Trachyphyllia boring shrimp/crab

[louist]

Leslie, thank you for ID'ng this guy, the guys from the Museum of Victoria (Australia) haven't got back to me. I suspect they prioritise Christmas over gall-crabs

I never saw the 2 crabs leave the Trachyphyllia that they live in. However, this piece used to be in a larger tank and thus close observation wasn't possible. That said, this Trachyphyllia never extended its polyps for feeding in the 2.5 months I had it, despite my best efforts. After the removal of the 2 crabs, it extends its polyps 24/7. I have suspicions that mine might not have been commensal, but this is based on my limited observations.

Perhaps a comparison of the anatomy of the mouth parts and pincers might yield further clues to the different species' behaviours?

Lastly, I don't want my thread to turn people into gun-ho invert terminators. There are many inverts that make their homes in the corals that we purchase so perhaps people should think twice before conducting prophylactic fresh water dips on all purchases.

PS. Leslie, if you want to use the photos I posted for educational illustrations, let me know and I'll send you some high-res versions.

 

[LeslieH]

Louis - I'd love high-res versions, that would be great. Please send them to lharris(at)nhm(dot)org

I sent your images to Roy Kropp, an expert on cryptochirids and the author of this article which applies to your area - http://rmbr.nus.edu.sg/rbz/biblio/42/42rbz521-538.pdf He can't tell what it is because of the algae & debris on the crab's back. Interesting enough, he can't find previous records of any gall crab on Trachyphyllia.

Morphological studies do help, as do stomach analysis. In the case of the one I mentioned above a stomach analysis proved it ate the algae it farmed.

I agree with you completely Louis. We don't know the interactions of most of the inverts we see and many turn out to be beneficial or even necessary in reef ecosystems. Besides, if you look at them without bias they're fascinating. It's a shame to judge them guilty without evidence.

 

[louist]

Just to add a little more info to this thread:

Leslie's ID was correct. Not long after posting this thread, I submitted an ID request to the Museum Victoria in Australia. The Principal Curator of Marine Biology has identified the crustacean in the images as a gall crab. Brachyura family Cryptochiridae.

 

[NorthernCF]

Nice, I would love to have a nano with one of these. I would assume it wouldn't kill off something like blastos or acans. That would suck on your trach though.

 

[A.T.T.R]

i removed once of those from the mouth of a plate coral once.

coral recovered slowly

 

[rsisman]

I removed one of these gall crabs from a dead elegance about a year ago. Dont know if the crab was related to the death of the elegance.

 

[colubrid]

I removed two of the ones like the OP had from my ouphyllia crispa after noticing lack of poly extension. Mine also seemed parasitic as the brain was in definite health decline.

 

[RDHDDRAGON]

gall crab

gall crab

Sorry about bringing back up a dead post, but i just found one of these in my Lobo and this thread helped me id it!

The flesh started to die from one side, i have only had the lobo about 2 weeks. Couldn't figure out what was wrong with it. Kept spreading further. Finally I was trying to take pics of it so i could zoom in on it and see what was causing the damage. I saw something move in an adjacent lobo head mouth. My husband stuck a screwdriver in it and below is what popped out. Belly huge with yellow eggs.

Damaged Lobo:

The moving spot:

The crab: That yellow circle is the head of a straight pin. Small!

Closeup of her:

underside with flap pulled up (full of yellow eggs)

Does anyone know How long the eggs incubate? I am hoping since it has only been two weeks she hadn't released another clutch into my tank!

 

[ssavader]

Too coincidental- I have a favia that has been slowly dying and decided to pitch it since it only had a few polyps left. When I pulled the favia out of the tank, I noticed something moving in one of the empty polyp skeletons. I puled out a small crab that is exactly the same as the one louist posted. I removed him with forcepts and have placed the favia back in the tank to see if it now recovers.

 

[RDHDDRAGON]

Another gall crab

Another gall crab

Another evil gall crab! lol

I was reading online about them, don't quote me but it was something like 1400 different species of them?

Not alot seems to be known about their specifics. They do know they will burrow or attatch to a coral skeleton and the coral will grow around them usually entrapping the female. Males are smaller and can come and go. Supposedly they just feed off the mucus of the coral and don't actually eat it but i found many forum posts about the coral recovering and flourishing after the crabs were removed which sounds like they were the cause of the problems with the coral.

I can see a larger hole where it looks like she came from in the coral. I am just curious why she came out and apparantly was trying to make a new home in a different head of the lobo.

The hole she had made closed very quickly after she was removed. I attempted to feed the coral and it ate very well. Hopefully yours and mine both will recover!