Cancer (genus)
Crab (Cancer pagurus )
Cancer is a crab genus of the family of crabs ( Cancridae ). The species of this genus are widespread in the Pacific and Atlantic. The company also has the famous crab (Cancer pagurus ) from the North Sea.
Features
The carapace of shrimps is approximately egg-shaped, wherein the length is 58 % to 66 % of the width. At the front edge there are five small peaks between the orbits. The distance between the eyes to each other is 22 % to 29 % of the carapace. On the front side edge of the carapace are nine, rather square teeth that are separated by distinct columns. These teeth are usually dull, but can also be extended as small teeth. The posterior margin is more or less concave, and provided with a mandrel. The rear edge of the carapace is convex. The ornamentation of the carapace is unclear to clear the surface may be smooth or grainy provided with tubercles. The scissors can have a smooth or granular surface. They are rather short and have three to four ridges on. The scissors have large finger blunt teeth on their inner sides.
Dissemination
Types of Cancer are native in the littoral of the eastern Pacific along the coasts of North and South America and in the North Atlantic. The oldest fossil find is Cancer fujinaensis from Japan and dates back to the Miocene. It therefore locates the origin of the genus Cancer in the North Pacific during the Miocene. The species then spread over the Northeast Pacific, both across the equator in the South Eastern Pacific and through the Panama road into the Atlantic.
System
Species
The types of cancer differ from other crabs by ornamentation and shape of the carapace. In addition to the morphology of the scissors is also intra- generic of the carapace, especially the shape of the teeth on the front side edge, the main distinguishing feature. The genus Cancer includes the following eight recent as well as three known fossil species:
- Cancer bellianus Johnson, 1861
- Cancer borealis Stimpson, 1859
- † Cancer fissus Rathbun, 1908
- † Cancer fujinaensis Sakumoto, Karasawa & Takayasu, 1992
- Cancer irroratus Say, 1817
- Cancer johngarthi Carvacho, 1989
- Crab (Cancer pagurus Linnaeus, 1758)
- † Cancer parvidens Collins & Fraaye, 1991
- Cancer plebejus Poeppig, 1836
- Cancer porteri Rathbun, 1930
- Cancer productus J. W. Randall, 1840
History of Research
The term " Cancer " ( ancient Greek καρκίνος karkinos "cancer" ) used Carolus Linnaeus in the tenth edition of Systema Naturae, to summarize all known at that time, crab -like crustaceans. The taxon Cancer was thus originally understood as a synonym of Crustacea. With increasing knowledge about the diversity of crustaceans and crabs to adapt the definition of Cancer was necessary. 1802 Pierre André Latreille limited taxon to the present meaning as crab genus. In 1810 he determined the crab as the type species. Even after Latreilles demarcation various cancers were counted on Cancer, which is why it required constant adjustments. J. Dale Nations divided the genus in 1975 in four subgenera, which in turn were considered by Carrie E. Schweitzer and Rodney M. Feldmann in 2000 as an autonomous genres besides Cancer: Glebocarcinus, Metacarcinus and Roma Leon. The once over 30 kinds of species of is thus limited to eight known species. The Classification of Cancer and the family of crabs is still under discussion, as molecular genetic studies tend not to support the current system.