Viril crayfish
| Viril crayfish | ||||||||||||
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Viril crayfish |
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| Orconectes virilis | ||||||||||||
| ( Hagen , 1870) |
The viril crayfish ( Orconectes virilis ) is a species of the superfamily of crayfish . It is originally found in the northeastern United States and southeastern Canada , but was introduced into Europe. The European Union has listed the species as a neozoon in the list of invasive alien species of Union-wide importance since 2016 .
description
The front body of the Viril crayfish is covered by a smooth, egg-shaped shell, the carapace , which ends in a pointed process, the rostrum . The rostrum is longer than it is wide and covered with small tubercles; it is not keeled on top. The carapace length is measured without the rostrum and is called the postorbital carapace length. The border between the rostrum and the carapace is marked in the Viril crayfish by an appendage. Five pairs of legs ( pereiopods ) sit on the front body, the first pair of legs being transformed into large claws . These are mostly smooth and robust, with a series of tubercles and teeth on the edges. In the males they are about as long as the carapace, in the females the claws are smaller and reach about three quarters of the length of the carapace. The remaining four pairs of legs serve as walking legs. The gills hang from them for breathing. The third pair of legs in the males is characterized by the formation of copulation hooks on the third leg link. The first pair of swimming legs ( pleopods ) in males has two curved end links. In females, between the fourth and fifth pair of legs of the pereiopods, there is a rhombus-shaped organ with a deep indentation in the middle, the access to the receptaculum seminis . The rear end of the crab is formed by the telson and uropods .
The young are greenish gray, but the color is more vivid in adult crabs. The carapace is then reddish to chestnut brown, towards the rostrum dark brown to black. The top of the scissors can be blue-gray to emerald green, the other striding legs are similar in color. The scissors are often dark marbled or spotted, the tubercles and teeth are light yellow to cream-colored.
distribution
The autochthonous distribution area of the Viril crayfish is southern Canada from the province of Alberta via Manitoba , Ontario and Saskatchewan to the province of Quebec and the north of the USA from New York via Ohio , Oklahoma , Illinois , Indiana , Michigan , Wisconsin and Nebraska to Montana and Wyoming . Its habitat is the fresh water of the Great Lakes and the river systems connected to them, as well as the headwaters of the Mississippi .
However, the cancer is spreading rapidly to other areas of the United States and Mexico , and has been detected in the United Kingdom since 2008 .
Web links
- Orconectes virilis in the endangered Red List species the IUCN 2010 Posted by: S. Adams, GA & Schuster CA Taylor, 2010. Accessed July 14, 2016th
Individual evidence
- ↑ Itis.gov accessed on July 14, 2016
- ↑ Orconectes virilis in the endangered Red List species the IUCN 2010 Posted by: S. Adams, GA & Schuster CA Taylor, 2010. Accessed July 14, 2016th
- ↑ List of Invasive Alien Species of Union Concern (PDF) accessed on July 15, 2016
- ↑ a b P. W. Fofonoff, GM Ruiz, B. Steve & JT Carlton: Orconectes virilis at NEMESIS - National Exotic Marine and Estuarine Species Information System, 2003, accessed on July 15, 2016
- ^ Horton H. Hobbs & Joan P. Jass: The Crayfishes and Shrimp of Wisconsin (Cambaridae, Palaemonidae). Milwaukee Public Museum, Milwaukee, 1988
- ^ Daniel Ahern, Judy England & Adam Ellis: The virile crayfish, Orconectes virilis (Hagen, 1870) (Crustacea: Decapoda: Cambaridae), identified in the UK . Aquatic Invasions 3, 1, pp. 102–104, 2008 doi : 10.3391 / ai.2008.3.1.18 PDF ( Memento of the original from February 19, 2009 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
