41ea0e04de2b46c7b5c4d8c5d51ecbfb 11...Class Cephalopoda • Shell – Reduced or absent except in...
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11/30/18 1 Chapter 11 Molluscan Success Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Evolu4onary Perspec4ve • Triploblas4c • Coelomate • Very successful – 100,000 living species • Rela4onships to other animals – Lophotrochozoans Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Figure 11.1 Evolu4onary Rela4onships of Molluscs to Other Animals. Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Table 11.1. Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Molluscan Characteris4cs 1. Body of two parts: head-foot and visceral mass 2. Mantle that secretes a calcareous shell and covers the visceral mass 3. Mantle cavity func4ons in excre4on, gas exchange, elimina4on of diges4ve wastes, and release of reproduc4ve products. 4. Bilateral symmetry 5. Trochophore larvae, spiral cleavage, and schizocoelous coelom forma4on 6. Coelom reduced 7. Open circulatory system (except Cephalopoda) 8. Radula usually present Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education. Body Organiza4on • Head-foot – Elongate – Mouth – Foot for aWachment and locomo4on • Visceral mass – Dorsal to head-foot – Organs of diges4on, circula4on, reproduc4on, excre4on • Mantle – Enfolds body – Secretes shell • Mantle cavity – Gas exchange, excre4on, elimina4on of diges4ve wastes and reproduc4ve products • Radula – Supported by odontophore – Rasping food Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
Transcript of 41ea0e04de2b46c7b5c4d8c5d51ecbfb 11...Class Cephalopoda • Shell – Reduced or absent except in...
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Chapter11
MolluscanSuccess
Copyright © 2016 McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
Evolu4onaryPerspec4ve
• Triploblas4c• Coelomate• Verysuccessful
– 100,000livingspecies• Rela4onshipstootheranimals
– Lophotrochozoans
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Figure11.1Evolu4onaryRela4onshipsofMolluscstoOtherAnimals.
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Table11.1.
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MolluscanCharacteris4cs1. Bodyoftwoparts:head-footandvisceralmass2. Mantlethatsecretesacalcareousshellandcoversthevisceralmass3. Mantlecavityfunc4onsinexcre4on,gasexchange,elimina4onofdiges4ve
wastes,andreleaseofreproduc4veproducts.4. Bilateralsymmetry5. Trochophorelarvae,spiralcleavage,andschizocoelouscoelomforma4on6. Coelomreduced7. Opencirculatorysystem(exceptCephalopoda)8. Radulausuallypresent
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BodyOrganiza4on• Head-foot
– Elongate– Mouth– FootforaWachmentandlocomo4on
• Visceralmass– Dorsaltohead-foot– Organsofdiges4on,circula4on,reproduc4on,excre4on
• Mantle– Enfoldsbody– Secretesshell
• Mantlecavity– Gasexchange,excre4on,elimina4onofdiges4vewastesandreproduc4ve
products• Radula
– Supportedbyodontophore– Raspingfood
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Figure11.2Molluscanbodyorganiza4on.
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Figure11.3Molluscanshellandmantle.
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Figure11.4Radularstructure.
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ClassGastropoda• Snails,limpetsandslugs• 35,000livingspecies• Torsion
– 180ocounterclockwisetwis4ngofvisceralmass,mantle,andmantlecavityduringdevelopment
– Possibleadap4vesignificance• Headentersshellfirst.• Cleanwaterentersanteriorlyorientedmantlecavityopening.
• Mantlesensoryorgansmovetoheadregion.
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Figure11.5TorsioninGastropods.(a)Apretorsiongastropodlarva.(b)A\ertorsionthediges4vetractisloopedandmantleopensnearhead.(c)Hypothe4caladultancestorpriortotorsion.(d)Modernadultgastropoda\ertorsion.
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ClassGastropoda• Shellcoiling
– Earliestfossils,oneplane– Modern,asymmetrical
• Morecompact• Internalorgansasymmetricalandsome4mesnolongerpaired
• Locomo4on– FlaWenedfoot– Ciliapropelovermucoustrail– Muscularwaves
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ClassGastropoda• Feedinganddiges4on
– MostscrapealgaeandaWachedorganisms– Herbivores,predators,scavengers– Diges4vetract
• Ciliated• Foodincorporatedintomucousmasscalledprotostyle.
• Gasexchange– Oneortwogillsinmantlecavity– Landsnails(pulmonates)
• Mantlecavityrichlyvascularforgasexchangewithair
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Figure11.6Gastropodstructure.
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OtherMaintenanceFunc4ons• Opencirculatorysystem
– Bloodbathes4ssuesinsinuses.– Heart
• Singleventricleandsingleauricle– Func4ons
• Transportsnutrients,wastesandgases• Hydraulicskeleton
• Nervoussystem– Sixgangliaplusnervecords
• Sensorystructures– Eyesatbaseorendoftentacles– Statocystsinfoot– Osphradiainmantlecavity
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OtherMaintenanceFunc4ons
• Excre4on– Singlenephridium
• Resultofshellcoiling– Dischargesintomantlecavityoradjacenttomantlecavity(pulmonates)
– Ammonia(aqua4cspecies)– Uricacid(pulmonates)
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Reproduc4on• Dioecious
– Externalfer4liza4on• Eggsshedsinglyorinmasses• Somedioeciousmarinespecies
• Monoecious– Copula4onforinternalfer4liza4on
• Spermtransfermaybemutualorone-way.• Eggsshedinstringsorinmasses
– Larvalstages• Trochophore• Veliger–foot,eyes,tentacles,shell
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GastropodDiversity• Subclasses
– Prosobranchia• 20,000species• Mostlymarine
– Opisthobranchia• 2,000species• Mostlymarine• Seahares,seaslugs• Shell,mantlecavity,andgillsreducedorlost
– Pulmonata• 17,000species• Freshwaterorterrestrial• Vascularmantlecavityservesaslung
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Figure11.7Varia4onsintheGastropodBodyForm.
