User:FunkShway/Red sea urchin

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A sea urchin's spherical body is completely covered by sharp spines. These spines grow on a hard shell called the "test", which encloses the animal. It can vary in color from red to dark burgundy. Rarely, albino specimens are found. It has a mouth located on its underside, which is surrounded by five teeth. During larval development, the body of a sea urchin transitions from bilateral to radial symmetry.

This bilaterally symmetrical larva, called an echinopluteus, subsequently develops a type of pentaradiate symmetry that characterises echinoderms. It crawls very slowly over the sea bottom using its spines as stilts, with the help of its tube feet. Scattered among its spines are rows of tiny tube feet with suckers that help it to move and stick to the sea floor.

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