what is this in my rock

M

msmooter

AC Members
Dec 26, 2004
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Indiana
I have a type of crab in my live rock. It is only about an 1" by 1 1/2". It is nocturnal. Contacted the store where I purchased the rock from, and they said that it could be a hitchhicker. It is brownish-red with white and brown striped legs. We plan on making this tank fish and reef, so is this crab going to endanger my stock when I add them? I noticed that the crab has black tips on his claws. Beady red eyes that are directly on his shell. It looks like he might also have spots on his claws.
 
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Does it look fairly heavy bodied (kinda like an emerald crab) with relatively fat, heavy claws? If so you may have an east coast delicacy, the stone crab. GET IT OUT! As a specie, they make neat and hardy pets, but can literally break smaller fingers when fully grown and will likely eat any invert, especially clams, snails, worms, etc.. that it can get. Look at the image below. If it looks like this (not my image btw) and if it looks ANYTHING like this little monster, get him out and give to someone who has a harlequin tuskfish for food. When in doubt, toss it out. Any live rock (especially rock cultured in Florida waters) from the eastern US has a good chance of carrying these little jerks.

You can usually catch him easily--- they are absolute gluttons. Feed it a time or two one day with shrimp near evening (very small pieces) to spoil his taste (make him hawngry). Then put a BIG (ie, lots of smell) piece in a fish net and lay the fish net near the last place you saw him. He'll either crawl in the net as soon as he smells it, or he'll try to eat it through the mesh. Either way you got him, since he will NOT let go of the shrimp (we catch them on strings with pieces of chicken here in SC all the time).

stone_crab_1.jpg
 
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This link might help.
 
The crab is only about an inch, so maybe if it is a baby that picture might be what it is. Although, the crab that I have has stripes on its six rear legs. It also has only red eyes. It seems to only stay in a 2 inch wide area, eating what I am assuming to be particles off of the rock. I tried to get a picture of it with my digital, but the picture won't come out right. I also have bristle worms. I get different responses from individuals that I talk to on whether or not they are harmful. The small ones do not worry me. It is the one that, I'm guessing, is over 6 inches visible. I'm sure that the part that is still under the rock is much larger than that. Any input?
 
I'm not exactly sure what a bably stone crab looks like, but if the body shape is similar, (heavy, with heavy "crusher" type claws) , you may be in for weeping and gnashing of teeth if you don't get him out. If you like him, toss him in the refugium if you have one.

Use the shrimp-in-the-net method I mentioned above to get him out, place him in a white bowl or dish, and snap a couple digital photos, and we may be able to more positively ID him (not that I'll have a clue what it is if it isn't actually a stone crab/relative). Beware that even small stone/mud crabs can have a rather bodacious pinch.
 
I went and looked at all of the stone crab pics that I could find. I'll have to try and catch him like you mentioned. I am just amazed by all of the species that I have in my tank, especially at night. They range anywhere from pin tip sized oblique bugs, to wiggly white worms, silky looking webs, tiny white shrimp. I even have what appears to be a species that has a see through body except for the center which has a orange color. Where would I find a book that would identify all of these items, or am I going to have to leave it up to my own imagination to figure them out?
 
There are a lot of crabs that come in with live rock, and many are OK. Have you looked at the hitchhiker sticky in the newbie forum yet?

A couple of other resources:
hhfaq
rshimek

There are some field guide to marine invertebrates, like Humann and Deloach's "Reef Creatures," which covers a lot of Caribbean animals, but maybe these links will start you off.
 
hmmmm

sounds more like a porcelain crab to me..
they are good guys... an easy way to tell most bad crabs from good crabs is the claws and the numbers of legs... most good crabs aren't really true crabs.. true crabs... aren't really reef safe most times and have 4 legs on each side plus the two larger front "arms".. the good crabs generaly have 3 legs on a side with the 2 front arms.... also good crabs seems to have rasps which they constantly fan water towards there mouths.... also most bad crabs have black tipped claws ..... and also most hairy crabs are bad...

Porcalin crabs can be bright pinks reds and flesh colors or dark green and drab colors but most have blueish eyes and orangish strips along there legs and joints.. some are lighter with reddish strippings.. just depends on where the porcelian crabs came from.... if it was off live rock probly form a reef and this would explain the more exotic colorings.. this crab is found all over and around in the atlantic they are darker with very muted blue eyes and dark oprange/brown stripes..

these crabs eat algaes and vegitation
 
Thank you. It seems that we are getting very close to the conclusion, except for that part about the black tip front pinchers. I plan on getting a better digital camera in the future, and maybe then I will have a good pic to go along with that.
 
Curious to know if you were ever able to ID this crab. By the description you've given of it I believe I have one too. Just got an order of coral in yesterday and it had to have come in on that. Looked it all over real well before putting it in the tank but I must have missed it. Either that or it's been hiding in it's rock hole for the last 4 1/2 months.

Closest thing I can find that even remotely resembles it is a Striated Squat Lobster . Not definite though because I can't get the little sucker to come out of the hole far enough to get a good look. Plus, the hole is at an angle that he's gonna have to be way out to get a picture. One thing to note is the claws on the squatter aren't black and the critter in my tank definetely has black claws.
 
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