Mystery Crab

Jay-Roc's Reef · Dec 23, 2023

I was checking out my tank and saw this on a rock. and thought it was the start of a new coral. When I looked closer I realized the orange were legs. I removed it and waited for it to open back up and this is what I found... It's got this creepy face on its back and bright orange legs.

Would anyone be able to tell me what kind of crab this is?

ISpeakForTheSeas · Dec 23, 2023

Lithoscaptus sp. Gall crab, probably Lithoscaptus aquarius; I know they've been found in Elegance Corals (Catalaphyllia jardinei), but they might be able to inhabit other corals too.

Jay-Roc's Reef · Dec 23, 2023

ISpeakForTheSeas said:
Lithoscaptus sp. Gall crab, probably Lithoscaptus aquarius; I know they've been found in Elegance Corals (Catalaphyllia jardinei), but they might be able to inhabit other corals too.

Is it a pest, or does it have a symbiotic relationship with the elegance coral?
I put it in my sump.

ISpeakForTheSeas · Dec 23, 2023

Jay-Roc's Reef said:
Is it a pest, or does it have a symbiotic relationship with the elegance coral?
I put it in my sump.

It has an obligate relationship with the coral - so I doubt the crab would survive long without it.

That said, gall crabs are considered parasites; they shouldn't kill a coral, but they burrow into the skeletons - so if it's a big crab and a small coral, it's a bad combination. If the coral is a decent size, then the crab should just cause a mild deformity; problems generally only arise from algae that grows on the deformed coral skeleton that sticks out through the dead skin.

So, basically, if the coral is big, it'll be fine; if the coral is small, it could die; if the coral is medium-sized, it'll probably be unhappy, but it should survive just fine.

Jay-Roc's Reef · Dec 23, 2023

ISpeakForTheSeas said:
It has an obligate relationship with the coral - so I doubt the crab would survive long without it.

That said, gall crabs are considered parasites; they shouldn't kill a coral, but they burrow into the skeletons - so if it's a big crab and a small coral, it's a bad combination. If the coral is a decent size, then the crab should just cause a mild deformity; problems generally only arise from algae that grows on the deformed coral skeleton that sticks out through the dead skin.

So, basically, if the coral is big, it'll be fine; if the coral is small, it could die; if the coral is medium-sized, it'll probably be unhappy, but it should survive just fine.

That helps a lot! Thank you for the info.