Sea Urchin

Sea urchin

Sea urchins or urchins are the class Echinoidea within the echinoderms. Approximately 950 species live on the seabed, inhabiting all oceans and depths from the intertidal zone to the deep sea. They typically have a globular body covered by spiny protective tests, typically from 3 to 10 cm 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 such as crinoids and sponges. Their predators include sharks, sea otters, starfish, wolf eels, triggerfish, and humans. When unchecked by predators, urchins can create urchin barrens, damaged environments devoid of large algae and the animals associated with them.

Sea

A sea is a very large body of salty water. The term has two distinct meanings. The first is the interconnected body of seawater that spans most of Earth, known as the sea or the ocean. The second is a named body of water: usually either a marginal sea, or a large, nearly landlocked body of water.

sea urchin

Noun

1. Any of many marine echinoderms, of the class Echinoidea, commonly found in shallow water, having a complex chewing structure named Aristotle's lantern.