r/Awwducational • u/SixteenSeveredHands • May 21 '23

Article Lamarckdromia Crabs: these fluffy crabs make their own protective "hats" out of living sea sponges; after selecting a suitable sponge, the crab trims it down to the right size, drapes the tailored sponge across its carapace, and carries it around

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u/SixteenSeveredHands May 21 '23

Lamarckdromia beagle is a newly classified species that was discovered off the coast of Western Australia just last year. It belongs to the genus Lamarckdromia, which is part of the Dromiidae family. Members of this clade are known to use living sea sponges and ascidians to protect themselves from predators, earning them the nickname "sponge crabs."

According to this article from The Guardian:

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.”

Two species of Lamarckdromia crabs are featured in the images for this post -- the first and second photos both show L. beagle, while the third photo depicts L. excavata.

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u/[deleted] May 21 '23

I'm having a lot of trouble articulating my reaction to this news