A New Species of Crab Found in Indian Ocean( By Ajay Kumar ) - manwithtech.com

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Friday, 2 March 2018

A New Species of Crab Found in Indian Ocean( By Ajay Kumar )

A New Species of Crab  Found in Indian Ocean

Crabs are generally covered with a thick exoskeleton,
 composed primarily of highly mineralizedchitin
 And armed with a single pair of chelae (claws).

 Crabs are found in all of the world's oceans, while many crabs live in fresh water and on land, particularly in tropical regions. Crabs vary in size from the pea crab, a few millimetres wide, to the Japanese spider crab, with a leg span of up to 4 metres (13 ft).
About 850 species of crab are freshwater, terrestrial or semi-terrestrial species they are found throughout the world's tropical and semi-tropical regions. They were previously thought to be amonophyletic group, but are now believed to represent at least two distinct lineages, one in theOld World and one in the New World.

The earliest unambiguous crab fossils date from the Jurassic, although Carboniferous Imocaris, known only from its carapace, may be a primitive crab.The radiation of crabs in the Cretaceousand afterward may be linked either to the break-up of Gondwana or to the concurrent radiation of bony fish, crabs' main predators.


Each species has a particular number of zoeal stages, separated by moults, before they change into a megalopa stage, which resembles an adult crab, except for having the abdomen (tail) sticking out behind. After one more moult, the crab is a juvenile, living on the bottom rather than floating in the water. This last moult, from megalopa to juvenile, is critical, and it must take place in a habitat that is suitable for the juvenile to survive.


 




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