Acro Crab

[DaveC]

I just thought I would tell everyone that I got my first Acropora crab the other day...I have located a fairly nice LFS in Providence RI a few weeks ago...this guy has some nice Acro's for sale...I purchase a misc acro (not sure yet) he told me but I forgot..anyways these pieces are approx 5 - 7 inches across and mine had about 15 -20 branches that were approx 2-3 inches tall..and the piece cost me $45.00...which I thought was a good price...I had in the past been buying frags for $25.00 that were only very small (2 inches, 1 branch) for another LFS...but for another 20.00 I could get a very nice colony I guess you could call it...but anyways in that piece I purchased I noticed down in the center a little crab which I can only assume is the much heard about acropora crab...since I was buying small frags I guess you don't get the crabs on them...where do these crabs come from..and what is there purpose...from what I understand you get one on all larger pieces of Acro's is this true..how big to the crabs get??? I just thought is was pretty neat..my friend who puchased a piece also got a crab in his...they must ride the coral during shipping and just stay attached until there final destination...will they travel at night, or just stay on the acro...will they travel from acro to acro??? since I never had one before I really don't know what they do..

Thanks
DaveC

[Chuck S]

Usually these crabs live a communal and parasitic life with the acropora. They ususally eat whatever organic material gets trapped and comes their way. Most times they get boxed in by the branches and can not escape. They can get rather large but should pose no problem. However with most any crab if they get too big for their britches I would watch them as they grow.

[David Grigor]

There are several different type of the commensal crabs.

If its the little flat white ones, I have had some for at least a year or two and hasn't grown at all.

I also have a dark red one that gets bigger but still less than a dime in size.

I have had them migrate to other acroporo corals to their liking. But they general do not roam around.

If you do an iodine dip of the coral with a crab depending on the dosage you will kill it.

[SueT]

There are several types of the "acropora" crabs. The bandit which is the white with the black band across the eyes. There is also a red/purple type crab that does get a bit bigger. I have both and they have never done any damage to the acropora. They will also catch any food that passes by and gets stuck on branches.

Not all wild acropora will have these crabs. IME, mine have even moved from colony to larger frags with multiple branches, or vise versa. The only bad acropora crabs I would watch out for are the hairy blue eyed ones. I have literally watched them start to eat polyps right out of the acropora. They ended up pinched out with tweezers.

[kevinpo]

Like other crabs they will molt as they grow and the shell will usually fall nearby. It appears that the crab has died but look carefully in the branches of the acro and you will find it.

Regards,
Kevin

[SueT]

Kevin, that happened to me. The pocillopora eydouxi I have has a nice reddish-pink crab in it and the other day I thought it had died as the shell lay, right side up nearby. After checking closely there it sat, eyes looking out at me and even bigger than it was. /ubbthreads/images/graemlins/shocked.gif