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shrimphombre

Is this an Acropora crab? Photos.

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shrimphombre

Hey guys i noticed a very small crab that is VERY well camouflaged in my green/yellow acropora. He is the exact same color and has the same hairy look that the polyps have. I've tried to identify him but no luck. He is about half the size of your pinky fingernail. I watched him for about twenty minutes and can't decide if he is plucking polyps off of my acropora or if he is being beneficial (cleaning detritus etc.). I tried to take some pics but the acro is too far into the tank and the macro on my camera just won't comply lol. Anybody have a link to species of acropora crabs and whether they are harmful or beneficial? All posts appreciated thanks!

Edited by shrimphombre

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scottyreef

he is a good guy here are a few links

 

http://www.chucksaddiction.com/coral_crabs.html

http://news.mongabay.com/2006/1023-ucsb.html

 

heres a good qoute

 

VARIOUS CORAL COMMENSAL CRABS / REEF SAFE

 

It is very common when buying or collecting corals and anemone to find small crab species living amongst the corals, these are invariably harmless species which have a symbiotic relationship with the coral. While the coral provides shelter and possibly a bit of mucus to feed upon, the crab also returns the favor by acting as the coral's guard, fending off coral predators and parasites. These are the only types of crabs that I allow within my reef aquarium since I know they will not wander the tank causing damage

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shrimphombre

hmm i read somewhere that if they're smooth they're okay... that post reinforces that statement; all of the crabs in that link were smooth and the one i'm looking at is noticeably hairy. I'll see if i can get a decent pic up by tomorrow. Thanks for the quick reply

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scottyreef

i have hads few with hairy legs and they have given me no problems just watch them and make sure they stay way from the coralites polyps that would be the main part they would eat if they were a bad types\.

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shrimphombre

He definitely seems to be "running" his claws over the polyps but i cant tell if this is harming them. The colony looks healthy during the day as a whole so i guess I'll just keep watching. He's so small he would be impossible to catch anyway. I'll just keep an eye on it and see what happens. In the meantime any more insight anyone?

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BKtomodachi

I have also heard that the hairy ones are not beneficial- but I must disagree.

 

I have seen a few colonies with hairy as well as smooth acro crabs living in the coral. They have all grown and shown the same level of health from what I've seen.

 

edited for my inconsistent vocabulary

Edited by BKtomodachi

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lakshwadeep

It seems that even the beneficial acro crabs can look like they're eating it since part of their diet is the coral's mucus.

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shrimphombre

Here's some pics... im surprised at how good they actually came out

post-37479-1216582352_thumb.jpg

post-37479-1216582452_thumb.jpg

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scottyreef

i have the same type of crab on two of my acro colonies and they are do great and i have had no problems with them they dont even leave the arco ever

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shrimphombre

okay great, thanks for the replies all!

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abe
Here's some pics... im surprised at how good they actually came out

you has gorilla crab buddy... its hairy.

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shrimphombre
you has gorilla crab buddy... its hairy.

 

Just because its hairy doesn't mean its a gorilla crab... can you provide any more insight besides "its hairy"??

 

edit: btw nice english "buddy"

Edited by shrimphombre

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abe
Just because its hairy doesn't mean its a gorilla crab... can you provide any more insight besides "its hairy"??

 

edit: btw nice english "buddy"

lol...

 

acro crabs are white with a black stripe on their forehead... only hairy "acro crabs" i seen... and i have seen a lot... exact same color as yours... that only eat polyps. just takes observation... you will see in time "buddy"

 

acro crab

AcroCrab512.jpg

 

gorilla crab

db_37_gorillacrab-patsan.jpg

 

somebody correct me if im wrong... but seriously... when i give advice, best thing someone's done was accept it, instead of getting defensive and sarcastic because its something they dont want it to be.

 

how's that for nice english?

 

EDIT: seriously... if i was trying to be a jerk... you would have known...

Edited by abe

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shrimphombre

My crab doesn't look like either of those.

 

Sorry, bad english just annoys me.

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Aliasnumber1

I have one bandit acro crab just like pictured, and on another colony i had two smooth brown colored crabs that i didn't ID. The acro crab abandoned the colony the other morning for no appearent reason, but has found his way back since then. I thought he took a midnight excursion. I also found a glass shrimp-like creature with 1" claws living on my acropora, I didn't think he was helping anything so he was fed to the garbage disposal. I think if that were my acro i'd evict that crab, I usually buy colonies and as expensive as SPS are i just wouldn't chance it. He looks like a questionable character.

