Intertidal Organisms EZ-ID GUIDES


on this species


Strongylocentrotus purpuratus (Purple sea urchin)

photo of purple sea urchin
Copyright © 2005 Mary Jo Adams


The purple sea urchin prefers high-energy beaches where it burrows a niche into soft rock.   Its spines are relatively short and stout; their length is about one third the diameter of the animal's test (shell).   The test may grow to a diameter of 4 inches.   Color is usually bright bluish-purple.   Occasionally an individual, especially a juvenile, may be found with green tinted spines.   The purple urchin feeds primarily on kelp.   Those individuals who find themselves too large to escape their crevice or burrow subsist on drifting seaweed and may absorb some nourishment directly from the water.   This species employs its tube feet to collect shell debris and seaweed, which it then uses as camouflage or shade.   The purple urchin may become prey to sea otters, sea stars, or fish and can be found from the lower intertidal to a depth of 525 feet.   


This page was created by Mary Jo Adams on 12/7/05.



photo of purple sea urchin

photo of red and purple sea urchins