Two new oxystominid species (Nematoda: Enoplida) from an abyssal plain in the southern Philippine Sea

Abstract

Two new species of free-living marine nematodes, Litinium dispariseta sp. nov. and Wieseria minor sp. nov. are described from an abyssal plain with a water depth of 4117–5035 m near the Southern Kyushu-Palau Ridge in the tropical Western Pacific Ocean. Litinium dispariseta sp. nov. is characterized by having distinct inner labial setae two times longer than the outer labial setae, wrench-like amphideal foveas, a single preanal midventral supplementary seta and a short cylindrical tail with bluntly rounded tip. It differs from congeners by its distinctly long inner labial setae relative to the outer labial setae (two times longer vs shorter or equal in length) and peculiar wrench-like amphideal foveas (vs horseshoe shaped or ovoid with round to oval anterior aperture). Wieseria minor sp. nov. has a clavate tail, a character found only in the four congeners W. glandulosa (Kreis, 1929), W. longiseta (Allgén, 1947), W. clavata Gerlach, 1956 and W. inaequalis Gerlach, 1956. However, Wieseria minor sp. nov. differs from these congeners by its much smaller body size (1045 µm vs 2120–3125 µm) and oblong amphideal foveas with double contour (vs a single oblong or ovoid loop). An emended diagnosis for Wieseria and pictorial keys for Litinium and Wieseria are provided.