Crab ID, please

[becnel]

Dr. Ron,

I saw these remains in my tank. I've never seen a crab like this out in the open, even on my occasional night viewings (but I use a flashlight, as I don't have any "moonlight" installed). Can you identify this critter from these few pieces of remains? Do you feel comfortable venturing a guess as to what this critter would do in a reef tank (friend, foe, or indifferent)? :confused:

I don't see any evidence of damage to corals. I have unfortunately lost a good number of hermits and a couple shrimp over time, but that certainly could be due to other factors.

Also, my LFS refers to a mysterious, elusive "stone crab" anytime someone claims a small livestock critter vanishes. Any ideas on this?


P.S. Thanks for all the help!! I really enjoy reading this forum.

[Reefcrazy]

Sure looks like the remains of a Florida stone crab to me. the black markings on the claw are what make it so identifiable. Either your live rock come from Florida or have you visited Joe's Stone Crab House in Miami recently. ;)

[gregt]

heh, I'd bet my wallet that those aren't remains. Probably just a molting. They look remarkable like the real thing. I think your crab is still alive and kicking.

[becnel]

Heh. Yeah, I meant remains of the molting :) I won't consider it a gonner until I find a whole body shell intact. That's why I'd like to know if it's friend, foe, or indifferent. Should I try to catch it? I will be moving in about six months, so I can incorporate some kind of extermination action in with that if needed.

I guess a good bit of rock came from who knows where. I have some really heavy pieces and some really light. Some I know are Fiji, some, well... I rummaged through a few different bins and tanks at the LFS for rock that would serve the structures I had in mind and the money I had in my wallet. :o

Thanks for the responses! :D

[gregt]

I'd get him out. It will probably be a nuisance as it grows, if it isn't now.

How to catch a crab (http://saltyzoo.com/PhotoAlbum.jsp?urlStr=/55_gal/invertebrates/crabs/010304)

[becnel]

Thanks!!! That critter looks like a spot on match to what I fished out the tank. I have never seen a stone crab before. I'm from Louisiana, and we eat those crabs from Lake Pontchatrain. Mmmmm... I just thought "small crab I've never seen before ... mabye those LFS guys _weren't_ full of crap." :rolleyes: I take it these crabs get big if people eat them, so of course you know, this means war! :uzi: Anyways, the glass trap is an awesome idea. Many tanks!

But back to another Q, could crab(s) like this be the cause of loss of hermits, cleaner shrimp, and peppermint shrimp? Or am I just looking for a scapegoat for one of my own fubars - like trusting a cheap kit and letting my Ca levels get down to 210ppm? :(

[gregt]

He could absolutely be the culprit, but then again it could be a 100 other things too. ;)

PS> Sorry for butting in the thread Dr. Ron, I didn't even realize this was in your forum. - thought it was the reef discussion forum.

[rshimek]

Hi,

Well, it could be a stone crab, or it could simply be one of hundreds of species of xanthid crabs (they are characterized by black tipped claws).

Xanthids are signficant predators on anything they can catch and will eat hermits, snails, shrimp, etc.

:bounce2:

[Rigdoc2000]

Hi , I don't know about very small stone crabs, but the larger ones have smooth shells .
Cliff

[Teresa]

Hi Doc, and everybody,
Besides the give away clue of the black tips on the claws of that crab that identify it as a "Florida stone crab", if it has spikey "hair like" projections on the body and upper arms, plus the black tips on the claws, then it is a stone crab. Tiny baby ones hitch a ride deep in holes and crevices in the rock, and can slip through un-noticed. We eat the claws only of big ones, BTW the claws alone can be almost the size of a man's fist, and are pretty yummy!
Good for eating, not good for reef tanks .

Teresa
www.sea-critters.com

[becnel]

Thanks for the help all! I have been able to catch a small, hairy crab, but I don't know if this is the one or not. It's about the right size for the discarded shell, but the coloration... well, how much do discarded crab exoskeletons look like the real thing?

This crab is a much darker brown, and the claws are not tipped in black, but have a reddish tinge to them. I have a pic, but you can't see the coloration. I'm sorry.. I can't take a better pic of this thing. I don't think it'll stay still if I turn it upside down on the scanner bed, and that seems a bit cruel.

You can see how hairy it is. If there is any other coloration specification that would be helpful, I can do my best to describe it. The guy at the LFS thinks it's a stone crab, but says it's likely an algae eater because the claws are not very pointed. I wanted a second opinion before dumping him back into my tank. Is he a danger to coral, shrimp, fish? If he hitchhiked in on rock, he's been in there at least half a year, so it does not seem it will grow to the size of one of these edible stone crabs.

So, Dr. Ron, what would you advise in this situation? Besides asking Santa for a better camera, that is... :rolleyes: I don't want to just kill it out of ignorance, but I don't want to put it back in to feast on the other livestock.

[rshimek]

Hi James,

It is not the same species as the molt that you found.

I would consider it dangerous to a lot of reef life. Small crabs can pretty well devastate a tank. It may well get much larger, crabs often take 5 to 10 years to mature.

My suggestion would be to kill it humanely or put it into a tank of its own.