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Friday, Aug. 16, 2002


Japanese crayfish

* Japanese name: Nihon zarigani
* Scientific name: Cambaroides japonicus
* Description: Japanese crayfish are crustaceans, the same as shrimps and crabs. They have a flat, segmented body and 5 pairs of legs. The first three pairs of legs are spineless claws, and the front pair are enlarged. If legs or claws get broken off (this might happen when males fight), they are regenerated. There are a pair of sensory antennae and two eyes on movable stalks. The body is usually 4-5 cm long, but can be up to 7 cm. To grow, crayfish must molt their hard exoskeleton. At this stage the crayfish is soft and vulnerable to predators. Before their new shell hardens, the body increases in size.
* Where to find them: All over Hokkaido and the Tohoku region of northeastern Japan. Crayfish live in clean water and hide in holes in stones and hollows in gravel and sand. They can't tolerate warm water and so are confined to the north.
* Food: Plant and animal matter. Crayfish prefer algae and aquatic plants, but will also eat worms, tadpoles, small fish and insect larvae and dead animals. Fish such as bass and trout are predators of crayfish. To escape danger, crayfish flick their tails, which quickly propels them away.
* Special features: Crayfish become sexually mature in their second year. Mating takes place from July to September, but the female stores the sperm in a special receptacle in her abdomen for later use. When she lays her eggs in the autumn, she releases the sperm and the eggs are fertilized. The eggs then stick to the bottom of her abdomen -- and stay there, safe under their mother, until they hatch in spring. Females carrying eggs are said to be "in berry" because the eggs look a bit like berries.

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