ANIMAL: Pacific Purple Sea Urchin Strongylocentrotus purpuratus Type of Animal: Echinoid Habitat: 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 Location(s): E Pacific from SE Alaska to Baja California Sur Appearance: 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 Food/Diet: Algae, kelp, decaying plant/animal matter, plankton, periwinkles, barnacles, mussels, carrion, sponges Status in Wild: Stable Lifestyle: Colonies often have hundreds to tens of thousands of urchins Additional Info: Called: Male Female Young: Pluteus Group: Colony Diameter: 4 in Gestation: 2 months Life Span: 30-70 years Height: 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.
