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Type: Article
Published: 2022-12-02
Page range: 337-364
Abstract views: 309
PDF downloaded: 205

Redescription of Bathymodiolus septemdierum Hashimoto and Okutani, 1994 (Bivalvia, Mytilida, Mytilidae), a mussel broadly distributed across hydrothermal vent locations in the western Pacific and Indian Oceans

Department of Biology and School of Earth & Ocean Sciences, University of Victoria, Victoria, BC, Canada.
Graduate School of Oceanography, University of Rhode Island, Narragansett, RI, USA.
Mollusca Bathymodiolinae species delimitation morphological taxonomy molecular barcoding cytochrome c oxidase subunit I COI NADH dehydrogenase subunit 4 ND4


Mussels of the genus Bathymodiolus Kenk & Wilson belong to the foundation fauna at hydrothermal vents in the global deep sea. In the western Pacific and Indian oceans, the three nominal taxa B. septemdierum Hashimoto and Okutani, B. brevior Cosel, Métivier & Okutani and B. marisindicus Hashimoto are currently recognized as separate species despite morphological and genetic evidence for their conspecificity. All three are listed with the International Union for Conservation of Nature Red List based on highly restricted ranges. We compile and supplement existing morphometric and molecular data to revise the Bathymodiolus septemdierum species group. We redescribe B. septemdierum as a single species with B. brevior and B. marisindicus recognized as junior synonyms. Given the exceptionally broad range of B. septemdierum, we propose removal of these three taxa from the IUCN Red List.



  1. Bandelt, H., Forster, P. & Röhl, A. (1999) Median-joining networks for inferring intraspecific phylogenies. Molecular Biology and Evolution, 16 (1), 37–48.
    Breusing, C., Johnson, S.B., Tunnicliffe, V. & Vrijenhoek, R.C. (2015) Population structure and connectivity in Indo-Pacific deep-sea mussels of the Bathymodiolus septemdierum complex. Conservation Genetics, 16, 1415–1430.
    Copley, J., Marsh, L., Glover, A., Hühnerbach, V., Nye, V.E., Reid, W.D.K., Sweeting, C.J., Wigham, B. D. & Wiklund, H. (2016) Ecology and biogeography of megafauna and macrofauna at the first known deep-sea hydrothermal vents on the ultraslow-spreading Southwest Indian Ridge. Scientific Reports, 6, 39158.
    Cosel, R. von, Métivier, C. & Hashimoto, J. (1994) Three new species of Bathymodiolus (Bivalvia: Mytilidae) from hydrothermal vents in the Lau Basin and the North Fiji Basin, western Pacific, and the Snake Pit area, Mid-Atlantic Ridge. The Veliger, 37, 374–392.
    Hashimoto, J. (2001) A new species of Bathymodiolus (Bivalvia: Mytilidae) from hydrothermal vent communities in the Indian Ocean. Venus, 60, 141–149.
    Hashimoto, J. & Okutani, T. (1994) Four new mytilid mussels associated with deepsea chemosynthetic communities around Japan. Venus, 53, 61–83.
    Hebert, P.D., Ratnasingham, S. & deWaard, J.R. (2003) Barcoding animal life: cytochrome c oxidase subunit 1 divergences among closely related species. Proceedings of the Royal Society of London B: Biological Sciences, 270 (Supplement 1), S96–99.
    Jang, S.-J., Ho, P.-T., Jun, S.-Y., Kim, D. & Won, Y.-J. (2020) A newly discovered Gigantidas bivalve mussel from the Onnuri vent field in the northern Central Indian Ridge. Deep Sea Research Part I: Oceanographic Research Papers, 161, 103299.
    Katoh, K., Misawa, K., Kuma, K. & Miyata, T. (2002) MAFFT: a novel method for rapid multiple sequence alignment based on fast Fourier transform. Nucleic Acids Research, 30 (14), 3059–3066.
