Sea Urchin

SEA URCHIN is a spherical marine invertebrate occuring along the rocky coastal shoreline at the tide line and subtidally. Urchins are related to the SEA STAR and SAND DOLLAR, all members of the phylum Echinodermata ("spiny-skinned"). The urchin's lumpish body is covered in spines, which are used for defence and movement. Between the spines are slender tube feet, which pass bits of food collected from the water to the animal's mouth, located in the middle of its underside and surrounded by small teeth. Like other echinoids, urchins are equipped with a complicated chewing apparatus of bone and muscle just inside the mouth, known as Aristotle's lantern after the Greek philosopher who first described it. Of many hundreds of species worldwide, 3 are found commonly along the BC coast. Green sea urchins (Strongylocentrotus droebachiensis) occur abundantly in tidal pools and KELP beds from Alaska to Puget Sound. Purple sea urchins (S. purpuratus) occur on rocky substrate along exposed shores, where they scrape out depressions in the stone. Giant red sea urchins (S. franciscanus), the largest of the local species (up to 17 cm across), actually range from pink to purple in colour and usually congregate in large beds. A commercial fishery (see FISHING, COMMERCIAL) for red urchins established in 1978 supplies roe to Japan as a delicacy, and there has been a green urchin fishery on the South Coast since 1987. Urchins are harvested by divers using hand rakes and mesh bags.