The mitochondrial gene cytochrome-c-oxidase subunit 1 (COI) is useful in many taxa for phylogenetics, population genetics, metabarcoding, and rapid species identifications. However, the phylum Ctenophora (comb jellies) has historically been difficult to study due to divergent mitochondrial sequences and the corresponding inability to amplify COI with degenerate and standard COI “barcoding” primers. As a result, there are very few COI sequences available for ctenophores, despite over 200 described species in the phylum. Here, we designed new primers and amplified the COI fragment from members of all major groups of ctenophores, including many undescribed species. Phylogenetic analyses of the resulting COI sequences revealed high diversity within many groups that was not evident from more conserved 18S rDNA sequences, in particular among the Lobata (Ctenophora; Tentaculata; Lobata). The COI phylogenetic results also revealed unexpected community structure within the genus Bolinopsis, suggested new species within the genus Bathocyroe, and supported the ecological and morphological differences of some species such as Lampocteis cruentiventer and similar undescribed lobates (Lampocteis sp. “V” stratified by depth, and “A” differentiated by colour). The newly designed primers reported herein provide important tools to enable researchers to illuminate the diversity of ctenophores worldwide via quick molecular identifications, improve the ability to analyse environmental DNA by improving reference libraries and amplifications, and enable a new breadth of population genetic studies.

中文翻译：

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新的线粒体COI引物和序列揭示了栉水母的隐藏多样性

线粒体基因细胞色素-c-氧化酶亚基 1 ( COI ) 在许多分类群中用于系统发育、种群遗传学、元条形码和快速物种鉴定。然而，栉水母门（梳状果冻）历来难以研究，因为线粒体序列不同，并且相应地无法用简并和标准COI “条形码”引物扩增COI 。因此，尽管该门中有 200 多种已描述的物种，但可用于栉水母的COI序列非常少。在这里，我们设计了新的引物并从所有主要栉水母群的成员中扩增了COI片段，包括许多未描述的物种。结果的系统发育分析COI序列揭示了许多群体中的高度多样性，这在更保守的18S rDNA 序列中并不明显，特别是在 Lobata（Ctenophora；Tentaculata；Lobata）中。COI系统发育结果还揭示了 Bolinopsis 属内意想不到的群落结构，表明了Bathocyroe属内的新物种，并支持了一些物种的生态学和形态学差异，例如Lampocteis cruentiventer和类似的未描述的叶状体 ( Lampocteissp。“V”按深度分层，“A”按颜色区分）。本文报道的新设计的引物提供了重要的工具，使研究人员能够通过快速分子鉴定阐明全球栉水母的多样性，通过改进参考文库和扩增来提高分析环境 DNA 的能力，并实现新的群体遗传学研究。