Lamarckdromia beagle: these crabs wear living sea sponges as protective "hats;" after selecting a sponge, the crab trims it, drapes the tailored sponge across its carapace, and then carries it around
Last year, a newly-classified species (referred to as Lamarckdromia beagle) was discovered off the coast of Western Australia. Like all other members of the genus Lamarckdromia, this species is part of the Dromiidae family, which contains many different types of crabs that are known to use living sea sponges and ascidians to protect themselves from predators. These crabs are often collectively referred to as "sponge crabs."
Lamarckdromia beagle: this new species is covered in a dense, shaggy layer of "fur," which is actually made up of hair-like structures called setae
Dr. Andrew Hosie, a curator of crustacea and worms at the Western Australian Museum, said sponge crabs had hind legs that were specially adapted for holding their protective hats.
“The sponge or ascidian just keeps growing and will mould to the shape of the crab’s back,” he said. “It will never attach … it forms a nice cap that fits quite snugly to the top of the crab."
Similar to how hermit crabs use shells for protection, the sponges help Dromiidae crabs to camouflage from predators such as octopuses and other crabs.
The sponges can be bigger than the crab itself, and also provide a chemical deterrent. “Some of the compounds that these sponges are producing are very noxious,” Hosie said. “There’s not a lot of active predators that would be interested in munching through a sponge just to get to a crab.”
Sponge crabs in general come in many different shapes and sizes; L. beagle (pictured above) has a uniquely dense, shaggy coat of "fur" covering its body, but other members of the genus Lamarckdromia have a much less shaggy appearance, and there are many sponge crabs that have no layer of "fur" at all.
Some examples of the other sponge crabs within the Dromiidae family:
I know this isn't exactly the type of arthropod that I'd normally discuss on my blog (given that it's not a moth or some other insect) but technically crustaceans are arthropods, and these ones are really weird/interesting...so I figured that I might as well just go with it.
