Crab is a generally broad, flat-bodied animal with a hard shell and 10 jointed legs. Some crabs live in shallow waters along seashores, and some are found in deeper waters. Others live in burrows on sandy beaches or muddy shores. Only a few species of crabs live in fresh water or on land. Certain species of crabs are popular seafood.
Crabs belong to a group of invertebrates (animals without backbones) called crustaceans. A crab’s abdomen, unlike that of other crustaceans, lies folded under the body. The male crab has a narrow abdomen, but the female’s abdomen occupies the entire space between the legs. A broad upper shell called the carapace covers the crab’s body.
A crab has five pairs of legs. The first pair usually bear large claws called chelae. The chelae vary greatly in shape and size among species and even in the same individual. In male fiddler crabs, for example, one chela is much larger than the other. The male waves this large chela about to attract female crabs and to threaten other male crabs (see Fiddler crab). Most crabs prowl sandy or muddy shores by walking or running sideways on the tips of their last four pairs of legs. In crabs that swim, the last pair of legs are modified to serve as paddles.
Crabs feed on many kinds of water organisms or the remains of organisms. Some species of crabs eat chiefly plants and simple organisms called algae. Almost all species of crabs spawn (release eggs) in salt water. Most newly hatched crabs cannot survive in fresh water.
The coral gall crab is the smallest crab known. It measures about 1/10 inch (2.5 millimeters) long and 1/12 inch (2.1 millimeters) wide. The coral gall crab lives in cagelike formations of coral in the Caroline Islands of the Pacific Ocean, just north of the equator. The giant spider crab of Japan ranks as the largest crab. The giant spider crab measures as much as 12 feet (3.7 meters) long between outstretched claws.
Loading the player...Red crab
The blue crab is the most common crab sold as food in eastern North America. After blue crabs molt (shed their shell) and before the new shell hardens, they are sold as soft-shelled crabs.
Several types of edible crabs live along the Pacific coast of North America. One type, the huge red king crab, inhabits deep waters from the Gulf of Alaska to the Bering Sea. It weighs about 12 pounds (5.5 kilograms). Other types include the snow crab and the Dungeness crab. Fishing crews catch all of these crabs with nets or traps. Other major food crabs include the gazami crab and blue swimming crab in eastern Asia and Europe’s edible crab.
See also Arthropod; Blue crab; Coconut crab; Crustacean; Fiddler crab; Hermit crab.
