Madagascar has an endemic genus, Astacoides, containing seven species.Europe is home to seven species of crayfish in the genera Astacus and Austropotamobius.
The body of a decapod crustacean, such as a crab, lobster, or prawn (shrimp), is made up of twenty body segments grouped into two main body parts, the cephalothorax and the abdomen.
Each segment may possess one pair of appendages, although in various groups these may be reduced or missing.
On average, crayfish grow to 17.5 centimetres (6.9 in) in length, but some grow larger. There are three families of crayfish, two in the Northern Hemisphere and one in the Southern Hemisphere.
A further genus of astacid crayfish is found in the Pacific Northwest and the headwaters of some rivers east of the Continental Divide.
Many crayfish are also found in lowland areas where the water is abundant in calcium, and oxygen rises from underground springs.
They prefer foods like shrimp pellets or various vegetables, but will also eat tropical fish food, regular fish food, algae wafers, and small fish that can be captured with their claws.