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 only in their adult years, before that juvenile purple urchins will have light green spines. On adult urchins, the spines are usually no longer than 2.5 cm, but can sometimes reach up to 6 cm when living in subtidal zones.

Habitat: Can be found in both subtidal and intertidal zones on shallow rocky ledges and in tidepools along the coast from Alaska to Mexico. Although Haystack Rock is included in their habitat range, it is unlikely that you will find them among the tide pools here, due to the lack of kelp in the area.

Diet: Purple sea urchins are a grazing species. Their diet consists mainly of algae that they source from kelp forests. 

Tide Pool Tidbits:

•  If their population size grows too large in a specific area they can turn full kelp forests into completely empty landscapes. 

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

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

• In greatly diminished kelp forests, urchins start staving and the size of their gonads are reduced, which results in them being less appealing to predators, and therefore increasing their population size.

  References: Oregon Conservation Society, Biodiversity of the Central Coast