During a survey of the siphonophore community in the Kuroshio Extension, Northwest Pacific Ocean, a new Halistemma Huxley, 1859 was described using integrated molecular and morphological approaches. The Halistemma isabu sp. nov. nectophore is most closely related morphologically to H. striata Totton, 1965 and H. maculatum Pugh and Baxter, 2014. These species can be differentiated by their nectosac shape, thrust block size, ectodermal cell patches and ridge patterns. The new species’ bracts are divided into two distinct types according to the number of teeth. Type A bracts are more closely related to ventral bracts in H. foliacea (Quoy and Gaimard, 1833) while Type B bracts are more similar to H. rubrum (Vogt, 1852). Each type differs, however, from the proximal end shape, distal process and bracteal canal. Both of the new species’ morphological type and phylogenetic position within the genus Halistemma are supported by phylogenetic analysis of concatenated DNA dataset (mtCOI, 16S rRNA and 18S rRNA). Integrated morphological and molecular approaches to the taxonomy of siphonophores showed a clear delimitation of the new species from the congeners. Halistemma isabu sp. nov. is distributed with the congeners of H. rubrum, H. cupulifera, H. foliacea and H. striata in the northwestern Pacific Ocean.

中文翻译：

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西北太平洋 Halistemma 物种的综合分类学

在对西北太平洋黑潮扩展区的虹吸管群落进行调查期间，使用综合分子和形态学方法描述了 1859 年的新 Halistemma Huxley。Halistemma isabu sp。十一月 nectophore 在形态学上与 H. striata Totton, 1965 和 H. maculatum Pugh and Baxter, 2014 最密切相关。这些物种可以通过它们的 nectosac 形状、推力块大小、外胚层细胞斑块和脊模式来区分。新种的苞片根据牙齿的数量分为两种不同的类型。A 型苞片与 H. foliacea 的腹侧苞片更密切相关（Quoy 和 Gaimard，1833），而 B 型苞片与 H. rubrum 更相似（Vogt，1852）。然而，每种类型在近端形状、远端过程和鳃管方面都不同。连接 DNA 数据集（mtCOI、16S rRNA 和 18S rRNA）的系统发育分析支持了 Halistemma 属内新物种的形态类型和系统发育位置。虹吸管分类学的综合形态学和分子学方法表明，新物种与同系物之间有明确的界限。Halistemma isabu sp. 十一月 在西北太平洋与 H. rubrum、H. cupulifera、H. foliacea 和 H. striata 的同源物一起分布。