Crawfish, also called crayfish or crawdad and are closely related to the lobster. More than half of the more than 500 species occur in North America, particularly Kentucky (Mammoth Cave) and Louisiana in the Mississippi basin. Crawfish also live in Europe, New Zealand, East Asia and throughout the world, including the Tristan da Cunha Islands. Nearly all live in freshwater, although a few survive in salt water. Crawfish are characterized by a joined head and thorax, or midsection, and a segmented body, which is sandy yellow, green, or dark brown in color.  The head has two pairs of sensory antennae, a sharp snout, and the eyes are on movable stalks. The appendages, or pereiopods, of the thorax include four pairs of walking legs which, as well as walking, are to probe cracks and crevices between rocks looking for food. Crawfish also own one pair of clawbearing chelipeds, which it extends in front of its body while moving. These strong pinchers are specialised for cutting, capturing food, attack, and defence. The crawfish also has several pairs of specialized food handling “legs,” bailers to cycle water over the gills, and five pairs of swimmerets which are under the abdomen. All of these “legs” can be regenerated if broken off. Crawfish are usually about 3 inches long.

Crawfish have a hard outside skeleton. This jointed exoskeleton provides protection and allows movement, but limits growth. As a result, the crawfish regularly gets too big for its skeleton, sheds it, and grows a new larger one. This is called molting. and occurs six to ten times during the first year of rapid growth, but less often during the second year. For a few days following each molt, crawfish have soft exoskeletons and are more vulnerable to predators.

Most crawfish live short lives, usually less than two years. Therefore, rapid, high-volume reproduction is important for the continuation of the species. Many crawfish become sexually mature and mate in the October or November after they’re born, but fertilization and egg laying usually occur the following spring. The fertilized eggs are attached to the female’ swimmerets on the underside of her jointed abdomen. There the 10 to 800 eggs change from dark to translucent as they develop. The egg-carrying female is said to be “in berry,” because the egg mass looks something like a berry. Females are often seen “in berry” during May or June. The eggs hatch in 2 to 20 weeks, depending on water temperature. The newly-hatched crawfish stay attached to their mother until shortly after their second molt.