11 mollusca

Phylum MolluscaPhylum Mollusca

Phylum MolluscaPhylum Mollusca ProtostomesProtostomes Lophotrochozoan group Lophotrochozoan group Eucoelomates Eucoelomates

(coelomates)(coelomates)

Tridacna squamosa

Tridacna gigas

Phylum MolluscaPhylum Mollusca Soft BodiedSoft Bodied ShelledShelled

Some withoutSome without CephalizationCephalization

Sensory organsSensory organs MouthsMouths

Body DivisionsBody Divisions Visceral MassVisceral Mass Head-FootHead-Foot MantleMantle

Tonicella lineata

Phylum MolluscaPhylum Mollusca Complete digestive tractComplete digestive tract Digestive glandsDigestive glands Specialized feeding Specialized feeding

structuresstructures Circulatory system Circulatory system

Heart (2 chambers)Heart (2 chambers) Open system in most Open system in most

groupsgroups Closed in cephalopodsClosed in cephalopods

Coelom restricted to pericardium in Coelom restricted to pericardium in most casesmost cases

Octopus briareus

Phylum MolluscaPhylum Mollusca Advanced nervous Advanced nervous

systemsystem BrainBrain Sensory organsSensory organs

Eyes (simple and Eyes (simple and camera)camera)

Sensory papillae Sensory papillae Excretory systemExcretory system

Kidney-like nephridiaKidney-like nephridia ReproductionReproduction

Monoecious and Monoecious and dioeciousdioecious

External developmentExternal development External & internal External & internal

fertilizationfertilization

Mollusc PhylogenyMollusc Phylogeny

~50-80K ~50-80K extant speciesextant species

~40K extinct ~40K extinct speciesspecies

Fossil records Fossil records from from precambrian precambrian period of period of proterozoic proterozoic eon (>570my eon (>570my BP)BP)

Mollusc Mollusc PhylogenyPhylogeny Mantle Mantle

secreting secreting shellshell

Muscular footMuscular foot Chambered Chambered

heartheart

Mollusc TaxonomyMollusc Taxonomy

Major classesMajor classesPolyplacophora Polyplacophora

ChitonsChitons

Chiton tuberculatusChiton tuberculatus lives in the rocky lives in the rocky intertidal zones eat intertidal zones eat algae with its radulaalgae with its radula

8 shell plates8 shell plates

Mollusc TaxonomyMollusc Taxonomy

Major classesMajor classes Polyplacophora Polyplacophora

GastropodaGastropodaSubclasses:Subclasses:ProsobrancProsobranchiahia

Shelled Shelled marine marine gastropodsgastropods

Atlantic triton’s trumpet Atlantic triton’s trumpet ((Charonia variegataCharonia variegata))

Tiger cowrie (Tiger cowrie (Cypraea tigrisCypraea tigris))

Mollusc TaxonomyMollusc Taxonomy

Major classesMajor classes Polyplacophora Polyplacophora

GastropodaGastropodaSubclasses:Subclasses: ProsobranchiaProsobranchia

OpisthobranOpisthobranchiachia

Sea slugs Sea slugs (marine)(marine)

zebra sea goddesszebra sea goddess((Hypselodoris zebraHypselodoris zebra))

Spotted sea hare (Spotted sea hare (Aplysia dactylomelaAplysia dactylomela))

Phidiana hiltoni

Mollusc TaxonomyMollusc Taxonomy

Major classesMajor classes Polyplacophora Polyplacophora

GastropodaGastropodaSubclasses:Subclasses: ProsobranchiaProsobranchia OpisthobranchiaOpisthobranchia

PulmonataPulmonata Terrestrial Terrestrial

snails/slugssnails/slugs Freshwater Freshwater

snailssnails

Helminthoglypta walkeriana

Giant banana slug (Ariolimax columbians)

Mollusc TaxonomyMollusc Taxonomy Major classesMajor classes

PolyplacophoPolyplacophora ra

GastropodaGastropoda

BivalviaBivalvia Clams, Clams,

oysters, oysters, mussels, mussels, scallopsscallops

Bay scallop (Aequipecten irradians)

Edible mussels (Mytilus edulis)

Ostrea edulis

Mollusc TaxonomyMollusc Taxonomy

Major classesMajor classes Polyplacophora Polyplacophora GastropodaGastropoda BivalviaBivalvia

CephalopodaCephalopoda Octopus, squid, nautilusOctopus, squid, nautilus

Giant cuttlefish (Giant cuttlefish (Sepia latimanusSepia latimanus))

