the mouth in cuttlefish, squids and octopusesare called arms. Cuttlefish and squid also have a pair of specialized limbs attached between the bases of the third and fourth arm pairs [...].These are known as feeding tentacles and are used to shoot out and grab prey."

[5] What is this octopus thinking? (http:/ / www. fortunecity. com/ emachines/ e11/ 86/ cephpod. html). By Garry Hamilton.[6] NFW.org? (http:/ / www. nwf. org/ nationalwildlife/ article. cfm?articleId=604& issueId=53), Is the octopus really the invertebrate intellect of

the sea, by Doug Stewart. In: National Wildlife. Feb/Mar 1997, vol.35 no.2.[7] Giant Octopus—Mighty but Secretive Denizen of the Deep (http:/ / web. archive. org/ web/ 20080102230427/ http:/ / nationalzoo. si. edu/

Support/ AdoptSpecies/ AnimalInfo/ GiantOctopus/ default. cfm)[8] Slate.com (http:/ / www. slate. com/ id/ 2192211/ ), How Smart is the Octopus?[9] Yoram Yekutieli, Roni Sagiv-Zohar1, Ranit Aharonov, Yaakov Enge, Binyamin Hochner and Tamar Flash (2005). Dynamic Model of the

Octopus Arm. I. Biomechanics of the Octopus Reaching Movement J. Neurophysiology. 94:1443-1458. PMID 15829594[10] Zullo L, Sumbre G, Agnisola C, Flash T, Hochner B. (2009). Nonsomatotopic organization of the higher motor centers in octopus. Curr

Biol. 19(19):1632-6. PMID 19765993[11] Octopus intelligence: jar opening (http:/ / news. bbc. co. uk/ 2/ hi/ europe/ 2796607. stm)[12] What behavior can we expect of octopuses? (http:/ / www. thecephalopodpage. org/ behavior. php). By Dr. Jennifer Mather, Department of

Psychology and Neuroscience, University of Lethbridge and Roland C. Anderson, The Seattle Aquarium.[13] United Kingdom Animals (Scientific Procedures) act of 1986 (http:/ / www. archive. official-documents. co. uk/ document/ hoc/ 321/

321-xa. htm)[14] "Octopus snatches coconut and runs" (http:/ / news. bbc. co. uk/ 1/ hi/ sci/ tech/ 8408233. stm). BBC News. 2009-12-14. . Retrieved

2010-05-20.[15] http:/ / www. edutube. org/ video/ coconut-shelter-evidence-tool-use-octopuses[16] Hanlon, R.T. & J.B. Messenger 1996. Cephalopod Behaviour. Cambridge University Press, Cambridge.[17] Caldwell, R. L. (2005). "An Observation of Inking Behavior Protecting Adult Octopus bocki from Predation by Green Turtle (Chelonia

mydas) Hatchlings". Pacific Science 59 (1): 69–72.[18] Meyers, Nadia. "Tales from the Cryptic: The Common Atlantic Octopus" (http:/ / www. dnr. sc. gov/ marine/ sertc/ species_month. htm).

Southeastern Regional Taxonomic Center. . Retrieved 2006-07-27.[19] Norman, M.D., J. Finn & T. Tregenza (2001). Dynamic mimicry in an Indo-Malayan octopus. (http:/ / marinebio. org/ upload/ files/ mimic.

pdf)PDF (312 KB) Proceedings of the Royal Society 268: 1755–1758.[20] Norman, M.D. & F.G.Hochberg (2005). The "Mimic Octopus" (Thaumoctopus mimicus n. gen. et sp.), a new octopus from the tropical

Indo-West Pacific (Cephalopoda: Octopodidae). Molluscan Research 25: 57–70. Abstract (http:/ / www. mapress. com/ mr/ content/ v25/2005f/ n2p070. htm)

[21] Kawamura, G., et al. (2001). Color Discrimination Conditioning in Two Octopus Octopus aegina and O. vulgaris. (http:/ / rms1. agsearch.agropedia. affrc. go. jp/ contents/ JASI/ pdf/ society/ 62-1620. pdf)PDF (453 KB) . Nippon Suisan Gakkashi 67(1): 35–39.

[22] Wells. Martin John. Octopus: physiology and behaviour of an advanced invertebrate. London : Chapman and Hall ; New York : distributedin the U.S.A. by Halsted Press, 1978.

[23] Matt Walker (15 June 2009). "The cephalopods can hear you" (http:/ / news. bbc. co. uk/ earth/ hi/ earth_news/ newsid_8095000/ 8095977.stm). BBC. . Retrieved 2010-04-02.

[24] Locomotion by Abdopus aculeatus, C.L. Huffard 2006 (http:/ / jeb. biologists. org/ cgi/ content/ abstract/ 209/ 19/ 3697)[25] Science, vol. 307, p. 1927 (http:/ / www. sciencemag. org/ cgi/ content/ full/ 307/ 5717/ 1927)[26] Smithsonian National Zoological Park: Giant Pacific Octopus (http:/ / nationalzoo. si. edu/ Animals/ Invertebrates/ Facts/ cephalopods/

FactSheets/ Pacificoctopus. cfm)[27] Cosgrove, J.A. 1987. Aspects of the Natural History of Octopus dofleini, the Giant Pacific Octopus. M.Sc. Thesis. Department of Biology,

University of Victoria (Canada), 101 pp.

Octopus 32

[28] O'Shea, S. 2004. The giant octopus Haliphron atlanticus (Mollusca : Octopoda) in New Zealand waters. New Zealand Journal of Zoology31(1): 7–13.

[29] O'Shea, S. 2002. Haliphron atlanticus — a giant gelatinous octopus. Biodiversity Update 5: 1.[30] Norman, M. 2000. Cephalopods: A World Guide. ConchBooks, Hackenheim. p. 214.[31] High, W.L. (1976). "The giant Pacific octopus". U.S. National Marine Fisheries Service, Marine Fisheries Review 38 (9): 17–22.[32] Oktapous (http:/ / www. perseus. tufts. edu/ cgi-bin/ ptext?doc=Perseus:text:1999. 04. 0057:entry=#72829), Henry George Liddell, Robert

Scott, A Greek-English Lexicon, at Perseus[33] Scientific Latin from Greek ὀκτώποδ-, ὀκτώπους (also ὀκτάποδ- ὀκτάπους) "eight-footed" > ὀκτώ- or ὀκτά- [combination form of ὀκτώ

"eight"] and πόδ-, πούς "foot". Cf. Modern Greek χταπόδι < οκταπόδι < οκταπόδιον < ὀκτάπους.[34] Peters, Pam (2004). The Cambridge Guide to English Usage. Cambridge: Cambridge University Press. ISBN 0-521-62181-X, p. 388.[35] OED.com (http:/ / dictionary. oed. com/ cgi/ entry/ 00330051?single=1& query_type=word& queryword=octopus& first=1&

max_to_show=10) (subscription required). Retrieved February 1, 2010.[36] " centipede (http:/ / oed. com/ search?searchType=dictionary& q=centipede)". Oxford English Dictionary. Oxford University Press. 2nd ed.

1989.[37] Chambersharrap.co.uk (http:/ / www. chambersharrap. co. uk/ chambers/ features/ chref/ chref. py/ main?title=21st& query=octopus),

Retrieved October 19, 2007.[38] Askoxford.com (http:/ / www. askoxford. com/ concise_oed/ octopus), Retrieved October 19, 2007.[39] C. Michael Hogan. 2007 Knossos fieldnotes, The Modern Antiquarian (http:/ / www. themodernantiquarian. com/ site/ 10854/ knossos.

html#fieldnotes)[40] Berrin, Katherine & Larco Museum. The Spirit of Ancient Peru:Treasures from the Museo Arqueológico Rafael Larco Herrera. New York:

Thames and Hudson, 199 7.[41] Dixon, Roland Burrage (1916). The Mythology of All Races. 9. Marshall Jones. p. 15.[42] This article incorporates text from a publication now in the public domain: Chisholm, Hugh, ed (1911). Encyclopædia Britannica (Eleventh

ed.). Cambridge University Press.[43] Octopus Calories And Nutrition (http:/ / www. annecollins. com/ calories/ calories-octopus-squid. htm)[44] Archived Google video of an octopus catching a shark (http:/ / video. google. com/ videoplay?docid=-7004909622962894202), from The

Octopus Show by Mike deGruy

External links• CephBase: Octopoda (http:/ / www. cephbase. dal. ca/ spdb/ ordergroup. cfm?Orderr=Octopoda)• TONMO.COM – The Octopus News Magazine Online (http:/ / www. tonmo. com/ )• Tree of Life website: information about cephalopods along with pictures and videos (http:/ / tolweb. org/

tree?group=Cephalopoda)• Discussion about the plural (http:/ / itre. cis. upenn. edu/ ~myl/ languagelog/ archives/ 000813. html)• An octopus's shark encounter (http:/ / video. pbs. org:8080/ ramgen/ wnet/ nature/ octopus/ sharkT1. rm) –

footage of an octopus eating a shark ( also in Quicktime format (http:/ / www. archive. org/ download/Octopus_eats_a_shark_1/ octopus. mov))

• Camouflage in action (http:/ / www. mbl. edu/ mrc/ hanlon/ video. html)• Video showing an Octopus escaping through a 1 inch hole (http:/ / video. google. com/

videoplay?docid=4007016107763801953)• Bipedal Octopuses- Video, Information, Original paper (http:/ / ist-socrates. berkeley. edu/ ~chuffard/ index_files/

Bipedal_octopuses. htm)• Why Cephalopods Change Color (http:/ / www. thecephalopodpage. org/ cephschool/

WhyCephalopodsChangeColor. pdf)PDF (359 KB)• Video of walking octopuses (http:/ / berkeley. edu/ news/ media/ releases/ 2005/ 03/ 24_octopus. shtml)

Squid 33

Squid

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Bigfin Reef Squid, Sepioteuthislessoniana

Scientific classification [ e ]

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Superorder: Decapodiformes

Order: TeuthidaA. Naef, 1916

Suborders

†Plesioteuthididae (incertae sedis)MyopsinaOegopsina

Squid are marine cephalopods of the order Teuthida, which comprises around 300 species. Like all othercephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eightarms arranged in pairs and two, usually longer, tentacles. Squid are strong swimmers and certain species can 'fly' forshort distances out of the water.[1]

Modification from ancestral formsSquid have differentiated from their ancestral molluscs such that the body plan has been condensedantero-posteriorly and extended dorso-ventrally. What before may have been the foot of the ancestor is modified intoa complex set of tentacles and highly developed sense organs, including advanced eyes similar to those ofvertebrates.The ancestral shell has been lost, with only an internal gladius, or pen, remaining. The pen is a feather-shapedinternal structure that supports the squid's mantle and serves as a site for muscle attachment. It is made of achitin-like substance.

Squid 34

Anatomy

European Squid (Loligo vulgaris)

The main body mass is enclosed in the mantle, whichhas a swimming fin along each side. These fins, unlikein other marine organisms, are not the main source oflocomotion in most species.

The skin is covered in chromatophores, which enablethe squid to change color to suit its surroundings,making it effectively invisible. The underside is alsoalmost always lighter than the topside, to providecamouflage from both prey and predator.

Under the body are openings to the mantle cavity,which contains the gills (ctenidia) and openings to theexcretory and reproductive systems. At the front of themantle cavity lies the siphon, which the squid uses forlocomotion via precise jet propulsion. In this form of locomotion, water is sucked into the mantle cavity and expelledout of the siphon in a fast, strong jet. The direction of the siphon can be changed, to suit the direction of travel.

Inside the mantle cavity, beyond the siphon, lies the visceral mass, which is covered by a thin, membranousepidermis. Under this are all the major internal organs.

Nervous systemThe giant axon, which may be up to 1 mm (0.04 inches) in diameter in some larger species, innervates the mantleand controls part of the jet propulsion system.As cephalopods, squid exhibit relatively high intelligence among invertebrates. For example, groups of Humboldtsquid hunt cooperatively, using active communication. (See Cephalopod intelligence.)

Reproductive system

[[file:Onykia ingens withnon-erect penis.jpg|thumb|right

A dissected male specimen of Onykia ingens, showing a non-erect penis (thewhite tubular structure located below most of the otherorgans)]][[file:Onykia ingens with erect penis.jpg|thumb|right

A specimen of the same speciesexhibiting elongation of the penisto 67 cm in length]]

In females the ink sac is hidden from view by a pair of white nidamental glands, which lie anterior to the gills. Thereare also red-spotted accessory nidamental glands. Both organs are associated with food manufacture and shells forthe eggs. Females also have a large translucent ovary, situated towards the posterior of the visceral mass.Males do not possess these organs, but instead have a large testis in place of the ovary, and a spermatophoric glandand sac. In mature males, this sac may contain spermatophores, which are placed inside the female's mantle duringmating.Shallow water species of the continental shelf and epipelagic/mesopelagic zones are characterised by the presence ofhectocotyli, specially modified arms used to fertilise the female's eggs.[2] Most deep sea squid lack hectocotyli andhave longer penises; Ancistrocheiridae and Cranchiinae are exceptions.[2] Giant squid of the genus Architeuthis areunusual in that they possess both a large penis and modified arm tips, although it is uncertain whether the latter areused for spermatophore transfer.[2] Penis elongation has been observed in the deep water species Onykia ingens;when erect, the penis may be as long as the mantle, head and arms combined.[2] [3] As such, deep water squid havethe greatest known penis length relative to body size of all mobile animals, second in the entire animal kingdom onlyto certain sessile barnacles.[2]

Squid 35

Digestive systemLike all cephalopods, squid have complex digestive systems. The muscular stomach is found roughly in the midpointof the visceral mass. From there, the bolus moves into the caecum for digestion. The caecum, a long, white organ, isfound next to the ovary or testis. In mature squid, more priority is given to reproduction such that the stomach andcaecum often shrivel up during the later life stages. Finally, food goes to the liver (or digestive gland), found at thesiphon end, for absorption. Solid waste is passed out of the rectum. Beside the rectum is the ink sac, which allows asquid to rapidly discharge black ink into the mantle cavity.

Ventral view of the viscera of the female Chtenopteryx sicula

Cardiovascular system

Squid have three hearts. Two branchial hearts feed thegills, each surrounding the larger systemic heart thatpumps blood around the body. Squid blood contains thecopper-rich protein hemocyanin for transportingoxygen. The faintly greenish hearts are surrounded bythe renal sacs - the main excretory system. The kidneysare difficult to identify and stretch from the hearts(located at the posterior side of the ink sac) to the liver.

The systemic heart is made of three chambers, a lower ventricle and two upper auricles.

HeadThe head end bears 8 arms and 2 tentacles, each a form of muscular hydrostat containing many suckers along theedge. These tentacles do not grow back if severed. In the mature male, one basal half of the left ventral tentacle ishectocotylised — and ends in a copulatory pad rather than suckers. It is used for intercourse.The mouth is equipped with a sharp horny beak mainly made of chitin[4] and cross-linked proteins, and is used to killand tear prey into manageable pieces. The beak is very robust, but does not contain minerals, unlike the teeth andjaws of many other organisms, including marine species.[5] Captured whales often have indigestible squid beaks intheir stomachs. The mouth contains the radula (the rough tongue common to all molluscs except bivalvia andaplacophora).The eyes, on either side of the head, each contain a hard lens. The lens is focused through movement, much like thelens of a camera or telescope, rather than changing shape as the lens in the human eye does.Squids appear to have limited hearing.[6]

Size

Giant squid in Melbourne Aquarium

The majority are no more than60 centimetres (24 in) long, althoughthe giant squid may reach 13 metres(43 ft).[7]

In 1978, sharp, curved claws on thesuction cups of squid tentacles cut upthe rubber coating on the hull of theUSS Stein. The size suggested thelargest squid known at the time.[8]

In 2003, a large specimen of an abundant[9] but poorly understood species, Mesonychoteuthis hamiltoni (the Colossal Squid), was discovered. This species may grow to 14 metres (46 ft) in length, making it the largest invertebrate.[10]

Squid 36

Squid have the largest eyes in the animal kingdom. Giant squid are featured in literature and folklore with afrightening connotation. The Kraken is a legendary tentacled monster possibly based on sightings of real giant squid.In February 2007, a New Zealand fishing vessel caught a Colossal Squid weighing 495 kilograms (1090 lb) andmeasuring around 10 metres (33 ft) off the coast of Antarctica.[11] This specimen represents the largest cephalopodto ever be scientifically documented.

Classification

Bathyteuthis abyssicola

Grimalditeuthis bonplandi

Histioteuthis reversa

Squid are members of the class Cephalopoda, subclass Coleoidea,order Teuthida, of which there are two major suborders, Myopsinaand Oegopsina (including giant squids like Architeuthis dux). Teuthidais the largest cephalopod order with around 300 species classified into29 families.

The order Teuthida is a member of the superorder Decapodiformes(from the Greek for "ten legs"). Two other orders of decapodiformcephalopods are also called squid, although they are taxonomicallydistinct from Teuthida and differ recognizably in their gross anatomicalfeatures. They are the bobtail squid of order Sepiolida and the ram'shorn squid of the monotypic order Spirulida. The vampire squid,however, is more closely related to the octopuses than to any squid.

• CLASS CEPHALOPODA

• Subclass Nautiloidea: nautilus• Subclass Coleoidea: squid, octopus, cuttlefish

• Superorder Octopodiformes• Superorder Decapodiformes

• ?Order †Boletzkyida• Order Spirulida: Ram's Horn Squid• Order Sepiida: cuttlefish• Order Sepiolida: bobtail squid• Order Teuthida: squid

• Family †Plesioteuthididae (incertae sedis)

• Suborder Myopsina• Family Australiteuthidae• Family Loliginidae: inshore, calamari, and grass

squid• Suborder Oegopsina

• Family Ancistrocheiridae: Sharpear Enope Squid• Family Architeuthidae: giant squid• Family Bathyteuthidae• Family Batoteuthidae: Bush-club Squid• Family Brachioteuthidae• Family Chiroteuthidae• Family Chtenopterygidae: comb-finned squid• Family Cranchiidae: glass squid• Family Cycloteuthidae

Squid 37

Mastigoteuthis flammea

Onychoteuthis banksii

Pterygioteuthis giardi

• Family Enoploteuthidae• Family Gonatidae: armhook squid• Family Histioteuthidae: jewel squid• Family Joubiniteuthidae: Joubin's Squid• Family Lepidoteuthidae: Grimaldi Scaled Squid• Family Lycoteuthidae• Family Magnapinnidae: bigfin squid• Family Mastigoteuthidae: whip-lash squid• Family Neoteuthidae• Family Octopoteuthidae• Family Ommastrephidae: flying squid• Family Onychoteuthidae: hooked squid• Family Pholidoteuthidae• Family Promachoteuthidae• Family Psychroteuthidae: Glacial Squid• Family Pyroteuthidae: fire squid• Family Thysanoteuthidae: rhomboid squid• Family Walvisteuthidae• Parateuthis tunicata (incertae sedis)

Commercial fishing

According to the FAO, the cephalopod catch for 2002 was3173272 tonnes (6.995867×109 lb). Of this, 2,189,206 tonnes, or 75.8percent, was squid.[12] The following table lists the squid speciesfishery catches which exceeded 10000 tonnes ( lb) in 2002.

Squid 38

World squid catch in 2002[12]

Species Family Common name Catchtonnes

Percent

Loligo gahi Loliginidae Patagonian squid 24,976 1.1

Loligo pealei Loliginidae Longfin squid 16,684 0.8

Common squids nei[13] Loliginidae 225,958 10.3

Ommastrephes bartramii Ommastrephidae Neon flying squid 22,483 1.0

Illex argentinus Ommastrephidae Argentine shortfin squid 511,087 23.3

Dosidicus gigas Ommastrephidae Jumbo flying squid 406,356 18.6

Todarodes pacificus Ommastrephidae Japanese flying squid 504,438 23.0

Nototoda russloani Ommastrephidae Wellington Flying Squid 62,234 2.8

Squids nei[13] Various 414,990 18.6

Total squid 2,189,206 100.0

As food

Fried calamari: breaded, deep-fried squid

Many species are popular as food in cuisines as diverse as Chinese,Greek, Turkish, Japanese, Portuguese, Italian, Spanish, Korean, Indian,and Filipino.

In English-speaking countries, squid as food is often marketed usingthe Italian word calamari. Squid are found abundantly in certain areas,and provide large catches for fisheries. The body can be stuffed whole,cut into flat pieces or sliced into rings. The arms, tentacles and ink arealso edible; in fact, the only parts that are not eaten are the beak andgladius (pen). Squid is a good food source for zinc, manganese andhigh in the recommended daily intake of copper,[14] selenium, vitaminB12, and riboflavin.[15]

References[1] Jabr, F. 2010. Fact or Fiction: Can a Squid Fly Out of the Water? (http:/ / www. scientificamerican. com/ article. cfm?id=can-squid-fly&

sc=WR_20100804) Scientific American, August 2, 2010.[2] Arkhipkin, A.I. & V.V. Laptikhovsky 2010. Observation of penis elongation in Onykia ingens: implications for spermatophore transfer in

deep-water squid. Journal Molluscan Studies, published online on June 30, 2010. doi:10.1093/mollus/eyq019[3] Walker, M. 2010. Super squid sex organ discovered (http:/ / news. bbc. co. uk/ earth/ hi/ earth_news/ newsid_8792000/ 8792008. stm). BBC

Earth News, July 7, 2010.[4] Clarke, M.R. (1986). A Handbook for the Identification of Cephalopod Beaks. Oxford: Clarendon Press. ISBN 0-19-857603-X.[5] Miserez, A; Li, Y; Waite, H; Zok, F (2007). "Jumbo squid beaks: Inspiration for design of robust organic composites". Acta Biomaterialia 3:

139–149. doi:10.1016/j.actbio.2006.09.004.[6] Matt Walker (15 June 2009). "The cephalopods can hear you" (http:/ / news. bbc. co. uk/ earth/ hi/ earth_news/ newsid_8095000/ 8095977.

stm). BBC. . Retrieved 2010-04-02.[7] O'Shea, S. (2003.). "Giant Squid and Colossal Squid Fact Sheet" (http:/ / www. tonmo. com/ science/ public/ giantsquidfacts. php). The

Octopus News Magazine Online.. .[8] Johnson, C. Scott "Sea Creatures and the Problem of Equipment Damage" United States Naval Institute Proceedings August 1978 pp.106-107[9] Xavier, J.C., P.G. Rodhouse, P.N. Trathan & A.G. Wood 1999. A Geographical Information System (GIS) Atlas of cephalopod distribution in

the Southern Ocean. (http:/ / www. journals. cambridge. org/ production/ action/ cjoGetFulltext?fulltextid=219642)PDF Antarctic Science11:61-62. online version (http:/ / www. nerc-bas. ac. uk/ public/ mlsd/ squid-atlas/ )

Squid 39

[10] Anderton, H.J. (2007.). "Amazing specimen of world's largest squid in NZ" (http:/ / www. beehive. govt. nz/ ViewDocument.aspx?DocumentID=28451). New Zealand Government website. .

[11] "Microwave plan for colossal squid" (http:/ / news. bbc. co. uk/ 2/ hi/ asia-pacific/ 6478801. stm). BBC News. March 22, 2007. .[12] Rodhouse, Paul G (2005). "Review of the state of world marine fishery resources: Fisheries technical paper" (http:/ / www. fao. org/ docrep/

009/ y5852e/ Y5852E08. htm#ch3. 2). World squid resources (FAO) (447). ISBN 95-5-105267-0. .[13] nei: not elsewhere included[14] http:/ / www. foodmarketexchange. com/ datacenter/ product/ seafood/ squid/ detail/ dc_pi_sf_squid_0204. htm[15] http:/ / www. nmfs. noaa. gov/ fishwatch/ species/ market_squid. htm

External links• CephBase: Teuthida (http:/ / www. cephbase. utmb. edu/ spdb/ squid. cfm)• Colossal Squid at the Museum of New Zealand Te Papa Tongarewa (http:/ / www. tepapa. govt. nz/ TePapa/

English/ CollectionsAndResearch/ CollectionAreas/ NaturalEnvironment/ Molluscs/ ColossalSquid/ )• Market squid mating, laying eggs (video) (http:/ / diving. rogerbly. com/ video/ squid)• Scientific American - Giant Squid (http:/ / www. sciam. com/ article. cfm?chanID=sa003&

articleID=00030326-0783-133B-878383414B7F0000)• The Cephalopod Page (http:/ / www. thecephalopodpage. org)• The Octopus News Magazine Online (http:/ / www. tonmo. com)

Cuttlefish 40

Cuttlefish

Cuttlefish

Sepia latimanus, EastTimor

Scientific classification [ e ]

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Superorder: Decapodiformes

Order: SepiidaZittel, 1895

Suborders and Families

• †Vasseuriina

• †Vasseuriidae• †Belosepiellidae

• Sepiina

• †Belosaepiidae• Sepiadariidae• Sepiidae

Cuttlefish are marine animals of the order Sepiida. They belong to the class Cephalopoda (which also includessquid, octopuses, and nautiluses). Despite their name, cuttlefish are not fish but molluscs. Recent studies indicate thatcuttlefish are among the most intelligent invertebrates.[1] Cuttlefish also have one of the largest brain-to-body sizeratios of all invertebrates.[1]

The origin of the word cuttlefish can be found in the old English term cudele, which derived in the 15th century fromthe Norwegian koddi (cushion, testicle) and the Middle German kudel (pouch), a good description of thecephalopod's shape. The Greco-Roman world valued the cephalopod as a source of the unique brown pigment thatthe creature releases from its siphon when it is alarmed. The word for it in Greek and Latin, sepia (later seppia inItalian), is used to refer to a brown pigment in English.Cuttlefish have an internal shell (the cuttlebone), large W-shaped pupils, and eight arms and two tentacles furnishedwith denticulated suckers, with which they secure their prey. They generally range in size from 15 cm (5.9 in) to25 cm (9.8 in), with the largest species, Sepia apama, reaching 50 cm (20 in) in mantle length and over 10.5 kg (23lb) in weight.[2]

Cuttlefish eat small molluscs, crabs, shrimp, fish, octopuses, worms, and other cuttlefish. Their predators includedolphins, sharks, fish, seals and other cuttlefish. Their life expectancy is about one to two years.

Cuttlefish 41

Video of a cuttlefish in its natural habitat

Physiology

Cuttlebone

Cuttlefish possess an internal structurecalled the cuttlebone, which is porous and ismade of aragonite. This provides thecuttlefish with buoyancy. Buoyancy can beregulated by changing the gas-to-liquid ratioin the chambered cuttlebone via the ventralsiphuncle.[3] Each species has a distinctshape, size, and pattern of ridges or textureon the cuttlebone. The cuttlebone is uniqueto cuttlefish, one of the features thatdistinguishes them from their squidrelatives. Jewelers and silversmithstraditionally use cuttlebones as moulds for casting small objects[4] but they are probably better known as the toughmaterial given to parakeets and other caged birds as a source of dietary calcium.

This Broadclub Cuttlefish (Sepialatimanus) can go from camouflage tans

and browns (top) to yellow with darkhighlights (bottom) in less than a second.

Cuttlefish 42

Skin

An infant cuttlefish protects itself with camouflage

Cuttlefish are sometimes referred to as the chameleonof the sea because of their remarkable ability to rapidlyalter their skin color at will. Cuttlefish change color andlight polarity to communicate to other cuttlefish and tocamouflage themselves from predators.

This color-changing function is produced by groups ofred, yellow, brown, and black pigmentedchromatophores above a layer of reflective iridophoresand leucophores, with up to 200 of these specializedpigment cells per square millimeter, which correspondsto about 359 DPI. The pigmented chromatophores havea sac of pigment and a large membrane that is foldedwhen retracted. There are 6-20 small muscle cells onthe sides which can contract to squash the elastic sacinto a disc against the skin. Yellow chromatophores (xanthophores) are closest to the surface of the skin, red andorange are below (erythrophores), and brown or black are just above the iridophore layer (melanophores). Theiridophores reflect blue and green light. Iridophores are plates of chitin or protein, which can reflect the environmentaround a cuttlefish. They are responsible for the metallic blues, greens, golds, and silvers often seen on cuttlefish. Allof these cells can be used in combinations. For example, orange is produced by red and yellow chromatophores,while purple can be created by a red chromatophore and an iridophore. The cuttlefish can also use an iridophore anda yellow chromatophore to produce a brighter green. As well as being able to influence the color of light as it reflectsoff their skin, cuttlefish can also affect the light's polarization, which can be used to signal to other marine animals,many of which can also sense polarization.[5]

Eyes

Close up of a cuttlefish eye

Cuttlefish eyes are among the most developed in the animal kingdom.The organogenesis of cephalopod eyes differs fundamentally from thatof vertebrates like humans.[6] Superficial similarities betweencephalopod and vertebrate eyes are thought to be examples ofconvergent evolution. The cuttlefish pupil is a smoothly-curving Wshape. Although they cannot see color,[7] they can perceive thepolarization of light, which enhances their perception of contrast. Theyhave two spots of concentrated sensor cells on their retina (known asfoveae), one to look more forward, and one to look more backwards.The lenses, instead of being reshaped as they are in humans, are pulledaround by reshaping the entire eye to change focus. Unlike thevertebrate eye, there is no blind spot as the optic nerve is positionedbehind the retina.

Scientists have speculated that cuttlefish's eyes are fully developed before birth and start observing theirsurroundings while still in the egg. One team of French researchers has additionally suggested that cuttlefish preferto hunt the prey they saw before hatching.[8]

Cuttlefish 43

CirculationThe blood of a cuttlefish is an unusual shade of green-blue because it uses the copper-containing protein hemocyaninto carry oxygen instead of the red iron-containing protein hemoglobin that is found in vertebrates' blood. The bloodis pumped by three separate hearts: two branchial hearts pump blood to the cuttlefish's pair of gills (one heart foreach), and the third pumps blood around the rest of the body. Cuttlefish blood must flow more rapidly than mostother animals because hemocyanin carries substantially less oxygen than hemoglobin.

InkCuttlefish have ink, like squid and octopuses, which they use to help evade predators.

ToxicityLike octopuses and some squid, all cuttlefish have bacterially-produced neurotoxins in their saliva.[9]

Pfeffer's Flamboyant Cuttlefish from Sipadan, Malaysia

The muscles of Pfeffer's Flamboyant Cuttlefish containa highly toxic compound that is yet to be identified.[1]

Mark Norman with Museum Victoria in Victoria,Australia, has shown the toxin to be as lethal as that ofa fellow cephalopod, the blue-ringed octopus.[10]

Ecology

Diet

The preferred diet of the cuttlefish is crabs and fish.[11]

The cuttlefish uses its camouflage to hunt and sneak upon its prey. When it gets close enough, it opens its eight arms and shoots out two long feeding tentacles. On the endof each is a pad covered in suckers that grabs and pulls prey toward its beak.[11]

Range and habitatFamily Sepiidae, which contains all cuttlefish, inhabit tropical/temperate ocean waters. They are mostlyshallow-water animals although they are known to go to depths of about 600 metres (2000 ft).[12] They have anunusual biogeographic pattern: totally absent from the Americas, but present along the coasts of east and south Asia,western Europe, the Mediterranean, as well as all coasts of Africa and Australia. By the time the family evolved,ostensibly in the Old World, the north Atlantic possibly had become too cold and deep for these warm water speciesto cross.[13]

Cuttlefish 44

Taxonomy

Sepia officinalis from Turkish waters

There are over 120 species of cuttlefish currentlyrecognised, grouped into 5 genera. Sepiadariidaecontains seven species and 2 genera; all the rest are inSepiidae.

• CLASS CEPHALOPODA• Subclass Nautiloidea: nautilus• Subclass Coleoidea: squid, octopus, cuttlefish

• Superorder Octopodiformes• Superorder Decapodiformes

• ?Order †Boletzkyida• Order Spirulida: Ram's Horn Squid• Order Sepiida: cuttlefish

• Suborder †Vasseuriina• Family †Vasseuriidae• Family †Belosepiellidae

• Suborder Sepiina• Family †Belosaepiidae• Family Sepiadariidae• Family Sepiidae

• Order Sepiolida: bobtail squid• Order Teuthida: squid

Relation to humans

GastronomyCuttlefish are caught for food in the Mediterranean, East Asia, the English Channel and elsewhere. Although squid ismore popular as a restaurant dish all over the world, in East Asia dried, shredded cuttlefish is a popular snack food.

Linguine with cuttlefish and ink sauce served at aVenetian osteria

Cuttlefish is especially popular in Italy, where it is used in Risotto alNero di Seppia (literally black cuttlefish rice). The Croatian Crni Rižotis virtually the same recipe, which probably originated in Venice andthen spread across both coasts of the Adriatic. "Nero" and "Crni" meanblack, the color the rice turns because of the cuttlefish ink. Spanishcuisine, especially that of the coastal regions, uses cuttlefish and squidink for the marine flavor and smoothness it provides; it is included indishes such as rice, pasta and fish stews.

In Portugal, it is the regional dish of the city of Setúbal andsurrounding areas, where it is served as deep-fried strips or in a variantof feijoada, with red kidney beans.

