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The zebra mussel (''Dreissena polymorpha'') is a small freshwater mussel. This species was originally native to the lakes of southern Russia, being first described in 1769 by the German zoologist Peter Simon Pallas in the Ural, Volga, and Dnieper rivers. These mussels are still found nearby, as Pontic (Black Sea) and Caspian species.〔 Lisický M. J. (1991). (''Mollusca Slovenska'' ) (Slovak molluscs ). VEDA vydavateľstvo Slovenskej akadémie vied, Bratislava, 344 pp.〕 However, the zebra mussel has been accidentally introduced to numerous other areas, and has become an invasive species in many different countries worldwide. Zebra mussels get their name from a striped pattern commonly seen on their shells, though it is not universally present. They are usually about the size of a fingernail, but can grow to a maximum length of nearly . Shells are D-shaped, and attached to the substrate with strong byssal threads, which come out of their umbo on the dorsal (hinged) side. == Ecology == Zebra mussels and the closely related and ecologically similar quagga mussels are filter-feeding organisms. They remove particles from the water column. The zebra mussels process up to one liter of water per day, per mussel. Some particles are consumed as food, and feces are deposited on the lake floor. Nonfood particles are combined with mucus and other matter and deposited on lake floors as pseudofeces. Since the zebra mussel has become established in Lake Erie, water clarity has increased from 6 inches to up to three feet in some areas.〔 〕 This improved water clarity allows sunlight to penetrate deeper, enabling growth of submerged macrophytes. These plants, when decaying, wash up on shorelines, fouling beaches and causing water quality problems. Lake floor food supplies are enriched by zebra mussels as they filter pollution out of the water. This biomass becomes available to bottom-feeding species and to the fish that feed on them. The catch of yellow perch increased 5 fold after the introduction of zebra mussels into Lake St. Clair. Zebra mussels attach to most substrates including sand, silt, and harder substrates, but usually, juvenile mussels prefer harder, rockier substrates to which to attach. Other mussel species frequently represent the most stable objects in silty substrates, and zebra mussels attach to, and often kill these mussels. They build colonies on native American unionid clams, reducing their ability to move, feed, and breed, eventually leading to their deaths. This has led to the near extinction of the unionid clams in Lake St. Clair and the western basin of Lake Erie.〔 This pattern is being repeated in Ireland, where zebra mussels have eliminated the two freshwater mussels from several waterways, including some lakes along the River Shannon in 1997. In 2012, the National University of Ireland, Galway, said "The discovery of zebra mussels (''Dreissena polymorpha'') in Lough Derg and the lower Shannon region in 1997 (McCarthy et al 1997, a & b) has led to considerable concern about the potential ecological and economic damage that this highly invasive aquatic nuisance species can cause."〔(【引用サイトリンク】 New Zebra Mussel Webpage )〕 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「zebra mussel」の詳細全文を読む スポンサード リンク
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