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Unknown crab hitchhiker... Help identify, please?


Icewall42

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Hi all,

 

I am new to the nano reef forums, and new to saltwater tanks in general (I have been doing freshwater for over a decade). Everything looks fabulous, no deaths, and chemistry seems to be on track. However, I just found an unknown crab in a deep cave of my live rock, which explains the mysterious molt I found and why I haven't found him till weeks after I bought the rock. I have an emerald crab, but I saw these two at the same time, no mistaking one for the other!

 

This guy is maybe 1" across, white with brown marbeling and brown banded legs. claw tips on the molt were black, but tips on the live crab are white. A little hairy, but not terribly. Claws look pointed, more so than the emerald (which has rounded claws). Oh, and the underside is white.

 

Gimme a couple seconds, and I will post a pic. I have him trapped in a shot glass right now.

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WEll, since it has been in there for the past two weeks, and since I added a capnella sp. and a pachyclavularia/briareum sp., nothing has been damaged. I was worried about my fish though, since I have a Purple Firefish and a Hector's Goby that like to sit in caves, and this guy was living is a very deep cave.

 

I suppose I'll keep this guy in the Q-tank in a tupperware bowl, until I can take him to my LFS for an ID (or to see if they will take him, as I have no sump).

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WEll, since it has been in there for the past two weeks, and since I added a capnella sp. and a pachyclavularia/briareum sp., nothing has been damaged. I was worried about my fish though, since I have a Purple Firefish and a Hector's Goby that like to sit in caves, and this guy was living is a very deep cave.

 

I suppose I'll keep this guy in the Q-tank in a tupperware bowl, until I can take him to my LFS for an ID (or to see if they will take him, as I have no sump).

 

Do the claws end in points and are black while the rest of its body is light? If so its most likely a young gorilla crab. Coral eater.

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my guess would be gorilla crab as well. can u tell what color its eyes are? google gorilla crabs and see if it looks like anything that comes up

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Do you people just automatically call any crab you can't ID immediately "probably a gorilla crab"? Or do you actually see something in those pics that give you that impression?

 

For the record, in the first pic, I don't see black tips.

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Do you people just automatically call any crab you can't ID immediately "probably a gorilla crab"? Or do you actually see something in those pics that give you that impression?

 

For the record, in the first pic, I don't see black tips.

 

don't see black tips either, could it be a spotted guard crab (totally reef safe), any way to get a better pic?

guard_crab.bmp

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don't see black tips either, could it be a spotted guard crab (totally reef safe), any way to get a better pic?

 

Yes, I have a better camera I can use, just need to charge it. The crab is safely in a plastic bowl sitting on the bottom of the Q-tank, so I can pull him out safely for another shot.

 

To answer questions:

 

1. I checked Chuck's Hitchhiker Crab Guide, and this crab doesn't look like any of the ones pictures. I also Googled the gorilla crab but this crab isn't all that hairy (the hairs are so fine they are almost invisible), and it doesn't really look like one. Like I said, I'll try and get better pictures once my camera is charged up.

 

2. Claw tips are sharp and translucent white. No black on either claw. One claw is also wider/larger than the other. The claw itself is smooth, maybe a little ridged, but not spikey. The eyes are black/grey.

 

3. I do not have a sump or refugium. Either he stays in the Q-tank, or he goes to the LFS (which does have sumps/refugiums). I am not going to flush or crush this crab, since he doesn't deserve to die.

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It looks like a Xanthid crab, which have oval carapaces ("bodies"). Don't worry much about colors or "hairiness" since those are extremely variable and not as consistent as body shapes. Also, check out the xanthid links on chuck's addiction for many more reference images.

http://reefkeeping.com/issues/2003-12/rs/index.php

 

Seems more cube-like than oval, but then again I'm no expert. I know this crab can't go back in the main tank, but I suppose I still wish it could. I'll look a fourth time in case I missed something, but I couldn't find it on any of the reference pages either unless this is some sort of juvenile of something on that list, and I'm just not making the connection.... I'm guessing, at this point, it's just a matter of satiating my curiosity as to the crab's genus (can't help it, as I have been studying marine biology/ecology), although Xanthid still seems likely.

 

Although, looking at the link you provided (very detailed!) I want to say the carapace looks more like the Grapsid, but it really could go either way (Grapsid or Xanthid).

 

I managed to get this shot of the claws this morning, and might be able to get a better top shot this afternoon.

 

post-72047-1327410670_thumb.jpg

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Took it to the LFS, one of the guys there IDed it as a young mithrax sp. that hadn't developed its black claw tips yet. No one wanted it, and I didn't want to just outright kill it, so the LFS fed it to my favorite trigger -_-

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At least it was put to some good.. otherwise it probably would have ended up in the yard.

 

On a similar note, my LFS has offered to feed my emerald crab to their puffer if he keeps misbehaving.

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Do you people just automatically call any crab you can't ID immediately "probably a gorilla crab"? Or do you actually see something in those pics that give you that impression?

 

For the record, in the first pic, I don't see black tips.

 

What do you mean "you people?"

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My guess is "you people" as in "people in the forum community." Nothing more.

 

Luckily, my emerald crab seems to be behaving for the time being. I hope he stays that way for a while, since he's one of my favorite inhabitants.

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