Re: Commensal crab?  ID   5/8/06
Well,
<A deep subject>
I finally managed to trigger the right "phrases" in my Google search, and found my crab, commonly known as a Red Coral Crab.  I think these crabs are commonly grouped into a category called "guard" crabs.  My pair appear to be Trapezia cymodoce commonly found in Stylophora.
http://www.dafni.com/crustacea/Trapeziidae.htm
More information is here as well.
http://www.imagequest3d.com/pages/articles/trapezius.htm
Thanks.
Brett
<A very interesting genus... BobF out in HI seeing these most days>

Crab Identification - 10/18/06
Hello Crew,  <Hi Stachia, MacL here with you tonight.>
I am sure you have heard this scenario many times before, but here it goes. My husband and I recently found a mysterious crab in our 75 gal tank. We purchased 2 flame scallops a few weeks ago, went through all of the proper acclimation procedures, water tests were where they should be, nothing picking on them, and they died. The first died after about a week, the other died the night of the eleventh.
<Honestly these are extremely difficult to keep alive. They are what I would consider an expert animal. Most people I know who successfully keep them have refugiums and aged tanks.>
When taking the dead flame out of the tank, we found a strange crab inside it. It looked as if it ate most of the inner out of the scallop. The big question is if the scallop was already dead when the crab started eating it, and I guess that would depend on the type of crab it is.
<Definitely, the right question. Did you see any signs of decline before it died? A crab can scavenge very quickly when its dead or dying.>
I know that a picture can describe it better than I ever could verbally (writing), so I attached a few pictures, and have many others from different angles if needed. My local specialty fish store, who is very knowledgeable, has no idea what it could be, and I did not find any pictures on this site that seem to be even close to matching. I have typed every scientific name I could find for crabs into Yahoo and Google image searches and have come up empty handed. Help me please, we have it in a breeder box on the side of our 30gal invertebrate (no fish or coral) tank right now, and would like to let it go in the tank, but do not know what it eats or could hurt.
<I looked at the pictures. I love all types of crabs and invertebrates and couldn't identify this one but it does look similar to sand crabs found on the Florida beaches. Those crabs could kill your scallops but honestly I think they were probably in a weakened condition from their stay at your local store.>
When I shrunk the pictures down to a better e-mail size, they were slightly distorted. I do have a profile on the wet web forum, and actually asked for help a few days ago, but have not received any responses.
<I just left a message saying you have mail meaning this.  Honestly we are all swamped trying to keep up with the emails.  We appreciate your patience and I'm keeping this email in my box to try to look for more with the crab so don't give up on us.>
I try to be patient; I know everyone is very busy, but I do not know how long the crab will last in the breeder box. Anyway, my name in the forum is stace2001; I posted Mystery Crab on 10/12/2006 under marine invertebrates, and I have clearer pictures on my profile, along with descriptions.
Thank you very much for your help, patients, and time.  <Thank you Stachia, Good luck, MacL>
Stachia

Hitchhiker Crab ID...No Picture - 09/11/06
I have searched your site and many others looking for anything that resembles this creature.   It came on live rock that I received from Tampa Bay.  It is maybe ½” long.  In the picture its face is poking out of the water.  
<<I'm afraid the picture didn't get to us>>
Its face is not pointed and I could not get a picture of it from any different angle.  It was very interested in a small piece of sponge – it chose the piece of sponge over Caulerpa or rock rubble to cling to.  I had posted a picture of this creature on two or three forums and the closest “guess” was that it might be in the Pisidae family though the pictures that I could find had the correct body shape and the eyes were placed in the same manner but its face is not elongated as shown in the pictures of crabs from the Pisidae family.
<<Might still be...from what I can find, there are some fourteen genera in this family>>
I have removed the creature to our hospital tank as I didn’t want it to go through the live rock cycling in our curing tank.  I would like to know what this creature is and possibly what it eats as I would like to try to keep it healthy and happy in our reef tank.  
<<Most all crabs are too opportunistic for my taste, and some are downright destructive...I don't recommend keeping crabs in a reef tank.  An exception would be the small commensal crabs that sometimes accompany Acropora colonies, and even then they bear a close watch as not all of these are "safe"...is up to you to decide if you want to take the risk.  As for feeding, like most crabs/shrimp, this one will likely eat about anything (omnivorous) it finds (emergent life on your live rock) or can catch/overpower.  Regards, EricR>>