Nautilus sp

Octopus sp

Mollusc TaxonomyMollusc Taxonomy

Major classesMajor classes Polyplacophora Polyplacophora GastropodaGastropoda BivalviaBivalvia CephalopodaCephalopoda

Minor classesMinor classes MonoplacophoraMonoplacophora SolenogastresSolenogastres CaudofoveataCaudofoveata

Generalized Mollusc AnatomyGeneralized Mollusc Anatomy

Gastropod Feeding Gastropod Feeding ApparatusApparatus

Respiration: GillsRespiration: Gills

Shell Structure & FormationShell Structure & Formation

A Pearl Among the SwineA Pearl Among the Swine

Mollusc Reproduction & Mollusc Reproduction & DevelopmentDevelopment Indirect developmentIndirect development

Larval stagesLarval stages Trochophore larvaTrochophore larva

Free swimming, ciliated, shell formation Free swimming, ciliated, shell formation beginsbegins

Veliger larvaVeliger larva Free swimming, ciliated velium forms, Free swimming, ciliated velium forms, Shell/body torsion occursShell/body torsion occurs

SpatSpat Metamorphic form between veliger and Metamorphic form between veliger and

juvenilejuvenile Shell elaboratesShell elaborates

Trochophore LarvaTrochophore Larva

Gastropod Veliger LarvaGastropod Veliger Larva

Velia

Mouth

Shell

Zygote

Trochophore

Veliger

Spat

Juvenile

Adult

Adult AbaloneAdult Abalone

Class Polyplacophora - chitonsClass Polyplacophora - chitons

Polyplacophoran AnatomyPolyplacophoran Anatomy

Class Class GastropodaGastropodaThe Shell GameThe Shell Game

Class Gastropoda - TorsionClass Gastropoda - Torsion

Gastropod Shell Gastropod Shell CoilingCoiling

Gastropod Gastropod Gill/Mantle Cavity Gill/Mantle Cavity EvolutionEvolution

Generalized Gastropod Generalized Gastropod AnatomyAnatomy

Marine GastropodsMarine Gastropods

Cowries

Marine GastropodsMarine Gastropods

Sea Hare – Aplysia sp

Marine Gastropods - Marine Gastropods - NudibranchNudibranch

Terrestrial Gastropods Terrestrial Gastropods - Pulmonata- Pulmonata

The mantle cavity The mantle cavity serves as a “lung”serves as a “lung”

Glandular Glandular epidermisepidermis Secrete mucus Secrete mucus

(slime) upon which (slime) upon which gastropod glidesgastropod glides

Terrestrial Gastropod - Terrestrial Gastropod - PulmonataPulmonata

Slugs lack Slugs lack shellsshells

Mantle thickenedMantle thickened PneumostomePneumostome

Air intake into mantle cavityAir intake into mantle cavity

PneumostomePneumostome

Phylum Mollusca, Class Phylum Mollusca, Class BilvaliaBilvalia Two shellsTwo shells Incurrent & excurrent siphonsIncurrent & excurrent siphons No cephalizationNo cephalization

Generalized Bivalve AnatomyGeneralized Bivalve Anatomy

Generalized Bivalve Anatomy Generalized Bivalve Anatomy (XS)(XS)

Bivalve Anatomy (Sagittal)Bivalve Anatomy (Sagittal)

Bivalves are Typically Filter Bivalves are Typically Filter FeedersFeeders

Bivalve Life CycleBivalve Life Cycle

Glochidia – Unique Larval Stage of Glochidia – Unique Larval Stage of Freshwater BivalvesFreshwater Bivalves

Internal fertilization Internal fertilization Early development in Early development in

brood chamber brood chamber (region of mantle (region of mantle cavity)cavity)

Release of glochidia Release of glochidia veliger larvaeveliger larvae

Glochidia attach to Glochidia attach to gills of fish and are gills of fish and are distributeddistributed

Phylum Mollusca, Class Phylum Mollusca, Class CephalopodaCephalopoda Closed circulatory systemClosed circulatory system

Shell: lost in Octopus, extremely Shell: lost in Octopus, extremely reduced and enclosed in mantle in reduced and enclosed in mantle in squid, planar spiral in Nautilussquid, planar spiral in Nautilus

CephalizationCephalization eyeeye Beak around Beak around

mouthmouth Tentacles/armsTentacles/arms

Cephalopod AnatomyCephalopod Anatomy

Squid are the largest Squid are the largest CephalopodsCephalopods

Nautilus AnatomyNautilus Anatomy

Cephalopod EyeCephalopod Eye

MatingMating

Direct Development in Direct Development in CephalopodsCephalopods

Color & Morphology Changes for Color & Morphology Changes for CamouflageCamouflage