rocambarus clarkii, known variously as the red swamp crayfish, Louisiana crawfish or mudbug, is a species of cambarid crayfish native to freshwater bodies of northern Mexico, and southern and southeastern United States, but also introduced elsewhere (both in North America and other continents), where it is often an invasive pest.
P. clarkii is typically dark red, with long claws and head, small or no spines on the sides of its carapace just below the head, and rows of bright red bumps on the front and side of the first leg.
The native range of P. clarkii is from northern Mexico and far southeastern New Mexico, through the Gulf States to the Florida Panhandle, as well as inland north through the Mississippi Basin to southern Illinois and Ohio. It has also been introduced, sometimes deliberately, outside its natural range to countries in Asia, Africa, Europe and elsewhere in the Americas. In northern Europe, the populations are self-maintaining but not expanding, while in southern Europe, P. clarkii is multiplying and actively colonizing new territories at the expense of the native crayfish, Astacus astacus and Austropotamobius spp. Individuals are reported to be able to cross many miles of relatively dry ground, especially in wet seasons, although the aquarium trade and anglers may have hastened the spread in some areas (anglers using P. clarkii as fishing bait are thought to have introduced it to the state of Washington). Attempts have also been made to use P. clarkii as a biological control organism, to reduce levels of the snails involved in the lifecycle of schistosomiasis, leading to the dispersal of P. clarkii in, for instance, Kenya..
