1. Phylum Molluska

2. Characteristics of Mollusks Aquatic (freshwater, marine) & Terrestrial External or internal shell or no shell Size: small (i.e. grain of sand) to large (20 meter squid) Bilateral Symmetry

3. Circulatory System of Mollusks Open in most, blood not confined to vessels (example: snails, slugs) Closed in others, blood is confined to vessels (example: squid, octopi)

4. Larvae = trochophore Free swimming Young form of animal Looks and behaves differently from adult

5. Body Plan of ALL Mollusks FOOT - used for movement; contains mouth VISCERAL MASS - internal organs SHELL – made of calcium carbonate; not all mollusks have MANTLE – a thin membrane that surrounds and secretes the shell

6. Reproduction – mainly external fertilization Most are separate sexes ▫Release sperm and eggs into the water Some are hermaphrodites ▫Some water snails and some oysters Land mollusks have internal fertilizations ▫Male has a penis to transfer sperm

7. Class Bivalvia “Bivalves”

8. Bivalvia (Clam, oyster, scallop, mussel) Have 2 VALVES (shells) held together by a ligament held together Shell stays shut by adductor muscles They are FILTER FEEDERS ▫Food and water enter the incurrent siphon; food taken in by mouth ▫Can accumulate toxins from the surrounding environment GILLS for respiration

9. Mussels attach to rocks with their BYSSUS THREADS (sessile)

10. Scallops FLAP their shells to swim http://www.youtube.com/watch?v=_2iXHBuSIJY

11. Clams burrow into sand/mud with their FOOT http://www.youtube.com/watch?v=HrBijKf0Ywk