Gall crab?

[Reefkeepers Archive]

@ISpeakForTheSeas after some research, are Neotroglocarcinus a possibility, im using GBIF and they seem to live on the surface like i found mine, also is Troglocarcinus, Pseudocryptochirus and Opecarcinus a possibility?

 

[ISpeakForTheSeas]

No to Neotroglocarcinus (only two species in this genus, neither are it), Troglocarcinus (only one species in this genus, and it's not it), and Pseudocryptochirus (again, only one species, and it's not it).

Opecarcinus is a possibility, but I'm not confident it's correct.

 

[Reefkeepers Archive]

No to Neotroglocarcinus (only two species in this genus, neither are it), Troglocarcinus (only one species in this genus, and it's not it), and Pseudocryptochirus (again, only one species, and it's not it).

Opecarcinus is a possibility, but I'm not confident it's correct.

I'll keep looking, have you narrowed down the genus? (As in 3-4 possible genuses) do we know if it's for sure a gall crab?

 

[ISpeakForTheSeas]

do we know if it's for sure a gall crab?

No to this, so no the rest as well, unfortunately.

There are a handful of Gall Crab genera that I’ve looked into (I haven’t looked at all 21 genera yet) that it could fall into, but it may be a different kind of crab altogether too (lots or crabs can look deceptively similar without looking at the actual morphology, which I struggle with in crabs).

 

[Reefkeepers Archive]

No to this, so no the rest as well, unfortunately.

There are a handful of Gall Crab genera that I’ve looked into (I haven’t looked at all 21 genera yet) that it could fall into, but it may be a different kind of crab altogether too (lots or crabs can look deceptively similar without looking at the actual morphology, which I struggle with in crabs).

Do you think removal was the right decision?

 

[ISpeakForTheSeas]

Do you think removal was the right decision?

Probably, yeah.

 

[Reefkeepers Archive]

Probably, yeah.

Question, do you think it came in on the acantho? The coral itself hasn't been showing full polyp extension lately, I thought it was just the worms than I found this. Do you think this was the source of the irritation? And do you think it was eating the tissue?

 

[ISpeakForTheSeas]

Question, do you think it came in on the acantho? The coral itself hasn't been showing full polyp extension lately, I thought it was just the worms than I found this. Do you think this was the source of the irritation? And do you think it was eating the tissue?

It's possible that it came in on the Acantho (though I'm not currently aware of any gall crab species that are known to target Acantho's specifically), and it's possible it was a source of irritation.

I doubt it was eating the tissue - my understanding is that they eat either the coral's mucus, detritus trapped in the coral's mucus, or both. Regardless, they shouldn't eat the coral, it's just that their burrowing around inside/through the coral can cause health issues for the coral.

 

[Reefkeepers Archive]

@ISpeakForTheSeas I found this

#E has similar markings, after a bit of research it turns out that that one is a male, could mine be the male coloration? Here's the article https://zookeys.pensoft.net/articles.php?id=5170&display_type=list&element_type=8
If so we should look for body shape instead of coloration, also mine may be a juvenile. The article was on gall crabs in trachys, though I'm sure they can live in acanthos. Any thoughts @ISpeakForTheSeas? Thanks!

 

[ISpeakForTheSeas]

If so we should look for body shape instead of coloration, also mine may be a juvenile. The article was on gall crabs in trachys, though I'm sure they can live in acanthos. Any thoughts @ISpeakForTheSeas? Thanks!

The species discussed there is L. semperi:

(the closest Lithoscaptus species I know at the moment is L. semperi, and it's off too).

You need to keep both body shape and coloration in mind; with a lot of animals, body shape can help narrow down the list of possible critters to a few families or genera (this is often tougher to do with crabs, and crab body shape can can be tough to tell from pics as well), then you can use the color and pattern to figure out the exact species.

L. semperi doesn’t quite meet the right pattern for your specimen in either the adult or juvenile forms, and based on the specific patterns of both, the pattern your specimen displays wouldn’t appear in a transitional stage between juvenile or adult either. The body shape of yours seems a bit more compact/circular and wide and less elongated than the traditional Lithoscaptus shape too, so I’m doubtful it’s in that genus.

 

[Reefkeepers Archive]

The species discussed there is L. semperi:

You need to keep both body shape and coloration in mind; with a lot of animals, body shape can help narrow down the list of possible critters to a few families or genera (this is often tougher to do with crabs, and crab body shape can can be tough to tell from pics as well), then you can use the color and pattern to figure out the exact species.

L. semperi doesn’t quite meet the right pattern for your specimen in either the adult or juvenile forms, and based on the specific patterns of both, the pattern your specimen displays wouldn’t appear in a transitional stage between juvenile or adult either. The body shape of yours seems a bit more compact/circular and wide and less elongated than the traditional Lithoscaptus shape too, so I’m doubtful it’s in that genus.

Worth a shot, was suggesting that it could be male/juvenile coloration as they are usually less documented than female specimens but you might have already gone over that, if it helps, here's the rough size of my crab (on my hand)

 

[ISpeakForTheSeas]

Worth a shot, was suggesting that it could be male/juvenile coloration as they are usually less documented than female specimens but you might have already gone over that,

Ah, yeah, I should have specified - the “C” and “D” specimen in the image you shared (quoted below) are the adult males of the species, and the “E” specimen is a juvenile male. (“A” and “B” are a non-ovigerous - i.e. not pregnant/carrying eggs - female).

Thinking about it a bit more though - could you get a clear, close-up shot of the crab as it currently is (preferably on a black background)? It may be easier to compare it in its desiccated state to photos of some preserved specimens (no guarantees this would help with an ID, but it might).

 

[Reefkeepers Archive]

Ah, yeah, I should have specified - the “C” and “D” specimen in the image you shared (quoted below) are the adult males of the species, and the “E” specimen is a juvenile male. (“A” and “B” are a non-ovigerous - i.e. not pregnant/carrying eggs - female).


Thinking about it a bit more though - could you get a clear, close-up shot of the crab as it currently is (preferably on a black background)? It may be easier to compare it in its desiccated state to photos of some preserved specimens (no guarantees this would help with an ID, but it might).

I will give you all the photos I have of it after it dried. I did end up giving the specimen to my LFS for ID reasons (plus they probably wouldn't loose/damage it, unlike me) so here are the photos I have of it a day after it dried

I'll go to my LFS tommorow, while I'm there I'll get a close-up shot, really hard as it is a very small specimen

 

[Reefkeepers Archive]

Oh, also @ISpeakForTheSeas, found this in my sandbed, was taking out a coral skeleton and this thing was buried in the sand (not the astrea star)

Has very long and pronounced bristles unlike the other worms in my system, also much larger and has a pink head/tail. Thinking fireworm but I've never seen one so I don't know

 

[ISpeakForTheSeas]

Has very long and pronounced bristles unlike the other worms in my system, also much larger and has a pink head/tail. Thinking fireworm but I've never seen one so I don't know

The long and pronounced bristles are typically characteristic of Syllid worms, so that would be my assumption - most likely harmless/beneficial.

 

[littlefoxx]

Just pulled this off my acanto. Is it a gall crabs? @ISpeakForTheSeas ? @EeyoreIsMySpiritAnimal ? @encrustingacro? Will they reproduce? Please help, my Acanthophyllia hasn't been fully open the last few weeks and I think this is why. Will it recover? Is it a gall crab?

This totally looks like those nasty spiders with the bumps on the butt! I didnt even know this crab existed!