New hitchhiker crab

[DurTBear]

Anyone know what he is and if he's good or bad? I just noticed him for the first time as he was crawling out of a little cave today. I tried to attach a link to a video too but I don't know if it will work.

http://s79.photobucket.com/albums/j160/DurTBear/?action=view&current=Newcrab.flv

 

[Ziggy953]

Can you get a better pic of him? It looks a little like a mithrax crab....which would be a good crab....At least I think so...I have 3 in my tank but I paid for them. Does it look like this?
http://www.liveaquaria.com/product/prod_Display.cfm?pCatId=628

 

[DurTBear]

Sorry about the poor quality pic but I don't think I can do better than that. Don't even know if I'll see him for a while as it was a surprise to see him today for the first time. I haven't been able to find him since. But he does sort of resemble an emerald mithrax crab (I have one that I bought from the LFS) except he's not green. He's more gray/black and also seems to have hair on his body as well in addition to his legs.

 

[Ziggy953]

I'm not sure...I don't know a lot about crabs....we'll have to wait for some of the others to chime in....

 

[Fluff]

I agree it looks like it could be a mythrax but a better picture would be needed. Mythrax crabs are said to be reef safe but I would suggest caution and a watchful eye as crabs are opportunistic and will eat anything if it's hungry enough.

 

[roka64]

You sure that isn't a gorilla crab? It looks like it has hair in it's back (I didn't think the mithrax did). It is hard to tell, what color are the end of his pinchers?

 

[Sadielynn]

The pinchers look tan incolor either way I would not trust any crab in our system . If you have a sump that is a good home for him . I agree with Fluff they are opertunistic little boogers . I say pick him and flick him ....

 

[DurTBear]

Yeah, his pinchers are tan at the ends and he does appear to have hair on his back. If I see him again, I'll try and get better pictures but he was really shy and would run back toward that cave every time I got close.

Any suggestions on how to catch him? Any DIY crab traps? Thanks guys! You guys are always so helpful!

 

[roka64]

If his pinchers are that color, I would go with what Fluff and the others say. As for a trap, use a glass and lean it up next to where he hides. Put some food in the glass and once he gets in there, he should't be able to get back out.

 

[DurTBear]

Thanks roka64...Just did a search on crab traps and saw your suggestion of using the glass method. I will try to catch that sucker tonight but I bet the emerald crab gets in there too. He's a greedy little guy and when I throw a piece of algae mat/seaweed in there, he grabs at it and runs away while he munches away at it.

Thanks for the crab trap trick!

 

[Jarred Darque]

Taht is a Mithrix crab, but a mithrix is a family, not a specific species (emerald crabs are mithrix crabs as well, along with species known as anenome crabs or banded clinging crab) There are around 100 species in the mithrix family that I have seen named, I had to do a ton of research to find the type of mithrix hitchiker I have in my tank.

Not all are good, they for the most part stay small, most will simply eat algae or scavenge, but some are predatory, and some will out-host a clown fish on anenomes, and will kill any clown that tries to host that anenome if it can, or at least chase it away, and the anenome seems to prefer the crabs

BTW, almost all mithrix crabs have hair on their legs and/or back, tehy are chracterized by the shorter but muscular looking legs and claws, the very wide and thick, slightly bulbous body

 

[roka64]

Cool, thanks for the new info, Jarred.

 

[Ziggy953]

Wow...good information Jarred!!! Thanks

 

[DurTBear]

Yeah, that's great info. I'll try to do some more research and correctly ID him. In the meantime I've kept the glass in there to try and trap him to no avail. He's pretty shy still so I don't know how much he ventures around his rock but I'll keep trying.

 

[Fluff]

Taht is a Mithrix crab, but a mithrix is a family, not a specific species (emerald crabs are mithrix crabs as well, along with species known as anenome crabs or banded clinging crab) There are around 100 species in the mithrix family that I have seen named, I had to do a ton of research to find the type of mithrix hitchiker I have in my tank.

Not all are good, they for the most part stay small, most will simply eat algae or scavenge, but some are predatory, and some will out-host a clown fish on anenomes, and will kill any clown that tries to host that anenome if it can, or at least chase it away, and the anenome seems to prefer the crabs

BTW, almost all mithrix crabs have hair on their legs and/or back, tehy are chracterized by the shorter but muscular looking legs and claws, the very wide and thick, slightly bulbous body

Nice info Jarred, kudos to you. Could you please post your research/references? I'd be very interested in reading more of it. Thanks.

 

[roka64]

I would too!

 

[Jarred Darque]

Sure, I will try to find it all again, I didnt bookmark it or anything, I will start looking once I get to school, maybe I can try and find some actualy published info on the college library network.

Here is the first bit though to help out some.

Green Emerald Crap --Mithrax sculptus is the scientific name, Mithrax is the genus, or whatever, sculptus is the specific species, as we all know with all of the variations of fish that we keep. OH, and I was wrong on the family, t he family is Majidae, which includes even more crabs (teh family in english means Spider Crabs, which includes some 30+ genuses, mithrax being one, which on the list posted below has at least 16 variations on it)


http://animaldiversity.ummz.umich.edu/site/search?SearchableText=mithrax&Search.x=21&Search.y=6

and here is a link of 16 differant mithrax crabs, including the green emerald, BTW Mithrax seems to translate basically to clinging crab, I guess related to their stocky build and muscular claws

 

[Rambo64]

If it is an emerald mithrax crab its good because it will eat bubble algae if you get

 

[DurTBear]

So I'm pretty sure he's not an emerald mithrax crab since I have one in there and they don't look similar unless emerald crabs start out as black/grey when they're young. But there's a possibility he could a part of the mithrax family (I hope). He hasn't ventured into the glass yet so I think he's still pretty shy. I may just let him hang out in there unless I notice some damage being done to my coral.