Japanese researchers have described a new species of sea anemone that appears to share a mutually beneficial relationship with hermit crabs. The pale pink sea anemones, now named Paracalliactis tsukisome, were found attached to the shells of hermit crabs (Oncopagurus monstrosus). The researchers described the anemone based on 36 specimens that fishing trawlers collected between 2017 and 2024 from various locations off the coast of Japan at depths between 192 and 470 meters (630 and 1,542 feet). The anemones, the team observed, were all attached to the tops of hermit crab shells and spatially oriented in the same direction. “3D CT imaging revealed a consistent, unidirectional attachment pattern near the shell’s opening, suggesting a basic sense of orientation,” Akihiro Yoshikawa, the study’s lead author from Japan’s National Museum of Nature and Science, told Mongabay by email. The anemone’s asymmetry and sense of orientation were unusual because sea anemones, like starfish, usually display radial symmetry, meaning a line drawn through their middle can divide the animals into halves many different ways, like slicing a pie. Radial symmetry allows anemones to interact with their environment from all directions equally. P. tsukisome “can form asymmetric, snail-shaped structures—a phenomenon extremely rare in evolutionary terms,” Yoshikawa said. “This finding offers valuable insight into how simple animals perceive spatial orientation and could provide a model for studying early forms of body asymmetry.” The team’s analysis found that anemones feed partly on the waste of their host, hermit crabs, and on surrounding organic particles. So, the hermit crabs…This article was originally published on Mongabay

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