Cultural significanceEugenio Montale's ground-breaking debut collection of poetry Cuttlefish Bones (Ossi di seppia) was published in Turin in 1925. Montale, who grew up in Liguria along the Mediterranean Sea, was awarded the Nobel Prize for

Cuttlefish 45

Literature in 1975, for his long and prolific career. Cuttlefish Bones remains one of the best-known and influentialcollections of 20th-century Italian poetry.

SepiaCuttlefish ink was formerly an important dye, called sepia. Today artificial dyes have mostly replaced natural sepia.However, recently some Jews have resumed using sepia for the techelet dye on their Tallit strings.

References[1] NOVA, 2007. Cuttlefish: Kings of Camouflage. (http:/ / www. pbs. org/ wgbh/ nova/ camo/ ) (television program) NOVA, PBS, April 3,

2007.[2] Reid, A., P. Jereb, & C.F.E. Roper 2005. Family Sepiidae. In: P. Jereb & C.F.E. Roper, eds. Cephalopods of the world. An annotated and

illustrated catalogue of species known to date. Volume 1. Chambered nautiluses and sepioids (Nautilidae, Sepiidae, Sepiolidae, Sepiadariidae,Idiosepiidae and Spirulidae). FAO Species Catalogue for Fishery Purposes. No. 4, Vol. 1. Rome, FAO. pp. 57–152.

[3] Rexfort, A.; Mutterlose, J. (2006). "Stable isotope records from Sepia officinalis—a key to understanding the ecology of belemnites?". Earthand Planetary Science Letters 247: 212–212. doi:10.1016/j.epsl.2006.04.025.

[4] Casting Silver with Cuttlefish (http:/ / www. silverstall. com/ casting-silver-jewellery. html)[5] Mäthger, L. M., Shashar, N., and R.T. Hanlon. 2009. Do cephalopods communicate using polarized light reflections from their skin? Journal

of Experimental Biology 212: 2133–2140. doi:10.1242/jeb.020800[6] Muller, Matthew. "Development of the Eye in Vertebrates and Cephalopods and Its Implications for Retinal Structure" (http:/ / www. bio.

davidson. edu/ people/ midorcas/ animalphysiology/ websites/ 2003/ Muller/ development of the cephalopod eye. htm). The Cephalopod Eye.Davidson College Biology Department. . Retrieved 2007-04-06.

[7] Mäthger, Lydia M.. "Color blindness and contrast perception in cuttlefish (Sepia offcinalis) determined by a visual sensorimotor assay" (http:// www. mbl. edu/ mrc/ hanlon/ pdfs/ mathger_et_al_visres_2006. pdf). Vision Research, Volume 46, Issue 11, May 2006. Elsevier Ltd.. .Retrieved 2007-09-03.

[8] BBC News (2008-06-05). "Cuttlefish spot target prey early" (http:/ / news. bbc. co. uk/ 1/ hi/ sci/ tech/ 7435757. stm). . Retrieved2008-05-06.

[9] http:/ / news. nationalgeographic. com/ news/ 2009/ 04/ 090417-octopus-venom. html[10] Teacher's Guide (http:/ / www. pbs. org/ wgbh/ nova/ teachers/ viewing/ 3404_camo. html) to NOVA episode - Kings of Camouflage (http:/

/ www. pbs. org/ wgbh/ nova/ camo/ ) on PBS (After Watching: Activity 2).[11] Cuttlefish Basics (http:/ / www. tonmo. com/ articles/ basiccuttlefish. php)[12] Lu, C. C. and C. F. E. Roper. 1991. Aspects of the biology of Sepia cultrata from southeastern Australia. In: La Seiche, The Cuttlefish.

Boucaud-Camou, E. (Ed). Caen, France; Centre de Publications de l'Université de Caen: 192.[13] Young, R. E., M. Vecchione and D. Donovan, 1998. The evolution of coleoid cephalopods and their present biodiversity and ecology. South

African Jour. Mar. Sci., 20: 393-420.

External links• TONMO.com Community Forum - Keeping cuttlefish in the home aquarium (http:/ / www. tonmo. com/ forums/

forumdisplay. php?f=18)• Scientific Database with photos and videos of cuttlefish and other cephalopods (http:/ / www. cephbase. utmb.

edu/ )• YouTube video with examples of color and texture modulation. (http:/ / www. youtube. com/

watch?v=sFYX9D2RQUM)• Youtube video Cuttlefish changing colour and shape (http:/ / au. youtube. com/ watch?v=9XLObuvEryg)• Amazing cuttlefish - Cephalopods with natural camouflage and sepia ink (http:/ / www. users. on. net/

~jamesmosby/ cuttlefish/ index. html)• PBS.org - Nova - Kings of Camouflage (http:/ / www. pbs. org/ wgbh/ nova/ camo/ )

Nautiloid 46

Nautiloid

Nautiloids

Orthoceras

Scientific classification [ e ]

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Subclass: NautiloideaAgassiz, 1847

Orders

Palcephalopoda

• †Plectronocerida• †Ellesmerocerida• †Actinocerida• †Pseudorthocerida• †Ascocerida• †Endocerida• †Tarphycerida• †Oncocerida• †Discosorida• Nautilida

Neocephalopoda (in part)

• †Orthocerida• †Lituitida• †Bactritida

Nautiloids are a large and diverse group of marine cephalopods (Mollusca) belonging to the subclass Nautiloideathat began in the Late Cambrian and are represented today by the living Nautilus. Nautiloids flourished during theearly Paleozoic era, where they constituted the main predatory animals, and developed an extraordinary diversity ofshell shapes and forms. Some 2,500 species of fossil nautiloids are known, but only a handful of species survive tothe present day.

Taxonomic relationshipsNautiloids are among the group of animals known as cephalopods, an advanced class of mollusks which alsoincludes ammonoids, belemnites and modern coleoids such as octopus and squid. Other mollusks include gastropods,scaphopods and pelecypods.Traditionally, the most common classification of the cephalopods has been a three-fold division (by Bather, 1888),into the nautiloids, ammonoids, and coleoids. This article is about nautiloids in that broad sense, sometimes calledNautiloidea sensu lato.Cladistically speaking, nautiloids are a paraphyletic assemblage united by shared primitive (plesiomorphic) features not found in derived cephalopods. In other words, they are a grade group that is thought to have given rise to both ammonoids and coleoids, and are defined by the exclusion of both those descendent groups. Both ammonoids and

Nautiloid 47

coleoids have traditionally been assumed to have descended from bactritids, which in turn arose fromstraight-shelled orthocerid nautiloids.The ammonoids (a group which includes the ammonites and the goniatites) are extinct cousins of the nautiloids thatevolved early in the Devonian period, some 400 million years ago.Some workers apply the name Nautiloidea to a more exclusive group, called Nautiloidea sensu stricto. This taxonconsists only of those orders that are clearly related to the modern nautilus. The membership assigned variessomewhat from author to author, but usually includes Tarphycerida, Oncocerida, and Nautilida.

CharacteristicsThe subclass nautiloidea, in the broad original sense, is distinguished by two main characters, simple concave septa,concave in the forward direction, that produce generally simple sutures, and a siphuncle in which the septal neckspoint to the rear, i.e. is retrosiphonate, throughout the ontogeny of the animal.The septa between the chambers (camerae) of the phragmocone (the chambered part of the shell) are formed duringgrowth spurts of the animal. At that time the rear of the mantle secretes a new septum adding another chamber whilethe more forward part adds on to the shell. The body of the animal, its viscera, continues to occupy the last chamberof the shell – the living chamber.The septa are perforated by the siphuncle, which runs through each of the internal chambers of the shell.Surrounding the fleshy tube of the siphuncle are structures made of Aragonite (a polymorph of Calcium Carbonate –which during fossilisation is converted to Calcite): septal necks and connecting rings. Some of the earlier nautiloidsdeposited calcium carbonate in the empty chambers (called cameral deposits) or within the siphuncle(endosiphuncular deposits), a process which may have been connected with controlling buoyancy. The nature of thesiphuncle and its position within the shell are important in classifying nautiloids.Sutures (or suture lines) are visible as a series of narrow wavy lines on the surface of the shell, and they appearwhere each septum contacts the wall of the outer shell. The sutures of the nautiloids are simple in shape, being eitherstraight or slightly curved. This is different from the "zigzag" sutures of the goniatites and the highly complexsutures of the ammonites.

Modern nautiloids

Nautilus belauensis

Much of what is known about the extinct nautiloids isbased on what we know about the modern nautiluses,such as the Chambered Nautilus which is found in thesouth west Pacific Ocean, from Samoa to thePhilippines, and the in the Indian Ocean off of the coastof Australia. It is not usually found in waters less than100 meters deep and may be found as far down as 500to 700 meters (2,300 ft).

Nautiluses are free swimming animals that possess ahead with two simple lens-free eyes and arms (ortentacles). They each have a smooth shell, with a largebody chamber, which is divided into chambers that arefilled with an inert gas (similar to air but with morenitrogen and less oxygen) making the animal buoyant

in the water. As many as 90 tentacles are arranged in two circles around their mouth. The animal has jaws which arehorny and beak-like, and it is a predator, feeding mainly on crustaceans.

Nautiloid 48

Empty nautilus shells may drift a considerable distance and have been reported from Japan, India and Africa.Undoubtedy the same applies to the shells of fossil nautiloids, the gas inside the shell keeping it buoyant for sometime after the animal's death so that the empty shell was carried some distance from where the animal lived before itfinally sank to the sea-floor.Nautiluses propel themselves by jet propulsion, expelling water from an elongated funnel called the hyponome,which can be pointed in different directions to control their movement. They do not have an ink sac like that found inbelemnites and some of the other cephalopods, and there is no evidence to suggest that the extinct forms possessedan ink sac either. Unlike the extinct ammonoids, the modern nautiluses lack any sort of plate for closing their shell.With one exception, no such plate has been found in any of the extinct nautiloids either.The coloration of the shell of the modern nautiluses is quite prominent, and, although it is somewhat rare, the shellcoloration has been known to be preserved in fossil nautiloids. They often show color patterns on the dorsal sideonly, which suggests the living animals swam horizontally.

Fossil record

Fossil nautiloid Trilacinoceras from theOrdovician of China.

Fossil orthoconic nautiloid from the Ordovicianof Kentucky; an internal mold showing siphuncle

and half-filled camerae, both encrusted.

Nautiloids are often found as fossils in early Palaeozoic rocks (less soin more recent strata). The shells of fossil nautiloids may be eitherstraight (i.e., orthoconic as in Orthoceras and Rayonnoceras), curved(as in Cyrtoceras) coiled (as in Cenoceras), or rarely a helical coil (asin Lorieroceras). Some species' shells—especially in the late Paleozoicand early Mesozoic—are ornamented with spines and ribs, but mosthave a smooth shell.

The shells are formed of aragonite, although the cameral deposits mayconsist of primary calcite.[1]

The rocks of the Ordovician period in the Baltic coast and parts of theUnited States contain a variety of nautiloid fossils, and specimens suchas Discitoceras and Rayonnoceras may be found in the limestones ofthe Carboniferous period in Ireland. The marine rocks of the Jurassicperiod in Britain often yield specimens of Cenoceras, and nautiloidssuch as Eutrephoceras are also found in the Pierre Shale formation ofthe Cretaceous period in the north-central United States.

Specimens of the Ordovician nautiloid Endoceras have been recordedmeasuring up to 3.5 meters (13 ft) in length, and Cameroceras is(somewhat doubtfully) estimated to have reached 11 meters (36 ft).These large nautiloids must have been formidable predators of other marine animals at the time they lived.

In some localities, such as Scandinavia and Morocco, the fossils of orthoconic nautiloids accumulated in such largenumbers that they form Orthoceras limestones. Although the term Orthoceras now only refers to a Baltic coastOrdovician genus, in prior times it was employed as a general name given to all straight-shelled nautiloids that livedfrom the Ordovician to the Triassic periods (but were most common in the early Paleozoic era.

Nautiloid 49

Evolutionary historyNautiloids are first known from the late Cambrian Fengshan Formation of northeastern China, where they seem tohave been quite diverse (at the time this was a warm shallow sea rich in marine life). However, although four ordershave been proposed from the 131 species named, there is no certainty that all of these are valid, and indeed it islikely that these taxa are seriously oversplit.Most of these early forms died out, but a single family, the Ellesmeroceratidae, survived to the early Ordovician,where it ultimately gave rise to all subsequent cephalopods. In the Early and Middle Ordovician the nautiloidsunderwent an evolutionary radiation.[2] [3] Some eight new orders appeared at this time, covering a great diversity ofshell types and structure, and ecological lifestyles.Nautiloids remained at the height of their range of adaptations and variety of forms throughout the Ordovician,Silurian, and Devonian periods, with various straight, curved and coiled shell forms coexisting at the same time.Several of the early orders became extinct over that interval, but others rose to prominence.Nautiloids began to decline in the Devonian, perhaps due to competition with their descendants and relatives theAmmonoids and Coleoids, with only the Nautilida holding their own (and indeed increasing in diversity). Theirshells became increasingly tightly coiled, while both numbers and variety of non-Nautilid species continued todecrease throughout the Carboniferous and Permian.The massive extinctions at the end of the Permian were less damaging to nautiloids than to other taxa and a fewgroups survived into the early Mesozoic, including pseudorthocerids, bactritids, nautilids and possibly orthocerids.The last straight-shelled forms were long thought to have disappeared at the end of the Triassic, but a possibleorthocerid has been found in Cretaceous rocks. Apart from that exception, only a single nautiloid suborder, theNautilina, continued throughout the Mesozoic, where they co-existed quite happily with their more specialisedammonoid cousins. Most of these forms differed only slightly from the modern nautilus. They had a brief resurgencein the early Tertiary (perhaps filling the niches vacated by the ammonoids in the end Cretaceous extinction), andmaintained a worldwide distribution up until the middle of the Cenozoic Era. With the global cooling of the Mioceneand Pliocene, their geographic distribution shrank and these hardy and long-lived animals declined in diversity again.Today there are only six living species, all belonging to two genera, Nautilus (the pearly nautilus), and Allonautilus.

ClassificationClassifications vary and a subject to change as new information is found and in accordance with the perspective ofvarious workers. The taxonomy of the Taxo Box is one such scheme,Teichert's 1988 classification is another, that ofTeichert et al. 1964 in the Treatise Part K , still another.Wade (1988) divided the subclass Nautiloidea into 6 superorders, combing orders that are phylogenetically related.They are the:• Plectronoceratoidea = Plectronocerida, Protactinocerida, Yanhecerida,and Ellesmerocerida.• Endoceratoidea = Endocerida• Orthoceratoidea: = Orthocerida, Ascocerida, and Pseudorthocerida (the Orthoceratoidea of Kroger 1007)• Nautilitoidea = Tarphycerida, Oncocerida, and Nautilida.• Actinoceratoidea = Actinocerida• Discosoritoidea = DiscosoridaThree of them are established as equivalent places to put the Endocerida, Actinocerida, and Discosorida. Three uniterelated orders that share a common ancestor and form a branch of the nautiloid taxonomic tree; thePlectronoceratoidea which are mostly small Cambrian forms that include the ancestors of subsequent stocks; theOrthoceratoidea which unites different primarily orthoconic orders of which one is the source for the Bacritida andAmmonoidea; and the Nautilitoidea which includes the first coilded cephalopods, the Tarphycerida, as well as theNautilida which includes the recent Nautilus

Nautiloid 50

Another order, the Bactritida, which are derived from the Orthocerida are sometimes included with the Nautiloidea,sometimes with the ammonoidea, and sometimes are placed in a subclass of their own, the Bactritoidea.Recently some workers in the field have come to recognize the Dissidocerida as a distinct order, along with thePseudorthocerida, both previously included in the Orthoceridaas subtaxa.A more recent interpretation (Engeser 1997-1998) suggests that nautiloids, and indeed cephalopods in general, fallinto two main groups, the Palcephalopoda (including all the nautiloids except Orthocerida and Ascocerida) and theNeocephalopoda (the rest of the cephalopods).

References[1] Stehli, F. G. (8 June 1956). "Shell Mineralogy in Paleozoic Invertebrates" (http:/ / jstor. org/ stable/ 1750042). Science 123 (3206):

1031–1032. doi:10.1126/science.123.3206.1031. ISSN 00368075. PMID 17800970. .[2] KrÖger, B. �R.; Landing, E. (2008). "Onset of the Ordovician cephalopod radiation – evidence from the Rochdale Formation (middle Early

Ordovician, Stairsian) in eastern New York". Geological Magazine 145. doi:10.1017/S0016756808004585.[3] Kröger, B.; Yun-bai, Y. B. (2009). "Pulsed cephalopod diversification during the Ordovician". Palaeogeography Palaeoclimatology

Palaeoecology 273: 174–201. doi:10.1016/j.palaeo.2008.12.015.

• Doguzhaeva, Larisa. (1994) An Early Cretaceous orthocerid cephalopod from north-western Caucasus.Palaeontology 37(4): 889-899.

• Engeser, T., (1997-1998) The Palcephalopoda/Neocephalopoda Hypothesis (http:/ / userpage. fu-berlin. de/~palaeont/ fossilnautiloidea/ fossnautpalneocephalopoda. htm)

• Teichert, C. (1988) "Main Features of Cephalopod Evolution", in The Mollusca vol.12, Paleontology andNeontology of Cephalopods, ed. by M.R. Clarke & E.R. Trueman, Academic Press, Harcourt Brace Jovanovich,

External links• Nautiloids: The First Cephalopods (TONMO.com) (http:/ / www. tonmo. com/ science/ fossils/ nautiloids. php)• Palaeos (http:/ / www. palaeos. com/ Invertebrates/ Molluscs/ Cephalopoda/ Nautiloidea. htm)• CephBase: Nautiloidea (http:/ / www. cephbase. utmb. edu/ spdb/ subclassgroup. cfm?Subclass=Nautiloidea)

Nautilus 51

Nautilus

Nautilus

Nautilus belauensis

Scientific classification

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Subclass: Nautiloidea

Order: Nautilida

Superfamily: Nautilaceae

Family: NautilidaeBlainville, 1825

Genera

†Carinonautilus†Cenoceras†Eutrephoceras†Pseudocenoceras†StrionautilusAllonautilusNautilus

Nautilus (from Greek ναυτίλος, 'sailor') is the common name of marine creatures of cephalopod family Nautilidae,the sole extant family of the superfamily Nautilaceae and of its smaller but near equal suborder, Nautilina. Itcomprises six living species in two genera, the type of which is the genus Nautilus. Though it more specificallyrefers to species Nautilus pompilius, the name chambered nautilus is also used for any species of the Nautilidae.Nautilidae, both extant and extinct, are characterized by involute or slightly evolute shells that are generally smooth,with compressed or depressed whorl sections, straight to sinuous sutures, and a tubular, generally centralsiphuncle.[1] Having survived relatively unchanged for millions of years, nautiluses represent the only livingmembers of the subclass Nautiloidea, and are often considered "living fossils."The name "Nautilus" originally referred to the Argonauta, otherwise known as paper nautiluses, because the ancientsbelieved these animals used their two expanded arms as sails (cf. Aristotle Historia Animalium 622b). However, thisoctopus is not closely related to the Nautiloidea.

Nautilus 52

Anatomy

The anatomy of Nautilus. The top figure isdissected; the bottom just has the shell removed.

The nautilus is similar in general form to other cephalopods, with aprominent head and tentacles. Nautiluses typically have more tentaclesthan other cephalopods, up to ninety. These tentacles are arranged intotwo circles and, unlike the tentacles of other cephalopods, they have nosuckers, are undifferentiated and retractable. The radula is wide anddistinctively has nine teeth. There are two pairs of gills. These are theonly remnants of the ancestral metamerism to be visible in extantcephalopods.[2] :56

Nautilus pompilius is the largest species in the genus. One form fromwestern Australia may reach 26.8 centimetres (10.6 in) in diameter.However, most other nautilus species never exceed 20 centimetres (7.9in). Nautilus macromphalus is the smallest species, usually measuringonly 16 centimetres (6.3 in).

Shell

Nautiluses are the sole living cephalopods whose bony body structureis externalized as a shell. The animal can withdraw completely into itsshell and close the opening with a leathery hood formed from twospecially folded tentacles. The shell is coiled, aragonitic,[3] nacreous and pressure resistant, imploding at a depth ofabout 800 metres (2600 ft). The nautilus shell is composed of 2 layers: a matte white outer layer, and a striking whiteiridescent inner layer. The innermost portion of the shell is a pearlescent blue-gray. The osmena pearl, contrarily toits name, is not a pearl, but a jewelry product derived from this part of the shell.

Nautilus shells: N. macromphalus (left), A. scrobiculatus (centre), N. pompilius(right)

Internally, the shell divides into camerae(chambers), the chambered section beingcalled the phragmocone. The divisions aredefined by septa, each of which is pierced inthe middle by a duct, the siphuncle. As thenautilus matures it creates new, largercamerae, and moves its growing body intothe larger space, sealing the vacatedchamber with a new septum. The cameraeincrease in number from around four at themoment of hatching to thirty or more inadults.

The shell coloration also keeps the animalcryptic in the water. When seen from above, the shell is darker in color and marked with irregular stripes, whichhelps it blend into the dark water below. The underside is almost completely white, making the animalindistinguishable from brighter waters near the surface. This mode of camouflage is named countershading.

The nautilus shell presents one of the finest natural examples of a logarithmic spiral, although it is not a goldenspiral. The use of nautilus shells in art and literature is covered at nautilus shell.

Nautilus 53

A nautilus shell viewed from above (left), from underneath (centre), and a hemishell showing the camerae in a logarithmic spiral (right)

TentaclesNautilus tentacles differ from those of other cephalopods. Lacking pads, the tentacles stick to prey by virtue of theirridged surface.[4] Nautiloids have a powerful grip. Attempts to take an object already seized by a nautilus may teartentacles away from the creature, which remain firmly attached to the surface of the object.[4] Two pairs of tentaclesare separate from the other 90-ish, the pre-ocular and post-ocular, situated before and behind the eye. These are moreevidently grooved, with more pronounced ridges. They are extensively ciliated and serve an olfactory purpose.[4] [5]

[6]

Physiology

Buoyancy and movement

Nautilus with extended tentacles and hyponomevisible

In order to swim, the nautilus draws water into and out of the livingchamber with its hyponome, which uses jet propulsion. While water isinside the chamber, the siphuncle extracts salt from it and diffuses itinto the blood. The animal adjusts its buoyancy by osmoticallypumping gas and fluid into or out of the camerae along the siphuncles.This limits them; they cannot operate under the extreme hydrostaticpressures found at depths greater than approximately 800 metres (2600ft).

In the wild, nautiluses usually inhabit depths of about 300 metres (980ft), rising to around 100 metres (330 ft) at night to feed, mate and to layeggs.

Nautilus 54

Senses

Head of Nautilus pompilius showing the eye

Unlike many other cephalopods, they do not have good vision; theireye structure is highly developed but lacks a solid lens. They have asimple "pinhole" eye open to the environment.

Instead of vision, the animal is thought to use olfaction as the primarysense for foraging, locating or identifying potential mates.[7]

Reproduction and lifespan

Nautiluses reproduce by laying eggs. Gravid females attach thefertilized eggs to rocks in shallow waters, whereupon the eggs takeeight to twelve months to develop until the 30 millimetres (1.2 in) juveniles hatch. Females spawn once per year andregenerate their gonads, making nautiluses the only cephalopods to present iteroparity or polycyclic spawning.

Nautiluses are sexually dimorphic, in that males have four tentacles modified into an organ, called the "spadix,"which transfers sperm into the female's mantle during mating.The lifespan of nautiluses may exceed 20 years, which is exceptionally lengthy for a cephalopod.[8]

Ecology

DietNautiluses are predators that feed mainly on shrimp, small fish and crustaceans, which are captured by the tentacles.Due to the limited energy they expend in swimming, nautiloids only need to eat once a month.

Range and habitatNautiluses are only found in the Indo-Pacific, from 30° N to 30° S latitude and 90° to 185° W longitude. Theyinhabit the deep slopes of coral reefs.

EvolutionFossil records indicate that nautiluses have not evolved much during the last 500 million years. Many were initiallystraight-shelled, as in the extinct genus Lituites. They developed in the Cambrian period and became a significant seapredator in the Ordovician period. Certain species reached over 2.5 metres (8 ft 2 in) in size. The other cephalopodsubclass, Coleoidea, diverged from the Nautilidae long ago and the nautilus has remained relatively unchangedsince. Nautiloids were much more extensive and varied 200 million years ago. Extinct relatives of the nautilusinclude ammonites, such as the baculites and goniatites.The Nautilidae has its origin in the Trigonocerataceae (Centroceratina), specifically in the Syringonautilidae of theLate Triassic[1] and continues to this day with Nautilus, the type genus, and its close relative, Allonautilus.

Nautilus 55

Fossil generaThe Nautilidae begin with Cenoceras in the Late Triassic, a highly varied genus that makes up the JurassicCenoceras complex. Cenoceras is evolute to involute, and globular to lentincular; with a suture that generally has ashallow ventral and lateral lobe and a siphuncle that is variable in position but never extremely ventral or dorsal.Cenoceras is not found above the Middle Jurassic and is followed by the Upper Jurassic-Miocene Eutrephoceras.Eutrephoceras is generally subgobular, broadly rounded laterally and ventrally, with a small to occluded umbilicus,broadly rounded hyponomic sinus, only slightly sinuous sutures, and a small siphuncle that is variable in position.Next to appear is the Lower Cretaceous Strionautilus from India and the European ex-USSR, named by Shimankiyin 1951. Strionautilus is compressed, involute, with fine longitudinal striations. Whorl sections are subrectangular,sutures sinuous, the siphuncle subcentral.Also from the Cretaceous is Pseudocenoceras, named by Spath in 1927. Pseudocenoceras is compressed, smooth,with subrectangular whorl sections, flattened venter, and a deep umbilicus. The suture crosses the venter essentiallystraight and has a broad, shallow, lateral lobe. The siphuncle is small and subcentral. Pseudocenoceras is found inthe Crimea and in Libya.Carinonautilus is a genus from the Upper Cretaceous of India, named by Spengler in 1919. Carinonautilus is a veryinvolute form with high whorl section and flanks that converge on a narrow venter that bears a prominent roundedkeel. The umbilicus is small and shallow, the suture only slightly sinuous. The siphuncle is unknown.

Taxonomy

Shell characters of the genera Allonautilus and Nautilus

The family Nautilidae contains sixextant species and several extinctspecies.

• Genus Allonautilus

• A. perforatus• A. scrobiculatus

• Genus Nautilus

• N. belauensis• †N. cookanum• N. macromphalus• N. pompilius (type)

• N. p. pompilius• N. p. suluensis

• †N. praepompilius• N. stenomphalus

Dubious or uncertain taxa

The following taxa associated with the family Nautilidae are of uncertain taxonomic status:[9]

Nautilus 56

Binomial name and authorcitation

Current systematic status Type locality Type repository

N. alumnus Iredale, 1944 Species dubium [fide Saunders (1987:49)] Queensland,Australia

Not designated [fide Saunders(1987:49)]

N. ambiguus Sowerby, 1848 Species dubium [fide Saunders (1987:48)] Not designated Unresolved

N. beccarii Linne, 1758 Non-cephalopod; Foraminifera [fide Frizzell and Keen(1949:106)]

N. calcar Linne, 1758 ?Non-cephalopod; Foraminifera Lenticulina Adriatic Sea Unresolved; Linnean Society ofLondon?

N. crispus Linne, 1758 Undetermined Mediterranean Sea Unresolved; Linnean Society ofLondon?

N. crista Linne, 1758 Non-cephalopod; Turbo [fide Dodge (1953:14)]

N. fascia Linne, 1758 Undetermined Adriatic Sea Unresolved; Linnean Society ofLondon?

N. granum Linne, 1758 Undetermined Mediterranean Sea Unresolved; Linnean Society ofLondon?

N. lacustris Lightfoot, 1786 Non-cephalopod; Helix [fide Dillwyn (1817:339)]

N. legumen Linne, 1758 Undetermined Adriatic Sea Unresolved; Linnean Society ofLondon?

N. micrombilicatus Joubin, 1888 Nomen nudum

N. obliquus Linne, 1758 Undetermined Adriatic Sea Unresolved; Linnean Society ofLondon?

N. pompilius marginalis Willey,1896

Species dubium [fide Saunders (1987:50)] New Guinea Unresolved

N. pompilius moretoni Willey,1896

Species dubium [fide Saunders (1987:49)] New Guinea Unresolved

N. pompilius perforatus Willey,1896

Species dubium [fide Saunders (1987:49)] New Guinea Unresolved

N. radicula Linne, 1758 ?Non-cephalopod; Foraminifera Nodosaria Adriatic Sea Unresolved; Linnean Society ofLondon?

N. raphanistrum Linne, 1758 Undetermined Mediterranean Sea Unresolved; Linnean Society ofLondon?

N. raphanus Linne, 1758 Undetermined Adriatic Sea Unresolved; Linnean Society ofLondon?

N. semi-lituus Linne, 1758 Undetermined Liburni, AdriaticSea

Unresolved; Linnean Society ofLondon?

N. sipunculus Linne, 1758 Undetermined "freto Siculo" Unresolved; Linnean Society ofLondon?

N. texturatus Gould, 1857 Nomen nudum

Octopodia nautilus Schneider,1784

Rejected specific name [fide Opinion 233, ICZN(1954:278)]

Nautilus 57

References[1] Kümmel,B. 1964. Nautiloidae-Nautilida, in the Treatise on Invertebrate Paleontology, Geological Society of America and Univ of Kansas

Press, Teichert and Moore eds.[2] Wingstrand, KG (1985). "On the anatomy and relationships of Recent Monoplacophora" (http:/ / www. zmuc. dk/ inverweb/ Galathea/

Galathea_p5. html) (Link to free full text + plates). Galathea Rep. 16: 7–94. .[3] "Diagenesis of aragonite from Upper Cretaceous ammonites: a geochemical case-study". Sedimentology 28: 423–438. 1981.

doi:10.1111/j.1365-3091.1981.tb01691.x.[4] Willey, Arthur (1897). "The Pre-ocular and Post-ocular Tentacles and Osphradia of Nautilus" (http:/ / jcs. biologists. org/ content/ vols2-40/

issue157/ ). Quarterly Journal of Microscopical Science 40 (1): 197–201. .[5] Fukuda, Y. 1987. Histology of the long digital tentacles. In: W.B. Saunders & N.H. Landman (eds.) Nautilus: The Biology and Paleobiology

of a Living Fossil. Springer Netherlands. pp. 249–256. doi:10.1007/978-90-481-3299-7_17[6] Kier, W.M. 1987. The functional morphology of the tentacle musculature of Nautilus pompilius. (http:/ / biology. unc. edu/ faculty/ Kier/ lab/

pdf/ Kier_1987. pdf)PDF In: W.B. Saunders & N.H. Landman (eds.) Nautilus: The Biology and Paleobiology of a Living Fossil. SpringerNetherlands. pp. 257–269. doi:10.1007/978-90-481-3299-7_18

[7] Grasso, F.; Basil, J. (2009). "The evolution of flexible behavioral repertoires in cephalopod molluscs". Brain, Behavior and Evolution 74 (3):231–245. doi:10.1159/000258669. PMID 20029186.

[8] Saunders WB (June 1984). "Nautilus Growth and Longevity: Evidence from Marked and Recaptured Animals". Science 224 (4652):990–992. doi:10.1126/science.224.4652.990. PMID 17731999.

[9] Sweeney, M.J. 2002. Taxa Associated with the Family Nautilidae Blainville, 1825. (http:/ / tolweb. org/ accessory/Nautilidae_Taxa?acc_id=2324) Tree of Life web project.

• Ward, P.D. 1988. In Search of Nautilus. Simon and Schuster.• Nautilus: the biology and palaeontology of a living fossil (http:/ / www. springerlink. com/ content/

978-90-481-3298-0/ #section=639864& page=10& locus=96). ISBN 978-90-481-3299-7.• CephBase: Nautilidae (http:/ / www. cephbase. utmb. edu/ spdb/ familygroup. cfm?Family=Nautilidae)

External links• Nautilidae discussion forum (http:/ / www. tonmo. com/ forums/ forumdisplay. php?f=49), tonmo.com• Waikïkï Aquarium: Marine Life Profile: Chambered Nautilus (http:/ / www. waquarium. org/ MLP/ root/ pdf/

MarineLife/ Invertebrates/ Molluscs/ Nautilus. pdf), waguarium.org• A molecular and karyological approach to the taxonomy of Nautilus (http:/ / www. cephbase. utmb. edu/ refdb/

pdf/ 8036. pdf), utmb.edu

Ammonite 58

Ammonite

Ammonites

Artist's reconstruction ofAsteroceras

Scientific classification [ e ]

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Subclass: †AmmonoideaZittel, 1884

Orders and Suborders

Order Anarcestida

• Anarcestina• Pharciceratina• Prolobinina

Order Ammonitida

• Ammonitina• Ancyloceratina• Phylloceratina• Lytoceratina

Order Ceratitida

• Ceratitina• Otoceratina• Noritacina• Clydonitina

Order Clymeniida

• Clymeniina• Gonioclymeniina• Cyrtoclymeniina

Order Goniatitida

• Goniatitina• Tornoceratina

Order Prolecanitida

• Prolecanitina• Medlicottiana

Ammonites are an extinct group of marine invertebrate animals in the subclass Ammonoidea of the class Cephalopoda. These molluscs are more closely related to living coleoids (i.e. octopuses, squid, and cuttlefish) than

Ammonite 59

they are to shelled nautiloids such as the living Nautilus species.Ammonites are excellent index fossils, and it is often possible to link the rock layer in which they are found tospecific geological time periods. Their fossil shells usually take the form of planispirals, although there were somehelically-spiraled and non-spiraled forms (known as heteromorphs).The name ammonite, from which the scientific term is derived, was inspired by the spiral shape of their fossilizedshells, which somewhat resemble tightly-coiled rams' horns. Pliny the Elder (d. 79 AD. near Pompeii) called fossilsof these animals ammonis cornua ("horns of Ammon") because the Egyptian god Ammon (Amun) was typicallydepicted wearing ram's horns.[1] Often the name of an ammonite genus ends in -ceras, which is Greek (κέρας) for"horn".

