Description of a New Species, Microcotyle pacinkar n. sp. (Monogenea: Microcotylidae), Parasitic on Gills of Sebastes taczanowskii (Sebastidae) from off Usujiri, Hokkaido, Northern Japan

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Microcotyle pacinkar n. sp. (Monogenea: Microcotylidae) is described from the gills of Sebastes taczanowskii Steindachner, 1880 (Scorpionfishes: Sebastidae) (Japanese name: Ezo-mebaru) collected from off Usujiri in Hokkaido, northern Japan in the North Pacific Ocean. The new species is morphologically most similar to M. ditrematis Yamaguti, 1940 in having an elongated body and an inverted pear-shaped genital atrium but differs from the congener in the arrangement of the spines in the genital atrium and the shapes of the anterolateral sclerites of the clamps. The phylogenetic trees for species of Microcotyle van Beneden and Hesse, 1863 based on the partial cytochrome c oxidase subunit I region were estimated using new sequences of M. pacinkar n. sp.; the new species formed a sister group with M. sebastis Goto, 1894.