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Morphometric and genetic identification of Rhynchoconger ectenurus (Anguilliformes: Congridae) leptocephali with additional information about eel tails

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Abstract

Leptocephali collected from the East China Sea that were assigned to the genus Rhynchoconger (Jordan and Hubbs 1925) were identified by DNA sequences as Rhynchoconger ectenurus (Jordan and Richardson 1909). The leptocephali of R. ectenurus differ from other congrid larvae reported from Japan in having a moderately elongate body, acute tail, a row of moderately large subcutaneous melanophores just below mid-lateral line, and 173–184 total myomeres. Since R. ectenurus was reported for the first time from Taiwan in 1909, some studies may have noted their total number of vertebrae while including some specimens with an incomplete tail. We collected seven R. ectenurus specimens with complete tails from the East China Sea. The total length ratio and the total number of vertebrae are additionally given for R. ectenurus, the hypural is shown by transparent skeletal specimen photographs and line drawing illustrations, and morphological and pigment characteristics of leptocephali are presented by line drawing illustrations.

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Acknowledgments

We are grateful to Seiji Ohshimo (currently University of Hiroshima) for collecting the specimens used in this study during the Resources Direct Estimation Survey by Japan Fisheries Research and Education Agency (FRA); Taku Yoshimura for collecting the specimens by FRA; Atsushi Tawa (currently FRA) and Masanori Kawazu (currently Kagoshima Prefectural Government) for collecting and sorting the specimens while in the Fisheries Biology Laboratory, University of Kyushu. We also thank the captains and crews of the R/V Hokko Maru, FRA, the R/V Kagoshima Maru, Kagoshima University, and the R/V Kumamoto Maru, the former Kumamoto Prefectural Reiyou High School (commissioned by FRA), for their efforts. Michael J. Miller helped to improve the manuscript.

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Authors and Affiliations

  1. Laboratory of Fisheries Biology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, Motooka 744, Fukuoka, 819-0395, Japan

    Kyohei Sakai

  2. Fisheries Resources Institute, Japan Fisheries Research and Education Agency, Taira-machi 1551-8, Nagasaki, 851-2213, Japan

    Mari Yoda & Takeshi Sakai

  3. Laboratory of Fisheries Biology, Faculty of Agriculture, Kyushu University, Motooka 744, Fukuoka, 819-0395, Japan

    Noritaka Mochioka

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  1. Kyohei Sakai
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  4. Noritaka Mochioka
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Correspondence to Noritaka Mochioka.

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The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in the present study.

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The authors accorded to the administrative provision of animal welfare on the Japan Fisheries Research and Education Agency (https://www.fra.affrc.go.jp/kseika/experiment_on_animals/regulation.pdf). All research cruises and biological samplings of the trawl surveys were approved by Japan Government; the pair-trawl fisheries, which provided us the biological samples of several species, are strictly controlled by the Japan Government.

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Sakai, K., Yoda, M., Sakai, T. et al. Morphometric and genetic identification of Rhynchoconger ectenurus (Anguilliformes: Congridae) leptocephali with additional information about eel tails. Ichthyol Res (2024). https://doi.org/10.1007/s10228-024-00968-y

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