9 Metamerism & Repd
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Transcript of 9 Metamerism & Repd
Dr. PARVISH PANDYA’s presentation
“Metamerism & Reproduction in
Annelida”A presentation compiled from various sources by
Dr. PARVISH PANDYA,Zoology Dept. Bhavan’s College, Andheri.
Dr. PARVISH PANDYA’s presentation
Sites from which presentations have been downloaded and later editted. I am indeed thankful to them for their kindness and support :http://esg-www.mit.edu:8001/esgbio/cb/org/organelles.htmlhttp://faculty.pnc.edu/jcamp/parasit/parasit.htmlhttp://www.amnh.org/rose/hope/creatinghope/http://www.biology.eku.edu/SCHUSTER/bio%20141/POWERPOINT%20NOTES/Intro%20to%20Protozoa_files/fullscreen.htmhttp://www.biosci.ohio-state.edu/~zoology/eeob405/http://www.tulane.edu/~wiser/protozoology/pwpt/http://www.iep.water.ca.gov/suisun/photos/wildlife.htmlhttp://www.uta.edu/biology/marshall/2343/http://www.uta.edu/biology/faculty/faculty.htmlhttp://www.okc.cc.ok.us/biologylabs/Documents/Zoology/PowerPoint.htmhttp://bio.fsu.edu/http://www.aw-bc.com/http://www.nhm.org/http://www.geo.cornell.edu/eas/education/course/descr/EAS302/presentations/
It is very easy to find mistakes in these presentations…..I request you to kindly rectify them and supply me the modifications needed at [email protected] a lot and have fun in teaching & learning Zoology….
Phylum Phylum AnnelidaAnnelida
Dr. PARVISH PANDYA’s presentation
PHYLUM ANNELIDAPHYLUM ANNELIDA(Annulus: Little rings)(Annulus: Little rings)
•• HABIT: Free living or HABIT: Free living or EctoparasiticEctoparasitic..•• HABITAT:Sea water, fresh water, moist soil.HABITAT:Sea water, fresh water, moist soil.•• SIZE : It varies from 1 mm to 3SIZE : It varies from 1 mm to 3 metresmetres..•• SHAPE : Body is long, cylindrical or flattened.SHAPE : Body is long, cylindrical or flattened.
Dr. PARVISH PANDYA’s presentation
What is a segmented worm?What is a segmented worm?
•Long and narrow
•Closely related to crabs and snails
•Has a body built of ring-like segments
Dr. PARVISH PANDYA’s presentation
METAMERISMMETAMERISM
MetamerismMetamerism is the phenomenon in which the is the phenomenon in which the body of an animal is divided into body of an animal is divided into anteroantero--posterior row of similar part or sections.posterior row of similar part or sections.These sections are called as segments or These sections are called as segments or metamersmetamers or or somitessomites..It involves a longitudinal division of body of a It involves a longitudinal division of body of a bilaterally symmetrical organism into a linear bilaterally symmetrical organism into a linear series of similar segments.series of similar segments.
Dr. PARVISH PANDYA’s presentation
Metamerism
•Have an anterior prostomium and posterior pygidium; both nonsegmented • Body is divided into a linear series of similar parts or segments, and each segment is called a metamere• The pattern of repeated segmentation is called metamerism• Each metamere is separated from the next by a transverse septum• Each metamere acts as a hydrostatic skeleton• Each metamere has longitudinal and circular muscles; longitudinal muscle contraction causes segments to shorten; circular muscle contraction causes segments to elongate• Each segment usually bears one or more chitinous bristles called setae;help anchor segments
Dr. PARVISH PANDYA’s presentation
TYPES OF METAMERISMTYPES OF METAMERISM
•• True & false True & false metamerismmetamerism..•• Complete and incomplete Complete and incomplete metamerismmetamerism..•• External and internal External and internal metamerismmetamerism..
Dr. PARVISH PANDYA’s presentation
Nervous System• Consists of a brain, which is connected to a pair of ventral longitudinal nerve cords, with a ganglion in each segment (metameric)
Circulatory System• Closed circulatory system, in which the blood is always enclosed within blood vessels that run the length of the body and branch to every segment• Several hearts (5 in earthworms) are used to pump blood through the closed circuit
Dr. PARVISH PANDYA’s presentation
Excretory System
• Consists of paired (metameric) metanephridia• Excretory tubes with ciliated funnels that remove waste from the coelomicfluid; open to the outside via excretory pores.
