Austropotamobius pallipes
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[Photo] Austropotamobius pallipes (Deutsch: Dohlenkrebs, Fran??ais : ??crevisse ?? pattes blanches). photo by David.Monniaux (User:Dums)

Austropotamobius pallipes is an endangered European freshwater crayfish, and the only species of crayfish native to the British Isles. Its common names include white-clawed crayfish and Atlantic stream crayfish. It is found from the Balkan Peninsula to Spain and reaches its northerly limit in Great Britain and Ireland, where it also has its greatest population density.

A. pallipes is an olive-brown colour, with pale-coloured undersides to the claws (whence the specific epithet pallipes, meaning "pale-footed"). It may grow to 12 cm (5 inches) long, although sizes below 10 cm are more common. It typically lives in rivers and streams about 1 metre deep, where it hides among rocks and submerged logs, emerging to forage for food, and also in lakes.

The distribution of A. pallipes is rapidly shrinking and in Great Britain it is now more or less restricted to central and northern England and eastern Wales, though there is a regionally significant population in the River Frome in South Gloucestershire and Bristol, and a population has been discovered in Essex. There is also a population in Candover Brook, a tributary of the River Itchen in Hampshire. However, it was once found across most of England and Wales.

One of the major reasons for this decline is the introduction of the invasive North American signal crayfish (Pacifastacus leniusculus). The signal crayfish is a carrier of crayfish plague, an infectious disease to which it has resistance while the native crayfish have none. The British species is also sensitive to many kinds of pollution, such as insecticides.

http://en.wikipedia.org/wiki/Austropotamobius_pallipes

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