    Kenk, V.C. & Wilson, B.R. (1985) A new mussel (Bivalvia, Mytilidae) from hydrothermal vents in the Galapagos Rift zone. Malacologia, 26, 253–271.
    Kimura M. (1980) A simple method for estimating evolutionary rates of base substitutions through comparative studies of nucleotide sequences. Journal of Molecular Evolution, 16 (2), 111–120.
    Kyuno, A., Shintaku, M., Fujita, Y., Matsumoto, H., Utsumi, M., Watanabe, H., Fujiwara, Y. & Miyazaki, J.-I. (2009) Dispersal and differentiation of deep-sea mussels of the genus Bathymodiolus (Mytilidae, Bathymodiolinae). Journal of Marine Biology, 2009, 625672.
    Leigh, J.W. & Bryant, D. (2015) PopART: Full-feature software for haplotype network construction. Methods in Ecology and Evolution, 6 (9), 1110–1116.
    Leonard, G.H., Bertness, M.D. & Yund, P.O. (1999) Crab predation, waterborne cues and inducible defenses in the blue mussel, Mytilus edulis. Ecology, 80, 1–14.[0001:CPWCAI]2.0.CO;2
    McCowin, M.F., Feehery, C. & Rouse, G.W. (2020) Spanning the depths or depth-restricted: three new species of Bathymodiolus (Bivalvia, Mytilidae) and a new record for the hydrothermal vent Bathymodiolus thermophilus at methane seeps along the Costa Rica margin. Deep Sea Research Part I: Oceanographic Research Papers, 164, 103322.
    Miyazaki, J.-I., Martins, L.d.O., Fujita, Y., Matsumoto, H. & Fujiwara, Y. (2010) Evolutionary process of seep-sea Bathymodiolus mussels. PLoS ONE, 5, e10363.
    Nei, M. & Tajima, F. (1981) DNA polymorphism detectable by restriction endonucleases. Genetics, 97 (1), 145–163.
    Olu-Le Roy, K., Cosel, R.v., Hourdez, S., Carney, S.L. & Jollivet, D. (2007) Amphi-Atlantic cold-seep Bathymodiolus species complexes across the equatorial belt. Deep Sea Research Part I: Oceanographic Research Papers, 54, 1890–1911.
    Osores, S.J.A., Lagos, N.A., San Martín, V., Manríquez, P.H., Vargas, C.A., Torres, R., Navarro, J.M., Poupin, M.J., Saldías, G.S. & Lardies, M.A. (2017) Plasticity and inter-population variability in physiological and life-history traits of the mussel Mytilus chilensis: A reciprocal transplant experiment. Journal of Experimental Marine Biology and Ecology, 490, 1–12.
    Owada, M. (2015) Functional phenotypic plasticity of the endolithic mytilid Leiosolenus curtus (Lischke, 1874) (Bivalvia: Mytilidae). Molluscan Research, 35, 188–195.
    Paradis E. (2010) pegas: an R package for population genetics with an integrated-modular approach. Bioinformatics, Oxford, England, 26 (3), 419–420.
    Paradis, E. & Schliep, K. (2019) ape 5.0: an environment for modern phylogenetics and evolutionary analyses in R. Bioinformatics, Oxford, England, 35 (3), 526–528.
    R Core Team (2022) R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna. Available from:
    Rogers, A.D., Tyler, P.A., Connelly, D.P., Copley, J.T., James, R., Larter, R.D., Linse, K., Mills, R.A., Garabato, A.N., Pancost, R.D., Pearce, D.A., Polunin, N.V.C., German, C.R., Shank, T., Boersch-Supan, P.H., Alker, B.J., Aquilina, A., Bennett, S.A., Clarke, A., Dinley, R.J.J., Graham, A.G.C., Green, D.R.H., Hawkes, J.A., Hepburn, L., Hilario, A., Huvenne, V.A.I., Marsh, L., Ramirez-Llodra, E., Reid, W.D.K., Roterman, C.N., Sweeting, C.J., Thatje, S. & Zwirglmaier, K. (2012) The discovery of new deep-sea hydrothermal vent communities in the southern ocean and implications for biogeography. PLoS Biology, 10, e1001234.
