Phylum Mollusca
Phylum Mollusca Protostomes Lophotrochozoan group Eucoelomates (coelomates) Tridacna gigas Tridacna squamosa
Phylum Mollusca Soft Bodied Shelled Some without Cephalization Sensory organs Mouths Body Divisions Visceral Mass Head-Foot Mantle Tonicella lineata
Phylum Mollusca Complete digestive tract Octopus briareus Digestive glands Specialized feeding structures Circulatory system Heart (2 chambers) Open system in most groups Closed in cephalopods Coelom restricted to pericardium in most cases
Phylum Mollusca Advanced nervous system Brain Sensory organs Eyes (simple and camera) Sensory papillae Excretory system Kidney-like nephridia Reproduction Monoecious and dioecious External development External & internal fertilization
Mollusc Phylogeny ~50-80K extant species ~40K extinct species Fossil records from precambrian period of proterozoic eon (>570my BP)
Mollusc Phylogeny Mantle secreting shell Muscular foot Chambered heart
Mollusc Taxonomy Major classes Polyplacophora Chitons Chiton tuberculatus lives in the rocky intertidal zones eat algae with its radula 8 shell plates
Mollusc Taxonomy Atlantic triton s trumpet (Charonia variegata) Major classes Polyplacophora Gastropoda Subclasses: Prosobranchia Shelled marine gastropods Tiger cowrie (Cypraea tigris)
Mollusc Taxonomy Spotted sea hare (Aplysia dactylomela Major classes Polyplacophora Gastropoda Subclasses: Prosobranchia Opisthobranchia Sea slugs (marine) Phidiana hiltoni zebra sea goddess (Hypselodoris zebra)
Mollusc Taxonomy Helminthoglypta walkeriana Major classes Polyplacophora Gastropoda Subclasses: Prosobranchia Opisthobranchia Pulmonata Terrestrial snails/slugs Freshwater snails Giant banana slug (Ariolimax columbians)
Mollusc Taxonomy Major classes Polyplacophora Gastropoda Bivalvia Clams, oysters, mussels, scallops Ostrea edulis Bay scallop (Aequipecten irradians) Edible mussels (Mytilus edulis)
Mollusc Taxonomy Giant cuttlefish (Sepia latimanus) Major classes Polyplacophora Gastropoda Bivalvia Cephalopoda Octopus sp Octopus, squid, nautilus Nautilus sp
Mollusc Taxonomy Major classes Polyplacophora Gastropoda Bivalvia Cephalopoda Minor classes Monoplacophora Solenogastres Caudofoveata
Generalized Mollusc Anatomy
Gastropod Feeding Apparatus
Respiration: Gills
Shell Structure & Formation
A Pearl Among the Swine
Mollusc Reproduction & Development Indirect development Larval stages Trochophore larva Free swimming, ciliated, shell formation begins Veliger larva Free swimming, ciliated velium forms, Shell/body torsion occurs Spat Metamorphic form between veliger and juvenile Shell elaborates
Trochophore Larva
Gastropod Veliger Larva Mouth Velia Shell
Veliger Zygote Trochophore Juvenile Adult Spat
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 Glandular epidermis Secrete mucus (slime) upon which gastropod glides
Terrestrial Gastropod - Pulmonata Pneumostome Slugs lack shells Mantle thickened Pneumostome Air intake into mantle cavity
Phylum Mollusca, Class Bilvalia Two shells Incurrent & excurrent siphons 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 Early development in brood chamber (region of mantle cavity) Release of glochidia veliger larvae Glochidia attach to gills of fish and are distributed
Phylum Mollusca, Class Cephalopoda Closed circulatory system Shell: lost in Octopus, extremely reduced and enclosed in mantle in squid, planar spiral in Nautilus Cephalization eye Beak around mouth Tentacles/arms
Cephalopod Anatomy
Squid are the largest Cephalopods
Nautilus Anatomy
Cephalopod Eye
Mating
Direct Development in Cephalopods
Color & Morphology Changes for Camouflage