A crab is crustacean, which is an aquatic arthropod with a variety of distinguishing features. Its body is covered by a hard shell, called a carapace. The animal has five pairs of legs with the the front legs ending in claws, or pincers. It also has two eyes attached to a short, flexible stalk and two pair of antennae. Crabs are a popular food and commercial crab fishing is a lucrative business. Different crab species require different marine environments for survival.

A native of the western edge of the Atlantic Ocean, the blue crab ranges from Nova Scotia to Argentina. However, it is most commonly found in the area stretching from Texas to Massachusetts. The Chesapeake Bay, bordered by Virginia and Maryland, is famous for its blue crabs. This crab's most prominent feature is its large, powerful claws. Its carapace is greenish-blue, while the claws are blue. Female blue crabs have red tips on their claws. This crab possesses an aggressive nature, and can inflict serious injuries if mishandled. Many people eat blue crabs by steaming them and picking the meat out of the shell.

The stone crab is native to the American Gulf Coast, ranging from Florida to Texas. This creature prefers rock jetties, oyster reefs and the bottoms of bays, where it can burrow and hide from predators. It has a brownish-red carapace with gray spots and large pincers with black tips. People only eat this crab’s claws, because its small body has little meat. Stone crab meat tastes like lobster. Since these crabs can regenerate their claws, most states require that fishermen only cut off one claw and return the crab to the ocean to prevent over-harvesting, according to the Texas Department of Parks and Wildlife.

The Jonah crab, also called the sleepy crab, is native to the waters off the New England coast. It has a wide, oval, purplish-brown carapace, which is typically about 6 inches wide. Occasionally, the carapace is reddish-brown. Although it has thick legs and thick muscular claws, the Jonah crab is actually slow and easy to catch. This crab has a large amount of meat in its claws and legs, making it popular with fishermen and a favorite food for gulls.

The rock crab, also called the peekytoe crab, is native to the waters off the coast of North America. It ranges as far north as Labrador, Canada, and as far south as South Carolina. This crab can survive in either shallow or deep water. A scavenger, it moves between varying depths in search of food. The peekytoe is similar to the Jonah crab, but is smaller and has less meat in its claws. Its carapace, which is approximately 5 1/2 inches wide, ranges in color from yellow to reddish-brown. Its belly and legs are white. Female rock crabs shed their shell right before mating and carry fertilized eggs under their belly for almost a year. According to the Gulf of Maine Research Institute, females can lay up to 500,000 eggs.