Astacus's a genus of crayfish found in Europe and western Asia, comprising three species. Due to the American crayfish plague, crayfish of this genus have been almost wiped out in Europe and have in many European countries been replaced by the North American signal crayfish, which's often more resistant to the plague. This, often illegal, implantation of signal crayfish has made it very difficult to reintroduce Astacus in the wild since the signal crayfish does carry the plague and infects lake… (More on Astacus)