Description of a New Species of the Genus Deladenus Thorne, 1941 (Nematoda: Rhabditida: Neotylenchidae) from the City of Ramian, Golestan Province, a Morphological and Molecular Phylogenetic Study

A population of Deladenus, representing a new species, was recovered from a rhizospheric soil sample of a walnut tree collected in the forests of the city of Ramian, northeastern Iran. D. ramianensis sp. nov. is characterized by a moderately long body (872–1034 µm), a long distance from anterior end to dorsal pharyngeal gland end (255–288 µm), pharyngo-intestinal junction at nerve ring level, small lateral vulval flaps, absence of postvulval uterine sac (PUS) and tail short, conical, tapering uniformly towards the sharp tip. Additionally, it has a small-sized stylet (8.5 µm) with three knobs, a secretory-excretory pore (S-E pore) located posterior to nerve ring and behind hemizonid and seven lines in the lateral fields. The new species was compared with mycetophagous generation of all species of the genera Hexatylus, Deladenus and Rubzovinema. Based upon the position of the hemizonid, S-E pore, seven lines in the lateral fields, no pharyngeal chamber, no PUS and conical tail with the sharp tip, it is comparable to 12 species of the genus Deladenus, namely D. aridus, D. bonabensis, D. brevis, D. cocophilus, D. durus, D. parvus, D. pakistanensis, D. posteroporus, D. albizicus, D. apopkaetus, D. persicus and D. processus. In the molecular phylogenetic analyses using small and large subunits of ribosomal DNA (SSU and LSU D2-D3 rDNA) sequences, the newly generated SSU sequence of the new species formed a maximally supported clade with the SSU sequence of an unidentified tylenchid species and D. bonabensis. In the LSU phylogeny, the newly generated sequence of the new species formed a clade with the D2-D3 sequences of a sphaerularioid sp. and D. bonabensis.