The red sea urchin (Strongylocentrotus franciscanus) is a herbivore, and grazes on nearby algae. If large groups of these urchins are not kept in check by predators they will consume all surrounding algae (such as kelp forests) creating urchin barrens. Their long sharp spines are red to purple-black in colouration. The red sea urchin can grow to 12 inches (30 cm) across, with a range that includes Japan, as well as northern Alaska to northern Mexico.