Note:Not all organ systems are metamericFor example, the digestive system extends the length of the organism and is differentiated along its length
Dr. PARVISH PANDYA’s presentation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Development
of
Metameric,
Coelomic
Spaces
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Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Internal Structures of an Earthworm
Dr. PARVISH PANDYA’s presentation
Dr. PARVISH PANDYA’s presentation
NereisNereis
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Sedentary Polychaete LugwormSedentary Sedentary PolychaetePolychaete LugwormLugworm
MouthMouth
AnusAnus
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Sedentary PolychaeteAmphitriteSedentary Sedentary PolychaetePolychaeteAmphitriteAmphitrite
Dr. PARVISH PANDYA’s presentation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Earthworm Cross -Section
Dr. PARVISH PANDYA’s presentation
Dr. PARVISH PANDYA’s presentation
Class Polychaeta ("many bristles”)
General Characteristics
• Marine worms, including sandworms and clamworms.• Each segment is equipped with a pair of fleshy paddle-like structures -parapodia; used in locomotion• Parapodia contain a large number of chitinous bristles – setae; anchor the worms
Dr. PARVISH PANDYA’s presentation
Polychaetes: General Characteristics cont.
•Prostomium is well equipped with sensory and feeding structures
Dr. PARVISH PANDYA’s presentation
Polychaetes: General Characteristics cont.
• Mouth is located just below the prostomium, but in front of the modified segments - peristomium• Digestive system includes a muscular pharynx that can be everted through the mouth• Pharynx is equipped with pincer-like jaws
• Although many of the smaller polychaetes lack respiratory structures, the larger one do possess gills• Gills are usually modifications of the parapodia
Dr. PARVISH PANDYA’s presentation
• serial repetition of cavities and structures• transverse septa (mesoderm)• selection? • independent regulation• e.g., hydrostatic skeleton• hyp: burrowing efficiency enhanced - competitive edge
• relative energetic of cost of peristaltic waves• regional specialization - tagmatization• restriction of structures, divergence of repeated structures
Internal transport• closed• dorsal vessel is contractile (propels blood)• connected to ventral vessel at gut• hemoglobin• nephridial system• ciliated tube• uptake and removal of nitrogenous wastes• resorption of amino acids, H2O, ions
Dr. PARVISH PANDYA’s presentation
Class Polychaeta: Diversity• Although a number of polychaetes are active predators, some are sedentary and burrow into mud or live in protective tubes in themud• In several of these species filter feeding has evolved• A good example is the fan worm Sabella, with their feather-like head structures called radioles
Dr. PARVISH PANDYA’s presentation
Class Polychaeta: Diversity cont.
• Chaetopterus is tube dweller; lives in a U-shaped tube • Parapodia are highly modified into 3 fan-like structures that bring water into the tube• The notopodium secretes a mucous bag that traps food from the water flowing through the tube; the bag is periodically passed anteriorly toward the mouth
Dr. PARVISH PANDYA’s presentation
Class Polychaeta: Diversity cont.
• Arenicola lives in a J-shaped burrow• It employs peristaltic movements to generate a water flow• Food is filtered out from the front of the burrow
Dr. PARVISH PANDYA’s presentation
Class Oligochaeta cont.• Earthworms feed on vast quantities of soil that contains living and decaying organic material.• Digestive tract of the annelids shows specialization along its length: mouth, pharynx, crop (food storage), gizzard (grinding), calciferous glands (accessory glands that excrete excess calcium from the food) • Remainder of the gut is the intestine - for digestion and absorption• Its surface area is increased because of a dorsal longitudinal fold called the typhlosole
Dr. PARVISH PANDYA’s presentation
Class Oligochaeta ("few bristles")
• Many of the morphological structures are reduced when compared to the polychaetes• Prostomium lacks sensory structures• Parapodia are absent; each segment usually contains one or more pairs of setae; used in locomotion• Aquatic forms usually have larger setae than the terrestrial forms
Dr. PARVISH PANDYA’s presentation
Class Oligochaeta cont.