ClassificationOriginating from within the bactritoid nautiloids, the ammonoid cephalopods first appeared in the Devonian (circa400 million years ago) and became extinct at the close of the Cretaceous (65.5 Ma) along with the dinosaurs. Theclassification of ammonoids is based in part on the ornamentation and structure of the septa comprising their shells'gas chambers; by these and other characteristics we can divide subclass Ammonoidea into three orders and eightknown suborders. While nearly all nautiloids show gently curving sutures, the ammonoid suture line (the intersectionof the septum with the outer shell) was folded, forming saddles (or peaks) and lobes (or valleys).

Suture patternsThree major types of suture patterns in Ammonoidea have been noted:• Goniatitic - numerous undivided lobes and saddles; typically 8 lobes around the conch. This pattern is

characteristic of the Paleozoic ammonoids.• Ceratitic - lobes have subdivided tips, giving them a saw-toothed appearance, and rounded undivided saddles.

This suture pattern is characteristic of Triassic ammonoids and appears again in the Cretaceous "pseudoceratites".• Ammonitic - lobes and saddles are much subdivided (fluted); subdivisions are usually rounded instead of

saw-toothed. Ammonoids of this type are the most important species from a biostratigraphical point of view. Thissuture type is characteristic of Jurassic and Cretaceous ammonoids but extends back all the way to the Permian.

Orders and suborders

An ammonitic ammonoid with the body chambermissing, showing the septal surface (especially at

right) with its undulating lobes and saddles.

The Ammonoidea can be divided into eight orders, listed here startingwith the most primitive and going to the more derived.• Anarcestida, Devonian• Clymeniida, Upper Devonian• Goniatitida, Middle Devonian - Upper Permian• Prolecanitida, Upper Devonian - Upper Triassic• Ceratitida, Permian - Triassic• Phylloceratida, Triassic - Cretaceous• Lytoceratida, Jurassic - Cretaceous• Ammonitida, Lower Jurassic - Upper CretaceousNote that in some classifications these are referred to as suborders, included in only three orders: Goniatitida,Ceratitida, and Ammonitida.

Ammonite 60

Iridescent ancient ammonite fossil on display atthe American Museum of Natural History, New

York City, around 2.5 feet in diameter.

Taxonomy of the Treatise

The Treatise on Invertebrate Paleontology (1964) includes theAmmonitina, Lytoceratina, and Phylloceratina as separate suborderswithin the subclass Ammonoidea, without the use of orders, anddivides them into superfamilies. In other, subsequent taxonomies theAmmonitina, Lytoceratina, and Phylloceratina are placed within theorder, Ammonitida. The Ancyloceratina which is sometimes treated asa separate suborder is treated as a superfamily, the Ancylocerataceae inthe Lytoceratina in the Treatise.

According to the Treatise, the Ammonitina are derived from the Phyllocerarina and Lytoceratina beginning in theEarly Jurassic with the Psilocerataceae and ending with nine superfamilies, although not all extant at the same time.These are the Acanthocerataceae, Desmocerataceae, Eoderocerataceae, Haploceratacea, Hildocerataceae,Hoplitaceae, Perispinctaceae, Psilocerataceae, and Stephanocerataceae.The Eoderocerataceae, Hildocerataceae, Psilocerataceae, and Stephanocerataceae are strictly Jurassic groups. TheAcanthocerataceae, Desmocerataceae, and Hoplitaceae are known only from the Cretaceous. But theHaplocerataceae and Peripinctaceae extend from the Jurassic well into the Cretaceous.

Life

Jeletzkytes, a Cretaceous ammonite from theUSA

Because ammonites and their close relatives are extinct, little is knownabout their way of life. Their soft body parts are very rarely preservedin any detail. Nonetheless, much has been worked out by examiningammonoid shells and by using models of these shells in water tanks.Many ammonoids probably lived in the open water of ancient seas,rather than at the sea bottom. This is suggested by the fact that theirfossils are often found in rocks that were laid down under conditionswhere no bottom-dwelling life is found. Many of them (such asOxynoticeras) are thought to have been good swimmers with flattened,discus-shaped, streamlined shells, although some ammonoids were lesseffective swimmers and were likely to have been slow-swimmingbottom-dwellers. Synchrotron analysis of an aptychophoran ammoniterevealed remains of isopod and mollusc larva in its buccal cavity,indicating that at least this kind of ammonite fed on plankton[2] . Fossilized ammonoids have been found showingtooth marks from such attacks. They may have avoided predation by squirting ink, much like modern cephalopods;ink is occasionally preserved in fossil specimens.[3]

The soft body of the creature occupied the largest segments of the shell at the end of the coil. The smaller earliersegments were walled off and the animal could maintain its buoyancy by filling them with gas. Thus the smallersections of the coil would have floated above the larger sections.[4]

Ammonite 61

Asteroceras, a Jurassic ammonite from England

Shell anatomy and diversity

Basic shell anatomy

A variety of ammonite forms, from ErnstHaeckel's 1904 Kunstformen der Natur (Artforms

of Nature).

The chambered part of the ammonite shell is called a phragmocone.The phragmocone contains a series of progressively larger chambers,called camerae (sing. camera) that are divided by thin walls calledsepta (sing. septum). Only the last and largest chamber, the bodychamber, was occupied by the living animal at any given moment. Asit grew, it added newer and larger chambers to the open end of the coil.A thin living tube called a siphuncle passed through the septa,extending from the ammonite's body into the empty shell chambers.Through a hyperosmotic active transport process, the ammoniteemptied water out of these shell chambers. This enabled it to controlthe buoyancy of the shell and thereby rise or descend in the watercolumn.

A primary difference between ammonites and nautiloids is that thesiphuncle of ammonites (excepting Clymeniina) runs along the ventralperiphery of the septa and camerae (i.e., the inner surface of the outeraxis of the shell), while the siphuncle of nautiloids runs more or lessthrough the center of the septa and camerae.

Ammonite 62

Sexual dimorphism

Discoscaphites iris, Owl Creek Formation (UpperCretaceous), Ripley, Mississippi.

One feature found in shells of the modern Nautilus is the variation inthe shape and size of the shell according to the sex of the animal, theshell of the male being slightly smaller and wider than that of thefemale. This sexual dimorphism is thought to be an explanation for thevariation in size of certain ammonite shells of the same species, thelarger shell (called a macroconch) being female, and the smaller shell(called a microconch) being male. This is thought to be because thefemale required a larger body size for egg production. A good exampleof this sexual variation is found in Bifericeras from the early part of theJurassic period of Europe.

It is only in relatively recent years that the sexual variation in the shellsof ammonites has been recognized. The macroconch and microconchof one species were often previously mistaken for two closely relatedbut different species occurring in the same rocks. However, these"pairs" were so consistently found together that it became apparent that they were in fact sexual forms of the samespecies.

Variations in shapeThe majority of ammonite species feature a shell that is a planispiral flat coil, but other species feature a shell that isnearly straight (as in baculites). Still other species' shells are coiled helically, superficially like that of a largegastropod (as in Turrilites and Bostrychoceras). Some species' shells are even initially uncoiled, then partially coiled,and finally straight at maturity (as in Australiceras). These partially uncoiled and totally uncoiled forms began todiversify mainly during the early part of the Cretaceous and are known as heteromorphs.Perhaps the most extreme and bizarre looking example of a heteromorph is Nipponites, which appears to be a tangleof irregular whorls lacking any obvious symmetrical coiling. However, upon closer inspection the shell proves to bea three-dimensional network of connected "U" shapes. Nipponites occurs in rocks of the upper part of the Cretaceousin Japan and the USA.Ammonites vary greatly in the ornamentation (surface relief) of their shells. Some may be smooth and relativelyfeatureless, except for growth lines, and resemble that of the modern Nautilus. In others various patterns of spiralridges and ribs or even spines are shown. This type of ornamentation of the shell is especially evident in the laterammonites of the Cretaceous.

Ammonite 63

Aptychus

A drawing of an aptychus named "Trigonelliteslatus" from the Kimmeridge Clay Formation in

England

Some ammonites have been found in association with a single hornyplate or a pair of calcitic plates. In the past it was assumed that theseplates served to close the opening of the shell in much the same way asan operculum, however more recently it has been postulated that theywere instead a jaw apparatus.[5] [6] [7] [8]

The plates are collectively termed the aptychus or aptychi in the caseof a pair of plates, and anaptychus in the case of a single plate. Thepaired aptychi were symmetrical to one another and equal in size andappearance.

Anaptychi are relatively rare as fossils. They are found representingammonites from the Devonian period through those of the Cretaceousperiod.Calcified aptychi only occur in ammonites from the Mesozoic era. They are almost always found detached from theshell, and are only very rarely preserved in place. Still, sufficient numbers have been found closing the apertures offossil ammonite shells as to leave no doubt as to their identity as part of the anatomy of an ammonite.

Large numbers of detached aptychi occur in certain beds of rock (such as those from the Mesozoic in the Alps).These rocks are usually accumulated at great depths. The modern Nautilus lacks any calcitic plate for closing itsshell, and only one extinct nautiloid genus is known to have borne anything similar. Nautilus does, however, have aleathery head shield (the hood) which it uses to cover the opening when it retreats inside.There are many forms of aptychus, varying in shape and the sculpture of the inner and outer surfaces, but becausethey are so rarely found in position within the shell of the ammonite it is often unclear to which species of ammoniteone kind of aptychus belongs. A number of aptychi have been given their own genus and even species namesindependent of their unknown owners' genus and species, pending future discovery of verified occurrences withinammonite shells.

Non-mineralized anatomyAnnomoids bore a radula and beak, a marginal siphuncle, and probably ten arms.[9] They operated by directdevelopment with sexual reproduction, were carnivorous and had a crop for food storage. It is unlikely that anyammonoids dwelt in fresh or brackish water.[10]

Soft partsAlthough ammonites do occur in exceptional lagerstatten such as the Solnhofen limestone, their soft part record issurprisingly bleak - beyond a tentative ink sac and possible digestive organs, no soft parts are known at all.[11] It canbe tentatively assumed that they had numerous tentacles, each quite weak, and engulfed prey almost whole.[11]

Ammonite 64

Size

2-metre (6.5-foot) Parapuzosia seppenradensiscast in Germany

Few of the ammonites occurring in the lower and middle part of theJurassic period reach a size exceeding 23 centimetres (9 inches) indiameter. Much larger forms are found in the later rocks of the upperpart of the Jurassic and the lower part of the Cretaceous, such asTitanites from the Portland Stone of Jurassic of southern England,which is often 53 centimetres (2 feet) in diameter, and Parapuzosiaseppenradensis of the Cretaceous period of Germany, which is one ofthe largest known ammonites, sometimes reaching 2 metres (6.5 feet)in diameter. The largest documented North American ammonite isParapuzosia bradyi from the Cretaceous with specimens measuring137 centimetres (4.5 feet) in diameter, although a new 2.3-metre(7.5-foot) British Columbian specimen, if authentic, would appear to trump even the European champion.[12]

Distribution

A specimen of Hoploscaphites from the PierreShale of South Dakota. Much of the original

shell, including the nacre, has survived.

Starting from the mid-Devonian, ammonoids were extremely abundant,especially as ammonites during the Mesozoic era. Many generaevolved and ran their course quickly, becoming extinct in a few millionyears. Due to their rapid evolution and widespread distribution,ammonoids are used by geologists and paleontologists forbiostratigraphy. They are excellent index fossils, and it is oftenpossible to link the rock layer in which they are found to specificgeological time periods.

Due to their free-swimming and/or free-floating habits, ammonitesoften happened to live directly above seafloor waters so poor in oxygenas to prevent the establishment of animal life on the seafloor. Whenupon death the ammonites fell to this seafloor and were graduallyburied in accumulating sediment, bacterial decomposition of thesecorpses often tipped the delicate balance of local redox conditions

sufficiently to lower the local solubility of minerals dissolved in the seawater, notably phosphates and carbonates.The resulting spontaneous concentric precipitation of minerals around a fossil is called a concretion and isresponsible for the outstanding preservation of many ammonite fossils.

When ammonites are found in clays their original mother-of-pearl coating is often preserved. This type ofpreservation is found in ammonites such as Hoplites from the Cretaceous Gault clay of Folkestone in Kent, England.

The Cretaceous Pierre Shale formation of the United States and Canada is well known for the abundant ammonitefauna it yields, including Baculites, Placenticeras, Scaphites, Hoploscaphites, and Jeletzkytes, as well as manyuncoiled forms. Many of these also have much or all of the original shell, as well as the complete body chamber, stillintact. Many Pierre Shale ammonites, and indeed many ammonites throughout earth history, are found insideconcretions.

Ammonite 65

An iridescent ammonite from Madagascar.

Other fossils, such as many found in Madagascar and Alberta(Canada), display iridescence. These iridescent ammonites are often ofgem quality (ammolite) when polished. In no case would thisiridescence have been visible during the animal's life; additional shelllayers covered it.

The majority of ammonoid specimens, especially those of thePaleozoic era, are preserved only as internal molds; that it to say, theouter shell (composed of aragonite)[13] has been lost during thefossilization process. It is only in these internal-mold specimens thatthe suture lines can be observed; in life the sutures would have beenhidden by the outer shell.

The ammonoids as a group continued though several major extinctionevent, although it appears that often only a few species survived. Eachtime, however, this handful of species diversified into a multitude offorms. Ammonite fossils became less abundant during the latter part of the Mesozoic, with none surviving into theCenozoic era. The last surviving lineages disappeared, along with the dinosaurs, 65 million years ago in theCretaceous-Tertiary extinction event. The reason why no ammonites survived the extinction event at the end of theCretaceous, whereas some nautiloid cousins survived, might be due to differences in ontogeny. If their extinctionwas due to a bolide strike, plankton around the globe could have been severely diminished, thereby doomingammonite reproduction during its planktonic stage.

ExtinctionThe extinction of the ammonites along with other marine animals and of course, non-avian dinosaurs, has beenattributed to a bolide impact, marking the end of the Cretaceous Period. Regardless of what effect an impact mayhave had, many of these groups, including ammonoids, were already in serious decline. Previously ammonoidcephalopods barely survived several earlier major extinction events, often with only a few species surviving fromwhich a multitude of forms diversified.Eight or so species from only two families made it almost to the end of the Cretaceous, the order having gonethrough a more or less steady decline since the middle of the period. Six other families made it well into the upperMaastrichtian (uppermost stage of the Cretaceous) but were extinct well before the end. All told, 11 families enteredthe Maastrichtian, a decline from the 19 families known from the Cenomanian in the middle of the Cretaceous.One reason given for their demise is that Cretaceous ammonites, being closely related to coleoids, had a similarreproductive strategy in which a huge number of eggs is laid in a single batch at the end of the life span. These, alongwith juvenile ammonites, are thought to have been part of the plankton at the surface of the ocean where they werekilled off by the effects of an impact. Nautiloids, exemplified by modern nautiluses, are thought on the other hand tohave had a reproductive strategy in which eggs were laid in smaller batches many times during the life span and onthe sea floor well away from any direct effects of such a bolide strike, and thus survived.

MythologyIn medieval Europe, fossilised ammonites were thought to be petrified coiled snakes, and were called "snakestones"or, more commonly in medieval England, "serpentstones". They were considered to be evidence for the actions ofsaints such as Saint Hilda and Saint Patrick, and were held to have healing or oracular powers. Traders wouldoccasionally carve the head of a snake onto the empty, wide end of the ammonite fossil, and then sell them to thepublic. In other cases the snake's head would be simply painted on.[14] Ammonites from the Gandaki river in Nepalare known as saligrams, and are believed by Hindus to be a concrete manifestation of God or Vishnu.[15]

Ammonite 66

Terminological noteThe words ammonite and ammonoid are both used quite loosely in common parlance to refer to any member ofsubclass Ammonoidea. However, in stricter usage the term ammonite is reserved for members of suborderAmmonitina (or sometimes even order Ammonitida).

References[1] NH 37.40.167[2] The Role of Ammonites in the Mesozoic Marine Food Web Revealed by Jaw Preservation, Isabelle Kruta, Neil Landman, Isabelle Rouget,

Fabrizio Cecca, Paul Tafforeau, SCIENCE, JANUARY 2011 VOL 331[3] doi: 10.1007/978-1-4020-6806-5_11

This citation will be automatically completed in the next few minutes. You can jump the queue or expand by hand (http:/ / en. wikipedia. org/wiki/ Template:cite_doi/ . 0910. 1007. 2f978-1-4020-6806-5_11?preload=Template:Cite_doi/ preload& editintro=Template:Cite_doi/editintro& action=edit)

[4] "Introduction to Ammonoidea" (http:/ / www. bbm. me. uk/ portsdown/ PH_232_Ammonites. htm). The Geology of Portsdown Hill. .Retrieved 2007-04-26.

[5] Morton, N. 1981. Aptychi: the myth of the ammonite operculum. Lethaia 14(1): 57–61. doi:10.1111/j.1502-3931.1981.tb01074.x[6] Morton, N. & M. Nixon 1987. Size and function of ammonite aptychi in comparison with buccal masses of modem cephalopods. Lethaia

20(3): 231–238. doi:10.1111/j.1502-3931.1987.tb02043.x[7] Lehmann, U. & C. Kulicki 1990. Double function of aptychi (Ammonoidea) as jaw elements and opercula. Lethaia 23: 325–331.

doi:10.1111/j.1502-3931.1990.tb01365.x[8] Seilacher, A. 1993. Ammonite aptychi; how to transform a jaw into an operculum? American Journal of Science 293: 20–32.

doi:10.2475/ajs.293.A.20[9] Landman, Neil H; Tanabe, Kazushige; Davis, Richard Arnold (1996). Ammonoid paleobiology (http:/ / books. google. ca/

books?id=hKbkB4MzUIkC& pg=PA14). ISBN 9780306452222. .[10] Landman, Neil H; Tanabe, Kazushige; Davis, Richard Arnold (1996). Ammonoid paleobiology (http:/ / books. google. ca/

books?id=hKbkB4MzUIkC& pg=PA17). ISBN 9780306452222. .[11] Wippich, M. G. E.; Lehmann, J. (2004). "Allocrioceras from the Cenomanian (mid-Cretaceous) of the Lebanon and its bearing on the

palaeobiological interpretation of heteromorphic ammonites". Palaeontology 47: 1093–1107. doi:10.1111/j.0031-0239.2004.00408.x.[12] "Ammonites" (http:/ / web. archive. org/ web/ 20030210130400/ http:/ / www. hanmansfossils. com/ catalogs/ fossils/ ammonites/

ammonites. shtml). Hanman's Fossil Replicas and Minerals. Archived from the original (http:/ / www. hanmansfossils. com/ catalogs/ fossils/ammonites/ ammonites. shtml) on 2003-02-10. .

[13] "Diagenesis of aragonite from Upper Cretaceous ammonites: a geochemical case-study". Sedimentology 28: 423–438. 1981.doi:10.1111/j.1365-3091.1981.tb01691.x.

[14] Cadbury, D. the Dinosaur Hunters. (Fourth Estate, 2000) (ISBN 1-85702-963-1), p.7[15] "Fossils: myths, mystery, and magic" (http:/ / news. independent. co. uk/ sci_tech/ article2259490. ece). The Independent (London).

2007-02-12. . Retrieved 2010-04-23.

• Neal L. Larson, Steven D Jorgensen, Robert A Farrar and Peter L Larson. Ammonites and the other Cephalopodsof the Pierre Seaway. Geoscience Press, 1997.

• Lehmann, Ulrich. The Ammonites: Their life and their world. Cambridge University Press, New York, 1981.Translated from German by Janine Lettau.

• Monks, Neale and Palmer, Phil. Ammonites. Natural History Museum, 2002.• Walker, Cyril and Ward, David. Fossils. Dorling, Kindersley Limited, London, 2002.• A Broad Brush History of the Cephalopoda (http:/ / is. dal. ca/ ~ceph/ TCP/ evolution. html) by Dr. Neale Monks,

from The Cephalopod Page.• Ammonite maturity, pathology and old age (http:/ / is. dal. ca/ ~ceph/ TCP/ ammonage. html) By Dr. Neale

Monks, from The Cephalopod Page. Essay about the life span of Ammonites.• Cretaceous Fossils Taxonomic Index for Order Ammonoitida (http:/ / www. cretaceousfossils. com/ invertebrates/

ammonites/ ammonites_index. htm)• Deeply Buried Sediments Tell Story of Sudden Mass Extinction (http:/ / www. nsf. gov/ discoveries/ disc_summ.

jsp?cntn_id=100280& org=NSF)

Ammonite 67

External links• Descriptions and pictures of ammonite fossils (http:/ / www. fossilmuseum. net/ Fossil_Galleries/ Ammonites.

htm)• goniat.org, a palaezoic ammonoid database (http:/ / www. goniat. org/ )• paleozoic.org: gallery of ammonite photographs (http:/ / www. paleozoic. org/ gallery. htm)• photos of ammonites at Lyme Regis, UK (http:/ / y2u. co. uk/ & 002_Images/ Lyme Regis Fossils 01. htm)• TaxonConcept's data on cretaceous ammonites (http:/ / taxonconcept. stratigraphy. net/ source_main.

php?doctaxid=618& doctaxname=Ammonoidea)• The ammonites of Peacehaven - photos of giant cretaceous ammonites in Southern England (http:/ /

thinkingwithpictures. blogspot. com/ 2008/ 06/ ammonites-of-peacehaven. html)• tonmo.com: The octopus news magazine online (http:/ / www. tonmo. com/ science/ fossils/ fossilsjump. php),

Cephalopod fossil articles.

BelemnoideaBelemnites (or belemnoids) are an extinct group of marine cephalopod, very similar in many ways to the modernsquid and closely related[1] to the modern cuttlefish. Like them, the belemnites possessed an ink sac[2] , but, unlikethe squid, they possessed ten arms of roughly equal length, and no tentacles.[3] The name "belemnoid" comes fromthe Greek word belemnon meaning "a dart or arrow" and the Greek word eidos meaning "form". [4]

OccurrenceBelemnites were numerous during the Jurassic and Cretaceous periods, and their fossils are abundant in Mesozoicmarine rocks, often accompanying their cousins the ammonites. The belemnites become extinct at the end of theCretaceous period along with the ammonites. The belemnites' origin lies within the bactritoid nautiloids, which datefrom the Devonian period; well-formed belemnite guards can be found in rocks dating from the Mississippian (orEarly Carboniferous) onward through the Cretaceous. Other fossil cephalopods include baculites, nautiloids andgoniatites.

AnatomyBelemnites possessed a central phragmocone made of aragonite and with negative buoyancy.[5] To the rear of thecreature was a heavy calcite guard whose main role appears to have been to counterbalance the front of theorganism; it positions the centre of mass below the centre of buoyancy, increasing the stability of the swimmingorganism.[5] The guard would account for between a third and a fifth of the length of the complete organism, armsincluded.[5]

Like some modern squid, belemnite arms carried a series of small hooks for grabbing prey. Belemnites were efficientcarnivores that caught small fish and other marine animals with their arms and ate them with their beak-like jaws. Inturn, belemnites appear to have formed part of the diet of marine reptiles such as Ichthyosaurs, whose fossilizedstomachs frequently contain phosphatic hooks from the arms of cephalopods.

Belemnoidea 68

EcologyBelemnites were effectively neutrally buoyant, and swam in near-shore to mid-shelf oceans.[5] Their fins could beused to their advantage in all water speeds; in a gentle current they could be flapped for propulsion; in a strongercurrent they could be held erect to generate lift; and when swimming rapidly by jet propulsion they could be tuckedin to the body for streamlining.[5]

Preservation

A belemnite fossil from the Franconian Jura.

Normally with fossil belemnites only the back part of the shell (calledthe guard or rostrum) is found. The guard is elongated andbullet-shaped, that is to say, cylindrical and pointed or rounded at oneend. The hollow region at the front of the guard is termed the alveolus,and this houses a chambered conical-shaped part of the shell (called thephragmocone). The phragmocone is usually only found with the betterpreserved specimens. Projecting forwards from one side of thephragmocone is the thin pro-ostracum.

While belemnite phragmocones are homologous with the shells of other cephalopods and are similarly composed ofaragonite, belemnite guards are evolutionarily novel and are composed of calcite, thus tending to preserve well.Broken guards show a structure of radiating calcite fibers and may also display concentric growth rings.

The guard, phragmocone and pro-ostracum were all internal to the living creature, forming a skeleton which wasenclosed entirely by soft muscular tissue. The original living creature would have been larger than the fossilizedshell, with a long streamlined body and prominent eyes. The guard would have been in place toward the rear of thecreature, with the phragmocone behind the head and the pointed end of the guard facing backward.

Belemnites

The guard of the belemnite Megateuthis gigantea, which is found inEurope and Asia, can measure up to 46 cm in length (18 inches),giving the living animal an estimated length of 3 metres (10 feet).

Belemnoidea 69

Belemnite fossils at Bristol City Museum, Bristol,England. Found in the Lower Lias strata,

Gloucestershire, England.

Very exceptional belemnite specimens have been found showing thepreserved soft parts of the animal. Elsewhere in the fossil record,bullet-shaped belemnite guards are locally found in such profusion thatsuch deposits are referred to semi-formally as "belemnite battlefields"(cf. "orthocone orgies"). It remains unclear whether these depositsrepresent post-mating mass death events, as are common amongmodern cephalopods and other semelparous creatures.

Uses

The bulk geochemical signature contained within belemnite guards ofthe Peedee Formation (Cretaceous, southeast USA) has long been usedas a global standard ("PDB") against which all other geochemicalsamples are measured, for both carbon isotopes and oxygen isotopes.

Some belemnites (such as Belemnites) serve as index fossils, particularly in the Cretaceous Chalk Formation ofEurope, enabling geologists to date the age the rocks in which they are found.

ClassificationNote: all families extinct

Belemnite in the very top bedding plane of theZohar Formation (Jurassic) near Neve Atif, the

Golan. Note the central fold along the axischaracteristic of some genera.

Fossilised belemnite

• Cohort Belemnoidea

• Basal and unresolved• Genus Jeletzkya• Genus Belemnoteuthis

• Order Aulacocerida• Family Aulacoceratidae• Family Dictyoconitidae• Family Hematitidae• Family Palaeobelemnopseidae• Family Xiphoteuthididae

• Order Belemnitida• Suborder Belemnitina

• Family Cylindroteuthididae• Family Hastitidae• Family Oxyteuthididae• Family Passaloteuthididae• Family Salpingoteuthididae

• Suborder Belemnopseina• Family Belemnitellidae

• Family Belemnopseidae• Family Dicoelitidae• Family Dimitobelidae• Family Duvaliidae

• Suborder Belemnotheutina

Belemnoidea 70

• Family Belemnotheutididae• Family Chitinobelidae• Family Sueviteuthididae

• Order Diplobelida• Family Chondroteuthididae• Family Diplobelidae

• Order Phragmoteuthida• Family Phragmoteuthididae• Family Rhiphaeoteuthidae

See also• Nautiloidea• Ammonoidea• List of belemnites

References[1] Yancey, T. E.; Garvie, C. L.; Wicksten, M. (2010). "The Middle Eocene Belosaepia ungula (Cephalopoda: Coleoida) from Texas: Structure,

Ontogeny and Function" (http:/ / www. lakeneosho. org/ Belosaepia/ pdf/ Growth and skeleton characters of Belosaepia. pdf). Journal ofPaleontology 84: 267. doi:10.1666/09-018R.1. .

[2] Lehmann, U. 1981. The Ammonites: Their life and their world. London: Cambridge University Press.[3] Doyle, P.; Shakides, E. V. (2004). "The Jurassic Belemnite Suborder Belemnotheutina". Palaeontology 47: 983–998.

doi:10.1111/j.0031-0239.2004.00395.x.[4] Webster's New Universal Unabridged Dictionary. 2nd ed. 1979.[5] "The function of the belemnite guard" (http:/ / www. springerlink. com/ content/ p0pw7246ht1v78n1/ ). Paläontologische Zeitschrift 70:

425–431. 1996. doi:10.1007/BF02988082 (inactive 2010-05-02). .

External links• TONMO.com Cephalopod Fossils articles and discussion forums (http:/ / www. tonmo. com/ science/ fossils/

fossilsjump. php)

Argonaut 71

ArgonautFor other uses, see Argonaut.

Argonauts

Female Argonauta argo with eggs

Scientific classification

Kingdom: Animalia

Phylum: Mollusca

Class: Cephalopoda

Order: Octopoda

Superfamily: Argonautoida

Family: Argonautidae

Genus: ArgonautaLinnaeus, 1758

Species

†Argonauta absyrtusArgonauta argo (type)Argonauta bottgeriArgonauta cornuta*Argonauta hians†Argonauta itoigawai†Argonauta joanneusArgonauta nodosaArgonauta nouryiArgonauta pacifica*†Argonauta tokunagai*Species status questionable.

Synonyms

• ArgonautariusDumeril, 1806

• Todarus nom. nud.Rafinesque, 1815

• TodarusRafinesque, 1840

• TrichocephalusChiaje, 1827 in 1823-1831

Argonaut 72

The argonauts (genus Argonauta, the only extant genus in the Argonautidae family) are a group of pelagicoctopuses. They are also called paper nautiluses, referring to the paper-thin eggcase that females secrete. Thisstructure lacks the gas-filled chambers present in chambered nautilus shells and is not a true cephalopod shell, butrather an evolutionary innovation unique to the genus Argonauta.[1] It is used as a brood chamber and for trappedsurface air to maintain buoyancy.Argonauts are found in tropical and subtropical waters worldwide; they live in the open ocean, i.e. they are pelagic.Like most octopuses, they have a rounded body, eight arms and no fins. However, unlike most octopuses, argonautslive close to the sea surface rather than on the seabed. Argonauta species are characterised by very large eyes andsmall distal webs. The mantle-funnel locking apparatus is a major diagnostic feature of this taxon. It consists ofknob-like cartilages in the mantle and corresponding depressions in the funnel. Unlike the closely allied generaOcythoe and Tremoctopus, Argonauta species lack water pores.Of its names, "argonaut" means "sailor on the Argo"; "nautilus" is derived from the Greek ναυτίλος, meaning"sailor", because it was formerly supposed that Argonauta used their shell-secreting arms as sails when they were atthe surface.The chambered nautilus was later named after the argonaut, but belongs to a different order, the Nautilida.

