New free-living nematode species and records (Chromadorea: Plectida and Desmodorida) from the edge and axis of Kermadec Trench, Southwest Pacific Ocean.

One new nematode species is described and two new species records are provided from the edge (6,080 m depth) and axis (7,132 m) of Kermadec Trench, Southwest Pacific. sp. nov. is characterised by medium body 587-741 μm long, labial region not offset from body contour, inconspicuous labial sensilla, amphid located 12-19 μm from anterior end, female without supplements, male with four tubular precloacal supplements (alveolar supplements absent), tubular supplements almost straight with dentate tip, arcuate spicules and weakly cuticularized dorsal gubernacular apophyses strongly bent distally. In a previously published ecological survey of Kermadec Trench, sp. nov. was the most abundant species in a core obtained at 8,079 m water depth and third most abundant species in a core obtained at 7,132 m, while only one individual was found at 6,096 m depth, and none at 9,175 m depth (Leduc & Rowden, 2018). and are recorded for the first time from the Southwest Pacific region. Prior to the present study, had only been recorded from coastal locations and from the Weddell sea to a depth of 2,000 m. The record of at 6,080 m depth is the deepest record of a species to date, although unidentified specimens have been found as deep as 6,300 m in the South Sandwich Trench. The morphology of the Kermadec Trench and specimens bear a strong resemblance to their respective type populations from the Northern Hemisphere, but further morphological and molecular data are required to ascertain whether they in fact represent distinct species.