مطالعه ریخت شناسی و فیلوژنی یک جمعیت ناشناخته از جنس Deladenus Thorne, 1941 (Nematoda: Neotylenchidae) از استان گلستان

The genus Deladenus belongs to the family Neotylenchidae, has two free-living (mycetophagous generation) and entomoparasitic (infective stage) generations and is distributed worldwide. An unknown population of this genus was recovered from a rhizospheric soil sample of a walnut tree collected in the forests of Ramian city, Golestan province. The free-living phase of this population is mainly characterized by having a long body (872–1034 µm), pharynx lacking a median bulb, with slight swelling at subcentral glands orifice level, 255-288 µm long with long dorsal gland overlapping, small lateral vulval flaps, no postvulval uterine sac (PUS) and conical tail with pointed terminus. It is further characterized by having seven lines in the lateral fields, short stylet (8.5 µm), pharyngo-intestinal junction at or anterior to nerve ring, secretory-excretory pore 11-20 µm posterior the hemizoid and no male. The studied population was not compatible with the currently known species of the genus and could be compared with six species namely D. apopkaetus, D. cocophilus, D. durus, D. tonekabonensis, D. albizicus and D. persicus (having six or seven lines in lateral field) and D. pakistanensis (by having lateral vulval flaps). In the molecular phylogenic analyses using small and large subunit ribosomal DNA sequences, the phylogenetic relationships of these two sequences with other previously deposited sequences were reconstructed using Bayesian approach and the resulted topologies were discussed. In accordance with several previous studies, the non-monophyletic nature of Deladenus was observed in resolved phylogenies. The non-monophyletic nature was also observed for several other genera of the suborder Hexatylina.