Polyplacophora Gastropoda Bivalvia Cephalopoda Mollusks Polyplacophora Gastropoda Bivalvia Cephalopoda

Eucoelomates

Trochophore Larva Many mulloscs start as free swimming trochophore larva Larava pass through an intermediate stage called veliger

Basic Anatomy

Body Plan Head/Foot Visceral Mass Mantle Sense organs, locomotion, mouth Visceral Mass Organ systems Mantle Secretes shell Gaseous exchange (gills or lungs)

Radula Rasping tongue Scrapes food from surface Pulls food into mouth Drills holes into shells

Class Polyplacophora Chitons Shell made of plates Organs Three chambered heart 2 kidneys Mouth and anus open at opposite ends

Polyplacophora Body Plan

Class Gastropoda Snails, abalone, slugs, nudibranchs, limpets Slow moving predators or herbivores Organ systems Gills in most, some have lungs Single kidney Ganglia Some are hermaphrodites Coiling and torsion of visceral mass

Gastropoda Body Plan

Gastropoda Torsion

Gastropoda Coiling

Class Bivalvia Clams, muscles, scallops Organ systems Laterally compressed Shell in two halves, hinged Suspension feeders Organ systems Three chambered heart Three small ganglia Scallops have multiple complex eyes

Bivalvia Feeding

Bivalvia Body Plan

Ship Worms Bivalves that burrow into wood

Shipworm Specialized burrowing shell on one end Filter feeders – also eat wood fibers (not directly) Siphons Burrowing Shell

Class Cephalopoda Octopus, squid, nautilus Organ systems Foot developed into tentacles Very mobile predators Organ systems Highly advanced brain and eyes Closed circulatory system

Nautilus Anatomy

Squid Anatomy

Cephalopod Eye Develops from ectoderm Convergent evolution

Taningia danae Largest light producing squid - ~2 meters (7 ft)

Taningia danae Grips prey with rows of hooks – not suckers Eats fish and other squid

Architeuthis dux Largest invertebrate - ~18 meters (60 feet)

Architeuthis dux Catches prey with double row of spiny suckers Eats fish and other squid