Physical description

Sexual dimorphism and reproductionArgonauts exhibit extreme sexual dimorphism in size and lifespan. Females grow up to 10 cm and make shells up to30 cm, while males rarely surpass 2 cm. The males only mate once in their short lifetime, whereas the females areiteroparous, capable of having offspring many times over the course of their lives. In addition, the females have beenknown since ancient times, while the males were only described in the late 19th century.The males lack the dorsal tentacles used by the females to create their eggcases. The males use a modified arm, thehectocotylus, to transfer sperm to the female. For fertilization, the arm is inserted into the female's pallial cavity, thenis detached from the male. The hectocotylus when found in females was originally described as a parasitic worm.[2]

Mature female A.nodosa

Juvenile female A. hians Immature male A. hians

EggcaseFemale argonauts produce a laterally-compressed calcareous eggcase in which they reside. This "shell" has a double keel fringed by two rows of alternating tubercles. The sides are ribbed with the centre either flat or having winged protrusions. The eggcase curiously resembles the shells of extinct ammonites. It is secreted by the tips of the female's two greatly expanded dorsal tentacles (third left arms) before egg laying. After she deposits her eggs in the floating eggcase, the female takes shelter in it, often retaining the male's detached hectocotylus. She is usually found with her head and tentacles protruding from the opening, but she retreats deeper inside if disturbed. These ornate curved white eggcases are occasionally found floating on the sea, sometimes with the female argonaut clinging to it. It is not made

Argonaut 73

of aragonite as most other shells are, but of calcite, with a three-layered structure[3] and a higher proportion ofmagnesium carbonate (7%) than other cephalopod shells.[4]

The eggcase contains a bubble of air that the animal captures at the surface of the water and uses for buoyancy, in amanner similar to other shelled cephalopods, although it does not have a chambered phragmocone as do othershelled cephalopods.[3] Once thought to contribute to occasional mass strandings on beaches, the air bubble is undersophisticated control, evident from the behaviour of animals from which air has been removed under experimentaldiving conditions.[5] [6] [7]

Most other octopuses lay eggs in caves; Neale Monks and C. Phil Palmer speculate that, before ammonites died outduring the Cretaceous–Tertiary extinction event, the argonauts may have evolved to use discarded ammonite shellsfor their egg laying, eventually becoming able to mend the shells and perhaps make their own shells.[8] However,this is uncertain and it is unknown whether this is the result of convergent evolution.Argonauta argo is the largest species in the genus and also produces the largest eggcase, which may reach a lengthof 300 mm.[9] [10] The smallest species is Argonauta bottgeri, with a maximum recorded size of 67 mm.[11] [12]

FemaleA. nodosa

with itseggcase

The eggcase of A.argo

The eggcaseof A.

nodosa

The eggcase of A. hians

BeakThe beaks of Argonauta species are distinctive, being characterised by a very small rostrum and a fold that runs tothe lower edge or near the free corner. The rostrum is 'pinched in' at the sides, making it much narrower than in otheroctopuses, with the exception of the closely allied monotypic genera Ocythoe and Vitreledonella. The jaw angle iscurved and indistinct. Beaks have a sharp shoulder, which may or may not have posterior and anterior parts atdifferent slopes. The hood lacks a notch and is very broad, flat, and low. The hood to crest ratio (f/g) isapproximately 2-2.4. The lateral wall of the beak has no notch near the wide crest. Argonaut beaks are most similarto those of Ocythoe tuberculata and Vitreledonella richardi, but differ in 'leaning back' to a greater degree than theformer and having a more curved jaw angle than the latter.[12]

Feeding and defenseFeeding mostly occurs during the day. Argonauts use tentacles to grab prey and drag it toward the mouth. It thenbites the prey to inject it with poison from the salivary gland. They feed on small crustaceans, molluscs, jellyfish andsalps. If the prey is shelled, the argonaut uses its radula to drill into the organism, then inject the poison.Argonauts are capable of altering their color. They can blend in with their surroundings to avoid predators. They alsoproduce ink, which is ejected when the animal is being attacked. This ink paralyzes the olfaction of the attacker,providing time for the argonaut to escape. The female is also able to pull back the web covering of her shell, makinga silvery flash, which may deter a predator from attacking.Argonauts are preyed upon by tunas, billfishes, and dolphins. Shells and remains of argonauts have been recordedfrom the stomachs of Alepisaurus ferox and Coryphaena hippurus.[12]

Male argonauts have been observed residing inside salps, although little is known about this relationship.[13]

Argonaut 74

Classification

Shells of various Argonauta species

The genus Argonauta contains up to seven extantspecies. Several extinct species are also known.

†Argonauta absyrtusArgonauta argo (type)Argonauta bottgeriArgonauta cornuta*Argonauta hians†Argonauta itoigawai†Argonauta joanneusArgonauta nodosaArgonauta nouryiArgonauta pacifica*†Argonauta tokunagai

*Species status questionable.

The extinct species Obinautilus awaensis wasoriginally assigned to Argonauta, but has since beentransferred to the genus Obinautilus.[14]

Dubious or uncertain taxaThe following taxa associated with the family Argonautidae are of uncertain taxonomic status:[15]

Binomial name and authorcitation

Current systematic status Type locality Type repository

Argonauta arctica Fabricius,1780

Undetermined Unresolved; ?Tullukaurfak,Greenland

Unresolved

Argonauta bibula Röding,1798

Undetermined Unresolved Unresolved

Argonauta compressaBlainville, 1826

Undetermined Mer de Indes Unresolved; [other Blainville types atMNHN] [not reported by Lu et al.(1995)]

Argonauta conradiParkinson, 1856

Species of uncertain status [fideRobson (1932:200)]

"New Nantucket, Pacific Ocean" Unresolved

Argonauta cornu Gmelin,1791

Undetermined Unresolved Unresolved; LS?

Argonauta cymbium Linné,1758

Non-cephalopod; foraminiferousshell [fide Von Martens (1867:103)

Argonauta fragilis Parkinson,1856

Species of uncertain status [fideRobson (1932:200)]

Not designated Unresolved

Argonauta geniculata Gould,1852

Species of uncertain status [fideRobson (1932:200)]

Near Sugarloaf Mountain, Rio deJaneiro, Brazil

Type not extant [fide Johnson(1964:32)]

Argonauta maxima Dall,1871

Nomen nudum

Argonaut 75

Argonauta naviculaLightfoot, 1786

Species dubium [fide Rehder(1967:11)]

Not designated Unresolved

Argonauta rotunda Perry,1811

Non-cephalopod; Carcinaria sp.[fide Robson (1932:201)]

Argonauta rufa Owen, 1836 Incertae sedis [fide Robson(1932:181)]

"Indian seas" ["South Pacific ocean"fide Owen (1842:114)]

Unresolved; Museum of the RoyalCollege of Surgeons? Holotype

Argonauta sulcata Lamarck,1801

Nomen nudum

Argonauta tuberculata f.aurita Von Martens, 1867

Undetermined Unresolved ZMB

Argonauta tuberculata f.mutica Von Martens, 1867

Undetermined Coast of Brazil ZMB Holotype

Argonauta tuberculata f.obtusangula Von Martens,1867

Undetermined Not designated ZMB Syntypes

Argonauta vitreus Gmelin,1791

Undetermined Not designated Unresolved; LS?

Octopus (Ocythoe)raricyathus Blainville, 1826

Undetermined [Argonauta?] Not designated MNHN Holotype; specimen notextant [fide Lu et al. (1995:323)]

Ocythoe punctata Say, 1819 Argonauta sp. [fide Robson(1929d:215)]

Atlantic Ocean near the NorthAmerican coast (from stomach ofdolphin)

Unresolved; ANSP? Holotype [nottraced by Spamer and Bogan (1992)]

Tremoctopus hirondelleiJoubin, 1895

Argonauta or Ocythoe [fide Thomas(1977:386)]

44°28′56″N 46°48′15″W (AtlanticOcean)

MOM Holotype [station 151] [fideBelloc (1950:3)]

Argonaut 76

In designThe argonaut was inspiration for a number of classical and modern art and decorative forms including use on potteryand architectural elements. Some early examples are found in Minoan art from Crete.[16] A variation known as thedouble argonaut design was also found in Minoan jewelry.[17]

In literature and etymology

Argonauts surrounding the Nautilus, in JulesVerne's novel Twenty Thousand Leagues Under

the Sea

.• Argonauts are featured in Twenty Thousand Leagues Under the Sea,

noted for their ability to use their tentacles as sails. There is noevidence for this.

• A female argonaut is also described in Marianne Moore's poem"The Paper Nautilus."

• "Argonauta" is the name of a chapter in Anne Morrow Lindbergh'sGift from the Sea.

• Paper nautiluses were caught in the The Swiss Family Robinsonnovel.[18]

• Argonauts gave their name to an Arabidopsis thaliana mutation andby extension to Argonaute proteins.

References

[1] (German) Naef, A. (1923). "Die Cephalopoden, Systematik". Fauna Flora Golf.Napoli (35) 1: 1–863.

[2] (Italian) Delle Chiaje, S. (1825). Memorie sulla storia e notomia degli animali.Senza Vertebre del Regno di Napoli. I.

[3] Nixon, M. & J.Z. Young (2003). The Brains and Lives of Cephalopods. OxfordUniversity Press.

[4] Saul, L. & C. Stadum (2005). "Fossil Argonauts (Mollusca: Cephalopoda: Octopodida) From Late Miocene Siltstones Of The Los AngelesBasin, California" (http:/ / apt. allenpress. com/ aptonline/ ?request=get-abstract& issn=0022-3360& volume=079& issue=03& page=0520).Journal of Paleontology 79 (3): 520–531. doi:10.1666/0022-3360(2005)079<0520:FAMCOF>2.0.CO;2. .

[5] Finn, J.K. & M.D. Norman 2010. The argonaut shell: gas-mediated buoyancy control in a pelagic octopus. Proceedings of the Royal SocietyB: Biological Sciences, published online May 19, 2010. doi:10.1098/rspb.2010.0155

[6] " Museum Victoria 'Argonaut buoyancy' video" (http:/ / museumvictoria. com. au/ about/ mv-news/ 2010/ argonaut-buoyancy/ )museumvictoria.com.au. URL accessed on 19 May 2010.

[7] Pidcock, R. 2010. Ancient octopus mystery resolved (http:/ / news. bbc. co. uk/ 1/ hi/ science_and_environment/ 10127611. stm). BBC News,May 19, 2010.

[8] Monks, N. & P. Palmer (2002). Ammonites. Smithsonian Institution Press, Washington D.C..[9] Pisor, D. L. (2005). Registry of World Record Size Shells (4th ed.). Snail's Pace Productions and ConchBooks. pp. 12.[10] (Russian) Nesis, K. N. 1982. Abridged key to the cephalopod mollusks of the world's ocean. Light and Food Industry Publishing House,

Moscow, 385+ii pp. [Translated into English by B. S. Levitov, ed. by L. A. Burgess (1987), Cephalopods of the world. T. F. H. Publications,Neptune City, NJ, 351 pp.]

[11] Pisor, D. L. (2005). Registry of World Record Size Shells (4th ed.). Snail's Pace Productions and ConchBooks. pp. 12.[12] Clarke, M. R. (1986). A Handbook for the Identification of Cephalopod Beaks. Oxford University Press. pp. 273 pp.[13] Banas, P. T., D. E. Smith & D. C. Biggs (1982). "An association between a pelagic octopod, Argonauta sp. Linnaeus 1758, and aggregate

salps". Fish. Bull. U.S. 80: 648–650.[14] Martill, D.M. & M.J. Barker (2006). A paper nautilus (Octopoda, Argonauta) from the Miocene Pakhna Formation of Cyprus. (http:/ / www.

blackwell-synergy. com/ doi/ abs/ 10. 1111/ j. 1475-4983. 2006. 00578. x?journalCode=pala) Palaeontology 49 (5): 1035-1041.[15] Sweeney, M. J. Taxa Associated with the Family Argonautidae Tryon, 1879. (http:/ / www. tolweb. org/ accessory/

Argonautidae_Taxa?acc_id=2464) Tree of Life web project.[16] Eleni M. Konstantinidi, Jewellery Revealed in the Burial Contexts of the Greek Bronze Age, 2001, Hadrian Books, 322 pages ISBN

1841711659

Argonaut 77

[17] C.Michael Hogan, Knossos Fieldnotes, The Modern Antiquarian (2007) (http:/ / themodernantiquarian. com/ site/ 10857/ phaistos.html#fieldnotes)

[18] Johann David Wyss and Jenny H. Stickney, The Swiss Family Robinson, Ginn & Co., 1898, 364 pages

External links• CephBase: Argonauta (http:/ / www. cephbase. utmb. edu/ spdb/ genusgroup. cfm?Genus=Argonauta)• Tree of Life web project: Argonauta (http:/ / tolweb. org/ tree?group=Argonauta)

78

Anatomy and behaviour

Cephalopod intelligence

An octopus in a zoo

Cephalopod intelligence has an important comparative aspect in theunderstanding of intelligence, because it relies on a nervous systemfundamentally different from that of vertebrates.[1] The cephalopodclass of molluscs, particularly the Coleoidea subclass (cuttlefish, squidand octopuses), are considered the most intelligent invertebrates and animportant example of advanced cognitive evolution in animals.

The scope of cephalopod intelligence is controversial, complicated bythe challenges of studying these elusive and fundamentally differentcreatures. Classical conditioning of cephalopods has been reported, andone study (Fiorito and Scotto, 1992) even concluded that octopusespractice observational learning.[2] However, the latter idea is strongly disputed, and doubt has been shed on someother reported capabilities as well.[3] In any case, impressive spatial learning capacity, navigational abilities, andpredatory techniques remain beyond question.

Examples of intelligence

Predation techniquesUnlike most other molluscs, all cephalopods are active predators (with the possible exception of the bigfin squid).Their requirement to locate and capture their prey has been a probable driving force behind the development of theirintelligence, uniquely advanced in their phylum.The humboldt squid hunts schools of fish, showing extraordinary cooperation and communication in its huntingtechniques. This is the first observation of such behaviour in invertebrates.[4]

Crabs, the staple food source of most octopus species, present significant challenges with their powerful pincers andtheir potential to exhaust the cephalopod's respiration system from a prolonged pursuit. In the face of thesechallenges, octopuses will instead seek out lobster traps and steal the prize inside. They are also known to climbaboard fishing boats and hide in the containers that hold dead or dying crabs.[5]

DexterityDexterity, a trait essential for tool use and manipulation is also found in cephalopods. The highly sensitive suctioncups and prehensile arms of octopuses, squid, and cuttlefish are as effective at holding and manipulating objects asthe human hand. However, unlike vertebrates, the motor skills of octopuses do not seem to depend upon mappingtheir body within their brains, as the ability to organize complex movements is not thought to be linked to particulararms.[6]

One particularly clever octopus called Otto has been known to juggle his fellow tankmates around out of boredom,as well as throwing rocks and smashing the aquarium glass. On more than one occasion he even caused short circuitsby crawling out of his tank and shooting a jet of water at the overhead lamp.[7]

Cephalopod intelligence 79

Octopus opening a container with a screw cap

CommunicationAnother example of cephalopod intelligence is the communication that takes place between the more social speciesof squid. Some cephalopods are capable of rapid changes in skin color and pattern through nervous control ofchromatophores.[8] This ability almost certainly evolved primarily for camouflage, but squids use color, patterns, andflashing to communicate with one another in various courtship rituals. Caribbean Reef Squid can send one messagevia color patterns to a squid on their right, while they send another message to a squid on their left.[9] [10]

Tool useAs of 2009, the octopus is the only invertebrate animal which has been conclusively shown to use tools. At least fourspecimens of the Veined Octopus (Amphioctopus marginatus) have been witnessed retrieving discarded coconutshells, manipulating them, transporting them some distance, and then reassembling them to use as a shelter. Thisdiscovery was documented in the journal Current Biology and has been filmed on video.[11] [12] Most hermit crabsuse discarded shells of other species for habitation and other crabs choose sea anemones to cultivate on theircarapaces as camouflage; numerous insects use rocks, sand, leaves and so on as building materials, however none ofthis behavior compares to the complexity of the octopus's fortress behavior, which involves picking up and carryinga tool to use later on.

See also• Paul the Octopus• Paul II (octopus)

References[1] "Cephalopod intelligence" (http:/ / www. daviddarling. info/ encyclopedia/ C/ cephalopodintel. html) in The Encyclopedia of Astrobiology,

Astronomy, and Spaceflight.[2] "What is this octopus thinking?" (http:/ / www. fortunecity. com/ emachines/ e11/ 86/ cephpod. html) by Garry Hamilton[3] Is the octopus really the invertebrate intellect of the sea? (http:/ / www. nwf. org/ nationalwildlife/ article. cfm?articleId=604& issueId=53)

by Doug Stewart. In: National Wildlife. Feb/Mar 1997, vol.35 no.2[4] Behold the Humboldt squid (http:/ / outside. away. com/ outside/ features/ 200607/ sea-of-cortez-humboldt-squid-1. html). Tim Zimmermann,

Outside Magazine, July 2006.[5] Cousteau, Jacques Yves (1978). Octopus and Squid: The Soft Intelligence[6] Zullo L, Sumbre G, Agnisola C, Flash T, Hochner B. (2009). Nonsomatotopic organization of the higher motor centers in octopus. Curr Biol.

19(19):1632-6. PMID 19765993

Cephalopod intelligence 80

[7] "Otto the Octopus wreaks havoc" (http:/ / www. telegraph. co. uk/ news/ newstopics/ howaboutthat/ 3328480/Otto-the-octopus-wrecks-havoc. html)

[8] Cloney, R.A. & E. Florey 1968. Ultrastructure of cephalopod chromatophore organs. Z Zellforsch Mikrosk Anat 89: 250-280. PMID 5700268[9] "''Sepioteuthis sepioidea'', Caribbean Reef squid" (http:/ / www. thecephalopodpage. org/ Ssepioidea. php). The Cephalopod Page. . Retrieved

2010-01-20.[10] Byrne, R.A., U. Griebel, J.B. Wood & J.A. Mather 2003. Squids say it with skin: a graphic model for skin displays in Caribbean Reef Squid.

(http:/ / userpage. fu-berlin. de/ ~jevers/ data/ palbio3/ 05. pdf)PDF (3.86 MB) Berliner Geowissenschaftliche Abhandlungen 3: 29-35.[11] Morelle, Rebecca (2009-12-14). "Octopus snatches coconut and runs" (http:/ / news. bbc. co. uk/ 1/ hi/ sci/ tech/ 8408233. stm). BBC News.

. Retrieved 2010-01-20.[12] "Coconut shelter: evidence of tool use by octopuses | EduTube Educational Videos" (http:/ / www. edutube. org/ video/

coconut-shelter-evidence-tool-use-octopuses). Edutube.org. 2009-12-14. . Retrieved 2010-01-20.

Further reading• What behavior can we expect of octopuses? (http:/ / www. thecephalopodpage. org/ behavior. php) by Dr.

Jennifer Mather, Department of Psychology and Neuroscience, University of Lethbridge and Roland C.Anderson, The Seattle Aquarium.

• Is the octopus really the invertebrate intellect of the sea? (http:/ / www. nwf. org/ nationalwildlife/ article.cfm?articleId=604& issueId=53) by Doug Stewart. In: National Wildlife. Feb/Mar 1997, vol.35 no.2.

• Giant Octopus — Mighty but Secretive Denizen of the Deep (http:/ / nationalzoo. si. edu/ Support/ AdoptSpecies/AnimalInfo/ GiantOctopus/ default. cfm) from the Smithsonian National Zoological Park

• Living Fossils Have Long- And Short-term Memory Despite Lacking Brain Structures Of Modern Cephalopods(http:/ / www. sciencedaily. com/ releases/ 2008/ 05/ 080531074905. htm)

• M.J. Wells (1962). Brain and Behaviour in Cephalopods. Heinemann.• Roger T. Hanlon & John B. Messenger (1996). Cephalopod Behaviour. Cambridge University Press.• Marion Nixon and John Z. Young (2003). The Brains and Livees of Cephalopods. Oxford University Press.• Binyamin Hochner; Tal Shomrat & Graziano Fiorito (June 1, 2006). "The Octopus: A Model for a Comparative

Analysis of the Evolution of Learning and Memory Mechanisms" (http:/ / www. biolbull. org/ cgi/ content/ full/210/ 3/ 308). The Biol. Bull. 210 (210): 308–817. PMID 16801504.

• Octopuses are Smart Suckers!? (http:/ / www. thecephalopodpage. org/ smarts. php) By Dr. Jennifer Mather,Department of Psychology and Neuroscience, University of Lethbridge and Roland C. Anderson, The SeattleAquarium

• Through the Eye of an Octopus (http:/ / discovermagazine. com/ 2003/ oct/ feateye), by Eric Scigliano, DiscoverMagazine, October 1, 2003.

Cephalopod size 81

Cephalopod size

The giant squid (Architeuthis sp.) was for a long time thought to be the largestextant cephalopod. It is now known that the Colossal Squid (Mesonychoteuthis

hamiltoni) attains an even greater size.

Size has been one of the most interestingaspects of cephalopod science to the generalpublic. This article lists the largestcephalopods from various groups, sorted inorder of mantle length, total length, weight,and shell diameter. Extinct taxa are alsoincluded.

Mantle length

North Pacific Giant Octopus, Enteroctopus dofleini

Octopoda (octopuses)

Species Maximum mantlelength

References Notes

Haliphron atlanticus 0.69 m O'Shea (2004)

Enteroctopus dofleini 0.6 m Norman (2000:214)

Sepiida (cuttlefish)

Species Maximum mantlelength

References Notes

Sepia apama 0.5 m Reid et al. (2005:68)

Sepia latimanus 0.5 m Reid et al. (2005:92)

Sepia officinalis 0.49 m Reid et al. (2005:99)

Sepia pharaonis 0.42 m Reid et al. (2005:107)

Sepiolida (bobtail squid)

Cephalopod size 82

Species Maximum mantlelength

References Notes

Austrorossia antillensis 0.09 m Reid et al. (2005:192)

Rossia pacifica 0.09 m (female) Reid et al. (2005:185) Male grows to 45 mm in mantle length (Reid et al., 2005).

Rossia macrosoma 0.085 m Reid et al. (2005:184) More typically the mantle length is 20–60 mm (Reid et al., 2005).

Neorossia caroli 0.083 m (female) Reid et al. (2005:190) Male grows to 51 mm in mantle length (Reid et al., 2005).

Spirulida (Ram's Horn Squid) (only one extant species)

Species Maximum mantlelength

References Notes

Spirula spirula rarely exceeds 0.045m

Reid et al. (2005:211)

Teuthida (squid)

Species Maximum mantlelength

References Notes

Mesonychoteuthishamiltoni

4 m (estimate) O'Shea (2005a) Estimate based on largest known beak (LRL: 49 mm).

Galiteuthis phyllura 2.65–2.75 m(estimate)

Nesis (1985) Estimate based on 0.4 m long arm and 1.15 m tentacle.

Architeuthis sp.† 2.25 m O'Shea (2005a)

Onykia robusta 2 m Norman (2000:174) Kubodera et al. (1998) give maximum of at least 1.615 m.

Megalocranchia fisheri 1.8 m Tsuchiya & Okutani (1993)

Dosidicus gigas 1.75 m Glaubrecht &Salcedo-Vargas (2004)

Norman (2000:165) gives maximum of 1.5 m.

Taningia danae 1.7 m Nesis (1982)

Kondakovia longimana probably 1.15+ m(estimate)

O'Shea (2005b) Longest confirmed specimen measures 0.85 m (O'Shea, 2005b). Totallength to at least 2.3 m (Carrington, 2000).

Thysanoteuthisrhombus

1 m Roper et al. (1984) Commonly grows to a mantle length of 0.6 m (Roper et al., 1984).

cf. Magnapinna ~1 m (estimate) Vecchione et al. (2001) Estimate based on specimen observed by ROV Tiburon in May 2001,north of Oahu, Hawaii, at a depth of 3380 m.

Vampyromorphida (Vampire Squid) (only one extant species)

Species Maximum mantlelength

References Notes

Vampyroteuthisinfernalis

0.13 m Nesis (1982)

† The taxonomy of the giant squid has not been entirely resolved. Lumpers and splitters may propose as many as eight species or as few as one.

No genetic or physical basis for distinguishing between the named species has been proposed.

Cephalopod size 83

Total length

A long-arm squid (cf. Magnapinna) filmed in the Gulf of Mexico.

Octopoda (octopuses)Not to be confused with armspan, which is approximately double the total length.

Species Maximum totallength

References Notes

Enteroctopus dofleini > 6.1 m Cosgrove (1987)

Haliphron atlanticus 4 m (estimate) O'Shea (2004) Estimate based on incomplete 2.90 m specimen.

Teuthida (squid)Total length including long feeding tentacles.

Species Maximum totallength

References Notes

Mesonychoteuthishamiltoni

14 m (estimate) O'Shea (2005a) Estimate based on largest known beak (LRL: 49 mm).

Architeuthis sp. 13 m (female) O'Shea (2005a) Measured post mortem and relaxed. Older records were exaggerated by stretchingof the tentacles (O'Shea, 2005a).

cf. Magnapinna at least 8 m(estimate)

Bolstad (2003) Estimate based on video evidence.

Asperoteuthisacanthoderma

5.5 m Tsuchiya &Okutani (1993)

Length of immature specimen measuring 0.45 m ML. Largest known specimen(0.78 m ML) would presumably be longer if it were complete (Okutani, 1995).

Onykia robusta over 4 m Verrill (1876)

Galiteuthis phyllura over 4 m(estimate)

Nesis (1985) Estimate based on 0.40 m long arm and 1.15 m tentacle.

Cephalopod size 84

Weight

Sepia apama, the heaviest species of cuttlefish

Octopoda (octopuses)

Species Maximumweight

References Notes

Haliphron atlanticus 75 kg (estimate) O'Shea (2004) Estimate based on incomplete 61.0 kg specimen.

Enteroctopus dofleini 71 kg Cosgrove (1987) Weight of live specimen. There exists a highly dubious record of a 272 kgspecimen (High, 1976).

Sepiida (cuttlefish)

Species Maximumweight

References Notes

Sepia apama in excess of10.5 kg

Reid et al. (2005:68)

Sepia latimanus 10 kg Reid et al. (2005:92)

Sepia pharaonis 5 kg Reid et al.(2005:107)

Sepia officinalis 4 kg Reid et al. (2005:99)

Teuthida (squid)

Species Maximumweight

References Notes

Mesonychoteuthishamiltoni

495 kg [Anonymous] (2007) Weight of mature specimen caught in early 2007. Originally estimated toweigh 450 kg (Anderton, 2007).

Architeuthis sp. 275 kg (female) O'Shea (2005a)

Taningia danae 61.4 kg Kubodera et al.(2006)

Onykia robusta 50 kg Roper et al. (1984)

Dosidicus gigas 50 kg Nigmatullin et al.(2001)

Thysanoteuthis rhombus 30 kg Miyahara et al.(2006)

Cephalopod size 85

Shell diameter

Nautilus shells: N. macromphalus (left), A. scrobiculatus (centre),N. pompilius (right). Argonauta hians shell, 121.5 mm in diameter.

Internal shell of Spirula spirula.

Nautilida (nautiluses) (all extant species listed)

Species Maximum shelldiameter

References Notes

Nautilus pompiliuspompilius

268 mm [1] Pisor (2005:93) lists maximum shell diameter of 254.0 mm. Nautilus repertus is treatedhere in synonymy with N. pompilius pompilius. Pisor (2005:93) lists 230.0 mm record forN. repertus.

Nautilus belauensis 226 mm Jereb(2005:54)

Allonautilusscrobiculatus

215.0 mm Pisor(2005:93)

Nautilusstenomphalus

201.0 mm Pisor(2005:93)

Allonautilusperforatus

around 180 mm Jereb(2005:55)

Nautilusmacromphalus

180.0 mm Pisor(2005:93)

Nautilus pompiliussuluensis

148.0 mm Pisor(2005:93)

Cephalopod size 86

Octopoda (octopuses) (all extant Argonauta species listed)Females of the genus Argonauta produce a calcareous eggcase in which they reside.

Species Maximum shelldiameter

References Notes

Argonauta argo 300.0 mm Pisor(2005:12)

Argonauta nodosa 292.0 mm Pisor(2005:12)

Argonauta pacifica‡ 220.0 mm Pisor(2005:12)

Argonauta hians 112.6 mm Pisor(2005:12)

Argonauta cornuta‡ 98.6 mm Pisor(2005:12)

Argonauta nouryi 95.5 mm Pisor(2005:12)

Argonauta bottgeri 67.0 mm Pisor(2005:12)

Spirulida (Ram's Horn Squid) (only one extant species)The Ram's Horn Squid possesses a chambered internal shell, which it uses for buoyancy control.

Species Maximum shelldiameter

References Notes

Spirula spirula 28.8 mm [2] Pisor (2005:108) lists maximum shell diameter of 26.9 mm.

‡ Species status questionable.

Extinct taxa

Cast of Parapuzosia seppenradensisFossilised guards of Megateuthis gigantea (top

and centre)

Ammonoidea (ammonites)

Species Maximum shelldiameter

References Notes

Parapuzosiaseppenradensis

2.55 m (estimate) Kennedy & Kaplan(1995)

Estimate based on 1.95 m diameter specimen with an incompleteliving chamber.

Belemnoidea (belemnites)

Cephalopod size 87

Species Maximum rostrumlength

References Notes

Megateuthis gigantea 0.46 m Eyden (2003) The whole belemnite is estimated to have been 3–5 m long.

Nautiloidea (nautiloids)

Species Maximum shell length References Notes

Cameroceras sp. 11 m (estimate) Teichert & Kümmel(1960)

Vampyromorphida (vampire squid)

Species Maximum mantlelength

References Notes

Tusoteuthis longa over 1.8 m (estimate) Eyden (2004)

References• [Anonymous] 2007. Colossal squid may be headed for oven [3]. Associated Press.• Anderton, H.J. 2007. Amazing specimen of world's largest squid in NZ [4]. New Zealand Government website.• Bolstad, K. 2003. Deep-Sea Cephalopods: An Introduction and Overview [5]. The Octopus News Magazine

Online.• Carrington, D. 2000. Big squid breaks record [6]. BBC News, July 3, 2000.• Cosgrove, J.A. 1987. Aspects of the Natural History of Octopus dofleini, the Giant Pacific Octopus. M.Sc. Thesis.

Department of Biology, University of Victoria (Canada), 101 pp.• Eyden, P. 2003. Belemnites: A Quick Look [7]. The Octopus News Magazine Online.• Eyden, P. 2004. Cretaceous Giant Squid [8]. The Octopus News Magazine Online.• Glaubrecht, M. & M.A. Salcedo-Vargas 2004. The Humboldt squid Dosidicus gigas (Orbigny, 1835): History of

the Berlin specimen, with a reappraisal of other (bathy-)pelagic gigantic cephalopods (Mollusca,Ommastrephidae, Architeuthidae). Zoosystematics and Evolution 80(1): 53–69. doi:10.1002/mmnz.20040800105

• High, W.L. 1976. The giant Pacific octopus. U.S. National Marine Fisheries Service, Marine Fisheries Review38(9): 17-22.

• Jereb, P. 2005. Family Nautilidae. In: P. Jereb & C.F.E. Roper, eds. Cephalopods of the world. An annotated andIllustrated catalogue of species known to date. Volume 1. Chambered nautiluses and sepioids (Nautilidae,Sepiidae, Sepiolidae, Sepiadariidae, Idiosepiidae and Spirulidae). FAO Species Catalogue for Fishery Purposes.No. 4, Vol. 1. Rome, FAO. pp. 51–55.

• (German) Kennedy, W.J. & U. Kaplan 1995. Parapuzosia (Parapuzosia) seppenradensis (LANDOIS) und dieAmmoniten fauna der Dülmener Schichten, Westfalen. Geol. Paläont. Westf. 33: 127 p., 43 pls.

• Kubodera, T., U. Piatkowski, T. Okutani & M.R. Clarke. 1998. Taxonomy and Zoogeography of the FamilyOnychoteuthidae (Cephalopoda: Oegopsida). Smithsonian Contributions to Zoology 586: 277-291.

• Kubodera, T., Y. Koyama & K. Mori 2006. Observations of wild hunting behaviour and bioluminescence of alarge deep-sea, eight-armed squid, Taningia danae. [9]PDF (295 KB) Proceedings of the Royal Society B:Biological Sciences 274(1613): 1029–1034. doi:10.1098/rspb.2006.0236

• Miyahara, K., K. Fukui, T. Ota & T. Minami 2006. Laboratory observations on the early life stages of thediamond squid Thysanoteuthis rhombus. Journal of Molluscan Studies 72(2): 199–205.doi:10.1093/mollus/eyi068

• (Russian) Nesis, K.N. 1982. Abridged key to the cephalopod mollusks of the world's ocean. Light and FoodIndustry Publishing House, Moscow. 385+ii pp. [Translated into English by B. S. Levitov, ed. by L. A. Burgess1987. Cephalopods of the world. T.F.H. Publications, Neptune City, NJ. 351pp.]

Cephalopod size 88

• (Russian) Nesis, K.N. 1985. A Giant Squid in the Sea of Okhotsk. Priroda 10: 112-113. [Translated from Russianby Yuri Nektorenko.]

• Nigmatullin, C.M., K.N. Nesis & A.I. Arkhipkin 2001. A review of the biology of the jumbo squid Dosidicusgigas (Cephalopoda: Ommastrephidae). Fisheries Research 54(1): 9–19. doi:10.1016/S0165-7836(01)00371-X

• Norman, M.D. 2000. Cephalopods: A World Guide. ConchBooks.• Norman, M.D. & A. Reid 2000. A Guide to Squid, Cuttlefish and Octopuses of Australasia. CSIRO Publishing.• Okutani, T. 1995. Cuttlefish and squids of the world in color. Publication for the 30th anniversary of the

foundation of the National Cooperative Association of Squid Processors. 185 pp.• O'Shea, S. 2004. The giant octopus Haliphron atlanticus (Mollusca : Octopoda) in New Zealand waters. New

Zealand Journal of Zoology 31(1): 7-13.• O'Shea, S. 2005a. Giant Squid and Colossal Squid Fact Sheet [10]. The Octopus News Magazine Online.• O'Shea, S. 2005b. Kondakovia longimana [11]. In: Giant Squid and Colossal Squid Fact Sheet. The Octopus News

Magazine Online.• Pisor, D.L. 2005. Registry of World Record Size Shells: Fourth Edition - 2005. Snail's Pace Productions and

ConchBooks.• Reid, A., P. Jereb, & C.F.E. Roper 2005. Family Sepiidae. In: P. Jereb & C.F.E. Roper, eds. Cephalopods of the

world. An annotated and illustrated catalogue of species known to date. Volume 1. Chambered nautiluses andsepioids (Nautilidae, Sepiidae, Sepiolidae, Sepiadariidae, Idiosepiidae and Spirulidae). FAO Species Cataloguefor Fishery Purposes. No. 4, Vol. 1. Rome, FAO. pp. 57–152.

