Description and Molecular Characterization of a New Dorylaimid Nematode, Mesodorylaimus pini n. sp. (Nematoda: Dorylaimidae) from Korea

Mesodorylaimus pini n. sp., a new species isolated from the bark and cambium layer of a dead black pine tree is characterized herein using integrative taxonomy, considering both morphological and molecular phylogenetic analyses of the 18S- and 28S-rRNA genes. Mesodorylaimus pini n. sp. is characterized by having a medium-sized body 1.50–1.89 mm long; lip region angular and offset by a depression; a relatively long odontostyle (17.0–19.0 μm); vulval opening a transverse slit, positioned slightly posteriorly; pars refringens vaginae with two elongated drop-shaped to spindle-shaped sclerotizations; an intestine-prerectum junction with a long anteriorly directed conical or tongue-like projection; a relatively long female tail (115–187 μm); spicules 48.0–57.0 μm long; and regularly spaced 7–8 ventromedian supplements. It is closest to M. subtilis , especially in having similar body length and number of ventromedian supplements but can be differentiated from M. subtilis by the longer odontostyle, tongue-like projection, and longer spicules. The phylogenies based on the 18S- and 28S-rRNA sequences showed a well-supported sister relation of M. pini n. sp. with M. subtilis, M. japonicus, M. bastiani, M. pseudobastiani, Calcaridorylaimus castaneae, C. heynsi , and other member species of the group.