The Japanese Spider crab is the largest arthropod species in the world, with a body that grows to 15 inches in diameter and a leg span that reaches 15 feet across. Its adult body size is reached early in life, but as the crab ages its legs become longer, making its length a good age indicator. It tends to have a range of dark orange to a tan colored body with legs that are the same shade but have white mottled spots. Its tough exoskeleton is rough and spiny, helping it blend in textually with the rocks on the ocean floor.
Japanese spider crabs are entirely an oceanic species found almost exclusively on Japan's Pacific coast. They are most often found on the sea floor of the continental shelf at depths between 300 to 600 feet down. During the spawning season they do come into shallower coastal areas, and when young they prefer the shallows as well. The young crabs, like most spider crab species, have a habit of covering their shells with sea sponges and kelp to act as camouflage. As they grow larger, the crabs tend to stop using this camouflage because they have far fewer predators.
These giant crabs are omnivores, but they do not often actively hunt other animals for food. Instead, they search the ocean floor for the bodies of other dead sea creatures and plant matter, scavenging what they can. When they are young a variety of large fish and sea mammals will try to eat them, but once they are fully grown their size and tough shells make them a difficult meal to conquer. Humans are actually one of their few predators when fully grown, and the Japanese spider crab is considered a delicacy in Japan. Japanese diners eat the crab's meat both raw and cooked, and the large body shells are used for decorative purposes. The crab is also believed to have a long lifespan that can last up to 100 years, although 50 years seems more likely.
