Purple sea urchins that have dug themselves a protective recess into the surrounding rock rely on algae to drift and settle nearby as a food source. This urchin seems very interested in a piece of kelp as its tentacles are grasping towards the morsel.
Purple sea urchins, living close to the surface, use their strong spines to dig deep depressions into the rock to provide protection from crashing waves and violent storms that hammer the open ocean coastline. The purple sea urchin (Strongylocentrotus purpuratus) has a range that includes Japan, as well as northern Alaska to northern Mexico, and they can grow to 6 inches (15 cm) across. These urchins live in the intertidal zone down to around 215 feet (65 m) of depth, and may live as long as 70 years of age.