• Roper C.F.E., M.J. Sweeney & C.E. Nauen 1984. Cephalopods of the world. Food and Agriculture Organization,Rome, Italy.

• Teichert, C. & B. Kümmel 1960. Size of Endocerid Cephalopods. Breviora Mus. Comp. Zool. 128: 1–7.• Tsuchiya, K. & T. Okutani 1993. Rare and interesting squids in Japan -X. Recent occurrences of big squids from

Okinawa. Venus 52: 299-311.• Vecchione, M., R.E. Young, A. Guerra, D.J. Lindsay, D.A. Clague, J.M. Bernhard, W.W. Sager, A.F. Gonzalez,

F.J. Rocha & M. Segonzac 2001. Vecchione et al., 2001 [12]. Cephalopods in Action.• Verrill, A.E. 1876. Notes on gigantic cephalopods, a correction. American Journal of Science and Arts 12(3):

236-237.

References[1] http:/ / www. conchology. be/ ?t=68& u=118764& g=0d16facb6ebae4a31321e9f6e6298f46& q=a1d787a5674deb7b193549c6ccdff907[2] http:/ / www. conchology. be/ ?t=68& u=126690& g=e8a21ed471661c24ca2aea9f5ea70400& q=4e4d53268a89f2aef5613d13d96327f0[3] http:/ / news. yahoo. com/ s/ ap/ 20070322/ ap_on_sc/ colossal_squid;_ylt=ArrD9. iKLzOCbR7FKcFksAnMWM0F[4] http:/ / www. beehive. govt. nz/ ViewDocument. aspx?DocumentID=28451[5] http:/ / www. tonmo. com/ science/ public/ deepseacephs. php[6] http:/ / news. bbc. co. uk/ 2/ hi/ science/ nature/ 813394. stm[7] http:/ / www. tonmo. com/ science/ public/ belemnites. php[8] http:/ / www. tonmo. com/ science/ fossils/ cretaceousGS. php[9] http:/ / www. pubs. royalsoc. ac. uk/ media/ proceedings_b/ papers/ RSPB20060236. pdf[10] http:/ / www. tonmo. com/ science/ public/ giantsquidfacts. php[11] http:/ / web. archive. org/ web/ 20071227144307/ http:/ / www. tonmo. com/ science/ public/ giantsquidfacts2. php[12] http:/ / www. mnh. si. edu/ cephs/ vetal01/ vetal01. html

Cephalopod ink 89

Cephalopod ink

Ventral view of the viscera of Chtenopteryxsicula, showing the location of the ink sac

Cephalopod ink is a dark pigment released into water by most speciesof cephalopod, usually as an escape mechanism. All cephalopods, withthe exception of the Nautilidae and the species of octopus belonging tothe suborder Cirrina,[1] are able to release ink.

The ink is released from the ink sacs (located between the gills) and isdispersed more widely by accompanying its release with a jet of waterfrom the funnel. Its dark color is caused by its main constituent,melanin. Each species of cephalopod produces slightly differentlycoloured inks; generally, octopuses produce black ink, squid ink is blue-black and cuttlefish ink is brown (see Use byhumans).

A number of other aquatic molluscs have evolved similar responses to attack, including sea hares. This is an exampleof convergent evolution.

Inking behavioursI was much interested, on several occasions, by watching the habits of an Octopus or cuttle-fish ... they darted tail first, with therapidity of an arrow, from one side of the pool to the other, at the same instant discolouring the water with a dark chestnut-brownink.

Charles Darwin, The Voyage of the Beagle

Two distinct behaviours have been observed in inking cephalopods. The first is the release of large amounts of inkinto the water by the cephalopod, in order to create a dark, diffuse cloud (much like a smokescreen) which canobscure the predator’s view, allowing the cephalopod to make a rapid retreat by jetting away.The second response to a predator is to release ‘pseudomorphs’ (‘false bodies’); smaller clouds of ink with a greatermucus content, which allows them to hold their shape for longer. These are expelled slightly away from thecephalopod in question, which will often release several pseudomorphs and change color (blanch) in conjunctionwith these releases. The pseudomorphs are roughly the same volume and look similar to the cephalopod that releasedthem, and many predators have been observed attacking them mistakenly, allowing the cephalopod to escape (thisbehavior is often referred to as the ‘Blanch-Ink-Jet Maneuver’). Furthermore, green turtle hatchlings (Cheloniamydas) that have been observed mistakenly attacking pseudomorphs released by Octopus bocki have subsequentlyignored conspecific octopuses.[2] However, many cephalopod predators (for instance moray eels) have advancedchemosensory systems, and some anecdotal evidence[3] suggests that compounds such as tyrosinase found incephalopod ink can irritate, numb or even deactivate such apparatus. Unfortunately, few controlled experiments havebeen conducted to substantiate this. Cephalopod ink is nonetheless generally thought to be more sophisticated than asimple ‘smokescreen;’ the ink of a number of squid and cuttlefish has been shown to function as a conspecificchemical alarm.[4]

Octopuses have also been observed squirting ink at snails or crabs approaching their eggs.[4]

Cephalopod ink 90

Chemical compositionCephalopod ink contains a number of chemicals in a variety of different concentrations, depending on the species.However, its main constituents are melanin and mucus. It can also contain, among other things, tyrosinase, dopamineand L-DOPA,[5] and small amounts of amino acids, including taurine, aspartic acid, glutamic acid, alanine andlysine.[4]

Use by humans

Arròs negre owes its dark colour to squid ink

Cephalopod ink has, as its name suggests, been used in the past as ink;indeed, the Greek name for cuttlefish, and the taxonomic name of acuttlefish genus, Sepia, is associated with the brown colour ofcuttlefish ink (for more information, see Sepia (color)). Modern use ofcephalopod ink is generally limited to cooking, where it is used as afood colouring, for example in pasta and sauces. For this purpose it isgenerally obtainable from fishmongers or gourmet food suppliers. Theink is extracted from the ink sacs during preparation of the deadcephalopod, usually squid, and therefore contains no mucus. Recentstudies have shown that cephalopod ink is toxic to some cells, including tumor cells.[4]

References[1] Roger T. Hanlon, John B. Messenger: Cephalopod Behaviour, page 2. Cambridge University Press, 1999, ISBN 0521645832[2] Roy L. Caldwell (2005), "An Observation of Inking Behavior Protecting Adult Octopus bocki from Predation by Green Turtle (Chelonia

mydas) Hatchlings" http:/ / muse. jhu. edu/ journals/ pacific_science/ v059/ 59. 1caldwell. pdf[3] G.E. MacGinitie, N. MacGinitie (1968) Natural History of Marine Animals, Pages 395-397, 2nd ed. McGraw-Hill, New York.[4] Charles D. Derby (2007), "Escape by Inking and Secreting: Marine Molluscs Avoid Predators Through a Rich Array of Chemicals and

Mechanisms" http:/ / www. biolbull. org/ cgi/ reprint/ 213/ 3/ 274. pdf[5] http:/ / nationalzoo. si. edu/ Animals/ Invertebrates/ Facts/ cephalopods/ inking. cfm

External links• An article on harvesting squid ink (http:/ / www. instructables. com/ id/ How-to-Harvest-Squid-Ink/ )

Ink sac 91

Ink sac

Ventral view of the viscera of Chtenopteryxsicula

With the exception of nocturnal and very deep water cephalopods, allcoeloids which dwell in light conditions have an ink sac, which can beused to expel a cloud of dark ink to confuse predators.[1] This sac is amuscular bag which originated as an extension of the hind gut. It liesbeneath the gut and opens into the anus, into which its contents –almost pure melanin – can be squirted; its proximity to the base of thefunnel means that the ink can be distributed by ejected water as thecephalopod uses its jet propulsion.[1] The ejected cloud of melanin isbound by mucus particles, so it forms a lump approximately the sizeand shape of the cephalopod, fixing the predator's attention while the mollusc itself makes a hasty escape.[1]

A general level of provocation is necessary to trigger an octopus to release its ink, as it is biologically costly toproduce. Some species can even use their ink to stun or numb their predators.

References[1] Boyle, Peter; Rodhouse, Paul (2004). Cephalopods : ecology and fisheries (http:/ / books. google. com/ books?id=4UtCi2B4VnoC). Ames,

Iowa: Blackwell. doi:10.1002/9780470995310.ch2. ISBN 0632060484. .

Cephalopod arm

[[file:Illex illecebrosusarm.jpg|thumb|right

Arm of Illex illecebrosus with two rows of suckers along itslength]][[file:Illex illecebrosus tentacle.jpg|thumb|right

Tentacle of Illex illecebrosus with adistal tentacular club (right)]]

Octopus arm with two rows of suckers

A cephalopod arm is distinct from a tentacle, though the terms areoften used interchangeably.

Generally, cephalopod arms have suckers along most of their length, asopposed to tentacles, which have suckers only near their ends.[1]

Octopuses have eight arms and no tentacles, while squid and cuttlefishhave eight arms and two tentacles.[2] The limbs of nautiluses, whichnumber around 90 and lack suckers altogether, are called tentacles.[2]

[3] [4]

The tentacles of Decapodiformes are thought to be derived from thefourth arm pair of the ancestral coleoid, but the term arms IV is used torefer to the subsequent, ventral arm pair in modern animals (which isevolutionarily the fifth arm pair).[1]

The males of most cephalopods develop a specialised arm for spermdelivery, called a hectocotylus.

Abnormalities

Cephalopod arm 92

Many octopus arm anomalies have been recorded,[5] [6] including a 6-armed octopus nicknamed Henry the Hexapus,a 7-armed octopus,[7] a 10-armed Octopus briareus,[8] one with a forked arm tip,[9] an octopus with doublehectocotylization,[10] bilateral hectocotylization,[11] and specimens with up to 96 tentacle branches.[12] [13] [14]

Branched arms have also been recorded in cuttlefish.[15]

References[1] Young, R.E., M. Vecchione & K.M. Mangold 1999. Cephalopoda Glossary (http:/ / tolweb. org/ accessory/

Cephalopoda_Glossary?acc_id=587). Tree of Life web project.[2] Norman, M. 2000. Cephalopods: A World Guide. ConchBooks, Hackenheim. p. 15. "There is some confusion around the terms arms versus

tentacles. The numerous limbs of nautiluses are called tentacles. The ring of eight limbs around the mouth in cuttlefish, squids and octopusesare called arms. Cuttlefish and squid also have a pair of specialised limbs attached between the bases of the third and fourth arm pairs [...].These are known as feeding tentacles and are used to shoot out and grab prey."

[3] Fukuda, Y. 1987. Histology of the long digital tentacles. In: W.B. Saunders & N.H. Landman (eds.) Nautilus: The Biology and Paleobiologyof a Living Fossil. Springer Netherlands. pp. 249–256. doi:10.1007/978-90-481-3299-7_17

[4] Kier, W.M. 1987. The functional morphology of the tentacle musculature of Nautilus pompilius. (http:/ / biology. unc. edu/ faculty/ Kier/ lab/pdf/ Kier_1987. pdf)PDF In: W.B. Saunders & N.H. Landman (eds.) Nautilus: The Biology and Paleobiology of a Living Fossil. SpringerNetherlands. pp. 257–269. doi:10.1007/978-90-481-3299-7_18

[5] Kumph, H.E. 1960. Arm abnormality in octopus. Nature 185(4709): 334-335. doi:10.1038/185334a0[6] Toll, R.B. & L.C. Binger 1991. Arm anomalies: cases of supernumerary development and bilateral agenesis of arm pairs in Octopoda

(Mollusca, Cephalopoda) Zoomorphology 110(6): 313–316.doi:10.1007/BF01668021[7] Gleadall, I.G. 1989. An octopus with only seven arms: anatomical details (http:/ / mollus. oxfordjournals. org/ cgi/ content/ abstract/ 55/ 4/

479). Journal of Molluscan Studies 55: 479–487.[8] Minor birth defect resulting in 10-armed juvenile, all arms fully present and functional. (http:/ / cephbase. utmb. edu/ imgdb/ imgsrch3.

cfm?ID=66& PhotographerID=& CephID=510) CephBase.[9] Minor birth defect showing bifurcated arm tip. Both tips were fully functional. (http:/ / cephbase. utmb. edu/ imgdb/ imgsrch3. cfm?ID=65&

PhotographerID=& CephID=510) CephBase.[10] Palacio, F.J. 1973. On the double hectocotylization of octopods. (http:/ / ia311216. us. archive. org/ 2/ items/ nautilus87amer/

nautilus87amer. pdf)PDF The Nautilus 87: 99–102.[11] Robson, G.C. 1929. On a case of bilateral hectocotylization in Octopus rugosus. Journal of Zoology 99(1): 95–97.

doi:10.1111/j.1469-7998.1929.tb07690.x[12] Okada, Y.K. 1965. On Japanese octopuses with branched arms, with special reference to their captures from 1884 to 1964 (http:/ / www.

journalarchive. jst. go. jp/ english/ jnlabstract_en. php?cdjournal=pjab1945& cdvol=41& noissue=7& startpage=618). Proceedings of theJapan Academy 41(7): 618–623.

[13] Okada, Y.K. 1965. Rules of arm-branching in Japanese octopuses with branched arms (http:/ / www. journalarchive. jst. go. jp/ english/jnlabstract_en. php?cdjournal=pjab1945& cdvol=41& noissue=7& startpage=624). Proceedings of the Japan Academy 41(7): 624–629.

[14] Monster octopi with scores of extra tentacles (http:/ / pinktentacle. com/ 2008/ 07/ monster-octopi-with-scores-of-extra-tentacles/ ). PinkTentacle, July 18, 2008.

[15] Okada, Y.K. 1937. An occurrence of branched arms in the decapod cephalopod, Sepia esculenta Hoyle. Annotated Zoology of Japan 17:93–94.

Hectocotylus 93

Hectocotylus

Lateral view of adult male Tremoctopus violaceuswith hectocotylus

[[file:Ocythoe tuberculatahectocotylus.jpg|thumb|right

Detail of the hectocotylus of Ocythoe tuberculata]][[file:Haliphronatlanticus hectocotylus.jpg|thumb|right

Hectocotylus of a youngHaliphron atlanticus]]

A hectocotylus is one of the arms of the male of most kinds of cephalopods that is modified in various ways toeffect the fertilization of the female's eggs. It is a specialized, extended muscular hydrostat used to storespermatophores, the male gametophore. Males generally form a new hectocotylus in each new season.

Hectocotylus 94

The shape of the tip of the hectocotylus has been much used in octopod systematics. In many species it isconsiderably elaborated. However, in the males of some species, such as the Seven-arm Octopus (Haliphronatlanticus), the hectocotylus develops in an inconspicuous sac in front of the right eye that gives the male theappearance of having only seven arms.The term is also used to specifically refer to the greatly modified arm of Argonauta and allied genera. In argonauts,the male transfers the spermatophores to the female by putting its hectocotylus into a cavity in the mantle of thefemale. This mantle cavity is known as the pallial cavity. This is the only contact the male and female have witheach other during copulation, and it can be at a distance. During copulation, the hectocotylus breaks off from themale. The funnel-mantle locking apparatus on the hectocotylus keeps it lodged in the pallial cavity of the female.The name hectocotylus was devised by Georges Cuvier, who first found one embedded in the mantle of a femaleargonaut; supposing it to be a parasitic worm, Cuvier gave it a generic name. The hectocotyl arm was first describedin the biological works of Aristotle, and it was widely disbelieved until its rediscovery in the nineteenth century.[1] [2]

Rare examples of double and bilateral hectocotylization have been recorded in incirrate octopuses.[3] [4]

References[1] Thompson, Darcy Wentworth. 1913. On Aristotle as a biologist, with a prooemion on Herbert Spencer. Being the Herbert Spencer Lecture

before the University of Oxford, on February 14, 1913. Oxford University Press.[2] Nixon M. & J.Z. Young J.Z. 2003. The brains and lives of Cephalopods. Oxford University Press.[3] Robson, G.C. 1929. On a case of bilateral hectocotylization in Octopus rugosus. Journal of Zoology 99(1): 95–97.

doi:10.1111/j.1469-7998.1929.tb07690.x[4] Palacio, F.J. 1973. On the double hectocotylization of octopods. (http:/ / ia311216. us. archive. org/ 2/ items/ nautilus87amer/ nautilus87amer.

pdf)PDF The Nautilus 87: 99–102.

Tentacle

Cuttlefish with 2 tentacles and 8arms

A tentacle or bothrium (plural: bothria) is one of usually two or moreelongated flexible organs present in animals, especially invertebrates. The termmay also refer to the hairs of the leaves of some insectivorous plants. Usually,tentacles are used for feeding, feeling and grasping. Anatomically, they work likeother muscular hydrostats.

Tentacles in animals

Invertebrates

The phylum Mollusca includes many species with muscular hydrostats in theform of tentacles and arms. Octopuses do not have tentacles but rather have eightarms. Tentacles are distinguished in this context as being longer than arms, withsuckers at their tips only. Squid and cuttlefish have eight arms like octopuses,and two extra flexible tentacles.

The tentacles of the Giant Squid and Colossal Squid have powerful suckers andpointed teeth at the ends. The teeth of the Giant Squid resemble bottle caps, andfunction like small, circular saws; while the tentacles of the Colossal Squid wield two long rows of swiveling,tri-pointed hooks.

Tentacle 95

Front view of land snail showing upper and lowersets of tentacles

Abalone showing pallial tentacles

Snails are another class of Mollusca.They have less elaborate tentacles thanthe Cephalopods. Pulmonate landsnails usually have two sets oftentacles on the head: the upper pairhave an eye at the end; the lower pairare for olfaction. Both pairs are fullyretractable. Some marine snails such asthe abalone and the top snails,Trochidae have numerous smalltentacles around the edge of themantle. These are known as pallialtentacles.

Cnidarians, which include amongothers the jellyfishes, are anotherphylum with many tentacledspecimens. Cnidarians often have hugenumbers of cnidocytes on theirtentacles. Cnidocytes are cellscontaining a coiled thread-likestructure called a nematocyst, fired at

potential prey.

Many species of the jellyfishlike ctenophores have two tentacles, while some have none. Their tentacles haveadhesive structures called colloblasts or lasso cells. These cells burst open when prey comes in contact with thetentacle; sticky threads released from each of the colloblasts then captures food.

The tentacles of the Lion's mane jellyfish can reach 120 feet (37 meters).Bryozoa (Moss animals) are tiny creatures with a ring of tentacles surrounding the mouth.

Tentacle 96

AmphibiansSome wormlike amphibians have tentacles. The caecilians have two tentacles at their heads, which are probably usedfor smell.

MammalsThe star-nosed mole, Condylura cristata, possesses nasal tentacles which are mobile and extremely sensitive,helping the animal to find its way about the burrow and detect prey.

Tentacles in plants

Leaf and tentacle movement onDrosera capensis

In carnivorous plants, tentacles refer to the stalked glands of the upper surface ofthe leaves.

On a sundew plant, they are hairlike projections with a drop of nectar-like gluewhich attract insects. When an insect is captured, the tentacles bend inward andthe leaf rolls together as shown in the picture. The tentacles then secrete enzymesto dissolve and digest the insect.

External links

• Difference between arms and tentacles [1]

References[1] http:/ / www. cephbase. utmb. edu/ TCP/ faq/ TCPfaq2b. cfm?ID=50

Dactylus 97

DactylusThe dactylus is the tip region of the tentacular club of cephalopods and of the leg of some crustaceans (see arthropodleg). In cephalopods, the dactylus is narrow and often characterized by the asymmetrical placement of suckers (i.e.,the ventral expansion of the club) and the absence of a dorsal protective membrane. In crustaceans, the dactylus isthe seventh and terminal segment of their thoracic appendages. In certain instances the dactylus, together with thepropodus, form the claw.The term dactylus means "finger" in Greek.

References

Cephalopod eye

VertebrateOctopusVertebrates and octopuses developed the camera eye independently. In the vertebrate version the nerve fibers pass in front of theretina, and there is a blind spot where the nerves pass through the retina. In the vertebrate example, 4 represents the blind spot,which is notably absent from the octopus eye. In vertebrates, 1 represents the retina and 2 is the nerve fibers, including the opticnerve (3), whereas in the octopus eye, 1 and 2 represent the nerve fibers and retina respectively.

Cephalopods, as active marine predators, possess sensory organs specialized for use in aquatic conditions.[1] Theyhave a camera-type eye, which consists of a lens projecting an image onto a retina. Unlike the vertebrate camera eye,the cephalopods' form as invaginations of the body surface (rather than outgrowths of the brain), and consequentlythey lack a cornea. Unlike the vertebrate eye, a cephalopod eye is focused through movement, much like the lens of acamera or telescope, rather than changing shape as the lens in the human eye does. The eye is approximatelyspherical, as is the lens, which is fully internal.[2]

Cephalopod eye 98

Eye of Bathyteuthis sp.

The crystalins used in the lens appear to have developed independentlyfrom vertebrate crystalins, suggesting a homoplasious origin of thelens.[3]

Most cephalopods possess complex extraocular muscle systems thatallow for very fine control over the gross positioning of the eyes.Octopuses possess an autonomic response that maintains theorientation of their pupils such that they are always horizontal.[1]

Polarized light

It has been documented that several types of cephalopods, mostnotably squid and octopuses, and potentially cuttlefish, have eyes that can distinguish the orientation of polarizedlight. This sensitivity is due to the orthogonal organization of neighboring photoreceptors. It is theorized that thisability plays a role in communication among the color-changing cephalopods.[4]

Cephalopod eye 99

References[1] Budelmann BU. "Cephalopod sense organs, nerves and the brain: Adaptations for high performance and life style." Marine and Freshwater

Behavior and Physiology. Vol 25, Issue 1-3, Page 13-33.[2] Yamamoto, M. (Feb 1985). "Ontogeny of the visual system in the cuttlefish, Sepiella japonica. I. Morphological differentiation of the visual

cell". The Journal of Comparative Neurology 232 (3): 347–361. doi:10.1002/cne.902320307. ISSN 0021-9967. PMID 2857734.[3] SAMIR K. BRAHMA1 (1978). "Ontogeny of lens crystallins in marine cephalopods" (http:/ / dev. biologists. org/ cgi/ reprint/ 46/ 1/ 111.

pdf). Embryol. Exp. Morph. Vol. 46,pp. 111-118, 46: 111–8. PMID 359745. .[4] Shashar N, Rutledge P, and Cronin T. "Polarization vision in cuttlefish in a concealed communication channel?" Journal of Experimental

Biology, Vol 199, Issue 9 2077-2084

Chromatophore

Zebrafish chromatophores mediate backgroundadaptation on exposure to dark (top) and light

environments (bottom).

Chromatophores are pigment-containing and light-reflecting cellsfound in amphibians, fish, reptiles, crustaceans, and cephalopods. Theyare largely responsible for generating skin and eye colour incold-blooded animals and are generated in the neural crest duringembryonic development. Mature chromatophores are grouped intosubclasses based on their colour (more properly "hue") under whitelight: xanthophores (yellow), erythrophores (red), iridophores(reflective / iridescent), leucophores (white), melanophores(black/brown) and cyanophores (blue). The term can also refer tocoloured, membrane associated vesicles found in some forms ofphotosynthetic bacteria.

Some species can rapidly change colour through mechanisms thattranslocate pigment and reorient reflective plates withinchromatophores. This process, often used as a type of camouflage, iscalled physiological colour change. Cephalopods such as octopus havecomplex chromatophore organs controlled by muscles to achieve this,while vertebrates such as chameleons generate a similar effect by cellsignaling. Such signals can be hormones or neurotransmitters and maybe initiated by changes in mood, temperature, stress or visible changesin local environment.

Unlike cold-blooded animals, mammals and birds have only one classof chromatophore-like cell type: the melanocyte. The cold-blooded equivalent, melanophores, are studied byscientists to understand human disease and used as a tool in drug discovery.

ClassificationInvertebrate pigment-bearing cells were first described as chromoforo in an Italian science journal in 1819.[1] Theterm chromatophore was adopted later as the name for pigment bearing cells derived from the neural crest ofcold-blooded vertebrates and cephalopods. The word itself comes from the Greek words khrōma (χρωμα) meaning"color," and phoros (φορος) meaning "bearing". In contrast, the word chromatocyte (cyte or κυτε being Greek for"cell") was adopted for the cells responsible for colour found in birds and mammals. Only one such cell type, themelanocyte, has been identified in these animals.It wasn't until the 1960s that the structure and colouration of chromatophores were understood well enough to allow the development of a system of sub-classification based on their appearance. This classification system persists to this day even though more recent studies have revealed that certain biochemical aspects of the pigments may be

Chromatophore 100

more useful to a scientific understanding of how the cells function.[2]

Color-producing molecules fall into two distinct classes: biochromes and schemochromes.[3] The biochromes includetrue pigments, such as carotenoids and pteridines. These pigments selectively absorb parts of the visible lightspectrum that makes up white light while permitting other wavelengths to reach the eye of the observer.Schemochromes, also known as "structural colors", produce coloration by reflecting some wavelengths (colors) oflight and transmitting others, by causing light waves to interfere within the structure or by scattering light which fallsupon them.While all chromatophores contain pigments or reflecting structures (except when there has been a genetic mutationresulting in a disorder like albinism), not all pigment containing cells are chromatophores. Haem, for example, is abiochrome responsible for the red appearance of blood. It is primarily found in red blood cells (erythrocytes), whichare generated in bone marrow throughout the life of an organism, rather than being formed during embryologicaldevelopment. Therefore erythrocytes are not classified as chromatophores.

A veiled chameleon, Chamaeleo calyptratus.Structural green and blue colors are generated byoverlaying chromatophore types to reflect filtered

light.

Xanthophores and erythrophores

Chromatophores that contain large amounts of yellow pteridinepigments are named xanthophores; those with a preponderance ofred/orange carotenoids are termed erythrophores.[2] Pteridine andcarotenoid containing vesicles are sometimes found within the samecell, in which case the overall colour depends on the ratio of red andyellow pigments.[4] Therefore, the distinction between thesechromatophore types is not always clear.

The capacity to generate pteridines from guanosine triphosphate is afeature common to most chromatophores, but xanthophores appear tohave supplemental biochemical pathways that result in an excessaccumulation of yellow pigment. In contrast, carotenoids aremetabolised from the diet and transported to erythrophores. This wasfirst demonstrated by rearing normally green frogs on a diet ofcarotene-restricted crickets. The absence of carotene in the frogs' diet meant the red/orange carotenoid colour 'filter'was not present in their erythrophores. This resulted in the frogs appearing blue in colour, instead of green.[5]

Iridophores and leucophoresIridophores, sometimes also called guanophores, are pigment cells that reflect light using plates of crystallinechemochromes made from guanine.[6] When illuminated they generate iridescent colors because of the diffraction oflight within the stacked plates. Orientation of the schemochrome determines the nature of the colour observed.[7] Byusing biochromes as coloured filters, iridophores create an optical effect known as Tyndall or Rayleigh scattering,producing bright blue or green colors.[8]

A related type of chromatophore, the leucophore, is found in some fish, particularly in the tapetum lucidum. Likeiridophores, they utilize crystalline purines (often guanine) to reflect light. Unlike iridophores, however, leucophoreshave more organized crystals which reduce diffraction. Given a source of white light, they produce a white shine. Aswith xanthophores and erythrophores, in fish the distinction between iridophores and leucophores is not alwaysobvious, but generally iridophores are considered to generate iridescent or metallic colors while leucophores producereflective white hues.[8]

Chromatophore 101

Melanophores

At the bottom a mutant zebrafish larva that failsto synthesise melanin in its melanophores, at the

top a non-mutant, wildtype larva.

Melanophores contain eumelanin, a type of melanin, that appears blackor dark brown because of its light absorbing qualities. It is packaged invesicles called melanosomes and distributed throughout the cell.Eumelanin is generated from tyrosine in a series of catalysed chemicalreactions. It is a complex chemical containing units of dihydroxyindoleand dihydroxyindole-2-carboxylic acid with some pyrrole rings.[9] Thekey enzyme in melanin synthesis is tyrosinase. When this protein isdefective, no melanin can be generated resulting in certain types ofalbinism. In some amphibian species there are other pigmentspackaged alongside eumelanin. For example, a novel deep (wine) redcoloured pigment was identified in the melanophores ofphyllomedusine frogs.[10] This was subsequently identified aspterorhodin, a pteridine dimer that accumulates around eumelanin core, and it is also present in a variety of tree frogspecies from Australia and Papua New Guinea. While it is likely that other lesser studied species have complexmelanophore pigments, it is nevertheless true that the majority of melanophores studied to date do contain eumelaninexclusively.[11]

Humans have only one class of pigment cell, the mammalian equivalent of melanophores, to generate skin, hair andeye colour. For this reason, and because the large number and contrasting colour of the cells usually make them veryeasy to visualise, melanophores are by far the most widely studied chromatophore. However, there are differencesbetween the biology of melanophores and melanocytes. In addition to eumelanin, melanocytes can generate ayellow/red pigment called phaeomelanin.

Dendrobates pumilio, a poison dart frog. Somebrightly coloured species have unusualchromatophores of unknown pigment

composition.

Cyanophores

In 1995 it was demonstrated that the vibrant blue colors in some typesof mandarinfish are not generated by schemochromes. Instead, a cyanbiochrome of unknown chemical nature is responsible.[8] This pigment,found within vesicles in at least two species of callionymid fish, ishighly unusual in the animal kingdom, as all other blue colourings thusfar investigated are schemochromatic. Therefore a novelchromatophore type, the cyanophore, was proposed. Although theyappear unusual in their taxonomic restriction, there may becyanophores (as well as further unusual chromatophore types) in otherfish and amphibians. For example, bright coloured chromatophoreswith undefined pigments have been observed in both poison dart frogsand glass frogs.[12]

Pigment translocationMany species have the ability to translocate the pigment inside chromatophores, resulting in an apparent change incolour. This process, known as physiological colour change, is most widely studied in melanophores, since melaninis the darkest and most visible pigment. In most species with a relatively thin dermis, the dermal melanophores tendto be flat and cover a large surface area. However, in animals with thick dermal layers, such as adult reptiles, dermalmelanophores often form three-dimensional units with other chromatophores. These dermal chromatophore units(DCU) consist of an uppermost xanthophore or erythrophore layer, then an iridophore layer, and finally a basket-likemelanophore layer with processes covering the iridophores.[13]

Chromatophore 102

Both types of dermal melanophores are important in physiological colour change. Flat dermal melanophores willoften overlay other chromatophores so when the pigment is dispersed throughout the cell the skin appears dark.When the pigment is aggregated towards the centre of the cell, the pigments in other chromatophores are exposed tolight and the skin takes on their hue. Similarly, after melanin aggregation in DCUs, the skin appears green throughxanthophore (yellow) filtering of scattered light from the iridophore layer. On the dispersion of melanin, the light isno longer scattered and the skin appears dark. As the other biochromatic chomatophores are also capable of pigmenttranslocation, animals with multiple chromatophore types can generate a spectacular array of skin colors by makinggood use of the divisional effect.[14] ,[15]

A single zebrafish melanophore imaged bytime-lapse photography during pigment

aggregation

The control and mechanics of rapid pigment translocation has beenwell studied in a number of different species, particularly amphibiansand teleost fish.[16] ,[8] It has been demonstrated that the process can beunder hormonal, neuronal control or both. Neurochemicals that areknown to translocate pigment include noradrenaline, through itsreceptor on the surface on melanophores.[17] The primary hormonesinvolved in regulating translocation appear to be the melanocortins,melatonin and melanin concentrating hormone (MCH), that areproduced mainly in the pituitary, pineal gland and hypothalamusrespectively. These hormones may also be generated in a paracrinefashion by cells in the skin. At the surface of the melanophore thehormones have been shown to activate specific G-protein coupledreceptors that, in turn, transduce the signal into the cell. Melanocortinsresult in the dispersion of pigment, while melatonin and MCH results

in aggregation.[18]

Numerous melanocortin, MCH and melatonin receptors have been identified in fish[19] and frogs,[20] including ahomologue of MC1R,[21] a melanocortin receptor known to regulate skin and hair colour in humans.[22] It has beendemonstrated that MC1R is required in zebrafish for dispersion of melanin.[23] Inside the cell, cyclic adenosinemonophosphate (cAMP) has been shown to be an important second messenger of pigment translocation. Through amechanism not yet fully understood, cAMP influences other proteins such as protein kinase A to drive molecularmotors carrying pigment containing vesicles along both microtubules and microfilaments.[24] ,[25] ,[26]

Background adaptationMost fish, reptiles and amphibians undergo a limited physiological colour change in response to a change inenvironment. This type of camouflage, known as background adaptation, most commonly appears as a slightdarkening or lightening of skin tone to approximately mimic the hue of the immediate environment. It has beendemonstrated that the background adaptation process is vision dependent (it appears the animal needs to be able tosee the environment to adapt to it),[27] and that melanin translocation in melanophores is the major factor in colourchange.[18] Some animals, such as chameleons and anoles, have a highly developed background adaptation responsecapable of generating a number of different colors very rapidly. They have adapted the capability to change colour inresponse to temperature, mood, stress levels and social cues, rather than to simply mimic their environment.

