Description of a New Cryptic Rhabditid, Parasitorhabditis paraterebrana n. sp. (Nematoda: Rhabditidae), with Remarks on Two Known Species from Korea

A new cryptic species of the genus Parasitorhabditis isolated from the bark of a dead pine tree was characterized using morphological features, morphometrics, and DNA barcodes. Parasitorhabditis paraterebrana n. sp. is characterized by its stoma 20-24 μm in depth; tips of prorhabdions not bent inwards; metarhabdions with two subventral, and two subdorsal teeth; corpus longer than postcorpus; hemizonid 15.0-26.5 μm posterior to excretory pore; vulva-anus distance 21.5-31.5 μm, ca equal to or slightly less than vulval body diameter; rectum distinctly longer than anal body diameter; female tail cupola-shaped, conoid posteriorly, with an extended spike; male with slender spicules, nearly straight to minimally curved towards a nearly acute to a bluntly rounded tip; and bursa with 10 pairs of bursal rays, with a 2 + 3 + 2 + 3 typical pattern. It differs from the morphologically similar P. terebrana by the non-bent tips of prorhabdions, the corpus being longer than postcorpus, the bursal rays' pattern, and a more cupola-shaped tail in female and DNA barcodes. The DNA phylogenies using the 18S rRNA, 28S rRNA and COI gene markers showed well-supported sister relations of Parasitorhabditis paraterebrana n. sp. with P. terebrana and P. obtusa.