A Pretty Anemone Makes Space and Eats Waste

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This deep sea anemone seems to be a great roommate. Scientists recently discovered this creature, named Paracalliactis tsukisomeliving in harmony with hermit crabs off the coast of Japan in the Pacific Ocean. P. tsukisome lives on the shells of the hermit crab Oncopagurus monstrosuswhich live between 650 and 1,600 feet below the ocean surface.

According to a recent study published in Royal Society Open ScienceThe spiny sea anemone builds a shell-like structure called a carcinoecium, which adds more square footage to its companion hermit crab’s home. The name tsukisome ” is appropriate: it comes from a classic Japanese word meaning “pale pink color,” which is also associated with a “deep and faithful bond” described in ancient Japanese poetry.

Shell building is an unusual tactic for sea anemones, which often do not possess a rigid skeleton. In fact, it’s a “surprisingly sophisticated behavior” for a simple animal like a sea anemone, study author Akihiro Yoshikawa, an associate professor at Kumamoto University in Japan, said in a statement.

Beyond finding a place to settle down, P. tsukisome also takes advantage of its grumpy partner by munching on its feces – an “unusual but effective form of recycling on the seabed,” according to the release.

This is a rare look at an unexpected mutualistic relationship forged by coevolution in the deep ocean.

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Main image: Yoshigawa, A., et al. Royal Society Open Science (2025).

• Molly Glick

  Published on November 6, 2025

  Molly Glick is the newsletter editor of Nautilus.