1. Intertidal Organisms, Part B: Phylum Mollusca
Marine Ecology, April 16, 2008
Intertidal Organisms, Part B:
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
Diodora aspera

11. Phylum Mollusca Class Gastropoda
Lottia gigantea

12. Phylum Mollusca Class Gastropoda
Collisella digitalis

13. Phylum Mollusca Class Gastropoda
Collisella pelta

14. Phylum Mollusca Class Gastropoda
Comparison of common limpets
Copyright © 2006 Mary Jo Adams

15. Phylum Mollusca Class Gastropoda
Tegula funebralis

16. Phylum Mollusca Class Gastropoda
Littorina sp.

17. Phylum Mollusca Class Gastropoda
Nucella lamellosa

18. Phylum Mollusca Class Gastropoda
Nucella canaliculata
(Photo by: Dave Cowles July 2005)
Photo: Derrick Ditchburn

19. Phylum Mollusca Class Gastropoda
Nucella emarginata
Photos Ari Kornfeld, copyright ©
Copyright © 2006 Mary Jo Adams
nathistoc.bio.uci.edu/Molluscs/index.htm

20. Phylum Mollusca Class Gastropoda
Nudibranch (dorid)
Acanthodoris nanaimoensis
Photos courtesy of Ari Kornfeld, copyright ©

21. Phylum Mollusca Class Gastropoda
Nudibranch (dorid)
Archidoris montereyensis

22. Phylum Mollusca Class Gastropoda
Nudibranch (dorid)
Rostangia pulchra

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

24. Phylum Mollusca Class Gastropoda
Nudibranch (aeolid)
Aeolidia papillosa
Copyright © 2005 Mary Jo Adams

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

26. Phylum Mollusca Class Gastropoda
Nudibranch (arminacean)
Janolus fuscus

27. 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

28. Phylum Mollusca Class Bivalvia
Mytilus californianus
Mytilus trossulus
(Mytilus edulis)