Purple mithrax crab?

corosato · Jan 26, 2025

Trying desperately to get a clear photo. Been combing through posts here and crab ID lists and kinda stumped. I will keep trying but you can see the general body shape here. very smooth legs, white and purple banded, purple body. claws look more like an emerald crab's no black tips but it's a quick little bugger and ran once the lights when full white. I apologize for the potato quality photo, will keep trying. but has anyone seen a purple mithrax? Live rock came from Gulf Live Rock. Got an urchin and several serpent stars too, but this guy has just appeared last couple days. less than an inch across.

MoshJosh · Jan 27, 2025

Difficult to tell from the pictures, but based on your description I could not find anything in some Gulf specific hitchhiker guides:

https://tbsaltwater.com/hitchhikers/?s=crab&post_type=hitchhikers https://gulfliverock.com/hitchhiker-id
That said, generally crabs are considered not reef safe until proven otherwise, so I would try to catch it if possible. One caught, you can get some better pics for an ID.

Hope that helps.

EDIT: Looking at some red mithrax crabs (red "emerald" crab). . . can look a little purple, so I guess that is a possibility??? Also, in another ID thread I saw someone mention a Spineback Hairy Crab, as they can be purple, though they appear to be much spikey than what you have. Still I would try to catch it or get better pictures to confirm its ID.

corosato · Jan 27, 2025

I've considered Purple Shore Crab but the Gulf Live Rock site is 10 miles off shore and the legs don't quite match

ISpeakForTheSeas · Jan 27, 2025

corosato said:
I've considered Purple Shore Crab but the Gulf Live Rock site is 10 miles off shore and the legs don't quite match

Look up Chlorodiella nigra (or other Chlorodiella species) and see if that looks like a match.

Schulks · Jan 27, 2025

I had a red one and he grew rapidly. He was dragging an acan frag under a ledge over and over so I moved him to my sump. I think he was eating the acan.