Crayfish, also known as crawdads and crawfish, live in freshwater habitats such as streams, rivers, swamps, and ponds. There are over 500 species worldwide and about 150 species in North America. Crayfish are not native to Arizona. Originally released into reservoirs and large bodies of water as a food source for sport fish by people unaware of the devestating consequences, they have invaded previously pristine waters negatively impacting native fish and aquatic ecosystems. This primarily nocturnal, armor-covered crustacean has few natural predators, is omnivourous, and competes for resources with insects, frogs, turtles, and fish. The crayfish propels itself backward through the water by using its tail composed of a central section called a telson and uropods on each side. It is able to walk on land and in the water by using its 4 pairs of walking legs. Each leg has an attached gill that occupies the bronchial chamber. The crayfish senses its world with its eyes, two pairs of antennae, and pincers called chelipeds. Crayfish have the ability to regenerate lost limbs and molt as they grow, often eating the old shell.