Characterisation of a new dorylaim, Crassolabium asiaticum n. sp. (Nematoda: Qudsianematidae) from Korea with remarks on its phylogenetic relationships

Summary – A new dorylaim nematode of the genus Crassolabium, isolated from the bark and wood of a dead black pine tree, was characterised using morphometric data and molecular DNA barcodes. Crassolabium asiaticum n. sp. is characterised by its medium-sized body, 1.69-2.17 mm (female) and 1.69-2.13 mm (male) long; lip region angular and distinctly offset, 16.5-18.5 μm broad; odontostyle 16.5-18.5 μm long, with aperture occupying about 37-45% of its length; vulva opening pre-equatorial, a transverse slit (V = 40.5-48.3); prominent pre- and post-vulval cuticular wrinkles or folds; short tail (21.5-29.0 μm long, c^′ = 0.7-0.9); spicules 53.5-60.5 μm long; and 11-14 nearly contiguous ventromedian supplements. The new species was compared with the morphologically close C. plica, C. persicum, C. diversum and C. gracile. The phylogenetic relationships among species were reconstructed using 18S and 28S rRNA gene sequences. The phylogenies showed well-supported relations of C. asiaticum n. sp. with mainly the member species of the family Dorylaimidae. In addition, the partial ITS rRNA gene sequences of C. asiaticum n. sp. were supplied, representing the first characterisation of the gene for the genus.