Friday, April 13, 2012

Roses are red, this new crab is blue!

It's a new Crabday and a new crab! Christmas Island is known for it's crabby inhabitants and has been studied for quite awhile now because of the yearly red crab migration. So it's surprising that a new species has only just now been described, but better late than never!

Blue Crab
Discoplax celeste

What a beaut!

Much like the newly discovered crabs we learned about last week, researchers were well aware of these beautiful blue crabs, but simply thought they were a blue version of D. hirtipes (found in Fiji and are so elegantly described as "dark violet and the chela bright cinnabar red"). The trick was that D. celeste change color as they grow: small juvenile crabs are black and light tan, and don't become that brilliant blue until they reach 46 - 52 mm carapace width.

a color progression from small juvie (A) to adult (H)

Upon closer inspection of the carapace, male abdomin, and gonopods, the researchers discovered the blue version were in fact a completely different species from the dark purple/black one originally described, so they decided to name the new one after its sky blue color.

it makes me want to watch for animal-shaped clouds...

Our new D. celeste wasn't the only crab on Christmas Island thought to be D. hirtipes. This other sneaky crab  D. aff. hirtipes has the dark purple/black carapace known to D. hirtipes proper, but yellow chela (hence the "aff." in the name, which simply signifies the similarity to the original species while noting that, as a new species, it has yet to be defined)!

a lovely blue D. celeste next to a
flashy D. aff. hirtipes on Christmas Island

Those two will make a great color-coordinated pair next Leap Year Day! (Here's hoping they survive the next 4 years!)

Check out the paper:
Ng, P. K. L., and P. J. F. Davie. 2012. The blue crab of Christmas Island, Discoplax celeste, new species (Crustacea: Decapoda: Brachyura: Gecarcinidae). The Raffles Bulletin of Zoology 60: 89-100.

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