Bivalve hitchiker

[The Kapenta Kid]

I have this little bivalve hitchiker about 0.5 inch long. It's wedged in a crevice in the rock which is why I can't get a decent photo. It looks like a small comestible mussel. It appears to be able to move forward and backward in its crevice about 1/4 inch, possibly on a foot. It opens and closes its shell according to conditions and stimuli. It's been there for a few months.
Any idea what it is from this description? A mussel I suppose, but any more specific ID would be welcome.

 

[pagojoe]

Hard to give you a definite ID from that description, but the "moving forward and backward in its crevice" sounds suspiciously like some of the clams in the family Arcidae. Several species of Ark Clams behave in that way, and will withdraw if you touch them.

Cheers,


Don

 

[The Kapenta Kid]

Thanks Don. I was puzzled by this movement. Although it looks like a mussel, mussels (as far as I know) just have holdfast anchors and can't move other than swing in the current. I'll look up these clams
Bob

 

[TammyLiz]

Did you ever find out what it is you had? It seems like I have something that is at least similar. I can't get a good picture of it, either, down in a hole in the live rock.

 

[pagojoe]

If your animals look like true mussels, i.e., they are smooth, elongated, and brown...they may be Lithophaga species, commonly called Date Mussels. They bore into rock or coral, but I have no idea whether they might be able to withdraw farther into their holes. Tammy's animal being "down a hole" sounds like this family, although Kapenta Kid's description of being in a crevice sounds more like some other families. Check these pics:

http://images.google.com/images?um=1&tab=wi&hl=en&q=lithophaga

Do these images look close?

Cheers,



Don

 

[TammyLiz]

Don, possibly could be something like that. Mine have a pointed tip on them. I have seen what I think might have been a small feeding tube extended from one of them. But it could have been my imagination. The lighting was bad. Do they feed through tubes?

It looks most like a boring date mussel.

http://www.biosbcc.net/ocean/marinesci/06future/abrepro.htm

http://www.msc.ucla.edu/oceanglobe/...lusksw2shells/Lithophagaplumuladatemussel.JPG

I'm not sure how they are doing now since the tank move, but I'm going to try to check on them again soon. I might try to take some time with a flashlight, and now that they are positioned in the tank I need a mirror to look at one of them. There is not an incredible amount of flow over this area, but there is some, so we'll see how they do. I don't know how they were positioned before.