Two new and one known deep-sea Comesomatidae Filipjev, 1918 species (Nematoda: Araeolaimida) from New Zealand’s continental margin

Abstract

One new Sabatieria Rouville, 1903 and one new Hopperia Vitiello, 1969 species are described from Conway Trough off the east coast of New Zealand’s South Island based on light and scanning electron microscope observations and SSU and D2-D3 of LSU molecular sequences. Additional morphological observations and molecular sequence data are also provided for Vasostoma hexodontium Rosli, Leduc & Probert, 2014. Sabatieria articulata sp. nov. belongs to the Praedatrix group and differs from all other species of the genus in having jointed spicules. Hopperia novazelandica sp. nov. is characterized by a relatively stout body, cephalic setae 0.2–0.3 corresponding body diameter long, amphideal fovea with 3.0 turns in males and 2.2–2.5 turns in females, buccal cavity with three teeth, spicules 2.3–2.5 cloacal body diameters long, presence of 19 precloacal supplements, and conico-cylindrical tail with swollen tip and terminal setae. Scanning electron microscopy observations show that the outer cuticle surface of V. hexodontium is smooth and that the inner labial papillae are slightly larger than the outer labial papillae. The SSU consensus tree could not resolve relationships among most Comesomatidae Filipjev, 1918 species and genera included in our analysis. Analyses based on D2-D3 of LSU sequences suggest that Sabatieria, Hopperia, and Dorylaimopsis are not monophyletic; instead, species/genera from the same region tended to cluster together, suggesting that features that characterize the genera Hopperia and Dorylaimopsis, such as a buccal cavity with teeth and an expanded posterior portion, have evolved multiple times independently, possibly from a Sabatieria-like ancestor. This hypothesis, however, will have to be tested using more comprehensive molecular datasets.