Purple Sea Urchin

Strongylocentrotus purpuratus





This organism is a stationary herbivore, often referred as a grazer who feeds on kelp and is part of the benthic communities on the sea bed or rocky shores in the intertidal zone (1). These invertebrates can grow up to a width of 7cm and are found in the Northeastern Pacific Ocean off the coast of Canada, all the way down to Baja California(2). Common predators of this species are sea otters and spiny lobsters, while they also compete for resources with red sea urchins and sea snails; establishing an ecological network within kelp forests and preserving biodiversity. The purple sea urchin is covered by a shell known as a test, or hard shell that bears spines with cilia used for food capture and tube feet for locomotion and gas exchange (respiration). The Aristotle’s lantern, specific to echinoids, forms the mouth that has five calcareous teeth used to scrape algae (kelp) and create dugouts for protection(2).


(1) Pearse, J. S. (2006). Ecological role of purple sea urchins. Science, 314(5801), 940-941.

(2) Purple sea urchin. Monerey Bay Aquarium

(Photograph) ©2006 Joseph Dougherty/ecology.org



  • rocky intertidal