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Wednesday, Feb. 27, 2008

ANIMAL TRACKER

Snow crab


Japanese name: Benizuwaigani

Scientific name: Chionoecetes japonicus

Description: A huge crab, brown on the back and white on the ventral (belly) side, the snow crab's body is almost circular, reaching 15 cm in diameter and weighing about 1 kg. Females are smaller, only growing to about 10 cm in diameter. The snow crab is a crustacean, like shrimps and lobsters, but has five pairs of long legs, slightly flattened, and the first pair of legs carry a large set of claws. It's more likely to be seen with a bright-orange shell — the color it turns when cooked. It superficially resembles a giant spider (except that it has one too many pairs of legs) and indeed is sometimes called a spider crab. However, the scientific name Chionoecetes literally means "snow dweller."

Where to find them: Snow crabs live in deep, cold water in the Sea of Japan, from Hokkaido to central Honshu. They are also prominent in fish markets, where they are one of the most commercially important species fished in Japan. They are caught from baited pots at depths as great as 1,000 meters.

Food: Pretty much any ocean animal that the crab can attack and open with its claws. This includes fish, clams, marine worms, starfish and shrimp. Enemies of snow crabs are seals, especially, but their hard shells and formidable claws provide a good measure of protection. Otherwise, the greatest threat comes from man, as the snow crab's flesh is delicious and greatly valued.

Special features: Like many invertebrates, snow crabs grow by molting. A soft, new shell is grown under the old one, which splits and is shed in Spring. The new shell then expands, and the body can grow into it — though it takes a couple of weeks to fully harden, and during this time the crab is extremely vulnerable to both predators and injury. Parasites also can attack and gain entry at this stage. But then, even after the shell has hardened, it requires another two months, at least, for the insides to fill with muscle and body tissue. Snow crabs molt every year — for about six years — until they reach sexual maturity. They may then live for another six or so years, meaning their maximum lifespan is around 12 years. Females mate with many different males, and have specialized reproductive storage organs in which they store sperm from different males. It's a bit like a safety-deposit vault in a bank, where different items can be safely stored and accessed when needed.

PHOTO COURTESY OF BIO-IMAGE NET



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