Sea urchin
Sea urchins or urchins () are typically spiny, globular animals, echinoderms in the class Echinoidea. About 950 species live on the seabed, inhabiting all oceans and depth zones from the intertidal to . Their tests (hard shells) are round and spiny, typically from across. Sea urchins move slowly, crawling with their tube feet, and sometimes pushing themselves with their spines. They feed primarily on algae but also eat slow-moving or sessile animals. Their predators include sea otters, starfish, wolf eels, and triggerfish.
Diadema antillarum
"Diadema antillarum" is still, in some tropical areas, one of the most abundant, widespread, and ecologically-important shallow-water sea urchins. It is found in the tropical Western Atlantic Ocean, including the Caribbean Sea, Gulf of Mexico and the northern and eastern coasts of South America (as far south as Brazil). It is also found in the East Atlantic at the Canary Islands. This species is ecologically important because it consumes algae that can otherwise grow to such an extent that they can smother coral reefs. They live in holes that are in the reef.