mollusk: Quick Facts

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Also Known As	mollusc • Mollusca

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Conchyliologie Tableau de la Classification des Coquilles

Organizational levels and body diagrams of mollusks

blue-ringed octopus

Diagram of the tree of life based on the three-domain system, showing Archaea, Bacteria, and Eukaryota branching into four kingdoms: Plants, Animals, Fungi, and Protista, with illustrations of representative organisms for each group.

Representative mollusks. Bivalves have a shell with two halves. Filter feeders, they take in food and water through a tubular siphon. In the clam, a muscular foot is used for burrowing and creeping. The chitons, typically found adhering to rocks and shells, have shells divided into eight overlapping plates. Tusk shells, or scaphopods, are burrowing mollusks with a shell open at both ends; with the larger end buried in the sand, they feed on microorganisms captured by the tentacles. The whelks, like most gastropods (univalves), have a single shell, which is usually coiled; when threatened, the body can be pulled into the shell, which is closed by a plate (operculum). Cephalopods have a well-developed head and a foot divided into numerous tentacles. The two long tentacles of the squid are used to capture prey, and the short arms transfer food to the mouth. The nautilus is the only cephalopod that has retained an exterior shell; by regulating the amount of gas and fluid in the interior chambers, it can regulate its buoyancy.

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The structure of snail shells explained

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Topics

gastropod bivalve Visceroconcha Aculifera Aplacophora Loboconcha cephalopod chiton Nephridium monoplacophoran mammal reptile fish insect Bird annelid echinoderm crustacean amphibian flatworm

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Sepia albumen silver print portrait of Augustus Addison Gould seated beside an ornate table, wearing a dark suit and bow tie, photographed by F. L. Lay.

Augustus A. Gould

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William Brooks

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