Marine Ecology, April 16, 2008 Intertidal Organisms, Part B: Phylum Mollusca

Phylum Mollusca: The “soft-bodied” animals

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

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

Phylum Mollusca Class Polyplacophora Cryptochiton stelleri

Phylum Mollusca Class Polyplacophora Katharina tunicata

Phylum Mollusca Class Polyplacophora Tonicella lineata

Phylum Mollusca Class Polyplacophora Mopalia muscosa

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

Phylum Mollusca Class Gastropoda Diodora aspera

Phylum Mollusca Class Gastropoda Lottia gigantea

Phylum Mollusca Class Gastropoda Collisella digitalis

Phylum Mollusca Class Gastropoda Collisella pelta

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

Phylum Mollusca Class Gastropoda Tegula funebralis

Phylum Mollusca Class Gastropoda Littorina sp.

Phylum Mollusca Class Gastropoda Nucella lamellosa

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

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

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

Phylum Mollusca Class Gastropoda Nudibranch (dorid)  Archidoris montereyensis

Phylum Mollusca Class Gastropoda Nudibranch (dorid)  Rostangia pulchra

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

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

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

Phylum Mollusca Class Gastropoda Nudibranch (arminacean)  Janolus fuscus

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

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