Japanese Spider Crabs: Twelve Feet of Legs

by Kids Discover


So far, the world’s largest known living arthropod is the Japanese spider crab (Macrocheira kaempferi), a huge crab that may live up to 100 years. Let’s meet this leggy denizen of the deep.

Specifications: It’s the legs that make this crab big — its body stops growing at about 15 inches, but the legs keep growing and growing and can eventually extend 12 feet from claw to claw. Overall, the crab can weigh up to 44 pounds.

Location: Japanese spider crabs live in the Pacific Ocean near Japan, as deep as 500-1,000 feet or more. They like the vents and holes of the deeper ocean, which makes them harder for fishermen to find. So it’s no surprise that this crab is a delicacy in Japan.

Amputation: They can survive losing up to three walking legs, which sometimes grow back when they molt. They lose legs to marine predators and to nets (left by human predators).

Protection: As long as it keeps enough legs to get around, the crab’s armored exoskeleton helps protect it.

Ingestion: When it’s time to eat, the Japanese spider crab isn’t picky: it eats plants and animals, including dead fish and shellfish. Some have been known to pry open mollusks for dinner.

Decoration: This orange and white crab isn’t chameleonic (meaning it doesn’t change colors), but its mottled, bumpy carapace helps it blends into the ocean floor. Japanese spider crabs also go one (big) step further: They decorate themselves with sponges, anemones, and other animals that they cement to the tops of their carapaces.

Aspiration: When it’s young, in its larval stage, the young crab is small, round, transparent, and legless. Typically these larva drift like plankton on the ocean’s surface. Do they dream of the day when they’ll have the biggest legspan of all arthropods?


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