tadpole shrimp: see shrimp.

shrimp, 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.

mysid shrimp: see shrimp.

mantis shrimp, marine crustacean characterized by a pair of enlarged appendages, called maxillipeds, that form powerful claws for seizing prey. The last two segments of each of these legs are strong and sharp, and the end segment is folded back over the next segment to make a scissorslike cut. Mantis shrimps have stalked eyes and flattened abdomens with appendages bearing gills. They prefer warm shallow seas. A number of species are quite large, reaching 1 ft (30 cm) or more in size. Mantis shrimps are an important sea food outside the Western Hemisphere. They are classified separately from either true shrimps or praying mantises, whose forelimbs the maxillipeds superficially resemble. Mantis shrimps are grouped in the phylum Arthropoda, subphylum Crustacea, class Malacostraca.

fairy shrimp: see shrimp.

clam shrimp: see shrimp.

brine shrimp, common name for a primitive crustacean that seldom reaches more than 1/2 in. (1.3 cm) in length and is commonly used for fish food in aquariums. Brine shrimp, which are not closely related to true shrimp, can be found almost everywhere in the world in inland saltwaters, although they are completely absent from oceans. They can live in water having several times the salinity of seawater, but they can also tolerate water having only one tenth the marine salt concentration. Brine shrimp usually occur in huge numbers and can be seen in vast windblown lines in the Great Salt Lake. Their absence from the sea has been explained by their vulnerability to attack by predators and the absence of the latter in their inland saline habitat. Although brine shrimp are considered to be members of a single genus, Artemis, and possibly a single species, there are several varieties. Generally, they have stalked, compound eyes and tapered bodies with a trunk that bears 11 pairs of leaflike legs. Females have a brood pouch from which active young are liberated under favorable conditions. Otherwise eggs are laid parthenogenetically (unfertilized by sperm) or fertilized and can either hatch immediately or be dried and remain viable for many years. These eggs are remarkably resistant to adverse environmental conditions, which is why they can be hatched so easily in saltwater and used for fish food; adult brine shrimp are also used as food in aquariums and are generally sold frozen. Brine shrimp are classified in the phylum Arthropoda, subphylum Crustacea, class Branchiopoda, order Anostraca.

Any of approximately 2,000 decapod species (suborder Natantia) having a semitransparent body flattened from side to side and a flexible abdomen terminating in a fanlike tail. The appendages are modified for swimming, and the antennae are long and whiplike. Shrimps occur in shallow and deep ocean waters and in lakes and streams. Species range from less than an inch (a few millimeters) to about 8 in. (20 cm) long. Larger species are often called prawns. Shrimps swim backward by rapidly flexing the abdomen and tail. They eat small plants and animals; some species eat carrion. Many species are commercially important as food. Seealso fairy shrimp.

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Any of the crustaceans in the order Anostraca, named for their graceful movements and pastel colours. Some grow to 1 in. (2.5 cm) or more in length. They live in freshwater ponds in Europe, Central Asia, western North America, the drier regions of Africa, and Australia. Seealso shrimp.

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Any of several small crustaceans (genus Artemia) inhabiting brine pools and other highly salty inland waters throughout the world. A. salina, which occurs in vast numbers in Great Salt Lake, Utah, is commercially important. Young brine shrimp hatched there from dried eggs are used widely as food for fish and other small animals in aquariums. Up to 0.6 in. (15 mm) long, the brine shrimp's body has a distinguishable head and a slender abdomen. It normally swims upside down, and it feeds primarily on green algae, which it filters from the water with its legs.

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