Chromatophore 103

Development

Transverse section of a developing vertebrate trunk showing thedorsolateral (red) and ventromedial (blue) routes of chromatoblast

migration

During vertebrate embryonic development,chromatophores are one of a number of cell typesgenerated in the neural crest, a paired strip of cellsarising at the margins of the neural tube. These cellshave the ability to migrate long distances, allowingchromatophores to populate many organs of the body,including the skin, eye, ear and brain. Leaving theneural crest in waves, chromatophores take either adorsolateral route through the dermis, entering theectoderm through small holes in the basal lamina, or aventromedial route between the somites and the neuraltube. The exception to this is the melanophores of theretinal pigmented epithelium of the eye. These are notderived from the neural crest, instead an outpouchingof the neural tube generates the optic cup which, inturn, forms the retina.

When and how multipotent chromatophore precursorcells (called chromatoblasts) develop into theirdaughter subtypes is an area of ongoing research. It isknown in zebrafish embryos, for example, that by 3days after fertilization each of the cell classes found in the adult fish — melanophores, xanthophores and iridophores— are already present. Studies using mutant fish have demonstrated that transcription factors such as kit, sox10 andmitf are important in controlling chromatophore differentiation.[28] If these proteins are defective, chromatophoresmay be regionally or entirely absent, resulting in a leucistic disorder.

Practical applicationsIn addition to basic research into better understanding of chromatophores themselves, the cells are used for appliedresearch purposes. For example, zebrafish larvae are used to study how chromatophores organise and communicateto accurately generate the regular horizontal striped pattern as seen in adult fish.[29] This is seen as a useful modelsystem for understanding patterning in the evolutionary developmental biology field. Chromatophore biology hasalso been used to model human condition or disease, including melanoma and albinism. Recently the generesponsible for the melanophore-specific golden zebrafish strain, Slc24a5, was shown to have a human equivalentthat strongly correlates with skin colour.[30]

Chromatophores are also used as a biomarker of blindness in cold-blooded species, as animals with certain visualdefects fail to background adapt to light environments.[27] Human homologues of receptors that mediate pigmenttranslocation in melanophores are thought to be involved in processes such as appetite suppression and tanning,making them attractive targets for drugs.[21] Therefore pharmaceutical companies have developed a biological assayfor rapidly identifying potential bioactive compounds using melanophores from the African clawed frog.[31] Otherscientists have developed techniques for using melanophores as biosensors,[32] and for rapid disease detection (basedon the discovery that pertussis toxin blocks pigment aggregation in fish melanophores).[33] Potential militaryapplications of chromatophore mediated colour changes have been proposed, mainly as a type of activecamouflage.[34]

Chromatophore 104

Cephalopod chromatophores

An infant cuttlefish, using background adaptation to mimic the local environment

Coleoid cephalopods have complexmulticellular organs which they use tochange colour rapidly. This is most notablein brightly coloured squid, cuttlefish andoctopuses. Each chromatophore unit iscomposed of a single chromatophore celland numerous muscle, nerve, glial andsheath cells.[35] Inside the chromatophorecell, pigment granules are enclosed in anelastic sac, called the cytoelastic sacculus.To change colour the animal distorts thesacculus form or size by muscularcontraction, changing its translucency,reflectivity or opacity. This differs from themechanism used in fish, amphibians andreptiles, in that the shape of the sacculus isbeing changed rather than a translocation of pigment vesicles within the cell. However a similar effect is achieved.

Octopuses can operate chromatophores in complex, wavelike chromatic displays, resulting in a variety of rapidlychanging colour schemes. The nerves that operate the chromatophores are thought to be positioned in the brain in apattern similar to that of the chromatophores they each control. This means the pattern of colour change matches thepattern of neuronal activation. This may explain why, as the neurons are activated one after another, the colourchange occurs in waves.[36] Like chameleons, cephalopods use physiological colour change for social interaction.They are also among the most skilled at background adaptation, having the ability to match both the colour and thetexture of their local environment with remarkable accuracy.

BacteriaChromatophores are also found in membranes of phototrophic bacteria. Used primarily for photosynthesis, theycontain bacteriochlorophyll pigments and carotenoids.[37] In purple bacteria, such as Rhodospirillum rubrum thelight-harvesting proteins are intrinsic to the chromatophore membranes. However, in green sulfur bacteria they arearranged in specialised antenna complexes called chlorosomes.[38]

See also• Chromophore

Chromatophore 105

Notes[1] Sangiovanni G. Descrizione di un particolare sistema di organi cromoforo espansivo-dermoideo e dei fenomeni che esso produce, scoperto

nei molluschi cefaloso. G. Enciclopedico Napoli. 1819; 9:1–13.[2] Bagnara JT. (1966). "Cytology and cytophysiology of non-melanophore pigment cells". Int Rev Cytol 20: 173–205.

doi:10.1016/S0074-7696(08)60801-3. PMID 5337298.[3] Fox, DL. Animal Biochromes and Structural Colors: Physical, Chemical, Distributional & Physiological Features of Colored Bodies in the

Animal World. University of California Press, Berkeley, 1976. ISBN 0520023471[4] Matsumoto J (1965). "Xiphophorus helleri" (http:/ / www. pubmedcentral. nih. gov/ articlerender. fcgi?tool=pmcentrez& artid=2106771). J

Cell Biol 27 (3): 493–504. PMID 5885426. PMC 2106771.[5] Bagnara JT. Comparative Anatomy and Physiology of Pigment Cells in Nonmammalian Tissues. In: The Pigmentary System: Physiology and

Pathophysiology, Oxford University Press, 1998. ISBN 0-19-509861-7[6] Taylor JD. (1969). "The effects of intermedin on the ultrastructure of amphibian iridophores". Gen Comp Endocrinol 12 (3): 405–16.

doi:10.1016/0016-6480(69)90157-9. PMID 5769930.[7] Morrison RL. (1995). "A transmission electron microscopic (TEM) method for determining structural colors reflected by lizard iridophores".

Pigment Cell Res 8 (1): 28–36. doi:10.1111/j.1600-0749.1995.tb00771.x. PMID 7792252.[8] Fujii R. (2000). "The regulation of motile activity in fish chromatophores". Pigment Cell Res 13 (5): 300–19.

doi:10.1034/j.1600-0749.2000.130502.x. PMID 11041206.[9] Ito, S; Wakamatsu, K. (2003). "Quantitative analysis of eumelanin and pheomelanin in humans, mice, and other animals: a comparative

review". Pigment Cell Res 16 (5): 523–31. doi:10.1034/j.1600-0749.2003.00072.x. PMID 12950732.[10] Bagnara, J.T.; Taylor, JD; Prota, G (1973). "Color changes, unusual melanosomes, and a new pigment from leaf frogs" (http:/ / www.

sciencemag. org/ cgi/ content/ abstract/ 182/ 4116/ 1034). Science 182 (4): 1034–5. doi:10.1126/science.182.4116.1034. PMID 4748673. .[11] Bagnara, J.T. (2003). "Enigmas of Pterorhodin, a Red Melanosomal Pigment of Tree Frogs" (http:/ / www. ingentaconnect. com/ content/

mksg/ pcr/ 2003/ 00000016/ 00000005/ art00014). Pigment Cell Research 16 (5): 510–516. doi:10.1034/j.1600-0749.2003.00075.x.PMID 12950730. .

[12] Schwalm PA, Starrett PH, McDiarmid RW (1977). "Infrared reflectance in leaf-sitting neotropical frogs". Science 196 (4295): 1225–7.doi:10.1126/science.860137. PMID 860137.

[13] Bagnara JT, Taylor JD, Hadley ME (1968). "[http://www.jcb.org/cgi/reprint/38/1/67 "The dermal chromatophore unit" (http:/ / www.pubmedcentral. nih. gov/ articlerender. fcgi?tool=pmcentrez& artid=2107474). J Cell Biol 38 (1): 67–79. PMID 5691979. PMC 2107474.

[14] Palazzo RE, Lynch TJ, Lo SJ, Taylor JD, Tchen TT (1989). "Rearrangements of pterinosomes and cytoskeleton accompanying pigmentdispersion in goldfish xanthophores". Cell Motil Cytoskeleton 13 (1): 9–20. doi:10.1002/cm.970130103. PMID 2543509.

[15] Porras MG, De Loof A, Breuer M, Aréchiga H (2003). "Procambarus clarkii". Peptides 24 (10): 1581–9. PMID 14706537.[16] Deacon SW, Serpinskaya AS, Vaughan PS, Lopez Fanarraga M, Vernos I, Vaughan KT, Gelfand VI (2003). "Dynactin is required for

bidirectional organelle transport." (http:/ / www. jcb. org/ cgi/ content/ full/ 160/ 3/ 297). The Journal of cell biology 160 (3): 297–301.doi:10.1083/jcb.200210066. PMID 12551954. PMC 2172679. .

[17] Aspengren S, Sköld HN, Quiroga G, Mårtensson L, Wallin M (2003). "Noradrenaline- and melatonin-mediated regulation of pigmentaggregation in fish melanophores". Pigment Cell Res 16 (1): 59–64. doi:10.1034/j.1600-0749.2003.00003.x. PMID 12519126.

[18] Logan DW, Burn SF, Jackson IJ (2006). "Regulation of pigmentation in zebrafish melanophores". Pigment Cell Res 19 (3): 206–13.doi:10.1111/j.1600-0749.2006.00307.x. PMID 16704454.

[19] Logan DW, Bryson-Richardson RJ, Taylor MS, Currie P, Jackson IJ (2003). "Sequence characterization of teleost fish melanocortinreceptors". Ann N Y Acad Sci 994: 319–30. doi:10.1111/j.1749-6632.2003.tb03196.x. PMID 12851332.

[20] Sugden D, Davidson K, Hough KA, Teh MT (2004). "Melatonin, melatonin receptors and melanophores: a moving story". Pigment Cell Res17 (5): 454–60. doi:10.1111/j.1600-0749.2004.00185.x. PMID 15357831.

[21] Logan DW, Bryson-Richardson RJ, Pagán KE, Taylor MS, Currie PD, Jackson IJ (2003). "The structure and evolution of the melanocortinand MCH receptors in fish and mammals". Genomics 81 (2): 184–91. doi:10.1016/S0888-7543(02)00037-X. PMID 12620396.

[22] Valverde P, Healy E, Jackson I, Rees JL, Thody AJ (1995). "Variants of the melanocyte-stimulating hormone receptor gene are associatedwith red hair and fair skin in humans". Nat Genet 11 (3): 328–30. doi:10.1038/ng1195-328. PMID 7581459.

[23] Richardson J, Lundegaard PR, Reynolds NL, Dorin JR, Porteous DJ, Jackson IJ, Patton EE (2008). "mc1r Pathway regulation of zebrafishmelanosome dispersion". Zebrafish 5 (4): 289–95. doi:10.1089/zeb.2008.0541. PMID 19133827.

[24] Snider J, Lin F, Zahedi N, Rodionov V, Yu CC, Gross SP (2004). "Intracellular actin-based transport: how far you go depends on how oftenyou switch." (http:/ / www. pnas. org/ cgi/ content/ full/ 101/ 36/ 13204). Proceedings of the National Academy of Sciences of the UnitedStates of America 101 (36): 13204–9. doi:10.1073/pnas.0403092101. PMID 15331778. PMC 516548. .

[25] Rodionov VI, Hope AJ, Svitkina TM, Borisy GG (1998). "Functional coordination of microtubule-based and actin-based motility inmelanophores." (http:/ / www. sciencedirect. com/ science?_ob=ArticleURL& _udi=B6VRT-4D04MK2-4& _user=10& _coverDate=01/ 29/1998& _alid=412398039& _rdoc=1& _fmt=full& _orig=search& _qd=1& _cdi=6243& _sort=d& _docanchor=& view=c&_acct=C000050221& _version=1& _urlVersion=0& _userid=10& md5=53b4395208a20da195d9c1b3dbe0fe41& artImgPref=F). Currentbiology : CB 8 (3): 165–8. doi:10.1016/S0960-9822(98)70064-8. PMID 9443917. .

[26] Kashina AS, Semenova IV, Ivanov PA, Potekhina ES, Zaliapin I, Rodionov VI (2004). "Protein kinase A, which regulates intracellular transport, forms complexes with molecular motors on organelles." (http:/ / www. sciencedirect. com/ science?_ob=ArticleURL&

Chromatophore 106

_udi=B6VRT-4DMW0C4-11& _user=10& _coverDate=10/ 26/ 2004& _alid=412398862& _rdoc=1& _fmt=full& _orig=search& _qd=1&_cdi=6243& _sort=d& _docanchor=& view=c& _acct=C000050221& _version=1& _urlVersion=0& _userid=10&md5=96f1a14140773f1e898c1ef410db1cb9& artImgPref=F). Current biology : CB 14 (20): 1877–81. doi:10.1016/j.cub.2004.10.003.PMID 15498498. .

[27] Neuhauss SC. (2003). "Behavioral genetic approaches to visual system development and function in zebrafish" (http:/ / www3. interscience.wiley. com/ cgi-bin/ fulltext/ 101526009/ PDFSTART) (PDF). J Neurobiol 54 (1): 148–60. doi:10.1002/neu.10165. PMID 12486702. .

[28] Kelsh RN, Schmid B, Eisen JS (2000). "Genetic analysis of melanophore development in zebrafish embryos". Dev Biol 225 (2): 277–93.doi:10.1006/dbio.2000.9840. PMID 10985850.

[29] Kelsh RN (2004). "Genetics and evolution of pigment patterns in fish.". Pigment cell research / sponsored by the European Society forPigment Cell Research and the International Pigment Cell Society 17 (4): 326–36. doi:10.1111/j.1600-0749.2004.00174.x. PMID 15250934.

[30] Lamason RL, Mohideen MA, Mest JR, Wong AC, Norton HL, Aros MC, Jurynec MJ, Mao X et al. (2005). "SLC24A5, a putative cationexchanger, affects pigmentation in zebrafish and humans". Science 310 (5755): 1782–6. doi:10.1126/science.1116238. PMID 16357253.

[31] Jayawickreme CK, Sauls H, Bolio N, Ruan J, Moyer M, Burkhart W, Marron B, Rimele T et al. (1999). "Use of a cell-based, lawn formatassay to rapidly screen a 442,368 bead-based peptide library". J Pharmacol Toxicol Methods 42 (4): 189–97.doi:10.1016/S1056-8719(00)00083-6. PMID 11033434.

[32] Andersson TP, Filippini D, Suska A, Johansson TL, Svensson SP, Lundström I (2005). "Frog melanophores cultured on fluorescentmicrobeads: biomimic-based biosensing". Biosens Bioelectron 21 (1): 111–20. doi:10.1016/j.bios.2004.08.043. PMID 15967358.

[33] Karlsson JO, Andersson RG, Askelöf P, Elwing H, Granström M, Grundström N, Lundström I, Ohman L (1991). "The melanophoreaggregating response of isolated fish scales: a very rapid and sensitive diagnosis of whooping cough". FEMS Microbiol Lett 66 (2): 169–75.PMID 1936946.

[34] Lee I. Nanotubes for noisy signal processing: Adaptive Camouflage PhD Thesis. 2005; University of Southern California. Retrieved June2006 (http:/ / biron. usc. edu/ ~ianlee/ index_files/ thesis_ch5. pdf)PDF (799 KiB).

[35] Cloney RA, Florey E (1968). "Ultrastructure of cephalopod chromatophore organs.". Zeitschrift fur Zellforschung und mikroskopischeAnatomie (Vienna, Austria : 1948) 89 (2): 250–80. doi:10.1007/BF00347297. PMID 5700268.

[36] Demski LS (1992). "Chromatophore systems in teleosts and cephalopods: a levels oriented analysis of convergent systems.". Brain,behavior and evolution 40 (2-3): 141–56. doi:10.1159/000113909. PMID 1422807.

[37] Salton MR (1987). "Bacterial membrane proteins.". Microbiological sciences 4 (4): 100–5. PMID 3153178.[38] Frigaard NU, Bryant DA (2004). "Seeing green bacteria in a new light: genomics-enabled studies of the photosynthetic apparatus in green

sulfur bacteria and filamentous anoxygenic phototrophic bacteria.". Archives of microbiology 182 (4): 265–76.doi:10.1007/s00203-004-0718-9. PMID 15340781.

External links• Nature's Palette - how animals produce colour (http:/ / www. bioscience-explained. org/ EN1. 2/ pdf/ paletteEN.

pdf)PDF (1.20 MiB)• Video footage of octopus background adaptation (http:/ / www. funny-games. biz/ videos/ 78-octopus. html)• Video footage of squid chromatophore patterning (http:/ / www. gfai. de/ ~heinz/ historic/ biomodel/ squids/

squids. htm)• Tree of Life Web Project: Cephalopod Chromatophores (http:/ / tolweb. org/ tree/ eukaryotes/ animals/ mollusca/

cephalopoda/ glossary/ glossaryLichen/ chromatophoreLichen/ Chromatophore. html)

Mantle 107

Mantle

European Squid (Loligo vulgaris). The mantle isall that is visible behind the head: the outer body

wall and the fins are all part of the mantle.

The brightly coloured mantle of a Giant clamprotects it from bright sunlight.

The mantle (also known by the Latin word pallium meaning mantle,robe or cloak, adjective pallial) is a significant part of the anatomy ofmolluscs: it is the dorsal body wall which covers the visceral mass andusually protrudes in the form of flaps well beyond the visceral massitself.

In many, but by no means all, species of molluscs, the epidermis of themantle secretes calcium carbonate and conchiolin, and creates a shell.

The words mantle and pallium both originally meant cloak or cape, seemantle (vesture). This anatomical structure in molluscs often resemblesa cloak because in many groups the edges of the mantle extend farbeyond the main part of the body, forming flaps, double-layeredstructures which have been adapted for many different uses, includingfor example, the siphon.

The mantle cavity

The mantle cavity is a central feature of molluscan biology. This cavityis formed by the mantle skirt, a double fold of mantle which encloses awater space. This space contains the mollusc's gills, anus, osphradium,nephridiopores, and gonopores.

The mantle cavity functions as a respiratory chamber in all molluscs.In bivalves it is usually part of the feeding structure. In some mollusksthe mantle cavity is a brood chamber, and in cephalopods and somebivalves such as scallops, it is a locomotory organ.

The mantle is highly muscular. In cephalopods the contraction of the mantle is used to force water through a tubularsiphon, the hyponome, and this propels the animal very rapidly through the water. In other mollusks, it is used as akind of "foot" for locomotion.

Mantle 108

Formation of mollusc shellIn shelled molluscs, the mantle is what forms the shell, and what adds to the shell to increase its size and strength asthe animal grows. Shell material is secreted by the ectodermic (epithelial) cells of the mantle tissue.[1]

Mantle of gastropodsThe mantle of many gastropods is usually fully or partially hidden inside the gastropod shell.

The marine gastropod Cypraea chinensis, theChinese cowry, showing partially extended

mantle.

Cypraea chinensis with its mantle fullyextended.

The mantle of the land snail Indrellaampulla is off-white in color and it is partlyvisible under the shell. The head and foot

are red, and the foot fringe is off-white withnarrow black lines.

In species where the shell is small compared to the size of the body, more of the mantle shows. Shell-less slugs havethe mantle fully visible. The dorsal surface of the mantle is called the notum, while the ventral surface of the mantleis called the hyponotum. In the family Philomycidae, the mantle covers the whole back side of the body.[2]

The mantle and the head of this slug Bielziacoerulans is smooth, while the rest of the body is

tubercled.

Megapallifera mutabilis from Philomycidae shows enormouslydeveloped mantle

Mantle 109

Photo of Haliotis asinina with the shell removed.This drawing shows that the mantle (in gray)

covers the majority of the dorsal surface of theanimal.[3]

See also• Mollusc shell, which is formed by the mantle• Siphon (mollusc) which is a part of the mantle in some groups of mollusks

References[1] "integument (mollusks)."Encyclopædia Britannica. 2009. Encyclopædia Britannica 2006 Ultimate Reference Suite DVD[2] Tsai C.-L. & Wu S.-K. (2008). "A New Meghimatium Slug (Pulmonata: Philomycidae) from Taiwan". Zoological Studies 47(6): 759-766.

PDF (http:/ / zoolstud. sinica. edu. tw/ Journals/ 47. 6/ 759. pdf).[3] Daniel J Jackson, Carmel McDougall, Kathryn Green, Fiona Simpson, Gert Wörheide & Bernard M Degnan. 2006. http:/ / www.

biomedcentral. com/ 1741-7007/ 4/ 40 A rapidly evolving secretome builds and patterns a sea shell]. BMC Biology 2006, 4:4.0doi:10.1186/1741-7007-4-40.

Nidamental gland 110

Nidamental gland

Ventral view of the viscera of Chtenopteryx sicula, showing thepresence of the nidamental gland and accessory nidamental gland.

The nidamental gland is an internal organ found insome elasmobranchs and certain molluscs, includingcephalopods (specifically Decapodiformes andnautiluses) and gastropods.[1] [2] [3]

In cephalopods, the nidamental gland is a largeglandular structure found in the mantle cavity. Anaccessory nidamental gland may also be present.Nidamental glands are composed of lamellae whichsecrete egg cases or the gelatinous substancecomprising egg masses.[1]

References[1] Young, R.E., M. Vecchione & K.M. Mangold 1999. Cephalopoda Glossary (http:/ / tolweb. org/ accessory/

Cephalopoda_Glossary?acc_id=587). Tree of Life web project.[2] Prasad, R.R. (1948). "Observations on the Nidamental Glands of Hydrolagus colliei, Raja rhina and Platyrhinoidis triseriatus" (http:/ / www.

jstor. org/ pss/ 1438791). Copeia 1948 (1): 54–7. doi:10.2307/1438791. .[3] Bloodgood RA (1977). "The squid accessory nidamental gland: ultrastructure and association with bacteria" (http:/ / linkinghub. elsevier.

com/ retrieve/ pii/ 0040-8166(77)90016-7). Tissue Cell 9 (2): 197–208. PMID 906013. .

Siphon

A specimen of a venerid bivalve. The adductormuscles have been cut, the valves are gaping. Theinternal anatomy is visible, including the paired

siphons to the right

A siphon is an anatomical structure which is part of the soft parts ofaquatic molluscs in three classes: Gastropoda, Bivalvia andCephalopoda. In other words, a siphon is found in some saltwater andfreshwater snails, in some clams, and in octopus, squid and relatives.

Siphons are tube-like structures in which water flows (or more rarely inwhich air flows). In molluscs, the water flow is used for one or morepurposes such as locomotion, feeding, respiration, and reproduction.The siphon is part of the mantle of the mollusc, and the water flow isdirected to (or from) the mantle cavity.

A single siphon occurs in some gastropods. In those bivalves whichhave siphons, they are paired. In cephalopods, there is a single siphonor funnel which is known as a hyponome.

Siphon 111

The siphon of a large carnivorous marine volute,Cymbiola magnifica

The sea snail Nassarius tiarula is a scavenger.Siphon on the left

Melo amphora moving across coral at low tide.

In some (but not all) sea snails, marine gastropod molluscs, the animalhas an anterior extension of the mantle called a siphon, or inhalantsiphon, through which water is drawn into the mantle cavity and overthe gill for respiration.[1]

This siphon is a soft fleshy tube-like structure equipped withchemoreceptors which "smell" or "taste" the water, in order to hunt forfood.[2] [3] [4] Marine gastropods that have a siphon are either predatorsor scavengers.[5]

Although in gastropods the siphon functions perfectly well as a tube, itis not in fact a hollow organ, it is simply a flap of the mantle that isrolled into the shape of a tube.[1]

In many marine gastropods where the siphon is particularly long, the structure of the shell has been modified in orderto house and protect the soft tissue of the siphon. This shell modification is known as the siphonal canal. For agastropod whose shell has an exceptionally long siphonal canal, see Venus comb murex.

In the case of some other marine gastropod shells, such as the volute and the Nassarius pictured above, the shell hasa simple "siphonal notch" at the anterior edge of the aperture instead of a long siphonal canal.Aplysia gill and siphon withdrawal reflex is defensive reflex of Aplysia and it is valuable in neuroscience.

Siphon 112

Siphon as a snorkel

Pomacea canaliculata, seenthrough glass, has reached its

siphon up to the water surface tobreathe air

Engraving of Florida freshwater applesnailPomacea paludosa; siphon on lower right

Freshwater apple snails in the genera Pomacea and Pila have anextensible siphon made from a flap of the left mantle cavity. They usethis siphon in order to breathe air while they are submerged in waterwhich has a low oxygen content so they cannot effectively use theirgill.[6]

Apple snails use the siphon in a way that is reminiscent of a swimmerusing a snorkel, except that the apple snail's siphon can be retractedcompletely, or extended to various lengths as needed.[6]

For these freshwater snails, the siphon is an anti-predator adaptation. Itreduces their vulnerability to being attacked and eaten by birds becauseit enables the apple snails to breathe without having to come all theway up to the surface, where they are easily visible to predators.[6]

The shells of these freshwater snails have simple round apertures; thereis no special notch for the siphon.

Siphon 113

The paired siphons of bivalves

Three specimens of Panopea abrupta in aseafood tank; the paired siphons (or "necks") of

this species can be one meter long

Veneridae with siphons out

Drawing of the venerid Venus verrucosa showingpaired siphons (upper inhalant and lower exhalant

siphon), shell and foot.

Those bivalves that have siphons, have two of them. Not all bivalveshave siphons however: those that live on or above the substrate, as isthe case in scallops, oysters, etc, do not need them. Only those bivalvesthat burrow in sediment, and live buried in the sediment, need to usethese tube-like structures. The function of these siphons is to reach upto the surface of the sediment, so that the animal is able to respire,feed, and excrete, and also to reproduce.[7] [8]

The deeper a bivalve species lives in the sediment, the longer itssiphons are. Bivalves which have extremely long siphons, like theGeoducks pictured here, live very deeply buried, and are hard to dig upwhen clamming[9] .

Siphon 114

Diagramatic drawing of the inside of one valve ofa bivalve such as a venerid: pallial sinus on the

lower left, at the posterior end of the clam

Many bivalves that have siphons can withdraw them completely intothe shell when needed, but this is not true of all species. Bivalves thatcan withdraw the siphons into the shell have a "pallial sinus", a sort ofpocket, into which the siphons can fit when they are withdrawn, so thatthe two shell valves can close properly. The existence of this pocketshows even in an empty shell, as a visible indentation in the pallialline, a line which runs along parallel to the ventral margin of theshell.[10]

The bivalve's two siphons are situated at the posterior edge of themantle cavity.[11] There is an inhalant or incurrent siphon, and anexhalant or excurrent siphon.[12] The water is circulated by the actionof the gills. Usually water enters the mantle cavity through the inhalant

siphon, moves over the gills, and leaves through the exhalant siphon. The water current is utilized for respiration, butalso for filter feeding, excretion, and reproduction.

FeedingDepending on the species and family concerned, some bivalves utilize their inhalant siphon like the hose of avacuum cleaner, and actively suck up food particles from the marine substrate. Most other bivalves ingestmicroscopic phytoplankton as food from the general water supply, which enters via the inhalant siphon and reachesthe mouth after passing over the gill.[13]

Please also see pseudofeces.

The hyponome of cephalopods

Nautilus belauensis seen from the front, showingthe opening of the hyponome.

The hyponome or siphon is the organ used by cephalopods to expelwater, a function that produces a locomotive force. The hyponomedeveloped from the foot of the molluscan ancestor.[14]

Water enters the mantle cavity around the sides of the funnel, andsubsequent contraction of the hyponome expands and then contracts,expelling a jet of water.In most cephalopods, such as octopus, squid, and cuttlefish, thehyponome is a muscular tube. The hyponome of the nautilus differshowever, in that it is a one-piece flap that is folded over. The presenceor form of the ammonite hyponome is unknown.[15]

Siphon 115

References[1] Örstan A. 13 April 2007. Melongena's siphon (http:/ / snailstales. blogspot. com/ 2007/ 04/ melongenas-siphon. html). Snail's Tales.[2] Abbott, RT and Sandstrom, GF (2001) Seashells of North America (http:/ / books. google. co. nz/ books?id=i94pFP-Wb8YC& pg=PA142&

lpg=PA142& dq=Siphon+ taste+ smell+ sea|marine+ snail|gastropod& source=web& ots=3BE3ifHUL3&sig=bwd0bZmDja2tDF-aS-m9Ug9wGY4& hl=en& sa=X& oi=book_result& resnum=9& ct=result) Macmillan. ISBN 9781582381251 Nassamud snails, p. 142.

[3] Cone snails (http:/ / www. mauioceancenter. com/ index. php?id=11& ss=0& page=marine& content=marine_detail& cat=2& CRid=21&limitstart=0). Hawaiian Marine Life. Accessed 18 November 2008.

[4] Respiratory system (http:/ / www. applesnail. net/ content/ anatomy/ respiration. php). The apple snail website. Accessed 18 November 2008.[5] Los Marineros Marine Life. Caption Mollusca. (http:/ / mrt. tripod. com/ marinelife. html#anchor135905) Accessed 21 November 2008.[6] Respiratory system (http:/ / www. applesnail. net/ content/ anatomy/ respiration. php). The apple snail website, http:/ / www. applesnail. net,

accessed 26 February 2009.[7] Bales, SL and Venable, S. 2007. Natural Histories: Stories from the Tennessee Valley (http:/ / books. google. co. nz/

books?id=aIZmfXFGydwC& pg=PA66& lpg=PA66& dq=siphon+ bivalve+ reproduction& source=web& ots=2HSA3zeFIs&sig=WUMp4q52BuiZKw6Iz7Xlv1Z2XtI& hl=en& sa=X& oi=book_result& resnum=17& ct=result). University of Tennessee Press. ISBN9781572335615. p. 66.

[8] Barnes, H. (Ed.) 2008. Oceanography and Marine Biology (http:/ / books. google. co. nz/ books?id=h2BZZcjAdnkC& pg=PA77&lpg=PA77& dq=siphon+ bivalve+ reproduction& source=web& ots=0jd1EPDq19& sig=kFZiiEIDFAiYfXT9AONg9UD-9FQ& hl=en&sa=X& oi=book_result& resnum=22& ct=result) CRC Press. ISBN 9781420065749. p. 77.

[9] Washington Department of Fish and Wildlife. 2000. WDFW - Shellfish: Geoduck clam (http:/ / www. wdfw. wa. gov/ fish/ shelfish/ beachreg/2clam. htm). accessed 26 February 2009.

[10] M. Alan Kazlev. Palaeos Metazoa: Mollusca: Bivalvia: Bivalve Glossary (http:/ / www. palaeos. com/ Invertebrates/ Molluscs/ Bivalvia/bivalgloss. html). Page uploaded 11 January 2003, last change 7 July 2007, accessed 26 February 2009.

[11] Anatomy of a Bivalve (http:/ / www. marietta. edu/ ~biol/ mussels/ anatomy. html). accessed 26 February 2009.[12] Siphons (http:/ / www. marietta. edu/ ~biol/ mussels/ 11. html). accessed 26 February 2009.[13] S. Peter Dance. 1977. The Encyclopedia of Shells. Blandford Press Limited, Poole, Dorset, ISBN 0-7137-0698-8, pp. 288, page 8.[14] Class Cephalopoda: the Head-Feet (http:/ / userwww. sfsu. edu/ ~biol240/ labs/ lab_18molluscs/ pages/ cephalopods. html) Accessed 21

November 2008.[15] Discussion (http:/ / palaeo-electronica. org/ 1998_1/ monks/ discus. htm). http:/ / palaeo-electronica. org/ Accessed 21 November 2008.

External links• Glossary (http:/ / www. manandmollusc. net/ glossary. html)• Bivalve anatomy (http:/ / www. assateague. com/ nt-bival. html)• More bivalve anatomy (http:/ / www. marietta. edu/ ~biol/ mussels/ anatomy. html)

Squid giant axon 116

Squid giant axonThe squid giant axon is the very large (up to 1 mm in diameter; typically around 0.5 mm) axon that controls part ofthe water jet propulsion system in squid. It was discovered by English zoologist and neurophysiologist John ZacharyYoung in 1936. Squid use this system primarily for making brief but very fast movements through the water.Between the tentacles of a squid is a siphon through which water can be rapidly expelled by the fast contractions ofthe body wall muscles of the animal. This contraction is initiated by action potentials in the giant axon. Actionpotentials travel faster[1] in a larger axon than a smaller one, and squid have evolved the giant axon to improve thespeed of their escape response. The increased diameter of the squid axon decreases the internal resistance of theaxon, as resistivity is inversely proportional to the cross sectional area of the object. This increases the spaceconstant, λ=sqrt(rm/ri). The increased space constant propagates a given local depolarization further, which speeds upthe action potential, according to the equation E=Eoe(-x/λ).In their Nobel Prize-winning work uncovering ionic mechanism of action potentials, Alan Hodgkin and AndrewHuxley performed experiments on the squid giant axon. The prize was shared with John Eccles. The large diameterof the axon provided a great experimental advantage for Hodgkin and Huxley as it allowed them to insert voltageclamp electrodes inside the lumen of the axon.While the squid axon is very large in diameter it is unmyelinated which decreases the conduction velocity potentialsubstantially. The conduction velocity of a typical 0.5 mm squid axon is about 25 m/s. During a typical actionpotential in the cuttlefish Sepia giant axon, an influx of 3.7 pmol/cm2 (picomoles per centimeter2) of sodium is offsetby a subsequent efflux of 4.3 pmol/cm2 of potassium.[2]

References[1] Gazzaniga, Ivry and Mangun 1998, Cognitive Neuroscience - The biology of mind[2] Plonsey, Robert; Roger C. Barr (2007). Bioelectricity: A Quantitative Approach, 3rd. Edition. New York, NY: Springer. pp. 109.

