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Nature Nut: A real delicacy? Try urchin organs

January 14, 2019

I first learned about sea urchins many decades ago snorkeling in the Florida Keys and touching one with long spines. Penetrating the skin on my finger, and breaking off the spine, it was in to stay. I recall getting advice that urine would help to relieve the pain, but it didn’t.

Since that time, I have learned avoiding the spines is the best plan. Even doing so, when diving or snorkeling, occasional spine encounters will happen. So I learned it just takes time for the spines to dissolve, normally not causing any major problem.

Sea urchins are in the echinoderm family, which also includes starfish and brittle stars. They are found from a few feet to miles down in depth throughout all the oceans, with tropical waters being favored. There are hundreds of species, some with short spines, and some long. Much to my surprise, sand dollars are also a sea urchin.

Sea urchins, while looking rather immobile, do move by the aid of spines and tube feet. I recently picked up a short-spined urchin, put it on my hand and almost immediately felt the suction of dozens of tube feet adhering to my palm. I could turn it upside down and it would not drop off.

Going to retrieve my camera, I noticed once out of water the tube feet did not try attaching to me. Instead, the hundreds of spines on the body moved back and forth, presumably trying to move to water wherever it was.

The wall full of corals, sponges, and fish I wrote about last week also has hundreds of dark blackish-purple urchins with 4- to 9-inch spines. My daughter, Erin, commented that their numbers seem to have “increased significantly over the years,” which I agreed with.

During the day, many of these large urchins can be seen tucked into coral indentations in the wall, something I assume they do for protection from predators. But, when I dive or snorkel the wall at night, they are out of their protected spots looking for food. Urchins feed primarily on algae growing on the surfaces they move over, and occasionally will take in slow-moving animals.

The mouth of most sea urchins is made up of five teeth or plates, with a fleshy, tongue-like structure. They are part of the five-fold symmetry urchins develop as they change from a free-floating larval form to settling on the ocean floor. The five sections are easy to see on the pincushion-like skeletal structure, which is often left intact after an urchin dies and spines drop off.

The outer surface of this skeleton, also called a “test,” is where the spines and suction tubes were attached, and inner area is where digestive and reproductive systems were located. We sometimes find and collect these “skeletons” but they rarely last very long, as they are quite fragile.

We had not seen any urchin predation until this year when my snorkeling grandchildren twice witnessed unusual visitors to the wall, ocean triggerfish, feeding on urchins. Without predators, sea urchins dominate their environment, voiding it of kelp and other algae, as well as animals associated with those environments. Other major sea urchin predators include starfish, lobster, crabs, sea otters, and humans.

Sea urchins are considered a delicacy in many countries, especially Japan, where 80 percent of the global harvest is sent. There, reproductive organs of both male and female urchins, also called roe, provide culinary delights for millions.

I recall in the early 1980s, when on sabbatical in San Diego, I considered abandoning my teaching career and just diving for sea urchins. They often can bring more than $100 per pound.

Urchins also appeal to sea otters, which have mastered avoiding spine injury, and breaking open the hard shell to get into the edible organs of the urchins. And, it is sea otter recovery along the U.S. Pacific coast that has done most to improve ecosystem health there.

Although I haven’t done so yet, I may have to try some uni, the name for sea urchin roe, on my next visit to Ichi Tokyo with friend, Elise. And, for those tired of reading about sponges and urchins, I will be home to enjoy winter by the time this goes to print.

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