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| | Crabs or short “tail” lobsters belong to big class crustaceans, which sometimes are called “water insects”.
And really, crabs and their relatives - lobsters and shrimps - have many features, similar to beetles, grasshoppers and cockroaches - an external chitin skeleton, an eye - ocellus and many more, which is known only to biologists. The head of the crab is small. The short abdomen is symmetric and tucked into the cephalothorax. In male crabs, the abdomen limbs (1-2 pairs) are transformed into a copulative organ and (4 pairs) in female serve for nurturing eggs. Crabs are found in seas, freshwater and on land. Over 4000 species exist. Crabs eat carrions and invertebrates.
Crabs or short-tailed lobsters (Latin: Brachyura) and are the infra-order of ten-legged Crustacea.
Biology:
The head of the crab is small, a narrow abdomen symmetric and tucked under the thorax. The abdominal limbs in a male crab (1-2 pairs) are transformed into copulative organ & in female crab (4 pairs) serve for brooding. Crabs inhabit the seas, fresh water reservoirs and land. Sometimes, huge-sized crabs are also found. A gigantic crab, caught on the Japanese coast, had a 3.69m distance between the claw ends.
Classification:
24 super families, 93 families and more than 6780 species are found worldwide.
Synonyms:
* Archaeobrachyura Guinot, 1977;
* Brachyura Latreille, 1802;
* Brachyrhyncha Borradaile, 1907;
* Cancridea Latreille, 1803;
* Dromiacea De Haan, 1833;
* Oxyrhyncha Latreille, 1803;
* Oxystomata H. Milne Edwards, 1834.
Crab food consumption:
The white meat found in the legs, claws and at the joining place of the legs and also the eggs is used in food. The meat quantity in an individual can vary depending on the season. The main preparation method is boiling: the crab limbs are put into boiling water, which already contains salt, and boiled for 15-20 minutes. After boiling, the meat can be preserved or frozen and can be stored.
Crabs belong to the Anthropod suborder and the Decapoda Crustacea order. Crabs have a very small head and eyestalks. The cephalothorax is broad, the width of the thorax ranges from 2 to 20cm and the thorax width is up to 60cm in Japanese deep-water crabs (Macrocheira kaempferi). The first pair of ambulatory legs are equipped with claws (chelae). All crabs, except fresh-water, breed in the sea. The development of crabs take place with a metamorphosis; the zoaea larva comes out of the eggs, which later on turns into larva – megalope and then into an adult crab. Free-floating larva is not observed only in fresh-water crabs (family Potamidae). While chasing, crabs are capable of breaking-off their legs through sharp movements and new legs grow at the place of the broken legs. Predominantly, crabs feed on invertebrates. Many types of crabs are edible and serve as a trading object. The Kamchatkan crab is not close to crabs but to hermit lobsters. Some crabs destroy trade molluscs - oysters and mussels and the Chinese woolly-handed crab (Eriocheir sinensis) sometimes, coming into rivers, destroys dams, in which it makes holes and also spoils the fishing nets. More than 4000 kinds of crabs are available.
It is necessary to talk about the shedding of the outer skin. All Crustacea, and also crabs among them, are concluded in a hard shell and can grow in size only during a short period of time when they are in a new unhardened coat after shedding their old tight coat. The shedding process is the most difficult experience in the life of crabs, lobsters and shrimps. In nature, the process is finely regulated at a hormonal level. |
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