Integrated Taxonomy for <i>Halistemma</i> Species from the Northwest Pacific Ocean

• Main Authors: Nayeon Park, Andrey A. Prudkovsky, Wonchoel Lee
• Format: Article
• Language: English
• Published: MDPI AG 2020-11-01
• Series: Water
• Subjects: zooplankton; jellyfish; mitochondria; systematics; hydrozoa
• Online Access: https://www.mdpi.com/2073-4441/12/11/3283

During a survey of the siphonophore community in the Kuroshio Extension, Northwest Pacific Ocean, a new <i>Halistemma</i> Huxley, 1859 was described using integrated molecular and morphological approaches. The <i>Halistemma isabu</i> sp. nov. nectophore is most closely related morphologically to <i>H</i>. <i>striata</i> Totton, 1965 and <i>H</i>. <i>maculatum</i> 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 <i>H</i>. <i>foliacea</i> (Quoy and Gaimard, 1833) while Type B bracts are more similar to <i>H</i>. <i>rubrum</i> (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 <i>Halistemma</i> 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. <i>Halistemma isabu</i> sp. nov. is distributed with the congeners of <i>H. rubrum</i>, <i>H. cupulifera</i>, <i>H. foliacea</i> and <i>H. striata</i> in the northwestern Pacific Ocean.