My Urchin Likes to wear hats.

[rappo]

So I have a Green Urchin. He's awesome... goes everywhere, picks up things, poops. Typical Urchin stuff.

But he seems to like to put a shell on top of him, what I call his 'hat'. Last week he put on his hat and I took it off of him. A day later he put it back on! Over the weekend I introduced new shells for my hermits, and I took the hat off of my urchin while I was at it... and mixed it in with the shells. Later that day, he had the same damn shell on him! And then today, just to spite me, he put on a few more 'hats'. Is this in any way common?

pics:
his favorite hat:


you can never have too many hats.

 

[greenbean36191]

Yep, it's pretty common. Some people think it's a defense against predators that hunt by feel. If it feels like a rock instead of an urchin they don't know it's there.

 

[rappo]

ha! that's pretty cool thanks

 

[ophiuroid]

It is also considered to be a basic camouflage technique. They will often cover themselves...sometimes even with algae which they may consume. There were studies done, if I recall, showing that the urchin will actually move these items toward the direction the light is coming from. There are rather fascinating studies linking biology and physics as it pertains to the calcite plates of echinoids. Some echinoids have different types of calcite, to avoid a long discussion, and those species with the type of calcite that light may pass through easily often display this shielding response. So some argue that this behavior is a shield against light (being comprised of calcite could be rather unpleasant on a bright day). Effectively, the debris acts like an beach umbrella on a sunny day... (and as an aside it is also difficult to see who is under that umbrella )

A Paper turned up after a quick search:
http://jeb.biologists.org/cgi/reprint/33/3/508.pdf

 

[whatcaneyedo]

My urchin really likes to carry around bubble algae and one time carried around the skull of a mandarin fish for a week after my sebae anemone ate it... (the sebae spat the skull out)

 

[Sk8r]

Mine has not relinquished the nori clip ever since it bestowed algae on him: he ate it all, the pig, then kept the clip, and it's been a week...

I believe it's rudimentary religion. He believes if he keeps it, red algae will reappear.

It could happen, if I can ever get the clip away from him.

 

[cokemanmark]

can i put one of those in my reef tank

 

[TinaM]

I was at the LFS picking up a tuxedo urchin and the guy showed me a larger one that was carrying around a thermometer. It was too funny! So far mine only picked up a couple of small stones off the sand bed. Only had it a few days though...

 

[syddakyd]

my "girls" urchin always wears a hat