Phylum Mollusca

Protostomes Protostomes Lophotrochozoan group Lophotrochozoan group Eucoelomates (coelomates) Eucoelomates (coelomates) Tridacna squamosa Tridacna gigas

Phylum Mollusca Soft Bodied Soft Bodied Shelled Shelled Some without Some without Cephalization Cephalization Sensory organs Sensory organs Mouths Mouths Body Divisions Body Divisions Visceral Mass Visceral Mass Head-Foot Head-Foot Mantle Mantle Tonicella lineata

Phylum Mollusca Complete digestive tract Complete digestive tract Digestive glands Digestive glands Specialized feeding structures Specialized feeding structures Circulatory system Circulatory system Heart (2 chambers) Heart (2 chambers) Open system in most groups Open system in most groups Closed in cephalopods Closed in cephalopods Coelom restricted to pericardium in most cases Coelom restricted to pericardium in most cases Octopus briareus

Phylum Mollusca Advanced nervous system Advanced nervous system Brain Brain Sensory organs Sensory organs Eyes (simple and camera) Eyes (simple and camera) Sensory papillae Sensory papillae Excretory system Excretory system Kidney-like nephridia Kidney-like nephridia Reproduction Reproduction Monoecious and dioecious Monoecious and dioecious External development External development External & internal fertilization External & internal fertilization

Mollusc Phylogeny ~50-80K extant species ~50-80K extant species ~40K extinct species ~40K extinct species Fossil records from precambrian period of proterozoic eon (>570my BP) Fossil records from precambrian period of proterozoic eon (>570my BP)

Mollusc Phylogeny Mantle secreting shell Mantle secreting shell Muscular foot Muscular foot Chambered heart Chambered heart

Mollusc Taxonomy Major classes Major classes Polyplacophora Polyplacophora Chitons Chitons Chiton tuberculatus lives in the rocky intertidal zones eat algae with its radula 8 shell plates

Mollusc Taxonomy Major classes Major classes Polyplacophora Polyplacophora Gastropoda Gastropoda Subclasses: Subclasses: Prosobranchia Prosobranchia Shelled marine gastropods Shelled marine gastropods Atlantic triton’s trumpet (Charonia variegata) Tiger cowrie (Cypraea tigris)

Mollusc Taxonomy Major classes Major classes Polyplacophora Polyplacophora Gastropoda Gastropoda Subclasses: Subclasses: Prosobranchia Prosobranchia Opisthobranchia Opisthobranchia Sea slugs (marine) Sea slugs (marine) zebra sea goddess (Hypselodoris zebra) Spotted sea hare (Aplysia dactylomela) Phidiana hiltoni

Mollusc Taxonomy Major classes Major classes Polyplacophora Polyplacophora Gastropoda Gastropoda Subclasses: Subclasses: Prosobranchia Prosobranchia Opisthobranchia Opisthobranchia Pulmonata Pulmonata Terrestrial snails/slugs Terrestrial snails/slugs Freshwater snails Freshwater snails Helminthoglypta walkeriana Giant banana slug (Ariolimax columbians)

Mollusc Taxonomy Major classes Major classes Polyplacophora Polyplacophora Gastropoda Gastropoda Bivalvia Bivalvia Clams, oysters, mussels, scallops Clams, oysters, mussels, scallops Bay scallop (Aequipecten irradians) Edible mussels (Mytilus edulis) Ostrea edulis

Mollusc Taxonomy Major classes Major classes Polyplacophora Polyplacophora Gastropoda Gastropoda Bivalvia Bivalvia Cephalopoda Cephalopoda Octopus, squid, nautilus Octopus, squid, nautilus Giant cuttlefish (Sepia latimanus) Nautilus sp Octopus sp

Mollusc Taxonomy Major classes Major classes Polyplacophora Polyplacophora Gastropoda Gastropoda Bivalvia Bivalvia Cephalopoda Cephalopoda Minor classes Minor classes Monoplacophora Monoplacophora Solenogastres Solenogastres Caudofoveata Caudofoveata

Generalized Mollusc Anatomy

Gastropod Feeding Apparatus

Respiration: Gills

Shell Structure & Formation

A Pearl Among the Swine

Mollusc Reproduction & Development Indirect development Indirect development Larval stages Larval stages Trochophore larva Trochophore larva Free swimming, ciliated, shell formation begins Free swimming, ciliated, shell formation begins Veliger larva Veliger larva Free swimming, ciliated velium forms, Free swimming, ciliated velium forms, Shell/body torsion occurs Shell/body torsion occurs Spat Spat Metamorphic form between veliger and juvenile Metamorphic form between veliger and juvenile Shell elaborates Shell elaborates

Trochophore Larva

Gastropod Veliger Larva Velia Mouth Shell

Zygote Trochophore Veliger Spat Juvenile Adult

Adult Abalone

Class Polyplacophora - chitons

Polyplacophoran Anatomy

Class Gastropoda The Shell Game

Class Gastropoda - Torsion

Gastropod Shell Coiling

Gastropod Gill/Mantle Cavity Evolution

Generalized Gastropod Anatomy

Marine Gastropods Cowries

Marine Gastropods Sea Hare – Aplysia sp

Marine Gastropods - Nudibranch

Terrestrial Gastropods - Pulmonata The mantle cavity serves as a “lung” The mantle cavity serves as a “lung” Glandular epidermis Glandular epidermis Secrete mucus (slime) upon which gastropod glides Secrete mucus (slime) upon which gastropod glides

Terrestrial Gastropod - Pulmonata Slugs lack shells Slugs lack shells Mantle thickened Mantle thickened Pneumostome Pneumostome Air intake into mantle cavity Air intake into mantle cavity Pneumostome

Phylum Mollusca, Class Bilvalia Two shells Two shells Incurrent & excurrent siphons Incurrent & excurrent siphons No cephalization No cephalization

Generalized Bivalve Anatomy

Generalized Bivalve Anatomy (XS)

Bivalve Anatomy (Sagittal)

Bivalves are Typically Filter Feeders

Bivalve Life Cycle

Glochidia – Unique Larval Stage of Freshwater Bivalves Internal fertilization Internal fertilization Early development in brood chamber (region of mantle cavity) Early development in brood chamber (region of mantle cavity) Release of glochidia veliger larvae Release of glochidia veliger larvae Glochidia attach to gills of fish and are distributed Glochidia attach to gills of fish and are distributed

Phylum Mollusca, Class Cephalopoda Closed circulatory system Closed circulatory system Shell: lost in Octopus, extremely reduced and enclosed in mantle in squid, planar spiral in Nautilus Shell: lost in Octopus, extremely reduced and enclosed in mantle in squid, planar spiral in Nautilus Cephalization Cephalization eye eye Beak around mouth Beak around mouth Tentacles/arms Tentacles/arms

Cephalopod Anatomy

Squid are the largest Cephalopods

Nautilus Anatomy

Cephalopod Eye

Mating

Direct Development in Cephalopods

Color & Morphology Changes for Camouflage