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| Stylobates calcifer sp. nov. with host hermit crab Pagurodofleinia doederleini. Stylobates calcifer Yoshikawa & Izumi, in Yoshikawa, Izumi, Moritaki, Kimura & Yanagi, 2022. ヒメキンカライソギンチャク || DOI: 10.1086/719160 |
Abstract
Here we describe Stylobates calcifer sp. nov. (Cnidaria, Actiniaria, Actiniidae), a new carcinoecium-forming sea anemone from the deep-sea floor of Japan. Stylobates produces a carcinoecium that thinly covers the snail shells inhabited by host hermit crabs Pagurodofleinia doederleini. The new species is distinct from other species by the shape of the marginal sphincter muscle, the distribution of cnidae, the direction of the oral disk, and host association. The species’ novelty is supported by the data of its mitochondrial genes 12S, 16S, and COIII and nuclear genes 18S and 28S. Also, we conducted behavioral observation of this new species, focusing on the feeding behavior and interaction with the specific host hermit crab. Our observations suggest that this sea anemone potentially feeds on the suspended particulate organic matter from the water column or the food residuals of hermit crabs. When the host’s shell changed, intensive manipulation for transference of S. calcifer sp. nov. was recorded. However, although the hermit crab detached and transferred the sea anemone to the new shell after shell change, the sea anemone did not exhibit active or cooperative participation. Our data suggest that the sea anemone may not produce a carcinoecium synchronously to its host’s growth, contrary to the anecdotal assumption about carcinoecium-forming sea anemones. Conversely, the host hermit crab’s growth may not depend entirely on the carcinoecium produced by the sea anemone. This study is perhaps the first observation of the behavioral interaction of the rarely studied carcinoecium-forming mutualism in the deep sea.
Order ACTINIARIA
Suborder ENTHEMONAE
Superfamily ACTINIOIDEA Rafinesque, 1815
Family ACTINIIDAE Rafinesque, 1815
Genus Stylobates Dall, 1903
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| External morphology of Stylobates calcifer sp. nov. (holotype: NSMT-Co 1794) with host hermit crab Pagurodofleinia doederleini. The upper (A) and posterior (B) views and the marginal views of the right and left sides (C, D, respectively) of the living specimen. The upper and marginal views (E, F, respectively) of the preserved specimen. Scale bars = 5 mm. |
Stylobates calcifer sp. nov. Yoshikawa and Izumi
[Japanese name: Hime-kin-kara-isoginchaku
ヒメキンカライソギンチャク]
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| Behavioral sequence of the hermit crab Pagurodofleinia doederleini transferring the sea anemone Stylobates calcifer sp. nov. from the original snail Glossaulax reiniana shell to a new one. (A) The hermit crab begins tapping the pedal disk and column of the sea anemone with its walking legs and chelipeds. (B) The hermit crab uses one or both of its chelipeds to pinch and remove S. calcifer sp. nov. from the G. reiniana shell. (C) Stylobates calcifer sp. nov. displays no shell-mounting action after being removed from the original shell. (D) The sea anemone is turned to the upside-down position (facing up the pedal disk) by the crab. (C) The hermit crab rides on the pedal disk of the sea anemone and fits the shell to the curved line of the pedal disk. (E) The sea anemone settles down in a new shell of the host hermit crab with a usual position. |
Ecological note: Stylobates calcifer sp. nov. was exclusively found on the shells inhabited by Pagurodofleinia doederleini, consistent with previous studies (Uchida and Soyama, 2001; Yanagi, 2006; Yoshikawa et al., 2019). However, P. doederleini without S. calcifer sp. nov. was sometimes collected in this study. One individual was usually attached to one host hermit crab, consistent with previous studies (Uchida and Soyama, 2001; Yanagi, 2006; Yoshikawa et al., 2019).
Distribution and habitat: All of the samples were collected from the Sea of Kumano (Uchida and Soyama, 2001; Yoshikawa et al., 2019) and Suruga Bay. All of the previous records were from the Pacific Ocean facing the middle of Honshu Island to Kyushu (Uchida and Soyama, 2001; Yanagi, 2006). The specimens were distributed at 100–400 m from the fine sand and soft mud (Fig. 1; Table 1).
Etymology: The specific name “calcifer” is driven from the name of a resident fire-demon Calcifer, which appeared in Howl’s Moving Castle, a fantasy novel by British author Diana Wynne Jones, published in 1986; the story is the original version of the Japanese animated film of the same name, directed by Hayao Miyazaki (animated by Studio Ghibli). The shell-making ability of the new species in the species-specific relationship appears as if Calcifer was in a magical contract with the Wizard Howl, constructing his Moving Castle.
Akihiro Yoshikawa, Takato Izumi, Takeya Moritaki, Taeko Kimura and Kensuke Yanagi. 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 Bulletin. 242; DOI: 10.1086/719160 [2 April 2022]
Researchgate.net/publication/360192582_Stylobates_calcifer_sp_nov__from_the_Japanese_Deep-Sea_Floor
第65回 瀬戸海洋生物学セミナー
「ヤドカリの“宿”を作るヒメキンカライソギンチャクの分類・共生生態と進化学的研究への展望」
吉川 晟弘 特任研究員（東京大学 大気海洋研究所附属国際・地域連携研究センター）
