V.

Types of Shrimp

True shrimp belong to the order Decapoda—a group containing crustaceans that have ten walking legs. In the marine waters of the United States, three of the most common commercial species are the pink shrimp, the brown shrimp, and the white shrimp. Found in the waters along the East Coast and in the Gulf of Mexico, these shrimp have a maximum length of about 20 cm (8 in). On the West Coast, the Franciscan Bay shrimp is caught commercially.

Freshwater shrimp are most common in warm parts of the world. They include river shrimp, edible shrimp that are trapped or farmed in the tropics, and also all true shrimp that have become adapted for life in caves. Cave shrimp are typically pale, with vestigial (nonfunctioning) eyes, and they find their way mainly by touch.

Decapod shrimp also include animals that are rarely eaten by humans. Among the most specialized are pistol shrimp, also known as snapping shrimp, which grow to 6 cm (2.4 in) long. These shrimp have a pair of enlarged pincers, one of which can be almost as long as the rest of the animal’s body. The pincer can snap shut, creating a shock wave that is powerful enough to stun small fish. Some pistol shrimp form mutually beneficial partnerships with fish called gobies. A pistol shrimp shares its food with the goby and digs a burrow for it on the seabed. In turn, the goby warns the pistol shrimp of a predator's approach, at which point both will hide in the burrow.

Many other crustaceans are commonly called shrimp, but they are not members of the order Decapoda. They differ from true shrimp in their anatomy and in their ways of life. These animals include tadpole shrimp, which breed in temporary pools in deserts, and brine shrimp, which live in salt lakes. Mantis shrimp are often caught in shrimp nets. They have a pair of strong grasping legs that can painfully wound fishermen who handle them carelessly. Mantis shrimp are larger than most true shrimp, measuring up to 56 cm (22 in) long.