ISBN 978-0-387-48864-6.

117

Cephalopod shells

Cuttlebone

Cuttlebone from Sepia sp.

Cuttlebone of Sepia officinalis

Cuttlebone, also known as cuttlefish bone, is a hard, brittle internalstructure found in all members of the family Sepiidae, commonlyknown as cuttlefish.

Cuttlebone is composed primarily of aragonite. It is a chambered,gas-filled shell used for buoyancy control; its siphuncle is highlymodified and is on the ventral side of the shell.[1] The microscopicstructure of cuttlebone consists of narrow layers connected bynumerous upright pillars.

Depending on the species, cuttlebones implode at a depth of 200 to 600metres (660 to 2000 ft). Because of this limitation, most species ofcuttlefish live on the seafloor in shallow water, usually on thecontinental shelf.[2]

Human uses

In the past, cuttlebones were used in making polishing powder. Thepowder was added to toothpaste, and used as an antacid or as anabsorbent.

Today, cuttlebones are commonly used as calcium-rich dietarysupplements for caged birds, chinchillas, hermit crabs, snails, andturtles.[3]

Jewelry making

Because cuttlebone is able to withstand high temperatures and is easily carved, it serves as mold-making material forsmall metal casting for the creation of jewelry and small sculptural objects.Jewelers prepare cuttlebone for use as a mold by cutting it in half and rubbing the two sides together until they fitflush against one another. Then the casting can be done by carving a design into the cuttlebone, adding the necessarysprue, melting the metal in a separate pouring crucible, and pouring the molten metal into the mold through thesprue. Finally, the sprue is sawed off and the finished piece is polished.[4]

Cuttlebone 118

References[1] Rexfort, A.; Mutterlose, J. (2006). "Stable isotope records from Sepia officinalis—a key to understanding the ecology of belemnites?". Earth

and Planetary Science Letters 247: 212–212. doi:10.1016/j.epsl.2006.04.025.[2] Norman, M.D. 2000. Cephalopods: A World Guide. ConchBooks.[3] Norman, M.D. & A. Reid 2000. A Guide to Squid, Cuttlefish and Octopuses of Australasia. CSIRO Publishing.[4] Casting Silver with Cuttlefish (http:/ / www. silverstall. com/ casting-silver-jewellery. html)

• Neige, P. 2003. Combining disparity with diversity to study the biogeographic pattern of Sepiidae. (http:/ /biogeosciences. u-bourgogne. fr/ cv/ neige/ PDF/ NeigeBerlin. pdf)PDF Berliner Paläobiologische Abhandlungen3: 189–197.

Septum

Cutaway of a nautilus shell showing thechambers

Septa (singular septum) are thin walls or partitions between theinternal chambers (camerae) of the shell of a cephalopod, namelynautiloids or ammonoids.

As the creature grows, its body moves forward in the shell to a newliving chamber, secreting septa behind it. This adds new chambers tothe shell, which can be clearly seen in cross-sections of the shell of theliving nautilus, or in ammonoid and nautiloid fossils. The septa areattached to the inside wall of the shell, thus dividing the phragmoconeinto camerae.

Where the septum meets the shell a suture line forms; in someammonoids these lines became extremely complex and elaborate,providing strength without the necessity of added weight. Elaborate sutures allowed for thinner shells, and hence lesstime needed for shell growth and less time spent in the vulnerable juvenile stage.

The nature and structure of the septa, as with the camerae, and siphuncle, and the presence or absence of deposits,are important in classification of nautiloids. In some nautiloids, such as the Orthoceratidae, the septa tend to bewidely spaced, resulting in large, long camarae. In others such as the Ellesmerocerida, Oncocerida and Discosoridathe septa are crowded closely together. In some straight-shelled forms like Actinoceras, calcium carbonate depositsextend from the camera (mural deposits) to the septa (episeptal deposits).Septa can be used to identify extinct coral Order Rugosa and may be arranged as cardinal proseptum, counterproseptum, alar proseptum orcounter lateral proseptum.

Aptychus 119

Aptychus

A pair of fossil aptychi. The picture is 1 cmacross.

One of what would have been a pair of aptychi,(at first given the name "Trigonellites latus" and

described as a bivalve) from the KimmeridgeClay Formation in England

An aptychus is a type of marine fossil, a hard anatomical structure likea curved shelly plate, which was part of the body of an ammonite.Paired aptychi have, on rare occasions, been found at or within theaperture of ammonite shells.

Aptychi are often found well-preserved as fossils, but are only veryrarely found connected to ammonite shells. This circumstance led tothem being initially classified as the valves of bivalves, which theysomewhat resemble. Aptychi are found in rocks from the Devonianperiod through to the those of the Cretaceous period. The aptychus wasusually composed of calcite, whereas the ammonite shell wasaragonite.

There are many forms of aptychus, varying in shape and in thesculpture of the inner and outer surfaces. However, because they are sorarely found in position within the ammonite shell, it is often unclear asto which species of ammonite many aptychi belong.When only a single plate is present, as is sometimes the case, the term"anaptycus" is used.

Function

Aptychi seem to have most often existed as bilaterally-symmetricalpairs, and were first described (incorrectly) as being the valves ofbivalve mollusks. Aptychi are now considered to be either: (1) atwo-valved closing hatch on the shells of extinct ammonites; or (2) adouble-plate jaw-piece similar to that of some modern cephalopods.[1]

[2] [3] [4]

Set close to or against the shell's terminal opening (the livingchamber), the aptychi usually consisted of two identical but mirror image valves. Some authors consider theaptychus to be a jaw apparatus (mandibles), while others believe them to be paired opercula. If the latter is the case,then aptychi may have had a function similar to the head shield of modern nautiluses.

References[1] Morton, N. 1981. Aptychi: the myth of the ammonite operculum. Lethaia 14(1): 57–61. doi:10.1111/j.1502-3931.1981.tb01074.x[2] Morton, N. & M. Nixon 1987. Size and function of ammonite aptychi in comparison with buccal masses of modem cephalopods. Lethaia

20(3): 231–238. doi:10.1111/j.1502-3931.1987.tb02043.x[3] Lehmann, U. & C. Kulicki 1990. Double function of aptychi (Ammonoidea) as jaw elements and opercula. Lethaia 23: 325–331.

doi:10.1111/j.1502-3931.1990.tb01365.x[4] Seilacher, A. 1993. Ammonite aptychi; how to transform a jaw into an operculum? American Journal of Science 293: 20–32.

doi:10.2475/ajs.293.A.20

• Morphological Terminology: the Aptychus (http:/ / www. calfrye. com/ aptychi/ morphological_terminology.htm) from "North American Late Devonian Cephalopod Aptychi". Kirtlandia 46 (August 1991):49-71. By CalvinJ. Frye and Rodney M. Feldmann.

Orthocone 120

Orthocone

Fossilised Orthoceras orthocones.

An orthocone is a usually long straight shell of anautiloid cephalopod. During the 18th and 19thcenturies, all shells of this type were namedOrthoceras, but it is now known that many groups ofnautiloids developed or retained this type of shell.

An orthocone can be thought of as like a Nautilus shell,but with the shell straight and uncoiled. It waspreviously believed that these represented the mostprimitive form of nautiloid, but it is now known thatthe earliest nautiloids had shells that were slightlycurved. An orthoconic form evolved several timesamong cephalopods, and among nautiloid cephalopods is prevalent among the ellesmerocerids, endocerids,actinocerids, orthocerids, and bactritids.

Orthocones existed from the Late Cambrian to the Late Triassic, but they were most common in the early Paleozoic.Revivals of the orthocone design later occurred in other cephalopod groups, notably baculitid ammonites in theCretaceous Period. Orthocone nautiloids range in size from less than an inch to (in some giant endocerids of theOrdovician) seventeen feet (or five meters) long.

Phragmocone

Cutaway of a nautilus shell showing thechambers

The phragmocone is the chambered portion of the shell of acephalopod. It is divided by septa into camerae.

In most nautiloids and ammonoids, the phragmocone is a long, straight,curved, or coiled structure, in which the camarae are linked by asiphuncle which determines buoyancy by means of gas exchange.

Despite this benefit, such a large shell adds to the mass of the animal,and hence is not advantageous in catching fast-moving prey. Somenautiloids, such as the Silurian Ascocerida, dropped the phragmoconeupon maturity, presumably to increase speed and maneuverability.They thus became the early Paleozoic equivalent of coleoids. The earlycoleoids and belemnoids adopted a different approach. Thephragmocone was retained but became internal and reduced, and so like the shell in general it tends to be vestigial orabsent in most cephalopods.

Phragmocone 121

Fossil recordBeing the only biomineralised part of most cephalopods, the phragmocone is typically the only part to enter the fossilrecord. It is sometimes infilled with sediment, with sediment presumably getting in through the siphuncle.[1] Thereare occasions where trilobites have been preserved within phragmocones, presumably where they crawled in forrefuge.[2]

References[1] Henderson, ROBERT A.; McNamara, Kenneth J. (1985). "Taphonomy and ichnology of cephalopod shells in a Maastrichtian chalk from

Western Australia". Lethaia 18: 305. doi:10.1111/j.1502-3931.1985.tb00710.x.[2] Arnold Davis, R. H. B. Fraaye, Char, Richard (2001). "Trilobites within nautiloid cephalopods". Lethaia 34: 37.

doi:10.1080/002411601300068251.

SiphuncleThe siphuncle is a strand of tissue passing longitudinally through the shell of a cephalopod mollusk. Onlycephalopods with chambered shells have siphuncles, such as the extinct ammonites and belemnites, and the livingnautiluses, cuttlefish, and Spirula. In the case of the cuttlefish, the siphuncle is indistinct and connects all the smallchambers of that animal's highly modified shell; in the other cephalopods it is thread-like and passes through smallopenings in the walls dividing the chambers.The siphuncle is used primarily in emptying water from new chambers as the shell grows.[1] Essentially whathappens is the cephalopod increases the saltiness of the blood in the siphuncle, and the water moves from the moredilute chamber into the blood through osmosis. At the same time gas, mostly nitrogen, oxygen, and carbon dioxide,diffuses from the blood in the siphuncle into the emptying chamber. Note that the cephalopod does not pump up theshell; the gas moving into the chamber is a passive process, instead the energy is used in absorbing the water fromthe chamber.

An image showing the siphuncle, the tube whichconnects the current living shell to the previous

ones.

Removing water from the chambers of the shell reduces the overalldensity of the shell, and thus the shell behaves as a flotation devicecomparable to the swim bladder in bony fish. Typically, cephalopodsmaintain a density close to that of sea water, allowing them to swimwith the minimum of effort. In the geologic past, many cephalopodsgrew to an enormous size (over ten meters in length) thanks to this.

Generally, the siphuncle is unable to provide a way to change thedensity of shell rapidly and thus cause the animal to rise or sink at will;rather, the animal must swim up or down as required.The siphuncle found in fossilised cephalopods is assumed to haveworked in the same general way. The siphuncle itself only rarely getspreserved, but many fossils show the holes, called septal necks (orsiphuncle notches), through which the siphuncle passed. In most fossilnautiluses, the siphuncle runs more or less through the center of eachchamber, but in ammonites and belemnites it usually runs along the ventral surface. In some fossil straight shellednautiluses cylindrical calcareous growths ("siphuncular deposits") around the siphuncle can be seen towards the apexof the shell. These were apparently counterweights for the soft body at the other end of the shell, and allowed thenautilus to swim in a horizontal position. Without these deposits, the apex of the buoyant shell would have pointedupwards and the heavier body downwards, making horizontal swimming difficult. The siphuncle of the Endoceridaalso contained much of the organisms' body organs.[2]

Siphuncle 122

See also• Phragmocone• Orthoceras• Baculites

References[1] Mutvei, Harry; Zhang, Yun-bai; Dunca, Elena (2007). "Late Cambrian Plectronocerid Nautiloids and Their Role in Cephalopod Evolution".

Palaeontology 50 (6): 1327–1333. doi:10.1111/j.1475-4983.2007.00708.x[2] Kroger, B; Yun-Bai, Zhang (2008). "Pulsed cephalopod diversification during the Ordovician". Palaeogeography Palaeoclimatology

Palaeoecology 273: 174. doi:10.1016/j.palaeo.2008.12.015.

Body chamber

Nautilus pompilius

The body chamber, also called the living chamber, is the outermostor last chamber in the shell of a nautiloid or ammonoid cephalopod.The body of the animal occupies the living chamber, apart from thesiphuncle which extends through the rest of septa (the phragmocone) toprovide buoyancy.

Article Sources and Contributors 123

Article Sources and ContributorsCephalopod  Source: http://en.wikipedia.org/w/index.php?oldid=412094552  Contributors: AManWithNoPlan, Abigail-II, Abyssal, AdjustShift, Adrian.benko, Anaxial, Andonic, AnnaFrodesiak, Argo Navis, Arkuat, ArthurWeasley, Axl, AzaToth, Bender235, Bewareofdog, Bob the ducq, Bobo192, Brandon5485, Brothejr, CN0t3, CanadianLinuxUser, Cedders, Celithemis,Ceph, Cephal-odd, Cs california, Da Joe, Dan D. Ric, Daniel.Cardenas, DanielCD, Dbratland, Debresser, Derek Ross, Dfred, Dinoguy2, Dlloyd, DocWatson42, Dominus, Dorathaexplora,Dromiceiomimus, Dunning, Dureo, Dysmorodrepanis, Elassint, Eluchil404, Epolk, Eregli bob, Erianna, Estudiarme, Flutelover2008, Flyguy649, Fordmadoxfraud, FrancescaSF, Fubar Obfusco,Funandtrvl, Gadfium, Gary2863, Gentgeen, Georgehenries, Gf2tw, Glenn, Gnomon, GoingBatty, Hadal, HaeB, Headbomb, Hephaestos, IRP, Imo is emo, Inrerumnatura, Ipatrol, IronChris,Iustinus, J.H.McDonnell, J.delanoy, JNShutt, Jackhynes, Jamesofur, Jarry1250, Jerkov, Jimp, Jklin, John, John254, JohnCD, Jonadab, Jones8888, K-22-22, Katharineamy, Kazvorpal,Kembangraps, Kevmin, Kialari, Kils, Kipoc, Kleopatra, Kmg90, Kungfuadam, Lando5, Luigifan, Macdonald-ross, Mani1, Mark K. Jensen, Marskell, Mav, Maxim Razin, Maxinuk, MehrunesDagon, MetaruKoneko, Mgiganteus1, Mikeross, Morbit, Naddy, NatureA16, NawlinWiki, Neale Monks, Neptunerover, Netoholic, Nicolharper, Nishamgi, Noles1984, NorwegianBlue,Nuvitauy07, Omnipedian, Orangesquid, Paul Ferber, Peter, Peter b, Pgan002, Philip Trueman, Physis, PierreAbbat, Pinkpedaller, Polarpanda, Postdlf, Quantumobserver, Quintote, Qworensk,Radomil, Ranveig, Ratherhaveaheart, Reunionsystem, RexNL, Rich Farmbrough, Rjd0060, Rjwilmsi, Rkiko, Rob Hooft, Robin S, Rossumcapek, Rynosaur, SF007, SMC, Samwb123, Sasawat,Sayeth, Scarian, Scottandrewhutchins, Seaphoto, Seascapeza, SebastianHelm, Seglea, SidP, Siim, Slakr, Sluzzelin, Smallweed, Smith609, Snek01, Spotty11222, Stemonitis, SteveSims, Stui,Sylverfysh, T@nn, TUF-KAT, Template namespace initialisation script, Tengai, They Say, Thingg, Timotheus Canens, Timwi, Tomi, Tommy2010, Utcursch, UtherSRG, Vainamainien,Versus22, WAvegetarian, Watcharakorn, Where next Columbus?, WiccaIrish, WikipedianMarlith, Will Pittenger, William Avery, Wkpa678, Yamamoto Ichiro, Yandauph, Ybk33, Zannah,ZayZayEM, Zerokitsune, ^demon, 330 anonymous edits

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Squid  Source: http://en.wikipedia.org/w/index.php?oldid=411896754  Contributors: 119, 1ManWolfpack, 21655, 4playerpodcast, 62.253.64.xxx, A3RO, Aarchiba, Abce2, Abigail-II, Acalamari, Account986876789676, Acroterion, Adeybaby, Adrian.benko, Aesopos, Aflm, Agateller, Ageekgal, Agent Smith (The Matrix), Ahoerstemeier, Ajnauron, AlanBarrett, Alansohn, Alex.muller, Alexf, Alexius08, AlexiusHoratius, Alexthompson421, Allstarecho, Almerricksurfer, Alu369, Alvis, Alxeedo, Americanfreedom, Amickl1, Anaxial, Ancient Apparition, Andrevan, Andrew Klock, Andrewdalby123, Angela, Angrycrustacean, Antandrus, Apostrophe, Aquaimages, Are1998, Arthena, Ask123, Atroquininemylove, Attilios, Avtcaggy, Awopl122, Axeman89, Az1568, BOBATNIGHT, Baa, Bamjam15, Bassbonerocks, BazookaJoe, Ben Ben, Benjwong, Black Falcon, Blackbabylon, Blake-, Blanchardb, Bob91210, Bobo192, Bogey97, Bongwarrior, Brendaninct, Bryan Derksen, Bsadowski1, Buchanan-Hermit, Bumm13, ButOnMethItIs, CO, CS42, CSWarren, CWY2190, CWii, Cactus.man, Cadwaladr, Caggyavt, Calvin 1998, Can't sleep, clown will eat me, Canterbury Tail, CardinalDan, Carlosguitar, Caspian blue, Catgut, Causa sui, Celarnor, Cello06, Ceph, Cerebral67, Cheesecake13, Chensiyuan, Chinasaur, Christopher 2004oh, Chuckiesdad, Chun-hian, Cishaurim, Closedmouth, Cmdrjameson, Coffee, Colleenthegreat, Colonies Chris, Cometstyles, Coolio329, Cosmic Latte, Courcelles, Cowan1316, Cowjuice83, Cpl Syx, Crazycomputers, Csigabi, Cvhfgjhfgjfgj, Cyrius, DARTH SIDIOUS 2, DJ Clayworth, DVdm, Da Phire, Da Squid, Da guy who edits, Dandude90, DanielCD, Dantheman9242, Darth Livers, Davepape, David.Monniaux, Dawn Bard, Dayanne32, Deagle AP, Dec1213, Declan Clam, Decltype, Delldot, DerHexer, Dietary Fiber, Dina, Dinesh smita, Discordanian, Discospinster, Disgraced hobo, Distepheno, Dj Capricorn, Djp27, Dk81690, Dkozic, Dlohcierekim, Doc Tropics, Doggirl113, Dogposter, DouglasHeld, Doulos Christos, Download, Doyley, Dpeters11, Dr.frog, Drc79, Dreadstar, Dreamsinjava, Drmaik, Drmies, DuncanHill, Dysepsion, E.P.Y. Foundation, Earthlyreason, EdBever, Edpark88, Eleos, Eliz81, Elliskev, Emeraldcityserendipity, Enviroboy, Epbr123, Epipelagic, Eregli bob, Eric Wester, Eric-Wester, Ericoides, Esanchez7587, Esrever, Everlightgreen, EvilStorm, Ewx, Excirial, FaerieInGrey, Faradayplank, Fastily, Fieldday-sunday,

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Cuttlefish  Source: http://en.wikipedia.org/w/index.php?oldid=410884749  Contributors: 16@r, AZColumbine, Ac1917a, Adashiel, Alansohn, Alexf, Alexis.ohanian, Alfie66, Allen McC.,Allenwhite, Allstarecho, Alltat, Alvis, Alxeedo, Amartipu, Amillar, Analogdrift, Andrea105, Andy.goryachev, Angr, AnnaP, ArglebargleIV, Argo Navis, Asanagi, Ashcraft, Atarr, Azhyd,Badagnani, Bandaparte, Baralloco, Barny-the-barnicle, Bashgranderson, Benanhalt, Benjwong, Besha, Bethenco, Bfigura's puppy, Bgs022, BigrTex, Bilsonius, Bojicat, Borgx, Bradley10,BritishWatcher, Bryan Derksen, Bwithh, Bwsmith1, Caltas, CanadianLinuxUser, Cantor, CarTick, Catgut, Celithemis, Centerone, Ceph, Chris G, Chris19910, Chun-hian, Click23, Coelacan,Conversion script, Corpx, Cosmo the third, Courcelles, Cst17, Cuticles, D.tonyan, DVD R W, Daniel.Cardenas, DanielCD, Danski14, Dashavoo, DavidFarmbrough, DelftUser, Deliciouscarbuncle, Delldot, Destynova, Diliff, Discospinster, Diveadaytv, Dleisawitz, Doradus, Doubleg, Dougofborg, Download, Dr.frog, Drmies, Dysprosia, EagleFan, Easyas12c, Ec5618, Egg Centric,Ehn, Elendil's Heir, Epastore, Epbr123, Epipelagic, Erianna, Falcon8765, FayssalF, Freyr35, Fru1tbat, Funnyfarmofdoom, G-Flex, Gantry, Gdr, Ghosts&empties, Gilgamesh, Glandelf,Groovenstein, Guiltyspark, Gurchzilla, H, HHUK, Haifagreen, Hajatvrc, Hajhouse, Headbomb, Helixweb, Hellbus, Henryodell, HisSpaceResearch, Hmains, Htiw67, Iciac, Ilovehugecocks,Immunize, Invertzoo, Invisible Noise, Iustinus, Ixfd64, J.H.McDonnell, J.delanoy, Jacksinterweb, Jalwikip, Jaybo33, Jcf0987, Jeffq, Jimerb, Jjhake, JohnInDC, Junglecat, K-22-22, KCinDC,KGasso, Kandar, Katalaveno, Keilana, Ken Gallager, KiTA, Kodemage, Kori126, Kuru, Kvn8907, L'Aquatique, Ld5hkyplayer, Lear's Fool, Leon7, LesOrchard, Lfstevens, Lifetrance, Lin linao,Livajo, Lung 2 BB, Lusanaherandraton, Madhero88, Madler, Magister Mathematicae, Mahanga, Manticore, Maqs, Marc Venot, Mark.murphy, Martinp23, Mazca, McGeddon, Melnelsen,Mervyn, Mesame121489, Metalintheass, Mgiganteus1, Michael Glass, Michael93555, Michaeldrayson, Minervamoon, MisfitToys, Mkamensek, Mkdw, Mmdoogie, Moshe Constantine HassanAl-Silverburg, Mrmcgee, Mtcurado, Mwp, Mycroft7, Mygerardromance, NOVA-PBS, Naddy, Natalie Erin, NawlinWiki, NewEnglandYankee, Nhobgood, Nick125, NotAnonymous0, NovaDog,Ntse, Oknazevad, Olivier, Onthesessionkk, Parker1993, Patrickcharleshayes, Pc13, Peepeedia, Persian Poet Gal, Pgk, Philcha, PhilipC, Pili cal, Pip2andahalf, Pnkrockr, PoccilScript, Politepunk,Pseudomonas, Pwt898, R'n'B, Raul654, Razorflame, Rbarreira, RedRabbit1983, RexNL, Reywas92, Rezecib, Rfc1394, Richard D. LeCour, Richard Hock, RichardF, Richwil, Rj, Rjanag,Rjd0060, Rjwilmsi, Rklecka, Rockpocket, Rohan Jayasekera, RoyBoy, Rui Gabriel Correia, Ryulong, Samsara, Saturnv7890, Sbrockway, Sc2racing, Schellack, SchfiftyThree, Scientizzle,Scoops, ScottyBerg, Seglea, Shadowlynk, Silverhand, Skyluke, Slocombe, Sluzzelin, Smith609, SpaceFlight89, Spellmaster, Spotty11222, Sputnikcccp, Stonehut, StradivariusTV, Sylvieatwiki,THEODOREBANKS, TallNapoleon, Tbhotch, Tcncv, Template namespace initialisation script, Temporaluser, Tengai, The High Fin Sperm Whale, The Thing That Should Not Be, The bellman,TheReverend5, Thumperward, Tide rolls, Tim Ivorson, Tommy2010, Tony Corsini, Tony1, Tpingt, Umofomia, UtherSRG, VBGFscJUn3, Valley2city, Vicarious, Visik, WAvegetarian, Wetman,Wirbelwind, WorldSlayer, Wykymania, Xar Biogeek, Xnuala, Xuz, Yamamoto Ichiro, Yekrats, Ypacaraí, Zarius, ZayZayEM, Михајло Анђелковић, 584 ,ينام anonymous edits

Nautiloid  Source: http://en.wikipedia.org/w/index.php?oldid=411746505  Contributors: Abyssal, Adrian.benko, Apokryltaros, Bactrite, Bayle Shanks, Bigfun, Bobo192, Brandizzi, Causantin,Cephal-odd, Cremepuff222, Da Joe, DanielCD, Deinocheirus, Diucón, Dlloyd, Dr.Bastedo, Ferred, Gaius Cornelius, GrahamBould, Headbomb, Island, J.H.McDonnell, Katalaveno, Knotnic,Lexor, LilHelpa, Locomiguel, M Alan Kazlev, MeganWest, Mgiganteus1, Moon&Nature, Mushroom, Nakon, NatureA16, Neale Monks, Nik42, PenguinJockey, Postdlf, Rorro, SNP, SamHocevar, Schreibergasse, Skapur, Smith609, Spellmaster, StarManta, SteveSims, T callahan, The Rationalist, Tom harrison, UtherSRG, Wilson44691, Ziggy Sawdust, Zploskey, 50 ,ةيناريد دابعanonymous edits

Nautilus  Source: http://en.wikipedia.org/w/index.php?oldid=412562056  Contributors: A. B., ARUNKUMAR P.R, Abigail-II, Adrian.benko, After Midnight, Alansohn, Alex.tan, Altenmann,AndrewC, Anthony Appleyard, Apokryltaros, Ark-pl, ArthurWeasley, Aulus Gellius, BHC, BillC, BodvarBjarki, Brian0324, Bryan Derksen, Butuzov, Can't sleep, clown will eat me,CardinalDan, Charles Hawkins, Chris 73, Corpx, Cplbeaudoin, D.brodale, DJ Clayworth, DJFrankie2468, DanielCD, Dbenbenn, Deranged bulbasaur, Djinn112, Dominus, Doug Coldwell,Dpbsmith, Dysprosia, Elmoro, Emijrp, Eno-ja, Error, Felagund, Femto, Fenevad, Fogster, Gandalf61, Gbleem, Gdr, GeeJo, GeoGreg, Glane23, Glenn, Glennimoss, Gogo Dodo, GrahamBould,Hadal, Headbomb, Hemoptysis, Hongooi, IanOsgood, Invertzoo, Island, Jackthesnake, Jakewaage, Jalwikip, JayEsJay, Jedi of redwall, Johnbod, Juliancolton, Junglecat, Kariteh, Kelson,Keskival, Kintetsubuffalo, Krich, LeCire, Lectonar, Lewis tatnell, Lexor, Lfstevens, Lightdarkness, LorenzoB, Lotje, M Alan Kazlev, MacGyverMagic, Maddioldstone, Magnus Manske,Malcolm Farmer, Mani1, Mav, Mbabane, Melchoir, Mercer66, Metalhead94, Mgiganteus1, Michaelritchie200, MiltonT, Mlpearc, Moletrouser, Muriel Gottrop, Mycroft.Holmes, NHRHS2010,NatureA16, Naufana, Nautiliking, Neilc, Noe, Norm, Ocatecir, Oxxxo, Pearle, Phil Boswell, Piano non troppo, Plumbago, Portalian, Puckly, Qwertzy2, Rursus, SYSS Mouse, Scarian,Seascapeza, Seb az86556, Shadowjams, Sluzzelin, Smallpond, Smith609, Snek01, SoWhy, Stemonitis, Susfele, Template namespace initialisation script, TheMadBaron, TimVickers, Tomharrison, Toytoy, Travis.barnett33, Trento54, Trusilver, UtherSRG, Valodzka, Vinne2, Visik, Ward3001, Weft, Wimt, Winhunter, Xneonvisionx, Zoney, 219 anonymous edits

Ammonite  Source: http://en.wikipedia.org/w/index.php?oldid=412472112  Contributors: !!, Abigail-II, Abyssal, Adashiel, Adeliine, Adrian.benko, Amezcackle, Animum, AnonMoos,Apokryltaros, ArchologisticlY GD, Arpingstone, Avicennasis, Bahudhara, BillFlis, Blind designer, Bomlut, BorgQueen, Brian0918, Bryan Derksen, Carbuncle, Ceph, Cephal-odd, Cfailde,Chcknwnm, Clawed, CommonsDelinker, Complainer, Cookiecaper, Crocodile Punter, Cybercobra, DabMachine, Dandin1, DanielCD, Danilot, DaoKaioshin, Dendodge, Destroyer of evil,Dhzanette, Dinoguy2, Diucón, Divercol, Dlloyd, DocWatson42, Dr.Bastedo, EVula, Edgar181, Enlil Ninlil, Epbr123, EtotheMad, Fatapatate, Fenevad, Florentino floro, Fubar Obfusco, Galoubet,Gandalf61, Geoking42, Gioku, Gordon Stangler, Grenavitar, Hairy Dude, HalfShadow, Hashar, Headbomb, Hebrides, Hede2000, Hmains, Hryhorash, Hydrargyrum, IZAK, Invertzoo, Iustinus, J.Spencer, J.H.McDonnell, Jacen Aratan, JamesPFisherIII, Jimp, Jiy, JoanneB, Johnelson, Jonathan350, Jonathunder, Josh Grosse, Jusdafax, Karmosin, Kevmin, Khfan93, Kleopatra, Kukini,Laikayiu, Lejean2000, Likearock, Lilaac, Locomiguel, Lumos3, M.e, M1ss1ontomars2k4, MC10, MU, Mac Davis, Manop, MattDP, Mattbr, Mgiganteus1, Michael Slone, Monkeylover34, MurielGottrop, Nabokov, Naddy, NatureA16, Neale Monks, Numbo3, Parsa, Paul D. Anderson, Pedoleon, Piano non troppo, Postdlf, Psuanthguy, Ragesoss, Rbarreira, Rjwilmsi, Robert K S, Ronz,SWAdair, Santa Sangre, Saperaud, Shanes, Shrewpelt, Silly rabbit, Sjc, Sk741, Skyskraper, Slakr, Sligocki, Smith609, Snowolf, Spotty11222, Steinsky, Sterwick, Syrthiss, Tarquin, Tbc2,Template namespace initialisation script, The Thing That Should Not Be, TheRingess, Thingg, Thryduulf, Tjunier, Toadfosky, TomGreen, UninvitedCompany, UtherSRG, Velella, Vrenator,Vsmith, Whatnwas, Whoelius, Wikipelli, Wilson2, Wilson44691, WolfmanSF, Xana500, Zzzzz, 194 ,ةيناريد دابع anonymous edits

Belemnoidea  Source: http://en.wikipedia.org/w/index.php?oldid=412475067  Contributors: Abyssal, Adrian.benko, Aiko, Anthony Appleyard, Arpingstone, DanielCD, Dlloyd,Dysmorodrepanis, Felagund, FunkMonk, Headbomb, Huttarl, Invertzoo, J. Spencer, Jashiin, Katharineamy, Kencasey98, Kevmin, Marcelo-Silva, Mgiganteus1, Moon&Nature, NatureA16, NealeMonks, Obsidian Soul, Polarpanda, Rich Farmbrough, Richardleaky, Saintrain, Slawojarek, Smith609, UtherSRG, WOSlinker, Wetman, Wilson44691, WolfmanSF, ZeldaGamer31337, Zvar,anonymous edits 32 ,ةيناريد دابع

Argonaut  Source: http://en.wikipedia.org/w/index.php?oldid=407759059  Contributors: Abigail-II, Abyssal, Altenmann, Anthony Appleyard, Cakehelmit, CatherineMunro, Cewvero, Citron,D6, DanielCD, Dannajoy, Dysmorodrepanis, GrahamBould, Guidod, Headbomb, Iciac, InfernoXV, Invertzoo, Koven.rm, Kwamikagami, LilHelpa, Limonadis, M-le-mot-dit, Mgiganteus,Mgiganteus1, Montyy0, Neale Monks, Orangemarlin, Palpalpalpal, Peter Horn, Phphello, PurpleHz, Qwertzy2, Rajah, Rama, Rolf Schmidt, SteveSims, Template namespace initialisation script,TheAlphaWolf, Tonyrex, UtherSRG, Wetman, XQ fan, 18 anonymous edits

Cephalopod intelligence  Source: http://en.wikipedia.org/w/index.php?oldid=406848079  Contributors: Acaeton, Alan Liefting, Andy Dingley, Animalplanetemployee, Ashesofoak, Atarr, Ceph, ChildofMidnight, Coelacan, Coemgenus, Delicious carbuncle, Dentren, Eaefremov, Epastore, Epipelagic, Falcon982, Headbomb, HisSpaceResearch, Iam3dhomer, Invertzoo, Jefffire, Jonkerz,

