The Purple Sea Urchin is found along the eastern edge of the Pacific Ocean, from Mexico north to British Columbia, where it occurs in lower intertidal and nearshore subtidal communities and is a significant component of the
kelp forest (
Wikipedia 2011). This species is fairly easy to recognize. It looks a lot like a purple pin cushion because of its round inner shell, and generally reaches diameters of about 10 cm (
Race Rocks 2011). The shell is covered with pincers, tube feet and purple spines (adults are purple, juveniles have green spines) (Monterey Bay Aquarium 2011). The spines may be up to 2 cm in length are used to spear food and provide some protection (Monterey Bay Aquarium 2011, Race Rocks 2011). The tube feet serve several purposes: they are used for movement, to pass food down to the mouth, and to 'breathe' (gases are exchanged here). "An urchin uses its teeth and spines to dig holes in stones, which become the sea urchin’s hideaway." (Monterey Aquarium 2011). The Purple Sea Urchin feeds on a variety of species, from algae and plankton, to kelp, periwinkles, and occasional small barnacles or mussels (Race Rocks 2011). Predators include crabs, sunflower stars, snails, sea otters, some birds, fish, and people--a small Purple Sea Urchin fishery is present. Typical life span of the Purple Sea Urchin is70 years.
