Newly discovered black and white creature

[pegasus]

Several nights ago, I discovered a creature I had never seen before. It appears to live in one rock, as this is where I've found it every night. It has black and white bands on it's legs, and the body appears to have large white bands with thin black stripes. I'm guessing it's some kind of crab, but since I've never see it's whole body at once, it's really hard to tell. The best description I can give is that it looks similar to a black and white tarantula spider. I've tried several times to get a decent picture or video of this critter, and this is the best I've been able to accomplish...

 

[pegasus]

Here's another (shorter) video of it's body moving across the hole in the rock, followed by a picture(s) of it partially out of the rock. It's definitely a crab, and an actually kind of cute crab at that! Fortunately, the claws appear to be those of a herbivore...

 

[beth]

And that is why I love reef tanks.

 

[bang guy]

And that is why I love reef tanks.

+1

 

[flower]

Maybe it's just me...but it looks like a hermit crab, they are the only ones I know of with striped legs. There are so many strange critters in the ocean, you might be the first to see this species...AWESOME! ...If it is a hermit crab, it could have decided a hole in the the rock is a shell, or at least a safe place until it could find a more suitable one...Hermits grow too large for whatever shell they choose, and have to swap out for a new one, it may not be able to get out of whatever hole it got into.

Do you have moon lights? If so, watch and see if the crab emerges at night, then you might get a better idea of what type of crab, or if it stays in the hole, my theory might be correct.

 

[bang guy]

Hermits don't typically hide inside the live rock.

I think it's some type of Mithrax Crab. They are omnivores but have a very strong preference for hair algae. If it can easily catch a fish it will eat it. It would have to be a slow small pretty dumb fish though.

 

[flower]

Hermits don't typically hide inside the live rock.

I think it's some type of Mithrax Crab. They are omnivores but have a very strong preference for hair algae. If it can easily catch a fish it will eat it. It would have to be a slow small pretty dumb fish though.

LOL...Like a seahorse

 

[pegasus]

No, it's definitely not a hermit. The carapace is too wide, and it looks to be hard with small jagged edges. You can see it in the video. For orientation, the crab is facing down. It's beady little eyes barely protrude out of the carapace, close to it's claws. It's rather small compared to the hermits in the tank. Empty shells of all sizes are not in short supply in my tank... the sand bed looks like a snail graveyard. Literally...

 

[bang guy]

I'm sticking with Mithrax sp.

 

[spanko]

I'm with Bang Guy. Typically black tipped claws = potential problems.

 

[seecrabrun]

Definitely a crab, most likely from the xanthoidea superfamily.

In my opinion no crabs are truly reef safe, but I don't bother catching them until they become a problem.

At the size it is now it's not a threat. The most damage it will do is bore your rocks out to make a nice home for itself.

I'll try to find the species for you when I have some free time.

 

[pegasus]

Thanks for the replies. I have an emerald that's about 1" across it carapace, and had a couple more larger emeralds in the past, and none of them ever bothered any fish. This new crab is roughly 3/8" across, so it would have a very hard time bothering the smallest of my fish, which is a firefish. My two trapezia crabs are nearly twice it's size...