Japanese spider crab

Macrocheira kaempferi

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 and weighing up to 19 kilograms . It is the subject of small-scale fishery which has led to some conservation measures.
Japanese Spider Crab (Macrocheira kaempferi) Before you get upset that I posted a shot of an animal with a human, I asked if I could do this before posting. I wanted to share the deep water species with the group and this is the image I have. One of the largest crabs on Earth – this is the Japanese Spider Crab (Macrocheira kaempferi). Myth and lore surround this species as old stories tell of giant crabs dragging fishermen to their deaths, consuming them in the depths. The crabs are actually scavengers, they can not swim as adults, they are easy going, and are slow moving; however, one source pointed out that it isn’t impossible that they’d eat a corpse that made its way to the sea floor. This species appears to have a relative small range off of the Pacific side of the Japanese islands at a latitude between 30 and 40 degrees North. Adults inhabit water from 100 to 400 meters depths, juveniles appear to inhabit shallower areas with a mean of 50m depth. From the edge of the carapace to the tip of the claw can span some 4 meters length in this species. The individual depicted here isn't a particularly large individual. Adults have a mass between 16 and 20kg. The Japanese Spider Crab has two zoea stages and one megalops stage which, combined, last several months. The species enacts parental care in that females carry their eggs on their backs and the underside of the carapace to keep water moving around them in order to provide oxygen. Some biologists have hypothesized that these crabs can live for 100 years. The only commentary I could find on conservation status was that “catch has declined considerably across the past 40 years.” There is an active fishery for the species and there appears to be the means and methods to rear this crab from a juvenile stage by way of aquaculture facility. I would like to thank Masato Todate and Yuki Tsukamoto, both with the Takeshima Aquarium, Gamagori City, Aichi Prefecture, Japan, for the opportunity to see and photograph these amazing animals! The note on captive rearing: https://www.researchgate.net/publication/319592456_CULTURE_OF_THE_GIANT_SPIDER_CRAB_MACROCHEIRA_KAEMPFERI_DE_HAAN_FROM_EGG_TO_JUVENILE_STAGE Japanese Spider Crab,Japanese spider crab,Macrocheira kaempferi,benthic sea life,crustacean,deep water species,scavenger,sea floor

Appearance

The Japanese spider crab has the greatest wing span of any arthropod, reaching 3.8 metres from claw to claw. The body may grow to a size of 40 cm or 16 in and the whole crab can weigh up to 19 kilograms . The males have the longer 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, despite its ferocious appearance.
Japanese Spider Crab in captivity, London Japanses Spider Crab in Captivity. Japanese spider crab,Macrocheira kaempferi

Distribution

Japanese spider crabs are mostly found off the southern coasts of the Japanese island of Honshū, from Tokyo Bay to Kagoshima Prefecture. Outlying populations have been found in Iwate Prefecture and off Su-ao in Taiwan. Adults can be found at depths of up to 600 m , or as shallow as 50 m . They like to inhabit vents and holes in the deeper parts of the ocean.

Behavior

Female crabs carry the fertilized eggs attached to her abdominal appendages until they hatch into tiny planktonic larvae. Development of the planktonic larvae is temperature-dependent and takes between 54 and 72 days at 12–15 °C . During the larval stage the young crab looks nothing like its parents. It is small and transparent with a round, legless body and usually drifts as plankton at the surface of the ocean. The Japanese spider crab is an omnivore, consuming both plant matter and animals. It also sometimes acts as a scavenger consuming dead animals. Some have been known to scrape the ocean floor for plants and algae while others pry open the shells of mollusks. They live at depths of 150–300 metres or more. The giant spider crabs migrate up to a depth of around 50 metres during breeding season.

Evolution

The Japanese spider crab was originally described by western science 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 fossils.

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Taxonomy
KingdomAnimalia
DivisionArthropoda
ClassMalacostraca
OrderDecapoda
FamilyInachidae
GenusMacrocheira
SpeciesM. kaempferi
Photographed in
United Kingdom
Japan