Phylum Mollusca Fig. 16.CO
Phylum Mollusca Protostomes Lophotrochozoan group Eucoelomates (coelomates) Tridacna gigas Tridacna squamosa
Phylum Mollusca Soft Bodied Shelled Cephalization Body Divisions Some without Cephalization Sensory organs Mouths Body Divisions Visceral Mass Head-Foot Mantle Fig. 16.1a Tonicella lineata
Phylum Mollusca Complete digestive tract Digestive glands Octopus briareus Complete digestive tract 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 Excretory system Reproduction 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 Mantle secreting shell Muscular foot Chambered heart Fig. 16.42
Mollusc Taxonomy Polyplacophora Major classes Chitons Chiton tuberculatus lives in the rocky intertidal zones eat algae with its radula 8 shell plates Major classes Polyplacophora Chitons
Mollusc Taxonomy Gastropoda Major classes Subclasses: Prosobranchia Atlantic triton’s trumpet (Charonia variegata) Major classes Polyplacophora Gastropoda Subclasses: Prosobranchia Shelled marine gastropods Tiger cowrie (Cypraea tigris)
Mollusc Taxonomy Gastropoda Major classes Subclasses: Opisthobranchia Spotted sea hare (Aplysia dactylomela) Major classes Polyplacophora Gastropoda Subclasses: Prosobranchia Opisthobranchia Sea slugs (marine) Phidiana hiltoni zebra sea goddess (Hypselodoris zebra)
Mollusc Taxonomy Gastropoda Major classes Subclasses: Pulmonata Helminthoglypta walkeriana Major classes Polyplacophora Gastropoda Subclasses: Prosobranchia Opisthobranchia Pulmonata Terrestrial snails/slugs Freshwater snails Giant banana slug (Ariolimax columbians)
Mollusc Taxonomy Bivalvia Major classes Polyplacophora Gastropoda Bay scallop (Aequipecten irradians) Major classes Polyplacophora Gastropoda Bivalvia Clams, oysters, mussels, scallops Edible mussels (Mytilus edulis) Ostrea edulis
Mollusc Taxonomy Major classes Cephalopoda Polyplacophora Gastropoda Giant cuttlefish (Sepia latimanus) Major classes Polyplacophora Gastropoda Bivalvia Cephalopoda Octopus, squid, nautilus Octopus sp Nautilus sp
Generalized Mollusc Anatomy Fig. 16.2
Gastropod Feeding Apparatus Fig. 16.3
Respiration: Gills Fig. 16.4
Shell Structure & Formation Fig. 16.5a
A Pearl Among the Swine Fig. 16.5b
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 Fig. 16.6
Gastropod Veliger Larva Mouth Velia Fig. 16.7 Shell
Veliger Zygote Trochophore Juvenile Spat Adult
Adult Abalone Fig. 16.15a
Class Gastropoda The Shell Game Fig. 16.12
Class Gastropoda - Torsion Fig. 16.13
Gastropod Shell Coiling Fig. 16.14
Generalized Gastropod Anatomy Fig. 16.18
Marine Gastropods Cowries Fig. 16.20b
Marine Gastropods Sea Hare – Aplysia sp Fig. 16.21
Marine Gastropods - Nudibranch Fig. 16.22
Terrestrial Gastropods - Pulmonata The mantle cavity serves as a “lung” Glandular epidermis Secrete mucus (slime) upon which gastropod glides Fig. 16.23a
Terrestrial Gastropod - Pulmonata Pneumostome Fig. 16.23b Slugs lack shells Mantle thickened Pneumostome Air intake into mantle cavity
Phylum Mollusca, Class Bilvalia Two shells Incurrent & excurrent siphons No cephalization Fig. 16.25
Generalized Bivalve Anatomy Fig. 16.26
Bivalve Anatomy (Sagittal) Fig. 16.31b
Bivalves are Typically Filter Feeders Fig. 16.31a
Bivalve Life Cycle Fig. 16.34
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 Fig. 16.35a
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 Fig. 16.37
Cephalopod Anatomy Fig. 16.38a
Squid are the largest Cephalopods
Cephalopod Eye Fig. 16.39
Mating Fig. 16.40
Direct Development in Cephalopods
Color & Morphology Changes for Camouflage