Crab is a popular name for crustacea of the sub-order Brachyura and to many of the Anomura of the order Decapoda. The true crabs (Brachyura) are characterised by having a small abdomen and the head and breast are united, forming the cephalothorax, and the whole is covered with a strong carapace.
The mouth has several pairs of strong jaws, in addition to which the stomach has its internal surface studded with hard projections for the purpose of grinding the food. The stomach is popularly called the 'sand-bag'; a little behind it is the heart, which propels a colourless lymph (the blood) to the gills (' dead man's fingers'). The liver is the soft, rich yellow substance, usually called the fat of the crab. They 'moult' or throw off their calcareous covering periodically.
They have ten legs, of which the first pair are modified as claws, and the remaining pairs are used for locomotion. There are many genera, distinguished from the lobster and other macrurous or long-tailed decapods by the shortness of their tail, which is folded under the body. Their eyes are compound, with hexagonal facets, and are pedunculated, elongated, and movable. Like most individuals of the class, they easily lose their claws, which are as readily renewed. They are generally scavengers, living on decaying animal matter, though others live on vegetable substances, as the racer-crabs of the West Indies, which suck the juice of the sugar-cane.
Most crabs inhabit the sea, others fresh water, some the land, only going to the sea to spawn. Of the crabs several species are highly esteemed as an article of food, and the fishery constitutes an important trade on many coasts. The large edible crab (Cancer pagurus) is common on the British shores, and is much sought after. Research Crab
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Matt and Leela Probert
Abbreviations
Nature
Research Crab
