Plz help with hitchiker id

[2poor2reef]

I don't have a digital camera so I have no pic but I have a hitchiker that I have never seen before. It is about the size of a quarter and almost flat. It moves about on the rocks, spending the day in a crevice and moving out very slowly at night.

It is covered in dark brown quills, like a porcupine. I would say it resembles an urchin if the urchin were squashed almost completely flat. There are about 15 quills and they lay po8inting in every direction, about 1/2 inch long each. Does anyone know what this is?

 

[Mike02]

i have these "things" in my tank that looks really ugly, is flat, around 1/2" long (various sizes), has "scales", glides around on the rock very very slowly. it looks like its part of the rock but the things move around real slow. i guess its no harm, i think they're eating stuff off the rock (i hope not coraline). they havent bothered any corals, but overall they're just ugly and im afraid to touch them. well, since this kinda relates to the things you have in your tank, i thought i'd try to find out what my things are. thanks

 

[2poor2reef]

Mike, yours sounds like it might be a chiton. Take a look at the top pic in Arnjer's post in this thread http://reefs.org/phpBB2/viewtopic.php?t ... ght=chiton and see if it looks like what you have. If it is then people pay good money for those things as they are good maintenance crew critters, if a bit ugly. I had one on the side of a bucket where I was curing some live rock once and I learbed that they grip so tightly that they are impossible to move off of a surface. I had to let it crawl onto a seperate piece of plastic, and it took about two hours to move two inches. Fast they ain't.

 

[SPC]

I agree with 2poor that Mikes sounds like a chiton, what you have 2poor I have no idea. Have you seen the underside of it? Is the back as high as a chiton?
Steve

 

[Chucker]

Actually, it'd be worth giving it a gentle prod to see if the tissue is hard or soft too. That would help a bit in the ID process.

 

[2poor2reef]

That's my frustration. I can't really prod it because it is covered with long quills that lay flat over its fairly flat body. If you can picture a brittle star's central disk, about the size of a nickel, covered with porcupine quills about 3/8 of an inch long that lay flat and radiate out from the center, that's what this thing is. Sort of like a diadema urchin squashed flat from above.

When I prodded it just moved its spines a little. The spines are rigid, thick and pointy. I'll have to borrow someone's digital camera and learn how to use it.

 

[Chucker]

Sounds just like a flatter version of an urchin, like a sand dollar or sea biscuit. You might try entering those into google's image search, and seeing if you can find a similar photo with a good ID.

 

[Mike02]

Thanks!! thats what i have: chitons. here's a link i found: http://srd.yahoo.com/goo/chiton/2/T=103 ... hiton.html

it says they eat algae and diatoms. related to clams and snails. well at least i wont have to figure out a way to kill them anymore. i have had thoughts that they would crawl out of the tank and nite and blood suck me.

 

[2poor2reef]

My hitcher did turn out to be an unusual species of rock boring urchin. I'd never seen one that flat and where the spines all radiated horizontally. I did find an image. Thanks for the suggestion Chucker.