Species Fact Profile: Japanese Spider Crab (Macrocheira kaempferi)

Japanese Spider Crab

Macrocheira kaempferi (Temminck, 1836)

Range: Japan's Pacific Coast (Islands of Konshu and Kyushu)

Habitat: Continental Shelves with Sandy or Rocky Bottoms

Diet: Carrion, Small Invertebrates, Kelp, Algae

Social Grouping: Asocial

Reproduction: Mate in the spring (January through March).  Packets of sperm (called spermatohores) are inserted into the female's body.  Females may lay over one million eggs per season, less than 1 millimeter in diameter, which she carriers on her body.  Eggs hatch after 10 days, after which there is no parental care.

Lifespan: 50-100 Years (Speculation)

Conservation Status: Not Evaluated

• Largest (but not heaviest) living arthropod with longest legspan - up to 4 meters from the tip of one leg to the tip of the opposite.  Pear-shaped body is up to 37 centimeters long.  Females are wider but slightly smaller than males with shorter legs.  Weigh up to 20 kilograms
• Color is mottled red-orange, usually fading int a cream color on the underside.  Colors tend to be brighter after a molt
• The long legs are very fragile and somewhat weak.  Most crabs are missing at least one due to predation or getting tangled in nets; legs grow back with molts
• Folk tales describe spider crabs seizing sailors and dragging them underwater to eat; unlikely to be true, but have have been inspired by sights of crabs scavenging drowned humans
• Adults have few predators.  As such, they do not camouflage themselves by decorating their shells with sponges and other items as many other crabs due
• Specimens have occasionally been found at a considerable distance from Japan, as far as Taiwan - it's likely that these individuals were carried there either by fishing trawlers or by extreme weather conditions
• Considered a delicacy in Japan, though catch has declined significantly in recent years.  Law prohibits fishing for them during the mating season