small marine decapod crustacean with 10 jointed legs on the thorax, well-developed swimmerets on the abdominal segments, and a body that is compressed laterally. Shrimp differ from their close relatives, the lobsters and crabs, in that they are primarily swimmers rather than crawlers. As with other crustaceans, the body is covered with a smooth exoskeleton that must be periodically shed and re-formed as the animal grows. However, the shrimp's exoskeleton tends to be thinner than that of most other crustaceans; it is grayish and almost transparent. In some areas of the United States the term prawn is loosely applied to any large shrimp. However, in Europe, only members of the genus Crangon, distinguished from other shrimp by a slender body and a depressed abdomen, are considered true shrimp, while decapod crustaceans having toothed beaks (rostrums), long antennae, slender legs, and laterally compressed abdomens are called prawns. Tropical shrimp have bizarre shapes and colors. One of the most unusual shrimp is the pistol shrimp, a burrow dweller whose third right appendage is adapted into a huge claw with a moveable finger that can be snapped shut with so much force that the resulting sound waves kill or stun nearby prey.
Shrimp are widely distributed in temperate and tropical salt- and freshwaters. They may grow as long as 9 in. (23 cm), but most are smaller. They swim forward by paddling their abdominal swimmerets and can move backward with swift strokes of their fanlike tails. The common commercial shrimp, of the genus Peneus, is found in coastal waters from Virginia south. Shrimp flesh, which turns pink and white when cooked, is by far the most popular crustacean food and forms the basis of an important industry with centers in all the Gulf states, although most shrimp consumed in the United States are now imported. Shrimp are caught in large baglike nets that are dragged over the ocean floor, or may be raised in ponds on aquaculture farms. The flesh is canned in large quantities; fresh shrimp is packed in ice for shipping, or frozen and packaged. Dried shrimp is also common in Asia.
There are several other crustacean forms that are commonly called shrimp although they do not belong to the same order as the true shrimp, order Decapoda, which also includes the lobsters and crabs. The mantis shrimp, possessing strong grasping legs resembling those of a praying mantis, make up the order Stomatopoda. The tiny brine shrimp and fairy shrimp that seldom reach 1 in. (2.54 cm) in length belong to a completely separate subclass, Branchiopoda, order Anostraca. Two other branchiopods, tadpole shrimp and clam shrimp, are classified in the orders Notostraca and Diplostraca, respectively. Mysid shrimp are members of the order Mysidacea. True shrimp are classified in the phylum Arthropoda, subphylum Crustacea, class Malacostraca, order Decapoda.