A new genus and species of Nerillidae, Nipponerilla irabuensis gen. nov., sp. nov., is described from an anchialine cave in Shimoji Island, west of Irabu Island (Miyako Islands, Southwestern Japan). Its morphology was examined with light, scanning electron, and confocal laser scanning microscopy. This new species, along with two putative new cave species from the Turks and Caicos Islands and several closely related nerillids, was included in a phylogenetic analysis employing five concatenated gene markers (16S rRNA, 18S rRNA, 28S rRNA, H3, and COI). Nipponerilla irabuensis gen. nov., sp. nov. was found to be sister taxon to the cave-exclusive genus Speleonerilla Worsaae, Sterrer & Iliffe, in Worsaae et al., 2019, but shows morphological resemblance to both Speleonerilla and Mesonerilla Remane, 1949. Thus, Nipponerilla gen. nov. constitutes a new monotypic genus in Nerillidae diagnosed by a combination of the following characters: nine segments, compound chaetae, high palp and antennae to body length ratios, and gonochoristic reproduction with two pairs of spermioducts opening in segments VII and VIII. Its placement among Nerillidae is discussed, along with its putative adaptations to an anchialine environment.

Nerillidae的一个新属种，Nipponerilla irabuensis根。十一月，sp。11 月，来自伊良部岛（日本西南部宫古群岛）以西的下地岛的一个山洞。用光、扫描电子和共聚焦激光扫描显微镜检查其形态。这个新物种，连同来自特克斯和凯科斯群岛的两个推定的新洞穴物种和几个密切相关的 nerillids，被包括在使用五个串联基因标记（16S rRNA、18S rRNA、28S rRNA、H3 和 COI）的系统发育分析中。Nipponerilla irabuensis gen. 十一月，sp。十一月 在2019 年的 Worsaae 等人中被发现是洞穴独有属Speleonerilla Worsaae、Sterrer 和 Iliffe 的姊妹分类群，但在形态学上与两者相似Speleonerilla和Mesonerilla Remane，1949 年。因此，Nipponerilla gen。十一月 由以下特征组合诊断出的线虫属新单型属：九节，复合毛类，触须和触角与体长的比例高，生殖器生殖，两对精子管在 VII 和 VIII 节中开口。讨论了它在 Nerillidae 中的位置，以及它对 anchialine 环境的假定适应性。