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Freshwater bivalves are one kind of freshwater molluscs, along with freshwater snails. They are bivalves which live in freshwater, as opposed to saltwater, the main habitat type for bivalves. The majority of species of bivalve molluscs live in the sea, but in addition, a number of different families live in freshwater (and in some cases also in brackish water). These families belong to two different evolutionary lineages (freshwater mussels and freshwater clams), and the two groups are not closely related. Freshwater bivalves live in many types of habitat, ranging from small ditches and ponds, to lakes, canals, and rivers. Species in the two groups vary greatly in size. Some of the pea clams (''Pisidium'' species) have an adult size of only 3 mm. In contrast, one of the largest species of freshwater bivalves is the swan mussel, in the family Unionidae; it can grow to a length of 20 cm, and usually lives in lakes or slow rivers. Freshwater pearl mussels are economically important as a source of freshwater pearls and mother of pearl. ==Taxonomy== Order Unionoida The Unionoida, of worldwide distribution, are the pearly freshwater mussels. All reproduce by means of a larval stage that is parasitic on a fish or salamander. Many species are utilized as sources of mother-of-pearl. Families: *Margaritiferidae *Unionidae *Hyriidae *Etheriidae *Mutelidae *Mycetopodidaes * Iridinidae File:Margaritifera auricularia shell.jpg|Family Margaritiferidae, a shell of ''Margaritifera auricularia'' File:Quadrula metanevra.jpg|Family Unionidae, ''Quadrula metanevra'', the monkeyface mussel File:Anodonta cygnea1.jpg|Family Unionidae, ''Anodonta cygnea'' Order Veneroida The Veneroida is a large group of bivalve "clams", most of which are marine. However, several families occur in fresh and brackish waters. Families: *Corbiculidae *Sphaeriidae *Dreissenidae File:Toegeknepen korfmossel.jpg|Family Corbiculidae, shell of ''Corbicula fluminea'' File:Sphaerium_corneum.jpg|Family Sphaeriidae, ''Sphaerium corneum'', one of the small fingernail clams. File:Dreissena polymorpha1.jpg|Family Dreissenidae, ''Dreissena polymorpha'' 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Freshwater bivalve」の詳細全文を読む スポンサード リンク
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