Edited by Aliasnumber1

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scottyreef

ok well I really dont think it is a gorilla crab it is a type of trapezia crab it is debate if it will eat the coralites polyps. from what i have been reading the crabs life depends on the health of the coral to live. i have to disagree that if the crab is hairy its a bad type of crab. below is a picture of what i think is your crab (not my picture) just watch and see and if you dont want to risk it get rid of him

 

acroblueeyed.jpg

Trapeziacrabs.jpg

Edited by scottyreef

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shrimphombre
ok well I really dont think it is a gorilla crab it is a type of trapezia crab it is debate if it will eat the coralites polyps. from what i have been reading the crabs life depends on the health of the coral to live. i have to disagree that if the crab is hairy its a bad type of crab. below is a picture of what i think is your crab (not my picture) just watch and see and if you dont want to risk it get rid of him

 

acroblueeyed.jpg

Trapeziacrabs.jpg

 

 

yes that is him exactly... I am just going to leave him alone. The coral looks great and appears to be growing (i've had it for about 3 weeks) so i'll just wait and see. Thanks for your help!

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Avalon_Princess

I can't see how hairiness dictates how bad a crab is, I'd say claw shape and size in proportion to the body would be a lot more telling...

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charlesr1958

I wish I could name the crab off the top of my head but I can't, but do know there are a number of other crabs other than the trapezia and tetralia that can be found living within the shelter of branching corals, so far the species shown and discussed is most likely NOT a symbiot of corals and is instead more of a predator upon the corals. I've kept such crabs in an isolation tank with an Acropora colony and observed that they do indeed crush polyps and eat them, but they do so at a rate that the coral can recover from and leaves no long term or noticable damage. They also do not defend the coral as the commensal species will do. In other words they are not a "coral crab" in the manner in which we normaly think of such crabs.

 

Chuck

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SPS20

That crab is an obligate coral predator.

 

The good news: they are tiny, stay tiny, and don't need to eat much. If the colony is suffieciently healthy and large, it can regrow faster than the crab can eat it.

 

The bad news: they subsist almost entirely on living coral tissue.

 

Once again, that crab is *not* a commensal, it is a parasite. It will pick a spot in the branches of the coral and nip the polyps to prevent the coral from growing there. Eventually, the coral will grow around him and he will have a safe little hollowed-out area in the center of the colony.

 

This does not mean he will neccessarily kill your coral, but he absolutely will eat some polyps.

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gulfsurfer101

I have both the crabs posted above in some of my acro colonies. They seem to be benificial and dependant on the acro colonies. I have seperated one of the hairy ones thinking it was a gorrilla crab and put him in another tank with no SPS. He was dead in three days and my colony ended up growing some hair algea on it. I would leave him be if he seems to be doing no harm.

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shrimphombre
That crab is an obligate coral predator.

 

The good news: they are tiny, stay tiny, and don't need to eat much. If the colony is suffieciently healthy and large, it can regrow faster than the crab can eat it.

 

The bad news: they subsist almost entirely on living coral tissue.

 

Once again, that crab is *not* a commensal, it is a parasite. It will pick a spot in the branches of the coral and nip the polyps to prevent the coral from growing there. Eventually, the coral will grow around him and he will have a safe little hollowed-out area in the center of the colony.

 

This does not mean he will neccessarily kill your coral, but he absolutely will eat some polyps.

 

 

Well, looks like the jury is still out. The acro looks healthier than ever though, and has sprouted about 6 new branches since i got it. I wouldn't even be able to catch that little crab anyway... I'll keep you guys posted if there is a change in the coral's health.

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RayWhisperer

From my experience, if it has blue eyes it's an unwanted pest. Hairyness doesn't seem to matter among acro crabs. However, as Chuck and SPS pointed out, they are tiny and do little damage to a large healthy colony.

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lanman
From my experience, if it has blue eyes it's an unwanted pest. Hairyness doesn't seem to matter among acro crabs. However, as Chuck and SPS pointed out, they are tiny and do little damage to a large healthy colony.

 

This blue-eyed hairy crab has been eating the polyps off of a small efflo it moved into.

 

crab1.jpg

 

crab2.jpg

 

 

efflo.jpg

 

bob

Edited by lanman

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