1. Marine Ecology, April 9, 2007 Invertebrates 2: Phylum Mollusca

2. Phylum Mollusca: The “soft-bodied” animals

3. Molluscan body plan Hypothetical ancestral mollusc (HAM) Shell Mantle Mantle cavity Ctenidia Visceral mass Head and assocated sensory structures Radula Foot and epipodial tentacles

4. Class Polyplacophora: chitons “many plates” Differences from HAM  8 shell plates  Mantle cavity expanded around foot  Multiple ctenidia  Mantle grows over shell, thickened (new functions?)  Reduced head without sensory structures

5. Phylum Mollusca Class Polyplacophora Cryptochiton stelleri

6. Phylum Mollusca Class Polyplacophora Katharina tunicata

7. Phylum Mollusca Class Polyplacophora Tonicella lineata

8. Phylum Mollusca Class Polyplacophora Mopalia muscosa

9. Phylum Mollusca, Class Gastropoda: “stomach-foot” Representative members  Limpets, snails, abalones, nudibranchs Diff. from HAM  Undergo torsion What is torsion? Advantages of torsion Disadvantages of torsion

10. Phylum Mollusca, Class Gastropoda Key: Gastropods undergo torsion!

11. Phylum Mollusca Class Gastropoda Diodora aspera

12. Phylum Mollusca Class Gastropoda Lottia gigantea

13. Phylum Mollusca Class Gastropoda Collisella digitalis

14. Phylum Mollusca Class Gastropoda Collisella pelta

15. Phylum Mollusca Class Gastropoda Tegula funebralis

16. Phylum Mollusca Class Gastropoda Littorina sp.

17. Phylum Mollusca Class Gastropoda Nucella sp.

18. Phylum Mollusca Class Gastropoda Nudibranch (dorid)  Archidoris montereyensis

19. Phylum Mollusca Class Gastropoda Nudibranch (dorid)  Rostangia pulchra

20. Phylum Mollusca Class Gastropoda Nudibranch (dorid)  Discodoris (Dialula sandiegensis)

21. Phylum Mollusca Class Gastropoda Nudibranch (aeolid)  Hermissenda (Phidiana) crassicornis

22. Class Bivalvia: “two valves” Representative members: Clams, mussels and scallops Differences from HAM  Two shells  Mantle/sensory structures  Expanded mantle cavity  Enlarged ctenidia Respiration AND feeding  Reduced head  Foot more elongate; Minimal area for suction

23. Phylum Mollusca Class Bivalvia Mytilus californianus Mytilus edulis