Mollusca: Gastropoda

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Gastropods are the most diverse class of the phylum Mollusca, comprising almost three quarters of the 110,000 or so species of molluscs known. Over 50,000 of these species belong to the mostly marine and freshwater Caenogastropoda while another 20,000 species belong to the subclass Pulmonata, of which most are terrestrial. Gastropods have a univalve shell, and possess a file-like radula used in feeding on the periphyton coverings of rocks or plants. In North America, there are 49 genera and 364 species of caenogastropod snails, and 29 genera and 162 species of pulmonate snails. Caenogastropods possess a gill (ctenidium) and a horny (flexible) or calcareous operculum, or "trap door," which is pulled in after the foot to protect the animal. Pulmonates have secondarily reinvaded freshwaters from the terrestrial habitats used by their ancestors, use a modified portion of the mantle cavity as a lung, and lack an operculum. This chapter offers information on anatomy, phylogeny, physiology, developmental history, life history, and ecology of Gastropods, with focus on freshwater gastropods of North America. © 2010 Elsevier Inc. All rights reserved.

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Ecology and Classification of North American Freshwater Invertebrates

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