Shallow, muddy sea bottoms close to shore. BEHAVIOR
Has attracted special attention from biologists, because, when beached by tides or storms, it moves itself around and back into the ocean by rolling up its body and rolling like a self-propelled wheel, covering as far as 6.5 ft (2 m) at a sprint, rolling 20-40 times, at 72 revolutions per minute, or 1.5 body lengths per second. When the rolling animal slows down, it uses its entire body as a spring to propel itself upwards and forwards into the next roll. So far, it and the caterpillar of the mother-of-pearl moth (Pleurotya ruralis) are the only two known animal species above microscopic size that use this form of locomotion.
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