phylum mollusca. molluscan diversity
TRANSCRIPT
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Phylum MolluscaPhylum Mollusca
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Molluscan diversityMolluscan diversity
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PoriferaPoriferaPoriferaPorifera
CycliophoraCycliophoraCycliophoraCycliophora
CnidariaCnidariaCnidariaCnidariaCtenophoraCtenophoraCtenophoraCtenophora
SipunculaSipunculaSipunculaSipunculaMolluscaMolluscaMolluscaMolluscaAnnelidaAnnelidaAnnelidaAnnelida
OnychophoraOnychophoraOnychophoraOnychophoraTardigradaTardigradaTardigradaTardigrada
BryozoaBryozoaBryozoaBryozoa
PlatyhelminthesPlatyhelminthesPlatyhelminthesPlatyhelminthes
NemerteaNemerteaNemerteaNemertea
RotiferaRotiferaRotiferaRotifera
GnathostomulidaGnathostomulidaGnathostomulidaGnathostomulidaGastrotrichaGastrotrichaGastrotrichaGastrotricha
NematodaNematodaNematodaNematodaNematomorphaNematomorphaNematomorphaNematomorpha
PriapulidaPriapulidaPriapulidaPriapulidaKinorhynchaKinorhynchaKinorhynchaKinorhynchaLoriciferaLoriciferaLoriciferaLoricifera
PhoronidaPhoronidaPhoronidaPhoronidaBrachiopodaBrachiopodaBrachiopodaBrachiopoda
EchinodermataEchinodermataEchinodermataEchinodermata
ChordataChordataChordataChordataHemichordataHemichordataHemichordataHemichordata
ArthropodaArthropodaArthropodaArthropoda
Adapted from Lesser Known ProtostomeAdapted from Lesser Known ProtostomePhyla. SICB 2001. J.R. Garey. Phyla. SICB 2001. J.R. Garey.
Possess trochophore larvaePossess trochophore larvae
Mollusca and Annelida are closely allied phyla
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93,000 species of described molluscs (extant) + 70,000 more species from fossil record93,000 species of described molluscs (extant) + 70,000 more species from fossil record
Echinodermata
Ciliophora
Chordata
Mollusca
Platyhelminthes
Nematoda
PoriferaAnnelida
Other
Apicomplex
Sarcomastigophora
Arthropoda
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Defining characteristics of Mollusca• Bilateral symmetry, cephalization• Coelom (around heart)• Mantle
– draped over viscera– secretes shell
• Complete digestive tract, Radula • Trochophore larvae (often also veliger larvae)• Locomotion by muscular foot• Heart, liver, gills (ctenidia), kidney
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Phylum.Phylum. Mollusca MolluscaClass.Class. Aplacophora Aplacophora
Class.Class. Polyplacophora Polyplacophora
Class.Class. Monoplacophora Monoplacophora
Class.Class. Gastropoda Gastropoda
Class.Class. Cephalopoda Cephalopoda
Class.Class. Bivalvia Bivalvia
Class.Class. Scaphopoda Scaphopoda
Phylum.Phylum. Mollusca MolluscaClass.Class. Aplacophora Aplacophora
Class.Class. Polyplacophora Polyplacophora
Class.Class. Monoplacophora Monoplacophora
Class.Class. Gastropoda Gastropoda
Class.Class. Cephalopoda Cephalopoda
Class.Class. Bivalvia Bivalvia
Class.Class. Scaphopoda Scaphopoda
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Aplacophora Polyplacophora Mon
opla
coph
ora
Gas
tropo
daCep
halo
poda
Bivalvia Scaphopoda
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Mollusc origins?
Platyhelminthe-like ancestor with spicules on dorsal surface, cilia on ventral surface, and dorsoventral musculature.
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Mollusc origins?
Spicules fuse to form dorsal shell, cilia on ventral surface, and dorsoventral musculature.
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Mollusc origins?
Spicules fuse to form dorsal shell, cilia on ventral surface, dorsoventral musculature, gonads and excretory pores in mantle cavity
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Mollusc origins?
Spicules fuse to form dorsal shell, cilia on ventral surface, dorsoventral musculature, gonads, excretory pores, and ctenidia, in mantle cavity.
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HAM: Hypothetical ancestral molluscHAM: Hypothetical ancestral mollusc
Mantle cavityMantle cavityMantle cavityMantle cavity
CtenidiumCtenidiumCtenidiumCtenidium
Pericardial cavityPericardial cavityPericardial cavityPericardial cavity MetanephridiumMetanephridiumMetanephridiumMetanephridium
RadulaRadulaRadulaRadula
GonadGonadGonadGonad
Stomach and digestive glandStomach and digestive glandStomach and digestive glandStomach and digestive gland FootFootFootFoot
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Dorsal mantle covers the visceral mass.
Dorsal mantle covers the visceral mass.
Secretes the shellSecretes the shell
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Mollusc shellMollusc shell
PeriostracumPeriostracumPeriostracumPeriostracum
Prismatic layerPrismatic layerPrismatic layerPrismatic layer
Nacreous layerNacreous layerNacreous layerNacreous layer
Mantle epitheliumMantle epitheliumMantle epitheliumMantle epithelium
Mantle lobesMantle lobesMantle lobesMantle lobes
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Pearl formationPeriostracumPeriostracumPeriostracumPeriostracum
Prismatic layerPrismatic layerPrismatic layerPrismatic layer
Nacreous layerNacreous layerNacreous layerNacreous layer
Developing pearlDeveloping pearlDeveloping pearlDeveloping pearl
EpitheliumEpitheliumEpitheliumEpithelium
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Ctenidium (Respiration)Ctenidium (Respiration)
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Ctenidium (gill)Ctenidium (gill)InterlamellarInterlamellarjunctionsjunctionsInterlamellarInterlamellarjunctionsjunctions
OstiumOstiumOstiumOstium
FrontalFrontalciliacilia
FrontalFrontalciliacilia
Blood vesselBlood vesselBlood vesselBlood vessel
ExhalentExhalentwaterwaterExhalentExhalentwaterwater
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Paired ventral nerve cordsPaired ventral nerve cords
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Complete digestive systemComplete digestive system
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RadulaRadula
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RadulaRadula
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Aplacophora
Gill foldsGill foldsGill foldsGill folds MouthMouthMouthMouth
Pedal pitPedal pitPedal pitPedal pit
Pedal groovePedal groovePedal groovePedal groove
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Class Aplacophora
• 320 spp, all marine
• No fossil record (!) & poorly studied
• Calcareous spines and scales in epidermis (no true shell)
• Radula used for grasping
• Burrow in the substrate
• Eat cnidarians
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PolyplacophoraPolyplacophora
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Polyplacophora
Mantle cavityMantle cavityMantle cavityMantle cavityMouthMouthMouthMouth
CtenidiumCtenidiumCtenidiumCtenidium
FootFootFootFoot
AnusAnusAnusAnus
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PolyplacophoraPolyplacophora
MouthMouthMouthMouth
DigestiveDigestiveglandgland
DigestiveDigestiveglandgland
StomachStomachStomachStomach GonadGonadGonadGonadPericardial cavityPericardial cavityPericardial cavityPericardial cavity
NephridiumNephridiumNephridiumNephridium
AnusAnusAnusAnus
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Polyplacophora
• The “chitons”
• 800 spp, marine
• Typically, shell = 8 dorsal plates
• Ctenidia use counter-current gas exchange
• Commonly encountered in the intertidal zone