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Crab ID help please


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#1 Reefwreck

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Posted 23 February 2007 - 01:51 AM

I'd be grateful for some help in identifying these two crabs from the Tulamben area, Bali. The images were taken last weekend. Thanks!
Michael.

Crab 1, in a Featherstar, depth approx. 20 metres.
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Crab 2, on soft coral, depth approx. 25 metres.
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#2 scubamarli

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Posted 23 February 2007 - 07:19 AM

There's a photo of your second one in Coral Reef Animals of the Indo Pacific, but it is simply called an Unidentified Porcelain crab. I haven't been able to find the other one in my references; sorry.
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Marli
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#3 Leslie

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Posted 23 February 2007 - 09:20 AM

The first one is a Quadrella species, maybe coronata or boopsis. They look alike and I can't tell the difference from photographs. What's odd is that this genus, like all trapeziid crabs, is commensal on hard & soft corals but your specimen is sitting on a crinoid. Was it moved?

Marli's close but this is different from the image she mentioned. The colors are roughly the same but the patterns are quite different. The one in CRA has much more purple on the legs & alternating purple & orange lines on the carapace; it's always found on the same pinkish sponge judging by the pictures I've seen of it. Yours only has purple on the legs, big claws, and anterior margin of the carapace while the orange on the carapace is in spots. I haven't been able to find a picture or name of this one, sorry. Maybe Art will wander by and recognize it.

#4 Reefwreck

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Posted 23 February 2007 - 04:39 PM

The first one is a Quadrella species, maybe coronata or boopsis. They look alike and I can't tell the difference from photographs. What's odd is that this genus, like all trapeziid crabs, is commensal on hard & soft corals but your specimen is sitting on a crinoid. Was it moved?

Marli's close but this is different from the image she mentioned. The colors are roughly the same but the patterns are quite different. The one in CRA has much more purple on the legs & alternating purple & orange lines on the carapace; it's always found on the same pinkish sponge judging by the pictures I've seen of it. Yours only has purple on the legs, big claws, and anterior margin of the carapace while the orange on the carapace is in spots. I haven't been able to find a picture or name of this one, sorry. Maybe Art will wander by and recognize it.


Thanks for your efforts, Marli and Leslie. Much appreciated.

To answer your question Leslie, these were photographed where found. Why anyone would move one of these to a crinoid is beyond me. I can't recall whether or not the crinoid had possibly attached itself to some coral. If it did, is it possible the crab climbed in to investigate?

Any other ID input would be much appreciated.
Michael.
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#5 Leslie

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Posted 23 February 2007 - 07:13 PM

Well, the crab could have been wandering or perhaps another photographer moved it to get better contrast. These pale Quadrella species on equally pale hosts can be pretty hard to see.

#6 scubamarli

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Posted 24 February 2007 - 09:05 AM

Marli's close but this is different from the image she mentioned. The colors are roughly the same but the patterns are quite different. The one in CRA has much more purple on the legs & alternating purple & orange lines on the carapace; it's always found on the same pinkish sponge judging by the pictures I've seen of it.

Oh dear, I'll have to contradict Leslie. :)
Next page, #828. Spots, no stripes in sight, and on soft coral.
Cheers,
Marli
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#7 Leslie

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Posted 24 February 2007 - 10:10 AM

:) :excl: :o
You're absolutely right and I'm a perfect ass for not looking past critter #827. The extent of pigment can vary so #828 and Michael's crab could well be the same species. Thanks!

#8 scubamarli

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Posted 24 February 2007 - 10:12 AM

There's another photo of this guy on Graham's website:
http://www.diving4im.../perry_kuo.html
Can't link to the specific image but it's in the middle of the page.
Cheers,
Marli
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