    Rossi, G.S. & Tunnicliffe, V. (2017) Trade-offs in a high CO2 habitat on a subsea volcano: condition and reproductive features of a bathymodioline mussel. Marine Ecology Progress Series, 574, 49–64.
    Schöne, B.R. & Giere, O. (2005) Growth increments and stable isotope variation in shells of the deep-sea hydrothermal vent bivalve mollusk Bathymodiolus brevior from the North Fiji Basin, Pacific Ocean. Deep Sea Research Part I: Oceanographic Research Papers, 52, 1896–1910.
    Shintaku, M. (2003) Phylogenic relationships and divergence time of deep-sea mussels of the genus Bathymodiolus (Bivalvia, Mytilidae) in the western Pacific and Indian Oceans (Preliminary Report). Japanese Journal of Benthology, 58, 34–39.
    Sigwart, J.D., Chen, C., Thomas, E.A., Allcock, A.L., Böhm, M. & Seddon, M. (2019) Red Listing can protect deep-sea biodiversity. Nature Ecology & Evolution, 3, 1134.
    Thomas, E.A., Böhm, M., Pollock, C., Chen, C., Seddon, M. & Sigwart, J.D. (2022) Assessing the extinction risk of insular, understudied marine species. Conservation Biology, 36, e13854.
    Thomas, E.A., Chen, C. & Sigwart, J. (2019) Bathymodiolus marisindicus. The IUCN Red List of Threatened Species, 2019, e.T201085A2690857.
    Thomas, E.A. & Sigwart, J. (2020a) Bathymodiolus brevior. The IUCN Red List of Threatened Species, 2020, e.T200959A2686572.
    Thomas, E.A. & Sigwart, J. (2020b) Bathymodiolus septemdierum. The IUCN Red List of Threatened Species, 2020, e.T201075A2690611.
    Thubaut, J., Puillandre, N., Faure, B., Cruaud, C. & Samadi, S. (2013) The contrasted evolutionary fates of deep-sea chemosynthetic mussels (Bivalvia, Bathymodiolinae). Ecology and Evolution, 3, 4748–4766.
    Tunnicliffe, V., Davies, K.T., Butterfield, D.A., Embley, R.W., Rose, J.M. & Chadwick Jr, W.W. (2009) Survival of mussels in extremely acidic waters on a submarine volcano. Nature Geoscience, 2, 344–348.
    Van Dover, C.L., Arnaud-Haond, S., Gianni, M., Helmreich, S., Huber, J.A., Jaeckel, A.L., Metaxas, A., Pendleton, L.H., Petersen, S., Ramirez-Llodra, E., Steinberg, P.E., Tunnicliffe, V. & Yamamoto, H. (2018) Scientific rationale and international obligations for protection of active hydrothermal vent ecosystems from deep-sea mining. Marine Policy, 90, 20–28.
    Vrijenhoek, R.C. (2009) Cryptic species, phenotypic plasticity, and complex life histories: Assessing deep-sea faunal diversity with molecular markers. Deep Sea Research Part II Topical Studies in Oceanography, 56, 1713–1723.
    Watanabe, H.K., Shigeno, S., Fujikura, K., Matsui, T., Kato, S. & Yamamoto, H. (2019) Faunal composition of deep-sea hydrothermal vent fields on the Izu–Bonin–Mariana Arc, northwestern Pacific. Deep Sea Research Part I: Oceanographic Research Papers, 149, 103050.
    Zhou, Y., Chen, C., Zhang, D., Wang, Y., Watanabe, H.K., Sun, J., Bissessur, D., Zhang, R., Han, Y. & Sun, D. (2022) Delineating biogeographic regions in Indian Ocean deep‐sea vents and implications for conservation. Diversity and Distributions. [early view]