Mollusks

1. Mollusks Tough Softies!

2. Taxonomic Roadmap • Kingdom: Animalia • Phylum: Mollusca(Mollusks) • Class: Bivalvia(Bivalves) • Class: Cephalopoda(Cephalopods) • Class: Gastroboda(Gastropods) Mollusca is the second most diverse (second most number of species) phylum in the animal kingdom!

3. Mollusks • soft-bodied • bilateral symmetry • coelomates • allows for some organ movement • allows for organ filling and emptying • most have a shell • 3 part body plan • visceral mass • mantle • foot

4. Mollusks • have radula (except bivalves) • tongue-like organ covered with teeth • nephridia • tubular structure to filter sugars, salts to keep and toxins to expel • three chambered heart • open circulatory system (except octopuses)

5. Mollusks • most breathe with gills • located in mantle cavity • extract 50% of dissolved oxygen • terrestrial snails have primitive lungs that must stay moist • some sea snails breathe through skin • most have separate sexes • some snails and slugs are hermaphrodites • some slugs and oysters can change sex • trochophore larva

6. Gastropods • “stomach-feet” • snails and slugs • terrestrial, freshwater, or terrestrial • most have tentacles with eyes on head • most have one shell • slugs and nudibranches have none • slide on mucus or fly through water • use their radula in many different ways • herbivores or predators • nudibranches can capture and use nematocysts to hunt

7. Cephalopods • “head-feet” • Octopus, squid, cuttlefish, nautilus • tentacles • 8-90 • suction cups or hooks • lack shell • nautilus has a shell • squid and cuttlefish has internal shell • well-developed brain • jet propulsion • draw water into mantle cavity and expel it through siphon • squid and octopuses can release “ink”

8. Bivalves • “two-doors” • muscles, oysters, clams, scallops • nacre – mother-of-pearl coating in shells • no distinct head, no radula • most are sessile • scallops move • filter-feed • particles moved along gills to mucus-covered groove into mouth