Little crab on tridacna's mantle

[Betti Weiss]

About a week ago I spotted a little crab on the mantle of my clam. It didn't seem to be eating the clam or even bothering it. The crab is about 1/4" or less, whitish, looks like a baby emerald crab. The next day the clam closed up with about a 1/4" of mantle exposed. It has been closed like that since then. Every once in awhile I see the little crab emerging from the clam but doesn't come out. I've seen the clam try to 'blow' the crab out, I think, but with no success. If I go near the mantle to try and snatch the crab the clam closes up. I feel helpless. What can I do?

 

[Julio]

it might be an acro crab or an anemone cracb, if is not huritng it then leave it alone ia m sure there is some sort of simbiosys going on.

 

[kmk2307]

It sounds like the crab might be lost. Try looking up Trapezia and see if it looks similar. You may want to place a coral next to the clam and see if the crab moves. Do you have any acro or branching coral frags you could place very close to the excurrent siphon of the clam?

Kevin

 

[ozadars]

Might be a tiny porcelain crab too.
Does it look like this crab;

 

[Betti Weiss]

I'm sorry everybody, but I never got notification of you replies. I just tried looking again and there were the replies. Strange.
Anyway, 2 months later and the little crab is still there. The clam seems fine, but contracts its mantle when the little crab sits on it. I suspect the crab lives inside the clam. I'm just going to leave things be. I guess I'd like to know how common this is and has anyone experienced it.
Thanks.

 

[Betti Weiss]

Selim, I didn't receive the picture you sent. I'm not sure what the problem is.

 

[stiffljp]

Without the picture, the opinion is just a guess but there are small white crabs that actually prey on clams. The clam may live for quite some time before dying. I am pretty sure there is a pic in Knop's book so you might want to check it out for a reference.

Thanks

Jeff

 

[Betti Weiss]

Volume 4 of Fossa/Nilsen 'The Modern Coral Reef Aquarium' states under Tridacna crocea that the crab Xanthiasia murgiera lives commensally with T. crocea. Does anyone know what that crab looks like? I can't find a picture of it anywhere. Maybe that's the crab cohabitating with my clam.
Jeff, I looked in Knop but didn't find the little crab there.
I'll try to get a picture of my clam's crab