A “fluffy” crab has been discovered off the coast of Western Australia. The animal is now named after the ship that sailed Charles Darwin around the world. The new species, Lamarckdromia beagle, belongs to the sponge crab family.
Crustaceans in this family use sea sponges for protection. They clip sponges with their claws and wear them as hats. Sponge crabs have hind legs that have been specially adapted to hold their protective hats, says Dr Andrew Hosey, curator of crustaceans and worms at the Western Australian Museum.
“The sponge keeps growing and shaped like a crab’s back,” he says. “It will never be attached. It makes a great cover that fits perfectly on the top of the crab.” Just as hermit crabs use shells to protect themselves, sponges help crabs camouflage from predators like octopuses and other crabs.
The sponge can be larger than the crab itself, and it also provides a chemical deterrent. “Some of the compounds that this sponge produces are very harmful,” Hosey says. “Not many active predators are interested in chewing the sponge to get to the crab.”
A family in Western Australia found a specimen of the Lamarckdromia beagle that had washed up on a beach and sent it to the Western Australian Museum for identification. Then Husey and Colin McClay, a marine biologist at the University of Canterbury in New Zealand, described the crabs as a new species.
By comparing the new crab with other specimens in the museum’s collection, they discovered several Lamarckdromia beagle crab that had never been identified or misidentified before. The oldest specimen of a beagle they found dates back to December 1925.
Hozy said it wasn’t clear why the Lamarckdromia Beagle was so thin. “The sponges that these animals wear should provide adequate camouflage,” he says. “I would expect the extra fluffy legs to hide the outward appearance more.” Husey knows that hair also doesn’t help hold the sponge. “It’s not like Velcro, unlike some spider crabs that lay seaweed on their backs, their hair is hooked and stiff like Velcro.”
The crab’s name refers to the ship HMS Beagle, whose second voyage between 1831 and 1836 led to Charles Darwin’s theory of natural selection. The ship took Darwin to King George Sound, an Albany site on the southern coast of Western Australia, in 1836. “Because the crab is a little tanned, it also has a bit of a beagle color,” Husey says.
“Discovery of new species in Western Australia is not uncommon,” Husey said. “The amount of animals we don’t know we have in Australian waters is still very large.”
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