Morphological and molecular data of two species of the rare genera Thada Thorne, 1941 and Tenunemellus Siddiqi, 1986 (Nematoda: Tylenchidae) from Iran

Abstract

Thada populus n. sp. was found in the rhizosphere of Populus euphratica in the city of Dezful, south-western Iran. The new species is characterized by its 365–453 μm body length, cuticle with transverse annuli 0.9–1.2 μm wide, lateral fields with four lines, lip region low with one or two annuli, 7.0–8.5 μm wide at base, longitudinal or slightly sigmoid amphidial slit, delicate stylet 8.4–9.8 μm long with posteriorly directed knobs, dorsal pharyngeal gland opening at 1.0–1.5 μm posterior to the stylet knobs, non-muscular and valve-less median bulb, pyriform and offset basal bulb, almost oval spermatheca, posterior position of vulva (V = 75–79%) without lateral membrane, short post-vulval uterine sac and conical tail with finely to broadly rounded terminus. Morphological differences of the new species with those of the type species, Thada striata, are discussed. Molecular phylogenetic studies of the new species using partial sequences of small subunit ribosomal DNA revealed that the new species formed a clade with Malenchus spp., Filenchus facultativus, F. fungivorus and Filenchus sp. in Bayesian inference. Morphological and molecular phylogenetic studies were also performed on Tenunemellus indicus, the second recovered species, the latter analysis using partial sequences of large subunit ribosomal DNA. In the inferred Bayesian tree, T. indicus formed a clade with Labrys fuzhouensis, Lelenchus leptosoma from the Netherlands, Malenchus spp. and Filenchus discrepans.

Morphological and molecular characterization of two species of Neothada Khan, 1973 (Nematoda: Tylenchidae) from Iran, with notes on N. cancellata

“…Discopersicus iranicus (KM502982) and two sequences of Neopsilenchus (KP313832, JQ005018), other likely members of the subfamily Boleodorinae, are placed in other clades in the tree. According to Hosseinvand et al (2020c) , Thada forms a clade with Filenchus Andrássy, 1954 in the 18 S rDNA tree, which is not in agreement with the position of Thada along with Neothada in the subfamily Boleodorinae. We believe that in the subfamily Boleodorinae, the distance of dorsal esophageal gland orifice (DGO) from the stylet base and development of median bulb and stylet knobs are also important diagnostic characters as much as the shape of amphidial apertures.…”