Dead hitchhiker crab ID

[wwarby]

This little crab turned up dead on the rock in my mantis tank today. I had no idea it was in there, so it must have been a hitchhiker. Any idea what it was? (Just curious really, it was definitely already dead when I found it). It’s about the size of a penny.

 

[s_tooz_123]

Have you compared pictures with a gorilla crab? Looks very similar to me but the shell on yours appears to be smoother.

 

[wwarby]

Have you compared pictures with a gorilla crab? Looks very similar to me but the shell on yours appears to be smoother.

Yeah I had a look at gorilla crabs, didn’t look quite right to me. As you say, the body is very smooth, and lighter, though not sure if that’s because it’s dead.

 

[Alexopora]

This little crab turned up dead on the rock in my mantis tank today. I had no idea it was in there, so it must have been a hitchhiker. Any idea what it was? (Just curious really, it was definitely already dead when I found it). It’s about the size of a penny.

Looks like a molt to me. Is the crab solid or are you able to squish it easily?

 

[tbrown]

+1 possible molt.

 

[wwarby]

That's definitely what I thought at first, but no - it was definitely solid. I can't double check now unfortunately because it went in the bin, but I'm pretty certain of it

 

[JoJosReef]

Yeah, normally I'd say pointy black tips, get that out! But in a mantis tank? Haha

 

[tbrown]

The bodies can still be hard. Those legs just look mighty empty/hollow to me. As stated above, in a mantis tank it probably doesn't matter too much.

 

[olonmv]

Almost looks like an algae eating crab. The tips of its claws look like emerald crab claw tips.

 

[olonmv]

Black mithrax crab is the best match I can find. I believe they’re reef safe.

 

[tbrown]

Black mithrax crab is the best match I can find. I believe they’re reef safe.

Look up Xantho Crab. The black tips are fairly telling.

 

[olonmv]

Look up Xantho Crab. The black tips are fairly telling.

I’m not sure. Two reasons why. Body of xantho crab looks disproportionate to its legs whiles the crab OP posted looks in proportion. Also the tips in xantho come to a point and op’s claws have cup like appendages.

 

[WheatToast]

A quick Google search of "black mithrax crab" led me to the Chlorodiella genus, whose species look pretty similar to me:
https://www.inaturalist.org/taxa/1224570-Chlorodiella-cytherea

You're wee-beasty looks like this one to me:

This crab is Chlorodiella cytherea. This may not be your exact species, but they look very much alike to me. It's a xanthid and they typically spell trouble.

Not an emerald crab. Russellaqua has the right of it. It's a crab in the Chlorodiella genus. The typical acro crabs are crabs in the Cymo genus (bad), Tetralia genus (good), and Trapezia genus (good). Chlorodiella genus is in the Xanthidae family. I have read multiple posts of these guys hitching a ride on sps corals. These guys are not the typical acro crabs you hear about. I have never read of any damage they have caused. I'm not sure if this specific Chlorodiella species are found in these colonies because they are young/small and use the colony as a safe haven/food source and move on to live rock as they get larger (if they get larger). Or if they actually live in the coral for their whole life like an acro crab. Most reefers remove the crab to be safe. However, curiousity has me wondering.

 

[wwarby]

Yeah, normally I'd say pointy black tips, get that out! But in a mantis tank? Haha

Yeah I'm definitely not worried if turns out I'm wrong and it actually was a molt, although it really felt like it was the actual crab, by it's weight. I barely have any coral in this tank, nothing I'm worried about losing, and if anything I'd be quite glad of a crab to eat some algae until the mantis shrimp eventually finds and kills it (she's been treated to a few shore crabs lately and absolutely loves them!).

 

[wwarby]

A quick Google search of "black mithrax crab" led me to the Chlorodiella genus, whose species look pretty similar to me:
https://www.inaturalist.org/taxa/1224570-Chlorodiella-cytherea

Yeah, I think that's the one - Chlorodiella cytherea. Definitely looks like the closest match of the proposed matches