• Lack respiratory organs; gas exchanges occurs across the body wall• Hermaphroditic, but exchange sperm during copulation• During copulation, worms join their anterior ends; held together by mucous secretions from a clitellum• After reciprocal copulation, sperm is stored in seminal receptacles• Clitellum then secretes a mucous tube that serves as a cocoon• The cocoon moves anteriorly and eggs from the oviduct and sperm from the seminal receptacles are poured into it; fertilization occurs in the cocoon• Cocoon eventually slips off the anterior end of the worm• In time, young worms emerge from the cocoon
Dr. PARVISH PANDYA’s presentation
Class Hirudinea• Body is dorso-ventrally flattened• Anterior segments are modified as a small sucker which surrounds the mouth; posterior segments form a larger sucker• Setae are completely absent• Evidence of segmentation externally, but no internal septa• There is serial repetition of many of the organs (e.g., nephridia and testes)
Dr. PARVISH PANDYA’s presentation
tubes within tubes
dorsal vessel
c.musc.
l.musc.
septum2 layers
nephrostome
ventral vessel
nerve cord
cuticle(collagen)
epidermisglandularinnervated
G I tract
Dr. PARVISH PANDYA’s presentation
Tube Dwellers “Sedentaria”• straight or u-shaped• mucus, CaCO3 ,
sand “reefs”• modified setae• “tentacles”
Dr. PARVISH PANDYA’s presentation
gills (modified parapodia) cilia and gills move water
Dr. PARVISH PANDYA’s presentation
THEORIES ON METAMERISMTHEORIES ON METAMERISM
Different theories has been put forward because it Different theories has been put forward because it occurs both in occurs both in ArthropodaArthropoda & Vertebrates.& Vertebrates.
The various theories are as follows:The various theories are as follows:1)1) Fission theoryFission theory2)2) PseudometamerismPseudometamerism theorytheory3)3) CyclomerismCyclomerism theorytheory4)4) Embryological theoryEmbryological theory5)5) Locomotion theoryLocomotion theory
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SIGNIFICANCE OF SIGNIFICANCE OF METAMERISMMETAMERISM•• LocomotionLocomotion•• BurrowingBurrowing•• ReproductionReproduction•• Rapid evolution of high grade of Rapid evolution of high grade of
organizationorganization
Dr. PARVISH PANDYA’s presentation
REPRODUCTIONREPRODUCTION
•• It takes place both asexually & sexually.It takes place both asexually & sexually.•• Asexual reproduction occurs without the Asexual reproduction occurs without the
fusion of male and female gametes.fusion of male and female gametes.•• Sexual reproduction takes place by the Sexual reproduction takes place by the
fusion of male and female gametes(sex fusion of male and female gametes(sex cells).cells).
Dr. PARVISH PANDYA’s presentation
Reproductive System
• Most annelids are hermaphroditic, but they are usually cross fertilizers.• Earthworms and leeches form pairs and reciprocally fertilize one another• Some annelids (e.g. marine sandworms) are dioecious and they release eggs and sperm into the marine environment, where gametes unite to form trochophore larvae
Dr. PARVISH PANDYA’s presentation
ASEXUAL REPRODUCTION ASEXUAL REPRODUCTION
•• PolychetesPolychetes & & aqaq..oligochetesoligochetes show asexual show asexual reproduction.reproduction.
•• Budding & fragmentation occurs in Budding & fragmentation occurs in polychetespolychetes..
•• Fragmentation is divided into two Fragmentation is divided into two types:a)Orderly and b)Spontaneous. types:a)Orderly and b)Spontaneous.
Dr. PARVISH PANDYA’s presentation
SEXUAL REPRODUCTIONSEXUAL REPRODUCTION
•• It is shown by all the three type classIt is shown by all the three type class•• Class Class polychaetapolychaeta e.g. Aphrodite, e.g. Aphrodite,
AmphitriteAmphitrite, , ArenicolaArenicola etc.etc.•• Class Class oligochaetaoligochaeta e.g. Pheretima.e.g. Pheretima.•• Class Class hirudineahirudinea e.g. e.g. HirudinariaHirudinaria..
Dr. PARVISH PANDYA’s presentation
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.
Earthworm Reproduction
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Class Hirudinea con’t
• Leeches are hermaphroditic but engage in cross-fertilization; some use hypodermic impregnation• Leeches have a clitellum and are capable of generating a cocoon
Dr. PARVISH PANDYA’s presentation
Reproduction• dioecious• epitoky• atokes bud epitokes• dispersal -> mating• trocophore larvae
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MouthMouthMouth
AnusAnusAnus
Trochophore larvaTrochophoreTrochophore larvalarva Apical tuftApical tuftApical tuft
StomachStomachStomach
Ciliary bandCiliaryCiliary bandband
Dr. PARVISH PANDYA’s presentation
Annelid developmentAnnelid developmentAnnelid development
Dr. PARVISH PANDYA’s presentation
The EndThe End