2. Mollusk Characteristics Unsegmented soft body Mollusks have 3 main parts Visceral mass: contains the internal organs Modified Foot: –Muscular foot and/or tentacles Mantle: fold that wraps around visceral mass & secretes the shell Most have shell (internal or external) –Or remnants of a shell

3. Mollusk Characteristics Body Cavity- true coelom Symmetry- bilateral Organ systems- -have organs for circulation, respiration, digestion, excretion, & nervous system Respiration- most gills (some snails have simple lung) Circulation- 3 chambered heart- most have open circulatory system (but squids & octopuses have closed circ. system)

4. Digestion- one way digestive system: separate mouth and anus Reproduction- most are separate sexes and reproduce sexually by doing external fertilization (except snails which are hermaphrodites) Nervous- ganglia, eyes, and nerves Excretion- nephridia remove wastes

5. Classes of Mollusks There are 7 classes of mollusks but this course will look at the 3 main classes. Class Cephalopoda – “head-foot” octopus and squid Class Gastropoda – “stomach-foot” slugs and snails Class Bivalvia – “two shells” clams, mussels, scallops

6. Class Cephalopoda Types- octopus, squid, cuttlefish Exclusively marine Shell- “pen”- internal remnant of a shell Use fins and siphon to move (jet propulsion) Modified foot= tentacles Fast swimming predators -use tentacles to catch prey Use a beak-like jaw (radula) to eat prey Have a special camera like eye Ex- Giant Squid

7. OCTOPUS Octopus in Aquarium

8. SQUID

9. NAUTILUS

10. Cuttlefish Cuttlefish Video

11. Class Gastropoda Types- snails, conches, limpets free-living; marine, terrestrial, fresh water noticeable head single shell, often spiral muscular foot secretes mucus to form a slimy path to glide along Feeding-most herbivores that scrape algae off rocks with radula- toothed tongue Mantle- secretes shell

12. SNAIL

13. SLUG Sea slugs- reproduction

14. CONCH

15. Snail Anatomy

16. Class Bivalvia Types- clams, scallops, oysters marine and freshwater gill used for gas exchange all are sessile, filter feeders and filter food from the water all have two part shells (bivalves) Muscular foot- used to dig into sand

17. CLAM

18. OYSTER

19. MUSSEL

20. SCALLOPS

22. Squid External Anatomy Siphon Fins Mantle

23. Squid Internal Anatomy

24. Gills Reproductive Organs Siphon Fins