IT’S REALLY BORING!

By Pam Eastlick

Welcome to The Deep science and technology column where we cover topics from the deep sea to deep space and beyond.

Greetings everyone! Well, today the animal file won out and we’re going to talk about some sea animals that are familiar to most of us; the sea urchins. Probably the most familiar one is the black spiny sea urchin Diadema, that got that common name for a very good reason. Many of us have inadvertently stepped on one or backed into it and had to deal with the spines. Generally you can’t pull them out and the best way to deal with them is to club them with something blunt so that they’ll break up and your body can eventually deal with the debris.

But I’m not talking about Diadema. I’m talking about the ones that you may have never noticed. They’re common on Guam. All you have to do is find a large rock sticking out of the water and look on the seaward facing side near the bottom. Chances are you’ll see a smallish hole filled with spines.

I saw a little girl discover one of these ‘enclosed’ urchins once and she looked at her daddy and said “It’s moving Daddy! How did it get in there?” She was a budding scientist, because that is a very good question. The answer may one day help you carve a better steak.

Many sea urchins live in the tidal zone and protect themselves from predators and the crashing surf by literally eating into the rocks. This rock-boring behavior is pretty awesome, but what’s truly remarkable is that despite the constant grinding and scraping on stone, urchin teeth never, ever get dull. Now a team of scientists from the University of Wisconsin-Madison has peeled back the toothy mystery.

It seems that sea urchin teeth are quite complex and are one of the very few structures in nature that self-sharpen. The teeth, which are always growing, are made from calcite crystals in two forms: plates and fibers. They’re arranged crosswise and cemented together with super hard calcite cement. Between these crystals are layers of organic materials that are weaker than the calcite crystals.

The organic layers are the weak links of the chain and the teeth break at predetermined points. It’s like perforated paper in the sense that the tooth material breaks at these predetermined spots. The outer portion of the tooth sloughs away at these points revealing the new, fresh and sharp surface.

The scientists say that since they’ve discovered how urchins keep their teeth sharp, they may be able to adapt these techniques to create tools for humans that actually sharpen themselves with use.

Of course, I’m not really sure that would help you carve a better steak. First, you wouldn’t want your knife shedding used parts all over your steak and you’d also have to figure out how to accomplish the ever-renewing part that the living urchin manages so well. But for big jobs like mining, where the drills have to be periodically replaced anyway, the urchin’s secret may make the job easier.

Next time you’re at the beach, see if you can find a rock-drilling urchin. Tell them we’ve finally figured out how they do it!

The teeth of a living sea urchin. Scientists have recently discovered why a sea urchin’s teeth are always sharp, despite constant grinding and scraping to create the nooks that protect the marine animal from predators and crashing waves. (Credit: Photo courtesy of Pupa Gilbert)