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Alor - crab ID?


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#1 Bora_Horza

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Posted 05 March 2013 - 01:33 PM

Hi All,

 

Does anyone know the identity of this blue crab species?  Spotted living on a big barrel sponge at Alor, Indonesia.  Also any info on what the brittlestar (I think?) also seen in the picture might be.

 

In addition, any thoughts on what the crab is eating?  It seems to have gathered some yellowish 'stuff', more of which is visable on the rest of the sponge.  Maybe only ramdom plankton, or something excreted / secreted / digested from the sponge by the brittlestar?  I'm just curious really!

 

5695734963_6e9780ef5b_z.jpg
Blue crabs on sponge by bora_horza, on Flickr



#2 Leslie

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Posted 05 March 2013 - 05:30 PM

It's a still undescribed species of porcelain crab in the genus Aliaporcellana.  Judging by the amount of photos I've seen it's not rare and it's normally found on that pink sponge.

 

I'm more interested in the brittle star.  Do you have any pictures showing the central disk or a high-res image of the arms?



#3 Leslie

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Posted 05 March 2013 - 06:11 PM

I passed your photo along to Gordon Hendler, the museum's curator of echinoderms & an ophiuroid specialist.  He thinks the brittle may be Ophiothrix nereidina which comes in a variety of colors.



#4 Bora_Horza

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Posted 06 March 2013 - 01:08 PM

Thanks very much Leslie (and Gordon).  No pic of the central disc, but after reviewing my own photos a little more closely I've answered my question about the yellowish stuff the crab was eating (whoops!)

 

8535309860_1d4ca45812_c.jpg
Porcelain crab (Aliaporcellana) by bora_horza, on Flickr


Edited by Bora_Horza, 07 March 2013 - 11:37 AM.


#5 Leslie

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Posted 06 March 2013 - 06:25 PM

Crabs will eat anything.  I've seen a video of one dropping his own claw, picking it up, and eating the meat out of it.

 

Now a general question to anyone who's ever seen one of these blue porcelain crabs.  I'm curious to know if it's always on pink or red barrel sponges?  Is it ever on anything else? (and having a dive guide place it on black sand for contrast doesn't count!)



#6 MortenHansen

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Posted 09 March 2013 - 08:52 AM

Now a general question to anyone who's ever seen one of these blue porcelain crabs.  I'm curious to know if it's always on pink or red barrel sponges?  Is it ever on anything else? (and having a dive guide place it on black sand for contrast doesn't count!)

 

 

Undescribed ey that's pretty cool! 

 

I see these little guys on every dive I do in the Kubu/Tulamben area, they're everywhere.

They are always sitting on barrel-sponges, only saw them on and elephant ear sponge on a single occasion.

As far as I recall they are only to be found on the sponges that are also inhabited by the purple brittlestars. 

 

Hope this info helps! :)

 

Happy bubbles/worm identification,

Morten


Edited by MortenHansen, 09 March 2013 - 08:52 AM.