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Sea urchins or urchins (//) are typically spiny, globular animals, echinoderms in the class Echinoidea. About 950 species inhabit all oceans, and zones from the intertidal to deep. Their tests (hard shells) are round and spiny, typically from across. Sea urchins move slowly, crawling with their tube feet, and defended by their sharp spines, which are sometimes toxic. They feed primarily on algae but also eat slow-moving or sessile animals. Their predators include sea otters, starfish, wolf eels, and triggerfish. The name "urchin" is an old word for hedgehog, which sea urchins resemble; they have archaically been called sea hedgehogs. The name is derived from Old French herichun, from Latin ericius, hedgehog.
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