New deep-sea species of Aborjinia (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 Aborjinia 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. Aborjiniaprofundasp. nov. differs from A.eulagiscae 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 Aborjinia belongs to the family Leptosomatidae. Based on molecular and morphological characters the new genus Paraborjiniagen. nov. is proposed for A.corallicola. Within the family Leptosomatidae the new genus differs from all genera except Aborjinia by its endoparasitic lifestyle and hologonic ovaries. Paraborjiniagen. nov. differs from Aborjinia 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 Aborjinia).

Oloncholaimus piipi gen. et sp. nov. (Nematoda, Oncholaimidae) from Piip submarine volcano, the Bering Sea.

Oloncholaimus piipi gen. et sp. nov. is described from Piip submarine volcano, the Bering Sea. Oloncholaimus gen. nov. shows all main characters of Oncholaiminae: females monodelphic-prodelphic with antidromously reflexed ovary, three teeth with left ventrosublateral the largest, oncholaimoid type of Demanian system. New genus can be differentiated from all other genera of the family Oncholaimidae by the complex shape of dorsal and right ventrosublateral teeth with apical antler-shaped extension. Oloncholaimus piipi sp. nov. has large body (5960-7045 µm), six outer labial and four cephalic setae equal in size (5-7 µm), equal spicules (110-131 µm long) without gubernaculum, and complex precloacal supplementary organ composed of 8-9 cylindrical processes.

New species of Thoonchus (Enoplida, Enchelidiidae) from the Yellow Sea and redescription of T. giganticus Belogurova et al., 1986.

The family Enchelidiidae is recovered as monophyletic and appears to be a more recently derived taxon within the superfamily Oncholaimoidea. It combines nematodes with buccal cavity with three unequal teeth, crenate pharynx, and absence of demanian system. Genus Thoonchus was erected for nematodes characterized by the large buccal cavity with heavily cuticularized walls and several rows of denticles, short and arcuate spicules and gubernaculums with expanded corpus. One new species is described here from the Sishili Bay, located in the northern Yellow Sea. Thoonchus covidus sp. nov. is characterized by the body length 3195‒4339 µm, outer labial and cephalic setae in one circle, pocket shaped amphid above the buccal cavity base, secretory-excretory pore at the base of cephalic setae, arched spicules, gubernaculum with thin proximal extension parallel to spicules, preanal supplement absent, three pairs of preanal papillae. It differs from other congeners by the position of secretory-excretory pore, absence of supplementary organ in males and presence of three pairs of precloacal papillae. Redescription of T. giganticus is also provided. After critical evaluation of the genus we recognize 4 valid species and provide a taxonomic key to species.

Description of three new Sphaerolaimus species (Nematoda: Sphaerolaimidae) form the South China Sea.

The family Sphaerolaimidae Filipjev, 1918 combines nematodes characterized by finely striated cuticle, round amphids, broad buccal cavity with longitudinal ribs, and females with one anterior ovary. Sphaerolaimus Bastian, 1865 species from this family are found in intertidal and subtidal sediments and have also been reported from mangroves and estuary. Three new species of Sphaerolaimus were found and described from the South China Sea. Sphaerolaimus callisto sp. nov. is characterized by the relatively long body, small amphids and long spicules. Sphaerolaimus callisto sp. nov. is similar to S. cuneatus Paramonov, 1929, but differs by the longer body (2350-2690 µm vs 1980-1990 µm), index b (5.1-5.6 vs 3.9-4.1), absence of precolacal supplements, and longer spicules (321-356 µm vs 270 µm). Sphaerolaimus ganymede sp. nov. is characterized by large amphids and the presence of sexual dimorphism in amphid size. Sphaerolaimus ganymede sp. nov. is close to Sphaerolaimus maeoticus Filipjev, 1922, but differs by the presence of lateral alae, indexes a (12.3-17.5 vs 20-27) and c (7.9 vs 9-10), bigger amphids in male (14.6-15.7 µm vs 11 µm). Sphaerolaimus io sp. nov. is characterized by small amphids and short apophyses of gubernaculum. Sphaerolaimus io sp. nov. is similar to Sphaerolaimus pacificus Allgen, 1947, but differs by bigger size (1480-1525 µm vs 1140 µm), presence of lateral alae, and index c (7.5-8 µm vs 14.3 µm). After critical evaluation of the genus we recognize 35 valid species and provide dichotomous and pictorial keys to species.

Revision of the genus Parasphaerolaimus (Nematoda: Sphaerolaimidae) with description of new species.

The family Sphaerolaimidae Filipjev, 1918 includes nematodes that are characterized by the finely striated cuticle, round amphids, broad buccal cavity with longitudinal ribs, and single anterior ovary in females. Parasphaerolaimus species from this family are found in intertidal and subtidal sediments and have also been reported from mangroves and estuaries. Parasphaerolaimus pilosus sp. n. is characterized by the moderately plump body, presence of lateral alae, long cervical setae, small amphids in males, and relatively short spicules. As a result of a comprehensive evaluation of species descriptions, eight species in the genus Parasphaerolaimus are recognized valid, and an identification key to species level is provided.

Description of new species of Phanodermopsis (Enoplida, Phanodermatidae) with key to genera of family Phanodermatidae and pictorial key to Phanodermopsis species.

A new representative of the family Phanodermatidae, Phanodermopsis nana sp. n., is described. The new species is found in the Sea of Japan and characterized by its small body size, long anterior sensilla and short tail. The new species differs from P. ingrami in body length (~ 7000 µm in P. ingrami vs ~ 3000 µm in P. nana sp. n.). The De Man's ratios (a, b, c) are smaller in P. nana sp. n. and the outer labial setae are longer (1 corresponding body diameter) than in P. ingrami (1/2 corresponding body diameter). The vulva is more posterior in P. ingrami (V% = 58-61%) than in P. nana sp. n. (V% = 51-58%). A dichotomous key to the 9 valid genera of Phanodermatidae and a pictorial key to species of Phanodermopsis are provided. The length of the spicules is proposed as the main differentiating feature for distinguishing Phanodermopsis and Crenopharynx species. Phanodermopsis longisetae Chitwood, 1936 which has extremely long spicules (5.2 anal body diameters) is transferred to the genus Crenopharynx.