Pinhead ... The Long Spined Urchin
Diadema setosum
Hands Down, the most INTRIGUING creature to watch!!
Mostly nocturnal, Pinhead consumes the most algae of any othe creature in the tank. Most of it is coraline algae (the good kind). However, while he does eat the coraline, he also is very sloppy about it. His grazing actually acts as a way to speed up the spreading of the coraline algae. So while withing a week of adding him to the tank, I had barely any coraline left...about a week after that, I had way more coraline spots growing that I had originally. And all over the place now. Which in turn keeps him well fed. And for that reason, he's growing fast!
Ours is currently about 10" from spine to spine. And they're known to grow to about 15" (even bigger outside of captivity)...so even though he's huge now, apperantly, he's just going to get bigger.
These guys have one of the most intersting and complex oral structures in the animal kingdom. So much so that their "mouth" actual has a name all it's own. It's called Aristotle's lantern, and in essence, it's responsible for the strongest "jaws" on the planet. They are rumored to chew their way through concrete pier pillars. (More information on the Urchin, and Aristotle's lantern here.)
This is what the rock looks like after Pinhead gets through with it.
The Purple is coraline algae, and you can see the white, where the purple used to be.
You wouldn't know it to look at him, but this guy is actually VERY mobile. Urchins get around via two methods. Easiest being, they use their smaller spines, underneath, much like stilts. But they also have LOTS of very small tentacles that shoot out like grappling hooks, attach to something, and pull him that direction.
It's spines, while very rigid, are attached to a very flexible joint at it's body. So when moving around/under things, it can move its spines down and out of the way. While moving faster than a snail, it's every step and every movement of each spine appears VERY calculated. He takes VERY special care to not poke any of the fish or corals. It's actually amazing to watch him point his spines this way and that to avoid damaging any of the other inhabitants, as he moves around.
Special care must be taken with these guys though, as some of his spines are venomous, and are the equivelent of a bee sting.
Other species found in the wild even have stings that can be fatal!
Nice side shot of him, that gives you an idea how numerous his spines are.
To make matters worse, their spines are specially design in such a way that if one ever punctured your skin and broke off, until it's surgically removed, it would slowly continue working it's way through until it started poking out of the opposite side!
Here's a close up. Notice his orange fake eye (actually his anus),
and the deep blue spots around his real white eyes. Suprisingly colorful.
Just to give you an idea how big pinhead is compared to the tank, and other inhabitants...
Added to the tank on March 26th, 2005 from the Pet Loft, Mt Airy, MD.
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Last updated 6/21/05