New deep-sea species of (Nematoda, Leptosomatidae) from the North-Western Pacific: an integrative taxonomy and phylogeny.

Marimermithid nematodes parasitising invertebrates are mainly found in the deep-sea environments. Several adult and juvenile specimens marimermithids of the genus have been found in bottom sediments and inside Polychaeta during recent cruises to the Kuril-Kamchatka trench and the Kuril Basin (the Sea of Okhotsk). New species are described based on integrative study. differs from by the location of the ventral gland cell bodies (posterior to the nerve ring vs posterior to the cardia), by the smaller body size (23-28 mm vs 103-132 mm) and shorter tail (193-263 µm vs 500-850 µm). BI and ML phylogenetic analyses based on 18S and 28S rDNA suggest that genus belongs to the family Leptosomatidae. Based on molecular and morphological characters the new genus is proposed for . Within the family Leptosomatidae the new genus differs from all genera except by its endoparasitic lifestyle and hologonic ovaries. differs from by the position of cephalic sensitive organs (outer labial and cephalic papillae in two separate circles vs outer labial and cephalic papillae in one circle) and by the parasitic adult (vs free-living in ).