Red emerald Crabs?

[Glewis121]

A little while ago i bought 3 emerald crabs at a LFS, the guy told me that they were emerald crabs atleast but mine are red?

Are they emerald crabs? they look exactly like them it is just that they are red?

Are they true emeralds?

 

[randoma]

I've had a few emerald crabs, that have a diet high in nori, turn red. Assuming they are mithrax sculptus, they are 'real' emerald crabs. Without a picture or something it is a little hard to tell though.

 

[Qwank]

i thought i heard they come in a few colors, but green is just the most common.

 

[Andy V]

You would think they would be green...being Emerald crabs and all...

 

[RayD]

They're called Scarlet Crabs as opposed to Emerald Crabs. Emerald is a shade of green, Scarlet a shade of red.

 

[randoma]

There is a similar crab, Mithrax ruber which is red.

However, Mithrax sculptus coloration is very dependent on diet. An emerald crab that eats plenty of green algae, will be green. If it doesn't get enough green algae it will turn white. If you feed them lots of nori, in my experience, they turn reddish.

 

[Qwank]

so if your blue zoas suddenly dissapear and your emerald looks like papa smurf, is it safe to say he ate them?

on a seriouse note though. when i bought mine he was white. now hes green, is that because he was starved before i got him?

 

[stingythingy45]

Usually means he was getting ready to moult.
There's an article in one of the Aquarium magazines this month about red emerald crabs.Has really nothing to do with diet and more to do with location they come from.

 

[randoma]

Usually means he was getting ready to moult.

Actually, a healthy, emerald crab, whose diet is primarily green algae will be green right through its moult. An emerald crab that subsists mostly on non-green algae foods will be different colors - I've yet to see any blue ones though!

 

[stingythingy45]

Thanks for the info.Mine seem to have white coloration on the shell.
I've read where they can also eat coralline.
I'll see if I can find that article in the magazine.
It was about a group that will send you inverts if you're interested in tank raising them.And one of the inverts was the red emerald crab.

 

[Qwank]

Usually means he was getting ready to moult.

oh that makes sense. he did moult a few days later and thats when i noticed he was green.

 

[Angela]

A year a so ago I bought an orange one from Creatures in RI. He didn't last long unfortunatly. He was cool though. The guy called it a halloween crab if I remember correctly.

 

[mloebl]

I've had an emerald crab for a few years now, and started out as green. After all the green algae for him to feed on in the tank disappeared, he slowly vanished as well and I assumed had perished. One evening I noticed a purplish-red crab that was large but definitely a Mithrax, and I noticed he was feeding on coralline. He made quite distinct scratch marks on the rocks when feeding. When the green algae died off he seemed to shift to grazing on the harder algaes encrusting the rock and feeding at night rather than during the day so I didn't notice him. He is quite well camouflaged with the rocks.

-Mike