Article Sources and Contributors 125

Karlchwe, Kayau, LittleHow, Luigifan, Maproom, Marskell, MatthiasKabel, Mgiganteus1, Montyy0, Moshe Constantine Hassan Al-Silverburg, NEMT, Neurosojourn, Nibuod, Outriggr, PhilipTrueman, Proxima Centauri, Rjwilmsi, Serendipodous, Seric2, Simon80, Spotty11222, SteveSims, Steven Walling, Thumperward, Tktktk, Wood Thrush, Xanthine, 66 anonymous edits

Cephalopod size  Source: http://en.wikipedia.org/w/index.php?oldid=408489088  Contributors: Archelon, Cadwaladr, Dysmorodrepanis, Headbomb, J Milburn, Lambyte, Mattg82, Mgiganteus1,PenguinJockey, Rjwilmsi, Shaundakulbara, Taollan82, Twas Now, Uppland, Zuzster, 18 anonymous edits

Cephalopod ink  Source: http://en.wikipedia.org/w/index.php?oldid=407130384  Contributors: Anxietycello, Cedders, Headbomb, Ignacio Bibcraft, Igodard, Intelligentsium, K-22-22,Mgiganteus1, Scotsman240363, The Thing That Should Not Be, 9 anonymous edits

Ink sac  Source: http://en.wikipedia.org/w/index.php?oldid=405070305  Contributors: Brz7, Cdcdoc, Crazycomputers, EncycloPetey, GL, Iciac, Jcvamp, Jessicapierce, Jni, Jwbarnes,Mgiganteus1, Mukadderat, Skynoceanna, Smith609, Stevenharrower, UtherSRG, 17 anonymous edits

Cephalopod arm  Source: http://en.wikipedia.org/w/index.php?oldid=407805213  Contributors: Berek, Combatking0, Headbomb, Henryhartley, Materialscientist, Mgiganteus1, Montecarlocars,Stemonitis, Yobmod, ZayZayEM, 14 anonymous edits

Hectocotylus  Source: http://en.wikipedia.org/w/index.php?oldid=387215087  Contributors: Altenmann, Bansp, DanielCD, DragonflySixtyseven, Ginkgo100, Ickle Ronnie, Imnowei, Jpgordon,Kasyapa, MacRusgail, Macdonald-ross, Mgiganteus1, Ospalh, Robofish, UtherSRG, ZayZayEM, Zuzster, 5 anonymous edits

Tentacle  Source: http://en.wikipedia.org/w/index.php?oldid=394274034  Contributors: Andycjp, Arrowned, Bioform 1234, Bobo192, Bogey97, Bongwarrior, Burmiester, Cflm001, Chris Roy,Chrislk02, Clicketyclack, Delldot, Doulos Christos, Dragon's Light, E. Fokker, Ekko, Excirial, Ezzex, Facts707, Finn-Zoltan, Gadfium, Geary, Gene Nygaard, Gimme danger, Goodnightmush,GrahamBould, Gurko, Invertzoo, Isnow, JenniferGan, Joaoantonio, Jobba, John, KnightRider, Kodemage, Lcarscad, Legoo15, Liu Bei, Lokicarbis, LorenzoB, Lugnuts, Lycaon, MOGoss,Materialscientist, Mgiganteus1, Mmxx, Mnj21, Mohammedh15, Narvalo, NawlinWiki, Neutrality, No more bongos, Noloop, Okc, Omegatron, Owen, PhilHibbs, Piano non troppo, Pinkadelica,Proxima Centauri, PurpleHz, Quistnix, Reywas92, Rkitko, Rlandmann, Rodhullandemu, Rogutaan, Rossj81, ScottishGuy, Shoeofdeath, Silly rabbit, Skittle, Tavilis, The High Fin Sperm Whale,TheKMan, TheMadBaron, TheRanger, UnDeRsCoRe, Username381, Uyanga, Verbosemjp, Wombatcat, Woohookitty, Wyndclaw, Yair rand, Yobmod, ZayZayEM, 125 anonymous edits

Dactylus  Source: http://en.wikipedia.org/w/index.php?oldid=404288285  Contributors: Agamemnon2, Athurber, Kaarel, Mgiganteus1, Nono64, Pgan002, 1 anonymous edits

Cephalopod eye  Source: http://en.wikipedia.org/w/index.php?oldid=377389469  Contributors: Headbomb, Iciac, Komodo, Mgiganteus1, Smith609, Woohookitty, 2 anonymous edits

Chromatophore  Source: http://en.wikipedia.org/w/index.php?oldid=407119547  Contributors: Adamharvey182, AdultSwim, Alphachimp, Anville, Axeman89, BD2412, BhaiSaab, Bobo192,Boghog, BorgQueen, Brighterorange, Caesar Rodney, Ceyockey, Cinchjt, Dark Shikari, DeansFA, Deviator13, Dicklyon, Dispenser, Dj Capricorn, Djanvk, Dominus, DragonflySixtyseven,Drummie06, EagleFan, Edgar181, Ejdzej, Element16, Emvee, Floyd Landis, Gadfium, Gamesmasterg9, GregorB, Gudeldar, Harmil, Hegar, ISpamThisSite, Icey, InvictaHOG, Jaibobs108,Joyous!, Jpatokal, Kapuchinski, KimvdLinde, Kukini, LANA2007, Mav, Melchoir, MisfitToys, Mithril, Mr. Blackout, Nono64, NorwegianBlue, NuclearWarfare, P-Chan, PGWG, Pajast, Paulventer, Peter Delmonte, Philip Trueman, Raul654, Reywas92, Rich Farmbrough, Rintrah, Rjwilmsi, Robert Brockway, RobertG, Rockpocket, RupertMillard, Ryulong, Samir, Sandip90, Saravask,Savidan, Serephine, Stemonitis, Sucoyant, Super cyclist, Szquirrel, ToNToNi, Tpbradbury, Trevor MacInnis, Una Smith, Utcursch, UtherSRG, WoWFanatic, WolfmanSF, Zafiroblue05, 74anonymous edits

Mantle  Source: http://en.wikipedia.org/w/index.php?oldid=412714375  Contributors: Alexei Kouprianov, Altenmann, Barbara Shack, Brim, Daniel, DanielCD, Hadal, Hofoen, IlSoge,Invertzoo, Jamoche, Jimmy Figsworth, JoJan, Jomegat, Kaarel, MacGyverMagic, Mgiganteus1, Mild Bill Hiccup, Mr. Billion, Nuvitauy07, Pharos, Potatoswatter, Rettetast, SF007, Secretlondon,Serlin, Sidhekin, Snek01, Stfg, TheLimbicOne, TimBentley, UtherSRG, Versus22, Voyagerfan5761, Wickey-nl, 34 anonymous edits

Nidamental gland  Source: http://en.wikipedia.org/w/index.php?oldid=404289268  Contributors: Mgiganteus1, RDBrown, Snek01, 2 anonymous edits

Siphon  Source: http://en.wikipedia.org/w/index.php?oldid=404262442  Contributors: Amikake3, Arct, DanielCD, Epipelagic, Excirial, Invertzoo, Isthmus, J04n, JamesAM, Jeff G., Kaarel,Kesal, Mgiganteus1, Mukadderat, Nono64, Rror, Smith609, Snek01, Tabletop, UtherSRG, 14 anonymous edits

Squid giant axon  Source: http://en.wikipedia.org/w/index.php?oldid=407999385  Contributors: Alkaloids, Altenmann, Alvis, Diberri, Kalexander, MementoVivere, Mgiganteus1, Nrets,Orlandoturner, Pmjboyle, Synaptidude, Welsh, Whosasking, Wiseoldman123, Woreno, 14 anonymous edits

Cuttlebone  Source: http://en.wikipedia.org/w/index.php?oldid=397984794  Contributors: Darklilac, DavidFarmbrough, Dawynn, Dentren, Invertzoo, Lfstevens, Mervyn, Mgiganteus1,Obsidianearth, Paxsimius, Reywas92, Smith609, Speciate, Thumperward, 21 anonymous edits

Septum  Source: http://en.wikipedia.org/w/index.php?oldid=404262711  Contributors: Bobo192, DanielCD, Elkman, JHunterJ, Kaarel, M Alan Kazlev, Mgiganteus1, Nono64, Randomfrenchie,1 anonymous edits

Aptychus  Source: http://en.wikipedia.org/w/index.php?oldid=386681050  Contributors: DanielCD, Invertzoo, Kontos, Mgiganteus1, Snek01, UtherSRG

Orthocone  Source: http://en.wikipedia.org/w/index.php?oldid=410456513  Contributors: Apokryltaros, Cephal-odd, D053, Everyking, J.H.McDonnell, JukoFF, M Alan Kazlev, Mgiganteus1,UtherSRG, VanHelsing, 8 anonymous edits

Phragmocone  Source: http://en.wikipedia.org/w/index.php?oldid=365143443  Contributors: Cephal-odd, M Alan Kazlev, Mgiganteus1, Michael Devore, Sam Hocevar, Schmiteye, Smith609,UtherSRG, WolfmanSF, 3 anonymous edits

Siphuncle  Source: http://en.wikipedia.org/w/index.php?oldid=376016720  Contributors: Bucephalus, DanielCD, Hephaestos, Iciac, Mgiganteus1, Neale Monks, P4en, Pazuzu413, Smith609,Stewartadcock, UtherSRG, 7 anonymous edits

Body chamber  Source: http://en.wikipedia.org/w/index.php?oldid=409758989  Contributors: Dawynn, Dina, M Alan Kazlev, Mgiganteus1, UtherSRG

Image Sources, Licenses and Contributors 126

Image Sources, Licenses and Contributorsfile:Squid komodo.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Squid_komodo.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: User:NhobgoodImage:Sepia officinalis Linnaeus, 1758 .jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Sepia_officinalis_Linnaeus,_1758_.jpg  License: Public Domain  Contributors: User:ParentGéryImage:Benthoctopus sp.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Benthoctopus_sp.jpg  License: Public Domain  Contributors: NOAA/MBARIImage:Oktopus opening a container with screw cap 01.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Oktopus_opening_a_container_with_screw_cap_01.jpg  License: CreativeCommons Attribution 2.5  Contributors: User:MatthiasKabelImage:Euprymna scolopes (Bobtail squid) behavior .jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Euprymna_scolopes_(Bobtail_squid)_behavior_.jpg  License: CreativeCommons Attribution-Sharealike 3.0  Contributors: User:NhobgoodFile:Nautilus pompilius (head).jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Nautilus_pompilius_(head).jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors:User:LycaonImage:Cuttlefish color.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Cuttlefish_color.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: Nick HobgoodImage:Octopus3.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Octopus3.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: albert kokImage:Nautilus front.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Nautilus_front.jpg  License: Creative Commons Attribution 2.5  Contributors: Original uploader was Profbergerat en.wikipediaImage:Logy bay giant squid 1873.png  Source: http://en.wikipedia.org/w/index.php?title=File:Logy_bay_giant_squid_1873.png  License: Public Domain  Contributors: Original uploader wasMgiganteus1 at en.wikipediaImage:Tentacule Abraliopsis morisi.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Tentacule_Abraliopsis_morisi.jpg  License: unknown  Contributors: Carl ChunFile:Architeuthis beak.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Architeuthis_beak.jpg  License: Public Domain  Contributors: L. JoubinFile:Veined Octopus - Amphioctopus Marginatus eating a Crab.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Veined_Octopus_-_Amphioctopus_Marginatus_eating_a_Crab.jpg License: Creative Commons Attribution 2.0  Contributors: Silke BaronFile:SquidEggCases-MontereryAquarium-April2-07.png  Source: http://en.wikipedia.org/w/index.php?title=File:SquidEggCases-MontereryAquarium-April2-07.png  License: CreativeCommons Attribution-Sharealike 2.5  Contributors: User:CaptmondoImage:Chtenopteryx sicula paralarvae.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Chtenopteryx_sicula_paralarvae.jpg  License: Public Domain  Contributors: Liné1,MgiganteusImage:Chiroteuthis veranyi immature.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Chiroteuthis_veranyi_immature.jpg  License: Public Domain  Contributors: Javaprog,Kevmin, Liné1, MgiganteusImage:Chiroteuthis_veranyi.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Chiroteuthis_veranyi.jpg  License: Public Domain  Contributors: Citron, Javaprog, Liné1, MgiganteusImage:1212amma.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:1212amma.jpg  License: Public Domain  Contributors: Jonathan350File:Nautilus pompilius 3.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Nautilus_pompilius_3.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors:User:LycaonFile:Sepia officinalis (aquarium).jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Sepia_officinalis_(aquarium).jpg  License: Creative Commons Attribution-Sharealike 3.0 Contributors: User:LycaonImage:Sepiola atlantica.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Sepiola_atlantica.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: User:LycaonImage:Loligo vulgaris.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Loligo_vulgaris.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: User:LycaonImage:Octopus vulgaris2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Octopus_vulgaris2.jpg  License: GNU Free Documentation License  Contributors: BeckmannjanFile:Ammonites 180308.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ammonites_180308.jpg  License: Public Domain  Contributors: User:VassilFile:Ostenoteuthis siroi.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Ostenoteuthis_siroi.JPG  License: Creative Commons Attribution-Sharealike 3.0  Contributors:User:GhedoghedoFile:Fossil-Belemnoidea-complete.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Fossil-Belemnoidea-complete.jpg  License: Creative Commons Attribution-Sharealike 3.0 Contributors: user:Ra'ikeImage:Vampylarge.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Vampylarge.JPG  License: Public Domain  Contributors: User:Willsquishfile:Octopus2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Octopus2.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: albert kokFile:Tide pools octopus.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Tide_pools_octopus.jpg  License: GNU Free Documentation License  Contributors: Mila Zinkova Originaluploader was Mbz1 at en.wikipediaFile:Grimpoteuthis discoveryi.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Grimpoteuthis_discoveryi.jpg  License: Public Domain  Contributors: Mike Vecchione, NOAAFile:Oktopus opening a container with screw cap 01.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Oktopus_opening_a_container_with_screw_cap_01.jpg  License: CreativeCommons Attribution 2.5  Contributors: User:MatthiasKabelFile:Hapalochlaena lunulata2.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Hapalochlaena_lunulata2.JPG  License: Creative Commons Attribution 2.5  Contributors: JensPetersenFile:Octopus shell.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Octopus_shell.jpg  License: GNU Free Documentation License  Contributors: User:NhobgoodFile:Octopus vulgaris12p.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Octopus_vulgaris12p.jpg  License: Creative Commons Attribution-Sharealike 2.0  Contributors: (Photopersonnelle) Original uploader was Elapied at fr.wikipediaFile:Octopus3.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Octopus3.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: albert kokFile:Octopus.ogv  Source: http://en.wikipedia.org/w/index.php?title=File:Octopus.ogv  License: Creative Commons Attribution 2.0  Contributors: prilfish (Silke Baron)File:Enteroctopus dolfeini.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Enteroctopus_dolfeini.jpg  License: Public Domain  Contributors: NOAA/R. N. 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Image Sources, Licenses and Contributors 127

File:Grimalditeuthis bonplandi.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Grimalditeuthis_bonplandi.jpg  License: Public Domain  Contributors: Jeanne Le Roux & L. JoubinFile:Reversa1.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Reversa1.jpg  License: unknown  Contributors: Carl ChunFile:Mastigoteuthis flammea.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Mastigoteuthis_flammea.jpg  License: Public Domain  Contributors: EugeneZelenko, Javaprog, KeithEdkins, Kilom691, Kristof vt, Liné1File:Onychoteuthis banksii1.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Onychoteuthis_banksii1.jpg  License: Public Domain  Contributors: L. Joubin & Ch. RichardFile:Cephalop.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Cephalop.jpg  License: unknown  Contributors: Carl ChunImage:Fried calamari.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Fried_calamari.jpg  License: GNU Free Documentation License  Contributors: BanyanTree, Calvero, GveretTered, Lobo, Spellcastfile:Sepia latimanus (Reef cuttlefish) dark coloration.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Sepia_latimanus_(Reef_cuttlefish)_dark_coloration.jpg  License: CreativeCommons Attribution-Sharealike 3.0  Contributors: User:NhobgoodFile:Cuttlefish.ogv  Source: http://en.wikipedia.org/w/index.php?title=File:Cuttlefish.ogv  License: Creative Commons Attribution 2.0  Contributors: prilfish (Silke Baron)Image:Camouflage.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Camouflage.jpg  License: GNU Free Documentation License  Contributors: w:en:user:Raul654Raul654Image:Cuttlefishhead.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Cuttlefishhead.jpg  License: Public Domain  Contributors: User:FireFly5Image:Metasepia pfefferi 1.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Metasepia_pfefferi_1.jpg  License: Creative Commons Attribution 2.0  Contributors: Bricktop, Dodo,Liné1Image:kalamar.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Kalamar.jpg  License: Public Domain  Contributors: Original uploader was Borazont at en.wikipedia. Later version(s)were uploaded by Mgiganteus1 at en.wikipedia.Image:linguine with cuttlefish.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Linguine_with_cuttlefish.jpg  License: Public Domain  Contributors: Original uploader was Schellackat en.wikipediafile:Orthoceras BW.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Orthoceras_BW.jpg  License: Creative Commons Attribution 3.0  Contributors: User:ArthurWeasleyImage:Nautilus profile.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Nautilus_profile.jpg  License: GNU Free Documentation License  Contributors: Lee R BergerImage:Nautiloid trilacinoceras.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Nautiloid_trilacinoceras.jpg  License: GNU Free Documentation License  Contributors: User:DlloydImage:OrdNautiloidInternalMold.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:OrdNautiloidInternalMold.jpg  License: Public Domain  Contributors: User:Wilson44691file:Nautilus profile.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Nautilus_profile.jpg  License: GNU Free Documentation License  Contributors: Lee R BergerFile:Nautilus anatomy.png  Source: http://en.wikipedia.org/w/index.php?title=File:Nautilus_anatomy.png  License: Public Domain  Contributors: John Denis MacdonaldImage:Nautilus species shells.png  Source: http://en.wikipedia.org/w/index.php?title=File:Nautilus_species_shells.png  License: GNU Free Documentation License  Contributors:User:Mgiganteus1Image:NautilusTop.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:NautilusTop.jpg  License: GNU Free Documentation License  Contributors: DanielCD, Haplochromis, Javaprog,PetwoeImage:NautilusBottom.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:NautilusBottom.jpg  License: GNU Free Documentation License  Contributors: DanielCD, Haplochromis,Javaprog, PetwoeImage:NautilusCutawayLogarithmicSpiral.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:NautilusCutawayLogarithmicSpiral.jpg  License: Attribution  Contributors: User:Chris73Image:Nautilus oceanworld thailand.png  Source: http://en.wikipedia.org/w/index.php?title=File:Nautilus_oceanworld_thailand.png  License: Public Domain  Contributors: KeskivalFile:Allonautilus vs Nautilus.png  Source: http://en.wikipedia.org/w/index.php?title=File:Allonautilus_vs_Nautilus.png  License: Public Domain  Contributors: User:Antonovfile:Asteroceras BW.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Asteroceras_BW.jpg  License: Creative Commons Attribution 3.0  Contributors: User:ArthurWeasleyImage:Iridescent Ammonite Fossil.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Iridescent_Ammonite_Fossil.jpg  License: Creative Commons Attribution 3.0  Contributors:User:JamesPFisherIIIImage:Ammonite Jeletzkytes.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ammonite_Jeletzkytes.jpg  License: GNU Free Documentation License  Contributors: User:DlloydImage:Ammonite Asteroceras.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ammonite_Asteroceras.jpg  License: GNU Free Documentation License  Contributors: JackyR,Kevmin, Maksim, Rüdiger Wölk, UlrichstillImage:Haeckel Ammonitida.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Haeckel_Ammonitida.jpg  License: Public Domain  Contributors: Dysmorodrepanis, Kevmin, Pengo,Ragesoss, Ulrichstill, 1 anonymous editsImage:DiscoscaphitesirisCretaceous.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:DiscoscaphitesirisCretaceous.jpg  License: Public Domain  Contributors: User:Wilson44691File:Trigonellites latus.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Trigonellites_latus.jpg  License: Public Domain  Contributors: Cooke, A. H., Shipley, A. E. & Reed, F. R. C.File:Parapuzosia seppenradensis 5.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Parapuzosia_seppenradensis_5.jpg  License: GNU Free Documentation License  Contributors:User:Markus SchweissImage:Hoploscaphites ammonite.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Hoploscaphites_ammonite.jpg  License: GNU Free Documentation License  Contributors:User:DanielCD, User:DeadstarImage:IridescentAmmonite.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:IridescentAmmonite.jpg  License: GNU Free Documentation License  Contributors: DanielCD, Kevmin,Saperaud, Ulrichstill, 1 anonymous editsImage:Belemnit.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Belemnit.jpg  License: GNU Free Documentation License  Contributors: DanielCD, Glenn, Kevmin, Liné1, MurielGottrop, 1 anonymous editsImage:BelemniteDB2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:BelemniteDB2.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: DiBgd, Kevmin,Putnik, Ra'ikeImage:belemnite at bristol museum arp.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Belemnite_at_bristol_museum_arp.jpg  License: Public Domain  Contributors: Arpingstone,Kevmin, PurpleHzImage:ZoharBelemnite.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:ZoharBelemnite.JPG  License: Public Domain  Contributors: User:Wilson44691file:Papierboot Argonauta 200705181139.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Papierboot_Argonauta_200705181139.jpg  License: Creative CommonsAttribution-Sharealike 2.0  Contributors: Original uploader was Bernd Hofmann at de.wikipediaImage:Argonauta nodosa lithograph.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Argonauta_nodosa_lithograph.jpg  License: Public Domain  Contributors: Citron, Liné1,MgiganteusImage:Argonauta sp.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Argonauta_sp.jpg  License: unknown  Contributors: Ewald RübsamenImage:Argonauta hians male.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Argonauta_hians_male.jpg  License: unknown  Contributors: Ewald RübsamenImage:Argonauta nodosa with eggcase lithograph.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Argonauta_nodosa_with_eggcase_lithograph.jpg  License: Public Domain Contributors: Citron, Liné1, MgiganteusImage:Argonauta argo shell.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Argonauta_argo_shell.jpg  License: unknown  Contributors: Verrill, A. E.Image:Argonauta-nodosa-001.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Argonauta-nodosa-001.jpg  License: Public Domain  Contributors: Niccolò GualtieriImage:Argonauta-hians-001.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Argonauta-hians-001.jpg  License: Public Domain  Contributors: Niccolò GualtieriImage:Argonauta species.PNG  Source: http://en.wikipedia.org/w/index.php?title=File:Argonauta_species.PNG  License: GNU Free Documentation License  Contributors: User:Mgiganteus1Image:Nemo Aronax sail-fish.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Nemo_Aronax_sail-fish.jpg  License: Public Domain  Contributors: Bibi Saint-Pol, Dub, Jibi44,Notafish, Rama, Red devil 666Image:Octopus.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Octopus.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:ElinorDImage:Oktopus_opening_a_container_with_screw_cap_01.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Oktopus_opening_a_container_with_screw_cap_01.jpg  License:Creative Commons Attribution 2.5  Contributors: User:MatthiasKabel

Image Sources, Licenses and Contributors 128

Image:Oktopus_opening_a_container_with_screw_cap_02.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Oktopus_opening_a_container_with_screw_cap_02.jpg  License:Creative Commons Attribution 2.5  Contributors: User:MatthiasKabelImage:Oktopus_opening_a_container_with_screw_cap_03.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Oktopus_opening_a_container_with_screw_cap_03.jpg  License:Creative Commons Attribution 2.5  Contributors: User:MatthiasKabelImage:Oktopus_opening_a_container_with_screw_cap_04.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Oktopus_opening_a_container_with_screw_cap_04.jpg  License:Creative Commons Attribution 2.5  Contributors: User:MatthiasKabelImage:Architeuthis princeps image modified.PNG  Source: http://en.wikipedia.org/w/index.php?title=File:Architeuthis_princeps_image_modified.PNG  License: Public Domain  Contributors:Eleassar, Javaprog, Kilom691Image:Enteroctopus dolfeini.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Enteroctopus_dolfeini.jpg  License: Public Domain  Contributors: NOAA/R. N. LeaImage:LongArmSquid.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:LongArmSquid.jpg  License: Creative Commons Zero  Contributors: NOAAFile:GiantCuttlefish6.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:GiantCuttlefish6.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: Jacob BridgemanImage:Argonauta hians.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Argonauta_hians.JPG  License: Public Domain  Contributors: Original uploader was XQ fan aten.wikipediaImage:Spirula fg1.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Spirula_fg1.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:DysmachusImage:Parapuzosia seppenradensis cast.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Parapuzosia_seppenradensis_cast.jpg  License: GNU Free Documentation License Contributors: User:Markus SchweissFile:Megateuthis 1.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Megateuthis_1.JPG  License: Creative Commons Attribution-Sharealike 3.0  Contributors: User:GhedoghedoFile:Arrosnegre.png  Source: http://en.wikipedia.org/w/index.php?title=File:Arrosnegre.png  License: Public Domain  Contributors: Gveret Tered, Lobo, ToniherImage:Img octopus arm and suckers 057513.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Img_octopus_arm_and_suckers_057513.jpg  License: Creative Commons Attribution3.0  Contributors: User:HenryhartleyFile:Tremoctopus violaceus5.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Tremoctopus_violaceus5.jpg  License: unknown  Contributors: R. L. HudsonImage:Hectocotyle1.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Hectocotyle1.jpg  License: unknown  Contributors: Georges CuvierImage:Argonauta bottgeri hectocotylus.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Argonauta_bottgeri_hectocotylus.jpg  License: Public Domain  Contributors: Citron,Mgiganteus, MithrilImage:cuttlefish.png  Source: http://en.wikipedia.org/w/index.php?title=File:Cuttlefish.png  License: Public Domain  Contributors: unknown.Image:Snail-front-0A.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Snail-front-0A.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:AdamantiosImage:White abalone Haliotis sorenseni.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:White_abalone_Haliotis_sorenseni.jpg  License: Creative Commons Attribution-Sharealike3.0  Contributors: Original uploader was Geographer at en.wikipediaImage:Drosera capensis bend.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Drosera_capensis_bend.JPG  License: Creative Commons Attribution-Sharealike 2.5  Contributors:Infrogmation, NoahElhardt, Wim b, Yarl, 3 anonymous editsImage:Evolution eye.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Evolution_eye.svg  License: GNU Free Documentation License  Contributors: user:CaerbannogFile:Eye squid.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Eye_squid.jpg  License: unknown  Contributors: Carl ChunImage:Octopusv cropped.JPG  Source: http://en.wikipedia.org/w/index.php?title=File:Octopusv_cropped.JPG  License: Creative Commons Attribution-Sharealike 3.0  Contributors:User:Gronk, User:MgiganteusImage:Squid eye.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Squid_eye.jpg  License: Creative Commons Attribution 2.0  Contributors: wildxplorerImage:Sepia officinalis Linnaeus, 1758 cropped.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Sepia_officinalis_Linnaeus,_1758_cropped.jpg  License: Public Domain Contributors: User:Mgiganteus, User:Parent GéryImage:Nautilus pompilius (head).jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Nautilus_pompilius_(head).jpg  License: Creative Commons Attribution-Sharealike 3.0 Contributors: User:LycaonImage:Zfishchroma.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Zfishchroma.jpg  License: Public Domain  Contributors: Original uploader was Rockpocket at en.wikipediaImage:C Calyptratus female.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:C_Calyptratus_female.jpg  License: GNU Free Documentation License  Contributors: Original uploaderwas Geoff at en.wikipediaImage:Zebrafish embryos.png  Source: http://en.wikipedia.org/w/index.php?title=File:Zebrafish_embryos.png  License: Creative Commons Attribution 2.5  Contributors: Adam Amsterdam,Massachusetts Institute of Technology, Boston, Massachusetts, United States.Image:Dendrobates pumilio.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Dendrobates_pumilio.jpg  License: Public Domain  Contributors: GeorgHH, Poleta33, Pstevendactylus,Steveprutz, WolfmanSF, 5 anonymous editsImage:melanophore.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Melanophore.jpg  License: Public Domain  Contributors: Original uploader was Rockpocket at en.wikipediaImage:Neural.crest.cells.migration.svg  Source: http://en.wikipedia.org/w/index.php?title=File:Neural.crest.cells.migration.svg  License: Public Domain  Contributors: User:MithrilImage:Giant clam komodo.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Giant_clam_komodo.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors:User:NhobgoodFile:Cypraea chinensis with partially extended mantle.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Cypraea_chinensis_with_partially_extended_mantle.jpg  License: PublicDomain  Contributors: Bricktop, GrahamBould, JoJan, Kilom691File:Cypraea chinensis with fully extended mantle.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Cypraea_chinensis_with_fully_extended_mantle.jpg  License: Public Domain Contributors: Bricktop, GrahamBould, JoJanFile:SnailWynaad.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:SnailWynaad.jpg  License: Creative Commons Attribution-Sharealike 3.0  Contributors: User:ShyamalFile:Bielzia coerulans-3.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Bielzia_coerulans-3.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: User:Snek01File:Megapallifera mutabilis.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Megapallifera_mutabilis.jpg  License: Creative Commons Attribution-Sharealike 2.0  Contributors: PaulJ. MorrisFile:Haliotis asinina anatomy.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Haliotis_asinina_anatomy.jpg  License: Creative Commons Attribution 2.0  Contributors: Daniel JJackson, Carmel McDougall, Kathryn Green, Fiona Simpson, Gert Wörheide & Bernard M DegnanFile:Haliotis asinina anatomy 2.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Haliotis_asinina_anatomy_2.jpg  License: Creative Commons Attribution 2.0  Contributors: Daniel JJackson, Carmel McDougall, Kathryn Green, Fiona Simpson, Gert Wörheide & Bernard M DegnanFile:A clam.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:A_clam.jpg  License: Creative Commons Attribution 2.0  Contributors: FlickrLickr, FlickreviewR, Kersti Nebelsiek, 3anonymous editsFile:Cymbiola magnifica.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Cymbiola_magnifica.jpg  License: Creative Commons Attribution-Sharealike 2.0  Contributors: RichardLingFile:Nassarius tiarula.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Nassarius_tiarula.jpg  License: Public Domain  Contributors: Steve Lonhart (SIMoN / MBNMS)File:Heron Island Giant balor S01.OGG  Source: http://en.wikipedia.org/w/index.php?title=File:Heron_Island_Giant_balor_S01.OGG  License: Creative Commons Attribution-Sharealike 3.0 Contributors: User:Sirrob01File:Pomacea canaliculata siphonout.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Pomacea_canaliculata_siphonout.jpg  License: GNU Free Documentation License Contributors: Kristjan, Mattes, Pristigaster, SchimmelreiterFile:Pomacea paludosa drawing.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Pomacea_paludosa_drawing.jpg  License: Public Domain  Contributors: drawn by Helen Lawson (†1854), engraved by the Alexander Lawson firm, colored by Helen Lawson.File:GooeyduckSeafood.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:GooeyduckSeafood.jpg  License: GNU Free Documentation License  Contributors: Original uploader wasBachcell at en.wikipediaFile:Muscheln mit Sipho Nahaufnahme.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Muscheln_mit_Sipho_Nahaufnahme.jpg  License: Creative CommonsAttribution-Sharealike 3.0  Contributors: Stefan Didam - Schmallenberg

Image Sources, Licenses and Contributors 129

File:Venus verrucosa 3.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Venus_verrucosa_3.jpg  License: Public Domain  Contributors: Kurt Floericke (1869-1934)File:Valve-InternalView.png  Source: http://en.wikipedia.org/w/index.php?title=File:Valve-InternalView.png  License: unknown  Contributors: User:Muriel GottropImage:Cuttlebone.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Cuttlebone.jpg  License: Creative Commons Attribution-Sharealike 2.5  Contributors: Freaky Fries, Mgiganteus,Moumou82, Snek01, TomCatX, 1 anonymous editsFile:Herklots 1859 I 2 Sepia officinalis - schelp.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Herklots_1859_I_2_Sepia_officinalis_-_schelp.jpg  License: Public Domain Contributors: Herklots (scan by Tom Meijer, 26-6-2007)Image:Aptychus.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Aptychus.jpg  License: GNU Free Documentation License  Contributors: DanielCD, Kevmin, Saperaud, Snek01, 1anonymous editsFile:Ooland baculite Image0022 lo res 3 x1 7.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Ooland_baculite_Image0022_lo_res_3_x1_7.jpg  License: unknown  Contributors:Original uploader was Dcwade at en.wikipediaImage:Siphuncle.gif  Source: http://en.wikipedia.org/w/index.php?title=File:Siphuncle.gif  License: Attribution  Contributors: P4en, Smith609Image:Nautilus pompilius.jpg  Source: http://en.wikipedia.org/w/index.php?title=File:Nautilus_pompilius.jpg  License: Public Domain  Contributors: Citron, Daggerstab, Liné1

License 130

LicenseCreative Commons Attribution-Share Alike 3.0 Unportedhttp:/ / creativecommons. org/ licenses/ by-sa/ 3. 0/