Infra-order Brachyura, Superfamily Grapsoidae, Family Sesarmidae
White-stripe crab | Labuanium vitatum Ng & Davie, 2012
Photo: Chris Bray
This crab was previously known from Christmas Island under the name Labuanium rotundatum, but recent studies by carcinologists of previously collected specimens from the island, has led to it being recognised as a separate new species, Labuanium vitatum.
The last time one of these crabs was collected was in 1989; since then there has been only one documented sighting. The ex Chief Ranger of Christmas Island National Park, Max Orchard, had only “a fleeting glimpse of a small brown crab with purple claws and bright yellow eyes looking at him around a tree trunk at Anderson's Dale in the middle of a rainstorm on 15 April, 2010.”
Because of its rarity in museum collections, despite many scientists visiting the island over the last century, and because it had eluded three years of targeted searching since 2010 by experienced crab collectors specifically trying to find it, it was feared that this beautiful and elusive little crab may have become the victim of the yellow crazy ant invasion that has been so destructive on the island. The favoured habitat for Labuanium vitatum appears to be on the trunks and leaves of coastal vegetation high on the limestone terraces, a habitat also favoured by the exotic yellow crazy ants.
The above photo, taken by Chris Bray, is the first photo of the 'Christmas Island White-Stripe Crab’, Labuanium vitatum, taken for about 25 years. It was a random crab photo taken on 13th May, 2013 during a Christmas Island photography safari reccy trip by Chris. He leads photography safaris to locations all round the world. More information on Chris's photography safaris to Christmas Island, and other places, may be found at www.ChrisBray.net
Of the photo, Chris says, " It is so lucky I paused to snap the pic, lucky I included it in the ones I gave to Christmas Island Tourism Association, and lucky they decided to post it randomly to their Facebook page, where Max Orchard spotted it. Max informed me that it was only on a whim he checked the CI Tourism Association site, and to his amazement came eye to eye with a crusty critter that had eluded him for over twenty years!"
This was the first time this species had been seen since its formal description as a new species in 2011, and indeed the authors of the new species name (Peter Ng of the Lee Kong Chian Natural History Museum of Singapore, and Peter Davie of the Queensland Museum, Brisbane), never managed to find one in the wild themselves, and had only some old museum specimens and old colour photos on which to base their decision that it was new.
While we do know now that this great crab appears to be only just hanging on in its Christmas Island home, the good news is that it is also known from several localities to the north of Christmas Island in the eastern Indian Ocean, including the Nicobar and Nias Islands, and from west Java. The bad news is that we only know of these other localities from 3 collections in museums that were made in the early 1900s, and while we hope it still has healthy populations through southern Indonesia, the truth is we currently have no idea.
Photo: Liu Hung-Chang
This image of Labuanium vitatum was taken by Liu Hung Chang and his team from Taiwan. They observed three ovigerious females spawning at Dolly Beach during February 2014. Hung Chang's sighting expands the known range of the crab.
Read more about Christmas Island's white-stripe crab in the book
"Crabs of Christmas Island" by Max Orchard
Ng, P. K. L. & P. J. F. Davie, 2011. Labuanium vitatum (Crustacea: Decapoda: Brachyura: Sesarmidae), a new Indo-West Pacific species of arboreal crab. Zootaxa, 2889: 35–48.