Urchins, pretty in pink, use poison for protection
POSTED: Monday, May 10, 2010
As Craig and I sailed down the Sea of Cortez (Gulf of California) last week, the wind was fair and the direction favorable.
This posed a dilemma. Should we continue this slow, quiet downwind glide or start the noisy engine, hurry to the anchorage and go snorkeling while the sun was still up?
Well, sailing is nice but I started the motor.
May temperatures here in the mid-gulf are cold for my Hawaii blood—air 70 to 80 degrees, water 65 to 70—so after dropping the anchor, I then had to struggle into my unloved wet suit.
When I hit the water, though, it was worth all the trouble. Sitting there waiting for me were several adorable girl sea urchins.
OK, some were probably males, too, but all were pastel pink with delicate red flowers between their short spines. Since some shielded their bodies with shells and stones, I knew these must be collector urchins.
Collector urchins are softball-size creatures that sit on the ocean floor looking like pin cushions. Unlike the long, needle-sharp spines of the sea urchins we call wana in Hawaii, collector urchin spines are stubby and blunt. They are also usually black.
The charm of collector urchins is their habit of collecting things. Using sticky tube feet that can stretch beyond its hard body spines, the urchin walks around picking up items that are small and light enough to transfer, conveyor belt style, onto its back. Any item will do. I once saw a collector urchin gripping a white plastic spoon, another time a fork.
The reason for this collecting isn't clearly understood, but it has something to do with light. Researchers observe that some species cover themselves more in the summertime than in winter, and some drop their cover at night.
In a lab experiment, when biologists projected a narrow band of light across one side of a collector's body, it picked up its small stones and passed them from three different directions to the illuminated strip.
Still, it's common to see collector urchins sitting on the ocean floor bare naked in the bright summer sun. Only the urchins know why they sometimes cover up and sometimes don't.
One family of collector urchins possess, among their sticky tube feet, stalks tipped with three tiny biting jaws that contain poison. The toxin paralyzes small animals and drives away enemies. These formidable jaws, my textbook says, “;look like little parasols when open and can produce a painful reaction in humans.”;
Those were the things I called flowers on my pink urchin, and I wasn't far off. My Sea of Cortez marine guide says the common name of this pink beauty is the flower urchin. The creature's scientific name, though, puts it in the poisonous category. Clever, I thought. Sharp teeth disguised in a pink party dress.
Before I knew about those flowery jaws, I picked up one of the pink collectors to examine it. I felt no pain, but then I held it for only a few seconds, because the creature immediately dropped its shells and I felt bad about that. After putting it back, I piled new shells around it and left it alone to rebuild its shelter.
All sea urchins are algae grazers. Flower urchins, not surprisingly, eat only crusty red seaweeds.
The next time we're trying to decide whether to sail or swim, I'll remember finding those eye-popping flower urchins in the late afternoon sun.
Using a diesel engine on a sailboat when there's wind seems wrong. Sometimes, though, it's exactly right.
Susan Scott can be reached at www.susanscott.net.