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Japanese spider crab

Macrochaeira kaempferi

Description: The Japanese spider crab (Macrocheira kaempferi) gets its name from its resemblance to a spider. It has an orange body with white spots on its legs. The short, stubby eye stalks are located on the front of the carapace and two thin spines stick out between them. Short, spiny tubercles also cover the carapace. In male specimens, the limbs on which the claws are located become longer than its other limbs.

Size: The Japanese spider crab is one of the largest living arthropods. Fully grown it can reach a leg span of 12 feet (3.7 m), a body size (carapace width) of 15 inches (38 cm) and weigh as much as 44 pounds (20 kg). The width of the oval-shaped and vertically rounded shell can reach up to 12 inches (30 cm) and can be up to 16 inches (41 cm) long. Males are larger than the females.

Behavior: In spite of its ferocious appearance, it has a gentle, calm disposition. Unable to swim, they spend much of their time crawling on the sea bed, foraging for food.

Diet: Japanese spider crabs are omnivorous and scavenge for food. In its natural habitat it feeds on shellfish and dead animals. They can eat algae, plants, mollusks and small fish, catching and tearing up the meat in their powerful pincers. Their long legs enable them to move quite quickly and stalk their prey.

Senses: Since Japanese spider crabs are not active hunters, live at deep depths and do not have
many predators, their sensory systems are not as acute as those of many other decapods.

Reproduction: Mating takes place with the abdominal surfaces of the crabs opposing each other and occurs as soon as the female completes her molt. Fertilization is internal. The female’s abdomen is wider than the males to provide space for the brooding egg mass, until they hatch in minute planktonic larvae.

Habitat/range: Preferring the deeper areas of the ocean, they are found at average depths of 344-984
feet (105-300 m), but have been found as deep as 1,000 feet (305 m). Spawning takes place in shallower waters; average depth of 164 feet (50 m). They inhabit the sandy and rocky bottoms in the Pacific Ocean around Japan.

Status: No status listed on IUCN or CITES.