Brachyura

Brachyura [‚bra·kē′yu̇r·ə]

(invertebrate zoology)

The section of the crustacean order Decapoda containing the true crabs.

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Brachyura 

a suborder of invertebrates of the order Decapoda. They have a small head and stalked eyes. The cephalothorax is broad, and the thoracic carapace measures 2–20 cm wide. In the Japanese spider crab (Macrocheira kaempferi) the thoracic carapace is up to 60 cm wide. The first pair of walking legs are chelate. The abdomen is reduced and folded underneath the cephalothorax. The abdominal extremities of the males (two pairs) are adapted for transferring the sperm; in the females these extremities (four pairs) are used to bear eggs.

Brachyurans are marine, freshwater, and land crustaceans. All of them, except the land species, reproduce in the sea. Their development is one of metamorphosis. The larval form, the zoea, emerges from the eggs and turns first into the megalops and then into the adult. Only the freshwater family Potamidae does not have free-swimming larvae. When pursued, brachyurans are able to break off their extremities by sudden movement; the extremities are then replaced by new limbs. The animals feed primarily on invertebrates. Many brachyurans are edible and are commercially valuable. The king crab (Paralithodes camtschatica) is not a brachyuran but a hermit crab (suborder Anomura). Some members of the Brachyura destroy such commercial mollusks as oysters and mussels. The species Eriocheir sinensis sometimes enters rivers, destroying dams by burrowing in them and damaging fishing nets. There are more than 4,000 known species of the Brachyura, of which approximately 50 are found in the USSR.

REFERENCE

Zhizn’ zhivotnykh, vol. 2. Moscow, 1968.

IA. A. BIRSHTEIN