Red Sea Urchin (Mesocentrotus franciscanus)

Description: Also known as the giant red urchin, these sea urchins tend to be much larger than the purple sea urchins, although they can both come in red and purple colors. In California, the large urchins can be up to 12.7 cm in diameter whereas the British Columbia individuals can be up to 18 cm. The spines on the red urchin are very large, sometimes up to 8 cm long!

Habitat: Red sea urchins are found in the deeper tide pools of the low intertidal down to subtidal depths with rocky substrate. They range from Alaska to Mexico and over in Japan.

Diet: Like other sea urchins, the red sea urchin eats algae, either as it drifts by and is caught by their spines and tube feet or by grazing and scraping the algae off rocks.

Tide Pool Tidbits:

• The lifespan of this species may be over 100 years!

• Their main predators include octopus, sea otters, sea stars, wolf eels, and humans.

• They have a sensitivity to light, likely as a predation response, and quickly move their spines around if a shadow suddenly appears over them.

• This species used to be classified as Strongylocentrotus franciscanus.

References: Aquarium of the Pacific, The New Beachcomber’s Guide to the Pacific Northwest by J Duane Sept