In Japanese waters, a newly described anemone lives on the back of a hermit crab

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  • A newly described species of anemone has been discovered off the coast of Japan and appears to live exclusively on the shells of a species of hermit crab.
  • The first such video recordings of the hermit crab and anemone duo show the hermit crab moving to a new shell and spending more than 40 hours poking, peeling and dragging the anemone for it to come.
  • Researchers believe that the hermit crab and the anemone have an obligate symbiotic relationship or that they need each other to survive.
  • The anemone eats falling debris and protects the hermit crab from pests and predators, and in turn may hitch a ride to new feeding grounds.

In the deep waters off the coast of Japan, a hermit crab wears high fashion. On its shell is the anemone species new to science Calciferous Stylobatesnamed after the fire demon Calcifer from the novel and film Studio Ghibli Howl’s Howl’s Moving Castle.

A research team led by Akihiro Yoshikawa, a professor at the University of Tokyo, collected the anemone-hermit crab-hermit duo from the seabed at a depth of 100 to 400 meters (330 to 1,300 feet) in the Sea of Kumano and Suruga Bay on the Pacific side of Japan. Researchers have published descriptions of the new species of anemone in The Biological Bulletin.

The newly described anemone species appears to live exclusively on the shells of the hermit crab species Pagurodofleinia doederleinia hint that these two species are in an obligatory symbiotic relationship, or that they need each other to survive.

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.

Much like a conch shell, anemones use their own secretions to form their shell-like attachments (in this case, to their hermit crab host). “The new species’ shell-making ability in the species-specific relationship seems as if Calcifer was in a magical contract with the Wizard Howl, building his Moving Castle,” Yoshikawa told Mongabay in an email.

In a series of first video recordings of the hermit crab and anemone duo, we see the crab moving around in a larger shell. What follows is a 40+ hour struggle to move the anemone into the new shell. The crab pinches, taps and maneuvers the anemone until it is positioned on top of the shell, its tentacles facing upwards.

The researchers say this immense effort by the hermit crab is further evidence that the hermit crab and the anemone are engaged in mutualism. The anemone eats debris that falls from the ocean above and in doing so protects the hermit crab from pests and predators. In return, the anemone can hitchhike to new feeding areas.

“Our study is perhaps the first observation of the behavioral interaction of the incredible mutualism rarely studied in the open ocean,” Yoshikawa said.

In lab records of the new species, the hermit crab is seen moving to a new shell and moving the anemone with it. Screenshots from video footage of Akihiro Yoshikawa. An edited version of the video footage can be viewed here.

There are at least 35 other species of symbiotic sea anemones known to science that live on the shells of hermit crabs. This newest species is the fifth of its kind but the first found in Japanese waters.

The shell-like attachments made by the anemone make them susceptible to ocean acidification, Yoshikawa said. As more CO2 is pumped into the atmosphere, some of it enters the ocean, changing the pH of seawater to make it more acidic. This change in ocean chemistry can to cause problems for shellfish and carcinoid-forming sea creatures.

The new anemone was also found in bycatch samples from deep-sea trawling in Suruga Bay. It lives in shallower water than some of the others Stylobates species, making it easier to catch by deep-sea trawling, a practice that involves dragging massive nets along the seabed, indiscriminately collecting ocean life. Yoshikawa told Mongabay that although scientists don’t know enough about the new species to be sure, the anemone, as well as its habitat, could be threatened by deep-sea trawling.

Quote:

Yoshikawa, A., Izumi, T., Moritaki, T., Kimura, T. and Yanagi, K. (2022). Sea anemone forming a carcinocea Calciferous Stylobates sp. nov. (Cnidaria, Actiniaria, Actiniidae) of the Japanese seabed: A taxonomic description with its ecological observations. The Biological Bulletin, 242(2), 127-152. do I:10.1086/719160

Banner image of the anemone species new to science Stylobates calcifer. Image by Akihiro Yoshikawa.

Liz Kimbrough is a writer for Mongabay. Find her on Twitter @lizkimbrough

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Animals, Environment, Green, Cheerful environmental, Marine animals, Marine biodiversity, New discovery, New species, Ocean acidification, Oceans, Wildlife

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