spider crab

any of various crabs of the family Majidae, having long, slender legs and a comparatively small, triangular body.

[1700-10]

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Any species of sluggish marine crab in the widely distributed family Majidae (or Maiidae).

Spider crabs have a beak-shaped head; thick, rounded body; and long, spindly legs. They use a mucuslike mouth secretion to fasten algae, sponges, and other organisms to the hairs, spines, and knobby projections covering the body. Most species are scavengers, especially of carrion. Their size varies greatly. The body of the European long-beaked spider crab (Macropodia rostrata) is less than 0.5 in. (1 cm) in diameter, whereas the Japanese giant crab (Macrocheira kaempferi), whose outstretched claws can measure 13 ft (4 m) from tip to tip, is perhaps the largest known arthropod.

Spider crab (Libinia)

Walter Dawn

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▪ crustacean

 any species of the decapod family Majidae (or Maiidae; class Crustacea). Spider crabs, which have thick, rather rounded bodies and long, spindly legs, are generally slow-moving and sluggish. Most are scavengers, especially of dead flesh.

      Majids, a widely distributed marine group, are fished commercially in temperate waters, such as in the North Pacific. Some are quite small; for example, the long-beaked spider crab (Macropodia rostrata) of European coastal waters has a body about 1 cm (less than 0.5 inch) in diameter. The largest spider crab, and perhaps the largest known arthropod, is the giant crab (q.v.) of the Pacific waters near Japan. The outstretched claws of this crab (Macrocheira kaempferi) measure more than 4 m (13 feet) from tip to tip.

      The head of the spider crab is rather beak-shaped; the body surface is generally covered with hairs, spines, and tubercles (knobby projections) that are frequently matted with algae, sponges, and other organisms. The crabs fasten a good deal of this material to themselves by means of a mucuslike secretion from the mouth.

      The kelp crab (Pugettia producta), a spider crab found among seaweed on the Pacific coast from Canada to Mexico, is about 1.25 cm (0.5 inch) wide and 2.5 cm (1 inch) long. It is green and red on top and green underneath.

      Parthenope investigatoris, a spider crab of the Indian Ocean, is camouflaged to resemble the coral on which it lives.

      Spider crabs of the genera Libinia, Hyas, Sternorhynchus, Pitho, and Lambrus are common on the Atlantic coast of North America. Pacific coast spider crabs include the genera Loxorhynchus, Pugettia, and Epialtus.

      Pisa, 1.3 to 6 cm (0.5 to 2.4 inches) long, is found in the Mediterranean Sea and in the eastern Atlantic Ocean. Maja squinado, which attains lengths of 18 cm (7 inches), is found in the Mediterranean Sea and along the southwest coast of Europe.

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