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ClassBivalvia
• Clams,oysters,mussels,scallops• 30,000species• Shellandassociatedstructures
– Singleshellconsis4ngoftwohingedvalves(figure11.8)
– Mantlesheetlikeandcoverslaterallycompressedbody.
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Figure11.8InsideViewofaBivalveShell.
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GasExchange,FilterFeeding,andDiges4on
• Sedentaryfilterfeeders– Lossofheadandradula– Expansionofcilia-coveredgillsintofoldedsheets(lamellae)
• Ciliacreatewatercurrentsintoandthroughmantlecavity.
– Gasexchangeinwatertubes(figure11.9)– Foodtrappedalonggillsurfaceandtransportedtofoodgroovesandlabialpalps(figure11.10).
– Diges4on(figure11.11)• Crystalinestyleandgastricshield
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Figure11.9Lamellibranchgillofabivalve.Bluearrowsshowwatermovement.Redarrowsshowbloodmovement.
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Figure11.10Bivalvefeeding.Solidpurplearrowsshowpathoffoodpar4cles.Dashedpurplearrowsshowpathofpar4clesbeingrejected.
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Figure11.11Bivalvestructure.
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OtherMaintenanceFunc4ons• Opencirculatorysystem
– Mantleandgillsoxygenateblood
• Nephridia– Belowpericardialcavity– Opentosuprabranchialchamber
• Nervoussystem– Threepairsofinterconnectedganglia– Sensoryreceptorsatmantlemargin
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Reproduc4onandDevelopment
• Mostlydioecious• Gonadswithinvisceralmass• Mostlyexternalfer4liza4on• Trochophoreandveligerlarvalstages(figure11.13a,b)
• FreshwaterinfamilyUnionidae– Parasi4clarvalstage– Glochidium(figures11.13cand11.14)
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Figure11.12BivalveCircula4on.
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Figure11.13Trochophore(a)andveliger(b)larvalstages.Glochidiaofanunionidbivalve.
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Figure11.14Mantlelureofafreshwaterbivalve(Lampsilisreeviana).
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Figure11.15aBivalveDiversity.Giantclam(Tridacnadersa).
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Figure11.15bBivalvediversity.Rockscallop(Hinnitesgiganteus).
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Figure11.15cBivalvediversity.Thegoeduck(Panopeagenerosa).
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ClassCephalopoda
• Squid,octopuses,cuWlefish,andnau4luses• Footmodifiedintocircleoftentaclesorarmsandincorporatedintosiphon
• Headinlinewithvisceralmass• Muscularmantle(figure11.17)
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Figure11.17Internalstructureofthesquid,Loligo.
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prior written consent of McGraw-Hill Education.
ClassCephalopoda• Shell
– Reducedorabsentexceptinnau4lus• Locomo4on
– Jetpropulsionusingmusclesofmantlecompressingwaterwithinmantlecavityandsiphon
• FeedingandDiges4on– Predators
• Tentacles,jaws,radula– Diges4vetractmuscularwithlargediges4veglands
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Figure11.18Cephalopodarmsandtentacles.
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OtherMaintenanceFunc4ons• Closedcirculatorysystem• Nervoussystem
– Largebrains– Complexsensorystructures
• Eyes• Statocysts
• Chromatophores– Colorchangesinvolvedwithcourtshipandotherdisplays
• Inkglands
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Figure11.19Thecephalopodeye.
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Learning
• Unparalleledincomparisontoanyotherinvertebrateandmanyvertebrates
• Evolvedinresponsetopredatorylifestyles
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Reproduc4onandDevelopment
• Dioecious• Maleproducesspermatophores
– Transferstofemale’smantlecavityusingmodifiedtentacle(hectocotylus)
• EggsdepositedsinglyorinmassesaWachedtosubstrate.
• Eggstendedbyparents.
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ClassPolyplacophora• Chitons• Reducedhead,flaWenedfoot,shellconsis4ngofeightdorsalvalves,muscularmantleextendsbeyondmarginofshell(figure11.20)
• FeedonaWachedalgae• Ladderlikenervoussystem• Dioeciouswithexternalfer4liza4on
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Figure11.20ClassPolyplacophora.(a)Tonicellalineata.
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ClassScaphopoda
• Toothshellsortuskshells• Marine,burrowing• Conicalshellopenatbothends• Dioeciouswithtrochophoreandveligerlarvae
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Figure11.21ClassScaphopoda.
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ClassMonoplacophora
• Marine• Undivided,archedshell• Broad,flatfoot• Seriallyrepeatedpairsofgillsandfootretractormuscles
• Dioecious• Embryologyunknown
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Figure11.22ClassMonoplacophora.
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Figure11.23ClassSolenogastres
ClassSolenogastres
• Marinesubstrates• Lackshell• Crawlonventralfoot• Minutecalcareousspicules
• Carnivores
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ClassCaudofoveata
• Deepsea• Wormlike• Feedonforaminifera• Lackshell,foot,andnephridia• 120species
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FurtherPhylogene4cConsidera4ons
• Morethan500millionyearsold• Lophotrochozoa• Shellandmuscularfootnotancestral
– Solenogasterspiculesmaybesimilartoancestral“shell”.
– MuscularfootfirstseeninPolyplacophora.
• Quicklydiversifiedintomodernclasses(figure11.24)
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Figure 11.24 Molluscan Phylogeny.
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