All across the globe, from the tropics to the poles, more than 900 species of sea urchin inhabit Earth’s oceans. Known by their spiny, spherical exteriors, they can be found from the shallows of the intertidal zone all the way down to depths exceeding 16,000 feet, making them some of the most adaptive creatures to inhabit the sea.
Ranging in color from pale orange, pink and yellow to bold, deep hues of red and purple, the sea urchin’s signature spines act as a brilliant defense mechanism. Protruding from the shell in ball-socket joints, each movable spine tapers to a needle-fine point and can orient itself toward any would-be attacker the urchin perceives. Though it lacks eyes or any semblance of a true brain, the urchin’s nervous system is made up of specialized sense-cells that line these spines as well as tubular feet the creature uses to slowly propel itself across the ocean floor.
Reputations to the contrary, only a few species of sea urchin are poisonous to humans, and none of them are deadly. While some spines carry toxins to paralyze predators, troubles that arise from close encounters are more often puncture wounds that aren’t properly cleaned and become infected.
Omnivorous, sea urchins exhibit a strong preference for algae and kelp but will eat just about anything that remains slow-moving enough for them to conquer. Positioning themselves over a chosen entrée, strong muscles aligned around a circular mouth on the urchin’s underside help push food into the oral cavity, where five arrow-shaped plates of bone work like teeth to grasp, grind, scrape and pull the food inside. This jaw-and-tooth mechanism is known as “Aristotle’s lantern,” and is named for the famous philosopher who first described it almost 2,500 years ago.
Sea urchin is revered as a delicacy in several cultures, most notably Japan, where wholesale prices for this tempting sushi, called “uni,” can soar to $130 a pound. Typically consumed raw, the only edible parts of the animal are the reproductive organs, which connoisseurs describe as creamy and buttery, with a texture like custard and an unsurpassed, delicate flavor of the sea. Some of the most prized samples are gathered by the “Haenyeo,” an all-female group of divers from the Japanese island of Jeju, who collect their wares without the aid of mechanical devices and whose history dates back to the 14th century.
Among the longest-living organisms on our planet, some species of sea urchin can live up to 200 years, and — like their close relative the sea star — can regenerate body parts lost to trauma or disease. Recent genome studies have identified specific DNA sequencing that appears to return cells to their stem cell state and may prove useful in the study and treatment of aging, Alzheimer’s disease and cancer.
Culturally, sea urchins have long been a sign of good fortune and ancient fossils of their shells are believed to have been worn and used as powerful amulets. In modern times, artists have depicted them in sculptures and paintings, none more famous than the surrealist Salvador Dali, who featured them regularly in his work and is reported to have one day enjoyed no less than 36 for a luncheon meal.
Locally, the most common sea urchin in our waters is the gorgeous purple sea urchin (Strongylocentrotus purpuratus), who makes regular appearances in regional tide pools. Upcoming summer low tides during daylight morning hours offer a great opportunity for exploration, specifically June 14 to 17, July 13 to 16 and Aug. 10 to 12. Check your local tide tables for exact times.