The giant spider crab of Japan dwarfs all other crustaceans, with a record span of eleven feet between outstretched claws. Spider crabs get their name from their likeness to a spider. They have rounded bodies that are covered with stubby projections (tubercles) and long spindly legs. Rarely seen, large adult spider crabs, Macrocheira kaempferi, normally live at depths of as great as 1,200 feet, migrating in spring to shallower waters to mate and lay eggs. Females lay as many as 1.5 million eggs at a time, though only a minute fraction of them survive. Largest of Japan's estimated one thousand crab species, the spiders reach adult size within ten years and may live half a century or more.
The giant crustacean is sometimes called shinin gani, dead mean's crab, for its practice of feeding on bodies of the drowned. These giant crabs are omnivorous so sometimes act like scavengers.
Although their normal diet consists of fish, clams, and other mollusks, some giant crabs scrape the floor of the ocean for plants and algae, while others pry open the shells of mollusks to eat the fleshy meat. Like most species of crabs, males are larger than females. Males are distinguished from females not only by their larger size but also by twin penises shaped like corkscrews that extend beneath the abdomen.
Despite the crab's enormous reach, its body is relatively small. The largest shell ever recorded measured les than two feet across. Ungainly and essentiually timid Macrocheira kaempferi is found only on Japan's Pacific coast from Honshu to Kyushu. They tend to prefer the deeper parts of the ocean, such as vents or holes, which makes them hard to catch by the Japanese anglers. Though mentioned in 17th-century Japanese literature, the crab was unknown to Western scientists until 1727, when...