Crayfish is the common name for almost exclusively freshwater crustaceans.
They are also known as crawfish, crawdads, freshwater lobsters, mountain lobsters, mudbugs, or yabbies.
There are more than 540 species of crayfish.
The greatest diversity of crayfish species is found in southeastern North America, with over 330 species. Australia has over 100 species.
Crayfish live in streams, rivers, swamps, ponds, and other freshwater habitats.
Most crayfish are strictly aquatic but some live in semi-aquatic environments. The semi-aquatic crayfish burrow into the soil to get to water (so that they can breathe).
The lifespan ranges from 1 to 20 years, depending on the species.
Most adult crayfish are about 7.5 cm (3 in) long.
Among the smallest is the 2.5-cm-long Cambarellus diminutus of the southeastern United States.
Among the largest is Astacopsis gouldi of Tasmania, which may reach 40 cm in length and weigh about 3.5 kg (8 pounds).
Crayfish are characterized by a joined head and thorax, or midsection, and a segmented body, which is sandy yellow, green, red, or dark brown in color.
The head has a sharp snout, and the compound eyes are on movable stalks.
The exoskeleton, or body covering, is thin but tough.
The front pair of the five pairs of legs have large, powerful pincers (chelae).
There are five pairs of smaller appendages on the abdomen, used mostly for swimming and circulating water for respiration.
They breathe through feather-like gills.
These crustaceans have a good eyesight and, like other related species, they can move their eyes independently from one another.
Crayfish molt – they usually eat their old skeleton in order to recover the calcium and phosphates contained in it.
They are most active at night, when they feed largely on snails, insect larvae, worms, amphibian tadpoles; some eat vegetation.
Crayfish walk forward; they move backward only when swimming with their abdomen movements.
Crayfish are eaten all over the world. Like other edible crustaceans, only a small portion of the body of a crayfish is edible.
Crayfish are kept as pets in freshwater aquariums, typically with bluegill or bass, rather than goldfish or tropical or subtropical fish.
The name “crayfish” comes from the Old French word escrevisse. The word has been modified to “crayfish” by association with “fish” (folk etymology). The largely American variant “crawfish” is similarly derived.
The Moche people of ancient Peru worshiped animals and often depicted crayfish in their art.
The study of crayfish is called astacology.