Fotolaimus cavussp. nov. was described from a submarine anchialine cave called Akuma-no-yakata on the Shimoji Island, Miyako Island Group, Ryukyu Islands, southwestern Japan. This is the first free-living marine nematode isolated from a submarine cave in Japan, and the third species of the genus Fotolaimus. This new species differs from its congeners by its small body size, wide amphids, long buccal cavity, long conico-cylindrical tail, and proximally curved gubernaculum. We provide amended dichotomous keys to genera in the subfamily Oncholaiminae and species in Fotolaimus. We also analyzed partial DNA sequences encoding ribosomal small subunit RNA and cytochrome c oxidase subunit I from Fotolaimus cavussp. nov. and six other species of Oncholaimidae collected from Japanese waters. The phylogenetic tree based on the ribosomal small subunit RNA sequences using maximum likelihood analysis suggested a close relationship between Fotolaimus and Wiesoncholaimus as well as Oncholaimus. The topology of the tree was similar to those from previous studies; however, it suggested a new phylogenetic position of Adoncholaimus as a sister clade for Viscosia and Oncholaimus.

中文翻译：

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自由生活的海洋线虫新种 Fotolaimus cavus sp. 十一月 （线虫纲、Oncholaimida、Oncholaimidae），从日本西南部琉球群岛的海底安奇阿林洞穴中分离出来

Fotolaimus cavussp. 十一月 描述于日本西南部琉球群岛宫古群岛下地岛上一个名为 Akuma-no-yakata 的海底洞穴中。这是从日本海底洞穴中分离出来的第一种自由生活的海洋线虫，也是 Fotolaimus 属的第三种。这个新物种与其同类的不同之处在于其体型较小，两栖动物较宽，颊腔较长，圆锥形尾部较长，以及近端弯曲的触须。我们提供了 Oncholaiminae 亚科属和 Fotolaimus 种的修正二分键。我们还分析了来自 Fotolaimus cavussp 的编码核糖体小亚基 RNA 和细胞色素 c 氧化酶亚基 I 的部分 DNA 序列。十一月 以及从日本水域收集的其他六种Oncholaimidae。使用最大似然分析基于核糖体小亚基 RNA 序列的系统发育树表明 Fotolaimus 和 Wiesoncholaimus 以及 Oncholaimus 之间存在密切关系。树的拓扑结构与之前的研究相似；然而，它提出了 Adoncholaimus 的新系统发育位置，作为 Viscosia 和 Oncholaimus 的姐妹进化枝。