Urchin body

Body size up to 1 inch across, spines up to 1/2 in.  Color dark purple to bright red or pink. The sea urchin mouth is on the underside of its body. It has a claw-like mouth with five teeth-like plates which are called Aristotle's lantern. If these break off, new ones are grown. The sea urchin body "skeleton" has with bumps and holes which the moveable spines and tube feet extend from (see diagram). The sea urchin eats red brown algae, kelp, periwinkles, and occasionally barnacles or mussels. People eat the gonads (sexual organs) of this urchin. It is especially a delicacy in Japan and other parts of Asia. Sunflower stars, some fish, birds, and sea otters also prey on them. The red sea urchin is found in deeper water than the purple sea urchin. It is seen from the low intertidal area to as deep as 300 feet. Their tube feet may also be used to sense or smell the chemicals in their surroundings. Like other urchins, the red sea urchin can regrow its spines if they are broken. Spines of adults sometimes shelter small juveniles. The red sea urchin can live 20 years. 

The green sea urchin has a circumpolar range.  In the eastern Pacific, it is found from northern Alaska southward to Washington.  It occurs in the Aleutian Islands and westward to Russia,  Korea, and Japan. It is found on the East Coast of the U.S. and Canada, and in Greenland, Iceland, and northern Europe. It is most abundant in the shallow subtidal zone on rocky, gravelly, or shelly bottoms. Green sea urchins mature in about three years, they spawn in winter or early spring.  Kelp is the preferred food.