A small invertebrate marine animal, sea urchins are spiny ball-shaped animals that inhabit seabeds throughout earth’s oceans. They are members of the class Echinoidea and are closely related to starfish and sandollars.
They live only in salt water; they never live in freshwater lakes or rivers. Sea urchins have a hard internal skeleton, and formidable spines yet they have many predators, including people.
The lantern-shaped mouth is located under the shell; it contains five teeth and is surrounded by an area that is free of spines. The mouth is sometimes referred to as “Aristotle’s lantern”.
Most sea urchins are grazers using their hard teeth to remove algae and encrusting organisms from the surface.
Sea urchins
