Mollusc Characteristics
- Coelom reduced
- Most viscera concentrated in dorsal visceral mass
- Body covered by thick mantle (epidermis) which forms a cavity
- Mantle secretes calcium carbonate shell (or spicules)
- Large ventral muscular foot
- Radula (band of teeth in esophagus)
- Additional classes not covered in lab:
- Aplacophora
- Monoplacophora
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Class Polyplacophora — Chitons
Characteristics
- Dorso-ventrally flattened and somewhat elongated
- 8 dorsal shell plates (valves)
- Mantle forms thick lateral girdle (and sometimes covers plates)
- Lack eyes, antennae
- Marine
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Conspicuous Chiton, Stenoplax conspicua, CA
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Lined Chiton, Tonicella lineata, CA
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Black Chiton, Katharina tunicata, CA
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Dorsal view of gumboot chiton, Crytpochiton stelleri, the world's largest species (30 cm); CA
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Ventral view of gumboot chiton; CA
See also labeled photo.
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Class Gastropoda — Snails & Slugs
Characteristics
- Coiled, asymmetric shell (lost in many)
- Visceral mass (gut, nervous system) becomes twisted 90-180°
- Muscular, flattened, creeping foot
- Head with eyes (may be reduced or lost), tentacles
- Mantle highly vascularized; becomes lung
- Marine, freshwater, and terrestrial
- Traditional Subclasses represented here are not monophyletic
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Veliger (larval) stage of Slipper Limpet, Crepidula sp.; stained whole-mount.
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Shell structure of a frogsnail, Bursa sp.
See also labeled photo.
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Dissection of a Garden Snail, Helix sp.
See also labeled photo.
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Subclass Prosobranchia:
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Giant Keyhole Limpet, Megathura crenulata; San Diego, CA
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Red Abalone, Haliotis rufescens
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Chestnut Cowry, Cypraea spadicea; San Diego, CA
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Flamingo Tongues, Cyphoma gibbosum; Belize
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Carinate Dovesnails, Alia carinata
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Turban Snail, Tectus sp.
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Dogwinkles, Thais lapillus; ME
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Scaled Worm Snail, Serpulorbis squamigerus; a tube-dwelling snail that captures food using sticky strands of mucus
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Subclass Opisthobranchia:
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Green Bubble Snail, Haminoea virescens; note reduced shell; San Diego, CA
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Sea Hare, Aplysia californica, a species with a reduced internal shell; LaJolla, CA
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Navanax, Navanax inermis; LaJolla, CA
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White-spotted Sea Goddess, Doriopsilla albopunctata; CA
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Black-tipped Spiny Doris, Acanthodoris rhodoceras; San Diego, CA
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Opalescent Nudibranch, Hermissenda crassicornis; San Diego, CA
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Hopkin's Rose, Hopkinsia rosacea; San Diego, CA
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Lion's Mane Nudibranch, Melibe leonina
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Coral-eating Nudibranch, Tritoniopsis elegans
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Subclass Pulmonata:
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Unidentified Blue Land Snail; CA
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African Giant Snail, Achatina fulica, a large (10-15 cm) terrestrial species; Kenya
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Unidentified slug; ME
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Bladder Snail, Physa sp., a small (8 mm) fresh water species.
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Banana Slug, Ariolimax columbianus; note pneumostome; CA
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Class Bivalvia — Clams, etc.
Characteristics
- Body and foot laterally compressed
- Shell with two hinged valves
- Reduced cephalization
- Edges of mantle usually fused to form siphons
- Radula lost
- Marine and freshwater; mostly filter-feeders
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Left Valve of a Northern Quahog, Mercenaria mercenaria.
See also labeled photo.
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Anatomy of a Clam (in right valve).
See also labeled photo.
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Flat-tipped Piddocks, Penitella penita, CA
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Bean Clam, Donax gouldii; note foot & siphons; LaJolla, CA
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California Mussels, Mytilus californianus; CA
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Giant Clam, Tridacna sp.; relies on endosymbiotic algae in its mantle for nutrients
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Swimming Scallop, Chlamys sp.
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Flame Scallop, Lima scabra (not a true scallop)
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Class Scaphopoda — Tusk Shells
Characteristics
- Single tubular, tapered shell
- Shell open at both ends
- Anterior adhesive tentacles
- Benthic marine environments
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Tusk Shell, Dentalium sp.; shell only
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Class Cephalopoda — Squid, etc.
Characteristics
- Shell chambered (if present), reduced, or absent
- Prehensile tentacles surround mouth
- Mouth with radula and beak
- Muscular siphon provides jet propulsion
- Well developed brain, eyes
- Closed circulatory system
- Marine
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Dissection of a Fresh Male Squid, probably Ommastrephes bartramii
See also labeled photo.
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Dissection of a Preserved Female Squid, probably Loligo sp.
See also labeled photo.
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Subclass Nautiloidea:
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Chambered Nautilus, Nautilus pompilius
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Fossil Orthoceras sp., polished (Morocco; Devonian)
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Internal mold of Nautiloid (Kentucky; Ordovician); note gaps (septa) are straight
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Subclass Ammonoidea†:
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Ammonite fossil, Pleuroceras sp., with pyrite replacement of original shell (Germany; Jurassic Period)
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Ammonite fossil Craspedites nodiger, showing sutures (Russia; Jurassic Period)
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Ammonite fossil (probably Phylloceras or Cleoniceras sp.) cut to show chambers (Morocco)
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Subclass Coleoidea:
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Broadclub Cuttlefish, Sepia latimanus (Order Sepioida)
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Pacific Giant Octopus, Enteroctopus dofleini (Order Octopoda)
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Giant Squid, Architeuthis sp., preserved specimen (Order Teuthoida)
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