Purple Sea Urchin

The purple sea urchin is a spiny marine invertebrate found along the rocky coastlines of the eastern Pacific Ocean, from Canada to Mexico, recognized by its rounded, ball-like purple test, or shell, covered in dense, moderately long spines used for both protection and slow locomotion across rocky and kelp-covered seafloor. It feeds primarily on kelp and other algae, using a complex, five-part chewing structure known as Aristotle's lantern to scrape and grind algae from rock surfaces, and under normal conditions its grazing helps maintain a healthy balance within kelp forest ecosystems. When natural predators such as sea otters and sunflower sea stars decline, however, purple sea urchin populations can explode unchecked, sometimes overgrazing entire kelp forests into barren, denuded rock in a process that has caused dramatic ecological collapses along parts of the West Coast of North America in recent years. Purple sea urchins can also live for remarkably long periods, with some individuals estimated to survive for well over a century, making them among the longest-lived marine invertebrates known.