By M. KATHY RAINES
Special to the PARADE
Lace-trimmed waters churn and swirl between jumbled granite blocks, exploding into shimmering mists. Plush carpets of sun-bathed algae glimmer, crabs scurry into cracks, and maroon-colored sea urchins nestle between boulders, their tiny spines and tube feet wiggling in the waves.
Treasures, including the Atlantic purple sea urchin (Arbacia punctulata), await those willing to venture along the jagged rocks of the jetties at Isla Blanca Park. This urchin is prominent among those resting on rocks in washes between boulders. In the phylum Echinodermata, the urchin, along with other echinoderms—including starfish, sand dollars and sea cucumbers— has an internal skeleton, five-pointed symmetry and a water vascular system. Also, the sea urchin, like its fellows, can regenerate appendages.
Before moving to the Valley, I considered sea urchins merely as elegantly patterned tests, or skeletons, widely available in shell shops, not little animals, who, like us, struggle to thrive on our planet. People sometimes pluck unsuspecting urchins from rocks, tossing them into buckets, for profit, food or decoration, but Texas law dictates that harvesters have a saltwater fishing license. (Woe to the creature with an ornamental corpse).
Also, Texas law forbids the harvesting of sea urchins, hermit crabs, starfish and shell-bearing mollusks from November 1 through April 30, the Island’s peak tourist season, within these boundaries, according to Texas Parks and Wildlife’s website: “the bay and pass sides of South Padre Island from the east end of the north jetty at Brazos Santiago Pass to the west end of West Marisol Drive in the town of South Padre Island, out 1,000 yards from the mean high-tide line, and bounded to the south by the centerline of the Brazos Santiago Pass.”
This creature’s name derives from Middle English “urcheon” meaning “hedgehog”, a spiny mammal. Spanish speakers call it el erizo de mar, and, interestingly, in Cuban slang, to “andar (to walk or go) erizo” means to break out in goosebumps or—reminiscent of a spiky sea urchin— have one’s hair standing on end.
The sea urchin’s test, a bumpy shell of fused plates, encircles this spherical creature whose colors include purple, brown and red. A water vascular system controls its tubular feet, which emerge from holes and end in suction cups that allow it to cling to rocks and grasp food. The urchin moves about on these, assisted by its spines. Also, it primarily “breathes” through its feet, which absorb oxygenated water.
The sea urchin’s mouth is underneath, its genital pores and anus on top. Lips, embedded with bony tissues, surround its mouth, protecting gill-like openings. It tears and scrapes algae and rock-dwelling organisms from rocks with its Aristotle’s Lantern, an assemblage of five teeth-like plates. Aristotle, in his History of Animals, first described the apparatus, suggesting it resembled a “horn lantern”—a then common device made from a flattened cow horn.
A nerve ring surrounding a sea urchin’s mouth serves as a brain or control center for its five principal nerves. Though eyeless, the urchin bears widely distributed photoreceptor cells that allow it to detect light stimuli and direct its spines where needed.
Though sharp spines protect it from many predators, a powerful wave can shatter a sea urchin. Gulls, oystercatchers, crabs, eels and other fish, especially sheepsheads may devour urchins, having adapted useful beaks, claws or teeth to manage spines. Sea urchins hide within crevices and may even dig their own holes, wearing away rocks. Small grooming organisms live symbiotically between urchins’ spines, keeping them clean.
Female sea urchins release millions of transparent eggs, which males find and fertilize. Unlike their parents, larvae are bilaterally symmetrical.
Some value sea urchins—particularly their gonads, called uni, from Japanese,—as an ingredient in sushi. Also, ceviche de erino, or ceviche with sea urchins, is a delicacy in coastal areas of Peru and Chili.
Sea urchins, a vital part of our ecosystem, scrape invasiv e algae from rocks. Also, scientists prize them for embryological studies because of their transparent, quickly maturing, manipulatable eggs. Urchin studies have advanced knowledge in fetal alcohol syndrome, anti-convulsant drugs, heredity, and toxicity of chemicals in marine waters. Anyone who steps on this sea urchin should carefully remove spines with tweezers and soak the area in warm water. This site offers more detailed instructions: https://www.webmd.com/first-aid/what-to-know-about-sea-urchin-stings.