Crab ID

[Sumfingwong]

So, I was planning on using my old magfloat to make a frag rack. So I went up to my office to grab it. My old tank is still running to keep the LR alive (heater and powerhead)

I look on top of my magfloat and see this:


Its mostly brown, and underbelly and inside claws is red

Actually, there might be a bunch of them. I see a bunch of crab parts everywhere, they must be picking each other off. I think ill set up a bottle trap and see how many more i can catch.

Does anybody know what kind of crab this is? I checked this website and i don't see it listed. This thing has big claws and 2 antennas

http://www.chucksaddiction.com/hitchcrabs.html

[Mandosh]

I only see 3 pairs of visible pereiopods and what looks like very long antennae. I think that puts it in the Porcellanidae family. Sorry, can't help you with species though.

[gregzz4]

My understanding of crabs is this ...
Large pincers and hooked ends means trouble
Maybe someone will tell us different

[Sumfingwong]

I posted this picture up in reefcentral, and someone replied with:

It is definitely a Petrolisthes. Possibly a P. lamarckii.
This guys very harmless filter feeder and very good for your tank and nice to watch them, if you see them. :-) I have some different Petrolishes in my nano tank.

Here are two different crabs of my own Petrolishes.

[christyf5]

Looks related to the porcelain crab to me. I used to have one something like this, the LFS called it a caribbean porcelain crab, however it didn't have those crazy antennae nor the hook thingys on the end of the pincers.

Have a look at its mouthparts between the eyes, if it reaches out with a fan appendage (I think I see one there in the photo), grabbing at the water, its a filterfeeder and likely harmless.

[Sumfingwong]

I see alot of crab body parts in my office tank still, I hope it wasnt from this guy. Hes in the sump now, ill wait till I get home to take a closer look.

[Mandosh]

I'd be pretty confident with the Id off RC. The lack of the fourth set of visible legs means it isn't a true crab. The large claws in porcelains are used for defense and territory disputes, rather than catching food. That bring said, if there was more than one of these guys in the tank the crab parts could be a result of intra or inter-species conflict...or maybe it's just molt?

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[toytech]

I have the same one in my cube , model citizen wont even eat the fishes food and has started eatin the hair algea.