Crab ID??

[LMSquire]

Posting on this again bc I got a better pic and I think you can see the hair on the legs. Gorilla crab?

Bought 6 emeralds from respected site and have two in my tank that grew into these monsters knocking stuff over. Worried they’re gonna snag a fish.

They appear to be more black in color.

 

[EeyoreIsMySpiritAnimal]

Pic is too blue...

 

[LMSquire]

Pic is too blue...

 

[LMSquire]

Pic is too blue...

Just posted another video that is very clear with an orange lens

 

[EeyoreIsMySpiritAnimal]

@ISpeakForTheSeas
@WheatToast

 

[ISpeakForTheSeas]

I always struggle a bit with ID'ing from videos, but I'm pretty confident those are just emerald crabs with hairy legs (it happens from time to time - you can google a few; some are hairier than others; KP Aquatics has a decent pic of one with hairy legs).

With regards specifically to emerald crabs (I was replying to a comment asking if they were gorilla crabs because of the hairy legs) and gorilla crabs:

Technically no because the hairy legs alone don’t make it a gorilla crab. Colloquially, you could almost make that argument, but they have the wrong kind/shape of claws for it.

Technically, the term gorilla crab pretty well only applies to crabs from the taxonomic family Xanthidae (emerald crabs are from the same taxonomic subsection - Heterotremata - but a different superfamily and - thus by default - a different family, Mithracidae).

Colloquially, however, the term is applied to pretty much any hairy crab with scissor-shaped claws (emerald crabs have more spoon-shaped claws), and, in the hobby, the term is basically used to mean any crab (regardless of claw shape or if it’s hairy or not) that isn’t reef-safe/would be likely to attack other inhabitants of the tank.

 

[LMSquire]

I always struggle a bit with ID'ing from videos, but I'm pretty confident those are just emerald crabs with hairy legs (it happens from time to time - you can google a few; some are hairier than others; KP Aquatics has a decent pic of one with hairy legs).

With regards specifically to emerald crabs (I was replying to a comment asking if they were gorilla crabs because of the hairy legs) and gorilla crabs:

Thanks for a great response!

So aside from being a bit aggressive with each other, and knocking a few things over (that I should have glued in tighter) you don’t see these guys as being a potential risk to my small fish? (Fire gobies, royal gramma, small leopard wrasse?)

They sure took care of my bubble algae- like spots I don’t even understand how they reached, and they are excellent CUC in general.

 

[ISpeakForTheSeas]

Thanks for a great response!

So aside from being a bit aggressive with each other, and knocking a few things over (that I should have glued in tighter) you don’t see these guys as being a potential risk to my small fish? (Fire gobies, royal gramma, small leopard wrasse?)

They sure took care of my bubble algae- like spots I don’t even understand how they reached, and they are excellent CUC in general.

I'm definitely not an expert - and I know there are some very mixed opinions on the reef-safeness of large emerald crabs - but I'd personally assume that as long as it's well fed and doesn't find itself hungry with easy access to very small, sleeping, fish, it'd probably be fine.

I haven't looked too in depth into the interaction of emeralds with fish, but to my understanding no one has actually seen one actively hunt healthy fish (at least not with any meaningful level of success). I've heard that they basically either only get sleeping fish (which I find less likely) or moribund (i.e. dying) fish (which I find more likely), and that sort of opportunistic predation would make sense to me.

That's my understanding, but I have no hands-on experience for this to say for sure.

 

[LMSquire]

I'm definitely not an expert - and I know there are some very mixed opinions on the reef-safeness of large emerald crabs - but I'd personally assume that as long as it's well fed and doesn't find itself hungry with easy access to very small, sleeping, fish, it'd probably be fine.

I haven't looked too in depth into the interaction of emeralds with fish, but to my understanding no one has actually seen one actively hunt healthy fish (at least not with any meaningful level of success). I've heard that they basically either only get sleeping fish (which I find less likely) or moribund (i.e. dying) fish (which I find more likely), and that sort of opportunistic predation would make sense to me.

That's my understanding, but I have no hands-on experience for this to say for sure.

Copy that…and that is part of my concern- the sleeping fish. One of these guys seems to have taken up residence in the cave where my 5 firefish sleep.

That said, they are pretty fast and I’m sure they’re aware that the bran is in there, so perhaps a Darwin type situation here lol.

Like I said, they were purchased as emerald crabs from a site many of us use that is very reliable in my experience. Unfortunately they weren’t able to separate females for me which I asked for, so I’m guessing the ones that remained small were the females and these big monsters are well fed and grown males.

Thanks for sharing your time and experience and I’ll keep you posted!

 

[Reefkeepers Archive]

Look up black mithrax crab, see if that matches. The first one looks more like an emerald but the second one looks like a black mithrax


@ISpeakForTheSeas it looks like one to me, what do you think?

 

[EeyoreIsMySpiritAnimal]

Copy that…and that is part of my concern- the sleeping fish. One of these guys seems to have taken up residence in the cave where my 5 firefish sleep.

That said, they are pretty fast and I’m sure they’re aware that the bran is in there, so perhaps a Darwin type situation here lol.

Like I said, they were purchased as emerald crabs from a site many of us use that is very reliable in my experience. Unfortunately they weren’t able to separate females for me which I asked for, so I’m guessing the ones that remained small were the females and these big monsters are well fed and grown males.

Thanks for sharing your time and experience and I’ll keep you posted!

If you can pull them out, its pretty easy to sex them

 

[EeyoreIsMySpiritAnimal]

 

[fishywishy]

Thats 100% an emerald crab, looks like a red one which are kind of a rare find. I have the exact same fish as you and mine never touch anyone, even if they wanted too the fish are way too fast and the crabs are too small.