National Institute of Water and Atmospheric Research (NIWA) Ltd, Wellington, New Zealand.
Zootaxa. 2021 Mar 25;4949(2):zootaxa.4949.2.7. doi: 10.11646/zootaxa.4949.2.7.
The Kermadec Trench is the world's fifth deepest trench and extends from approximately 26 to 36°S near the northeastern tip of New Zealand's North Island. Here, we describe a new species of Aegialoalaimus, a nematode genus with unusual buccal cavity and pharynx morphology, from a site at 9540 metres water depth in Kermadec Trench, and provide the first SSU and D2-D3 of LSU sequences for Aegialoalaimus, Manganonema, Metasphaerolaimus constrictus and Daptonema amphorum. Aegialoalaimus tereticauda n. sp. is characterised by body length 755-864 µm, cephalic sensilla papilliform ( 1 µm long), excretory pore located slightly anterior to posterior bulb in males and slightly anterior to nerve ring in females, arcuate spicules 18-22 µm long, gubernaculum present, precloacal supplements absent, and cylindrical tail 58-64 µm long with rounded tip. Relationships between Aegialoalaimus and Chromadorean orders could not be elucidated based on our SSU analysis; no link could be found with the Plectida, where the Aegialoalaimidae is currently placed, or with the Isolamiida or Cylindrolaimus (Areaolaimida), which share a similar and unusual buccal and pharynx morphology. Our SSU phylogenetic analysis confirms the placement of Manganonema within the Xyalidae, although relationships with other xyalid genera remain unclear. The Sphaerolaimidae formed a clade together with the Monhysteridae, which contradicts the current classification where the Sphaerolaimidae and Xyalidae are classified together into the superfamily Sphaerolaimoidea and the Monhysteridae into the Monhysteroidea. Although limited research has been conducted on the nematode diversity in Kermadec Trench to date, the available data show that half of all invertebrate species known from the trench are nematodes, which highlights the importance of conducting further taxonomic research on this group in hadal environments.
克马德克海沟是世界第五深海沟，位于新西兰北岛东北端附近的南纬 26 度至 36 度之间。在这里，我们描述了一种新的 Aegialoalaimus 物种，这是一个具有不寻常的口腔和咽形态的线虫属，来自克马德克海沟水深 9540 米的一个地点，并提供了 Aegialoalaimus、Manganonema、Metasphaerolaimus constrictus 和 Daptonema amphorum 的首个 SSU 和 LSU D2-D3 序列。Aegialoalaimus tereticauda n. sp. 的特征是体长 755-864 µm，头部感觉器乳突状（1 µm 长），雄性排泄孔位于后膨大部稍前，雌性位于神经环稍前，弧形刺 18-22 µm 长，存在交接刺，无前伸补充器，尾圆筒形长 58-64 µm，尾端圆。基于我们的 SSU 分析，无法阐明 Aegialoalaimus 与 Chromadorean 目之间的关系；无法与目前归入 Aegialoalaimidae 的 Plectida 或具有相似且不寻常的口腔和咽形态的 Isolamiida 或 Cylindrolaimus（Areaolaimida）联系起来。我们的 SSU 系统发育分析证实了 Manganonema 归入 Xyalidae，尽管与其他 Xyalidae 属的关系仍不清楚。Sphaerolaimidae 与 Monhysteridae 形成一个分支，这与目前的分类法相矛盾，在该分类法中，Sphaerolaimidae 和 Xyalidae 被归入 Sphaerolaimoidea 超科，而 Monhysteridae 归入 Monhysteroidea 超科。尽管迄今为止对克马德克海沟线虫多样性的研究有限，但现有数据表明，该海沟已知的所有无脊椎动物物种中有一半是线虫，这突出了在深海底栖环境中对该类群进行进一步分类研究的重要性。
