Pacific Purple Sea Urchin

Pacific Purple Sea Urchin Strongylocentrotus purpuratus

Type of Animal:

Rocky intertidal areas, kelp forests, rocky shores, intertidal/subtidal zones, exposed rocky areas, shallow rocky ledges, tide pools, shallow coastal waters w/ strong waves, sea/ocean floors, found as deep as 656.168 ft

E Pacific from SE Alaska to Baja California Sur

Purple urchin w/ lots of purple spines, round body, radially symmetrical shell called test, younger urchins have purple tinged spines w/ mostly pale green, domed upper surface, flattened underside

Algae, kelp, decaying plant/animal matter, plankton, periwinkles, barnacles, mussels, carrion, sponges

Status in Wild:

Colonies often have hundreds to tens of thousands of urchins

Additional Info:

Young: Pluteus 
Group: Colony
4 in

2 months 

Life Span:
30-70 years

2 in

Main predators are sea otters, sea stars, California sheephead, gulls, spiny lobsters, & wolf eels.
Use spines to grab food & in defense.
Use tube feet to walk along sea floor.
Urchin’s spines catch floating food & pass it to mouth.
Breed from January-March.
Reproduction occurs through external fertilization, w/ males releasing sperm into ocean & fertilizing female’s eggs.
Though destructive w/o predators to keep them in check, they’re important in keeping algae in check.
Active at night (nocturnal).
Maturity reached at 2 years old.
1st line of defense is sharp spines. They can also defend themselves w/ venomous pedicellariae (small wrench/claw-shaped appendages w/ movable jaws).

Fun Fact(s):
Single female can produce hundreds of millions of eggs throughout her lifetime.

They can regenerate external appendages that were lost & used in longevity studies for this reason.
Hermaphrodites occur on rare occasions.
Toothlike plates surrounding mouth called “Aristotle’s lantern.”
These urchins eaten by people & meat known as uni used as sushi delicacy.
Without predators to keep them in check, these animals can decimate kelp forests, leaving behind urchin barrens. 90% of N California’s kelp forests gone due to these animals. Climate change & declines in primary predators have caused populations to explode. Since 2014, there’s been a 10,000% increase in populations of these animals.
A possible solution to the dramatic explosion in these animals may be utilizing them as food.

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