Purple Sea Urchin (Strongylocentrotus purpuratus)

Description: Purple sea urchins are encased in a round endoskeleton, that is covered with spines, tube feet and pedicellariae (a tiny clawed appendage). The iconic purple color of this species only appears in their adult years, before that juvenile purple urchins (<3 cm) will have light green spines. The species is smaller than other urchin species, being 5-10 cm across.

Habitat: Can be found in mid intertidal to subtidal zones on shallow rocky ledges and in tide pools along the coast from Alaska to Mexico. In the intertidal, they are often found in cracks of rocks, shallow pools, and mussel beds. For subtidal individuals, they are typically around kelp forests.

Diet: Purple sea urchins are a grazing species. Their diet consists mainly of algae, either grabbed out of the water or scraped off the rocks.

Tide Pool Tidbits:

• If the urchin population size grows too large in a specific area they can turn full kelp forests into completely empty landscapes - termed urchin barrens.

• They are an important prey for many species including sea stars, crabs, and sea otters. 

• Sea urchin is considered a delicacy in some cultures, and is often harvested along the coasts of North America and Japan.

• Purple sea urchins reach sexual maturity at 2 years old, typically being only 2.5 cm diameter!

References: UCSC MARINe, Animal Diversity Web