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Friday, July 6, 2001
Beach wood louse
By ROWAN HOOPER
* Japanese name:Funamushi * Scientific name: Ligia exotica * Description: Beach wood lice are isopods, which are in the crustacean group, like shrimps. But unlike shrimps, their bodies are flattened parallel to the ground. Like regular wood lice, they have seven pairs of legs and large eyes. They also have two sensory "tails." They start breeding in spring from the age of 1 and may breed three times a year. They live up to three years. They're an ancient group of animals, having been around at least since the Carboniferous (300 million years ago). * Where to find them: They live at the seashore, just above the sea line, and venture into the intertidal zone, where rock pools form, when the tide is out. At high tide, they move higher up the beach. Turn over rocks, and you'll find many isopods of different sizes and colors. They have gills and can survive for short periods in seawater. For this reason, they are known as semiterrestrial isopods. They are also found in houses and boats near the sea, hence the Japanese name, funamushi, or "boat bug." * Food: These isopods are the cockroaches of the seashore (and are also known as sea roaches). They are scavengers, eating garbage, dead fish and algae (seaweed). They are harmless to humans. * Special features: Females don't lay eggs. After fertilization, the eggs are retained in a brood pouch in the female's body, where they hatch and remain for two months. Then they emerge as juveniles, which look like small adults. They have a neurogenic heart, which means that the heartbeat is controlled by a pacemaker. An impulse is sent by a special nerve to control the rate of the heart beat, like in a human heart. Unlike our hearts though, the isopod heart is tubular.