I got crabs (ID)...

[cbianco]

Hey all

I am trying to identify this hitchhiker. Its kind of funny I have had my tank set up for about 4 months and I just noticed this particular crab. The crab is camera shy, so I couldn't get a picture of him. I will describe the crab as best as possible.

The size is currently about the size of a dime. It is white with black speckles (like a white anemone crab). This crab also has a bit of hair and its claws have black on the very tips. What type of crab am I lookin at?

I read else where that this may be a "gorilla crab" (Xanthid). When I yahoo'ed gorilla crab I came up with very little to go on. Anyone have another scientific name or another common name for this crab? Will I have problems with this hitchhiker?

All information is welcome, I appreciate the help!

Christopher

[thedude]

What do its claws look like? That is going to be your best point of identifiation. If they're serrated like knives, yank him out. However all crabs are opportunistic feeders and they can all be problematic.

[Polkster13]

Where is the crab living? Is it in a hole, on a piece of coral, down on the sand bed? What is the shape of the carapace?

Check out this link (http://www.divegallery.com/reef_crab.htm).

[Thunderkat]

What do the serrated claws crabs do? When they get big enough do they attack fish? Will the small ones eat aptasia? I have a tiny one in my tank with my live rock.

[Polkster13]

Serrated claws usually indicates that the crab is a predator (helps the crab hold onto its prey). But this is not a precise indicator. Depends on the crab on whether or not it will get big enough to attack fish. Also depends on the size of the fish in comparison to the crab.

Can you get a picture of your crab (Thunderkat) and I will see if I can get an ID for you.

[Thunderkat]

I have only seen this crab twice, once when I first put it in my tank and when I was getting ready to get rid of my sand I saw someting squirming in there and it was the crab. It is very good at hiding and it survived the dinos. It was still about 2/3 the size of a dime. The live rock has so many holes I doubt I will be able to find that guy. When it get big though I will stick it in a pan and fry it up. :lol

[Instar]

That little orange crab in the link above looks like a harmless acro crab. Harmless crabs are hairless. I get rid of the black tips as those are usually predators and even when dime sized they can drag off little oysters and split them for lunch. If by some chance it stays dime size, then it should be fine, I've had some living in colonies of green star polyps for years that stay small. But, a black tip can mean its a baby rock crab that gets large and they are significant predators more often than not. I would say keep and eye on him and as long as he stays small enough to hide in little holes, you are fine with him. They grow very fast if they are predators, so it won't be long till you see more of him if he is going to be dangerous. I have kept the predators in the sump and feed them till they get large. They are fun to feed then. Some of the little crabs eat only algae, so if you have one that eats algaes, you sure don't want to waste him.

[Polkster13]

I have an acro crab in my Cat's Paw that has black tips on its claws. I have had it for over six months and it hasn't gotten any bigger. The sahpe of the carapace is a much better indicator than color. Mine is trapizoidal in shape which indicates it is an acro crab, which is commensial with the coral. It will attack anything, including my fingers, that get anywhere near the coral. It keeps it clean of algae and warns away fish with a flash of its claws. It is very beneficial to the health of my coral so it stays.

If your crab hasn't gotten any bigger, then I would say it is probably reef-safe.

I did pick up some baby crabs from Corpus once and ended up with a blue crab that got huge and ate everything in the tank. If ever in doubt, put it in the fuge or give it away.

[cbianco]

Hey all

Ok the crab stays in small holes in the live rock. I cannot see if the claws are serrated or not, the crab is very shy and runs from everything. I did find a picture on the web of the crab in my tank. I came across is by mistake. Hopefully this will shed some light on the situation. Here is the picture: http://www.tbsaltwater.com/thepackage/images/gorillacrab.jpg

Thanks for the assistance!

Christopher

[cvonseggern]

If that's what you've got, it needs to come out right away. Otherwise you're headed for trouble.

[Polkster13]

Yep, defininately NOT a reef-safe crab. Find the rock he is in and remove rock. Then try to coax that little bugger out into your fuge. Then replace rock back into your display tank.

[cbianco]

How do you know that he is not a reef safe crab? Is there an easier way to remove him? Pull the rock out of my aquarium would be difficult (rock on bottom).

Christopher

[Thunderkat]

Make a crab trap or a little box of sorts in there, put some clam meat in there and when it goes inside take the box out. I know when I went fishing I used to catch crabs simply because they refused to let go of the shrimp :lol

I have my live rock in a 10 gallon aquarium seperate from my 5 gallon with my mushrooms and zoos. Looks like I will not be using that live rock anymore. It has aptasia and majanos on it anyways. The one I have has brown claws and not proportially big. They were serrated too. I have an emerald crab and I noted the difference in claws when I looked at them.

[Polkster13]

From the picture you provided, that is definately a predator crab. The shape, claws, hairy body are all indications that it is a gorilla crab. Not something you want in your tank.

Here is some more info on Gorilla crabs (http://www.tbsaltwater.com/thepackage/watchout.html).

[cbianco]

Thanks polkster! The site you provided is actually where I got the picture from, lol. Unfortunately that was one of few sites that actually explain/give details about this particular crab. I was hoping to learn a bit more about the crab. I figured that someone may have had one before or found a decent site with infromation. Don't get me wrong I found tons of sites with crab info, just not a "gorilla crab." I'm thinking that this common name may not be so common! :lol

I have had an emerald crab in my tank since I set it up with no problems. I thought that the crabs look similar with regards to body type. Does this mean that the emerald is preditory also?

Thanks for any additional information! :)

[cvonseggern]

I've never had a problem with emeralds, unless something else in the tank died, in which case they'll munch on it. Any crab will be opportunistic and eat what it can get, but emeralds' claws are specialized for pulling algae off rocks, and they don't have much offensive power.

Chris

[Polkster13]

Check out Pilumnus hirtellus at the following link (http://www.glaucus.org.uk/CRABSX.htm).
Or Pilumnus hirtellus at link (http://www.marlin.ac.uk/species/Pilumnushirtellus.htm).

[Thunderkat]

Uh oh, think I made a boo boo. I think I may have an acro crab. When I first got it, it was in a rock that my zoos came on. Now its seperate from my corals. Ruh oh, gotta find it and put it in my coral tank.

[cbianco]

Thunderkat wouldn't you want to get it out of your coral tank, lol? Unless you have something against SPS.

Good luck :)

Christopher

[Thunderkat]

I don't want it to die from starvation (http://www.reefcorner.com/SpecimenSheets/acrocrab.htm).

[cbianco]

I see (after looking at the link!) :)

Christopher