This hermit crab dresses itself in style – with an anemone coat! Meet the newly described anemone that scientists have named Stylobates calcifer:

hermit crab with anemone on back
Stylobates calcifer on the back of a hermit crab’s shell. Image by Akihiro Yoshikawa.

This anemone is a little different than the ones you can find in a tide pool. It is found on the deep-sea floor, off the coast of Japan. And it lives on the back of a host – a hermit crab called Pagurodofleinia doederleini.

The new-to-science anemone species Stylobates calcifer on the back of its hermit crab host. Photos by Akihiro Yoshikawa from Yoshikawa et al 2022.

Hermit crabs use empty mollusk shells as a sort of shelter. The shell protects their soft abdomen. If a hermit crab outgrows its shell, it will search for a new, bigger shell to carry around.

Of the more than 800 species of hermit crabs, at least 35 species carry anemones on their shells. Scientists think that this relationship helps both the crab and the anemone in some way – this is called a mutualism.

In lab recordings of the new species, the hermit crab is seen moving to a new shell and moving the anemone with it. Screenshots from video footage by Akihiro Yoshikawa.

Being on the back of the hermit crab may help the anemone access small particles of food. And the anemone may help the crab in several ways. Some anemones create a structure called a carcinoecium that “grows” the shell that the crab occupies. Anemones may also protect hermit crabs from predators or other pests.

Watch this amazing video of a hermit crab positioning a Stylobates calcifer anemone onto its shell:

The research team was led by Akihiro Yoshikawa, a professor from the University of Tokyo in Japan.

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Yoshikawa, A., Izumi, T., Moritaki, T., Kimura, T., & Yanagi, K. (2022). Carcinoecium-forming sea anemone Stylobates calcifer sp. nov. (Cnidaria, Actiniaria, Actiniidae) from the Japanese deep-sea floor: A taxonomical description with its ecological observations. The Biological Bulletin242(2), 127-152. doi:10.1086/719160