Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. The bathyal swimming crab, Bathynectes longispina, is a species of crab in the Portunidae family.This species lives on seamounts and knolls, at depths as great as 600 metres (2,000 ft). It appears similar to other members of the portunid family, but has reduced swimming dactyls and long walking legs. As an adaptation to deep water, it has large eyes.Crabs are generally covered with a thick exoskeleton, 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).