Sea Urchins

These prickly animals have highly developed, moveable spines used for defense as well as for moving around. Sea urchins have colonized most types of seabed from rocky shores to deep-sea bottoms.

Sea urchins are echinoderms (spiny-skinned animals). They are related to the starfish, sea lilies, and sea cucumbers. They come in two basic body shapes. Round ones are called regular echinoids. Oval or heart-shaped ones are called irregular echinoids. All urchins have a chalky body called a test, which is covered in spines of varying lengths.