The Japanese spider
crab has the greatest leg span of any arthropod, reaching 3.8 metres (12 ft 6 in) from claw to claw. The body may grow to a size of 40 centimetres or 16 in (carapace width) and the whole crab can weigh up to 41 pounds (19 kg).
It is the males which have the longest chelipeds; females have much shorter chelipeds, which are shorter than the following pair of legs. Apart from its outstanding size, the Japanese spider
crab differs from other crabs in a number of ways. The first pleopods of males are unusually twisted, and its larvae appear primitive. The crab is orange, with white spots along the legs. It is reported to have a gentle disposition "in spite of its ferocious appearance".
The Japanese spider crab, Macrocheira kaempferi, is a species of marine crab that lives in the waters around Japan. It has the largest leg span of any arthropod, reaching up to 3.8 metres (12 ft 6 in) and weighing up to 41 pounds (19 kg). It is the subject of small-scale fishery.
Japanese Spider Crab Baby
The Japanese spider crab was originally described in 1836 by Coenraad Jacob Temminck under the name Maja kaempferi, based on material from Philipp Franz von Siebold collected near the artificial island Dejima. The specific epithet commemorates Engelbert Kaempfer, a German naturalist who lived in Japan from 1690 to 1692 and wrote about the country's natural history. It was moved to the genus Inachus, by Wilhem de Haan in 1839, but placed in a new subgenus, Macrocheira. That subgenus was raised to the rank of genus in 1886 by Edward J. Miers. Although currently placed in the family Inachidae, M. kaempferi does not fit cleanly into that group, and it may be necessary to erect a new family just for the genus Macrocheira. As well as the single extant species, four species belonging to the genus Macrocheira are known from