Labrys filiformis n. sp., the second species of the rare genus Labrys, was recovered from natural forests of Gilan province and is described based upon morphological and molecular characters. The new species is characterized by its smooth cuticle under light microscopy, lateral field with two incisures forming a single plain band, lip region continuous with body contour, dorso-ventrally flattened and forming four poorly prominent lobes, having a dorso-ventrally narrower protuberant labial plate laterally extended to the amphidial margins, oral area (oral plate) dorso-ventrally elongated and embedded in the labial plate with six small labial sensilla surrounding the slightly prominent oral aperture, amphidial apertures as longitudinally lemniscatic slits bordered by the labial plate extensions which are overlapped at the middle length of amphids, stylet delicate, 6 to 7 µm long, elongate weakly developed fusiform median bulb with weak valve, wide excretory pore with long and heavily sclerotized duct, offset spermatheca filled with small spheroid sperm cells, 106 to 127 µm long elongate-conoid tail with filiform distal region and finely rounded tip. Molecular phylogenetic analyses were performed using a near-full length fragment of the 18S rDNA and the D2-D3 expansion segments of the 28S rDNA using Bayesian inference and maximum likelihood methods. In the inferred phylogenetic tree with 18S rDNA, the new species has a close affinity with several isolates of the type species, Labrys chinensis. The reconstructed phylogenetic tree using partial 28S rDNA, revealed the new species is nested inside the putative monophyletic group of several populations of L. chinensis.

Three species belonging to the family Tylenchidae, Malenchus nanellus, M. undulatus and Tylenchus naranensis, are reported for the first time for Iran. These species are characterized based on morphological and morphometric data. The Iranian population of M. nanellus is characterized by its body length ranging from 410-485 μm, cuticle annuli 1.1- 1.5 μm wide at mid-body and lateral field with two crenate lines, starting at the mid-region of procorpus and ending near 1/3 of tail length. The population of M. undulatus is characterized by its 458-526 μm body length, cuticle coarsely annulated, annuli 1.8-2.4 μm wide at mid-body, lateral field with crenate incisures, beginning at about half of the stylet length, ending at middle of tail, head narrower than adjacent body, median bulb well developed with prominent valve plates and functional males in population. Iranian population of T. naranensis, is characterized by having a 631-774 μm body length, lateral field with four lines, outer lines crenate, a stylet length ranging from 10-11 μm and a tail of 102-131 μm long. Molecular phylogenetic analyses based on partial 28S rDNA sequences of T. naranensis revealed its close affinity with the genus Filenchus. Other Tylenchidae genera, such as Aglenchus (including the newly sequenced isolate from Iran) and Coslenchus were sister taxa and formed a well-supported clade. Malenchus exiguus, a previously reported species from Iran and sequenced in the present study, formed a monophyletic clade with other species of Malenchus and Lelenchus leptosoma.

Summary The genus Sakia is recorded from Iran for the first time and Sakia arboris n. sp., recovered from two geographical points in northern Iran, is described. The new species is characterised by its smooth cuticle under light microscopy (LM), absence of lateral fields, head continuous with body contour, flattened lip region, 9.3 (9.0-10.0) μm long stylet, vulva at 60.2 (59.3-61.3)%, bilobed spermatheca, 117 (102-128) μm long tail, and 14.3 (14-15) μm long spicules. By lacking lateral fields, the new species comes close to three known species of the genus, namely: S. alii, S. castori and S. indica. Molecular phylogenetic analyses using sequences of the near full-length fragment of the small subunit of ribosomal DNA (18S rDNA) and the D2-D3 expansion segments of the large subunit ribosomal DNA (28S rDNA) were performed using Bayesian inference (BI) and maximum likelihood (ML) methods. In the reconstructed Bayesian tree using the 18S rDNA sequence of the type population, the new species occupied a position in a clade including two isolates of Sakia sp. and some species of Lelenchus, with maximal BPP and high ML BS values (1.00/99%). In the reconstructed 28S rDNA phylogenetic tree, two newly sequenced isolates of S. arboris n. sp. formed a well-supported clade with Lelenchus spp.

Labrys khuzestanensis n. sp. was recovered from the rhizosphere of a palm tree in southwestern Iran and described using morphological and molecular data. The new species was characterized by combination of the following features: its 590–675 μm long body, finely annulated cuticle in light microscopy (LM), lateral field with two smooth incisures, cephalic region dorso-ventrally flattened with protuberant, elongate and laterally extended labial plate, appearing a V-shaped piece in lateral view, amphidial openings as longitudinal slits confined to labial plate in scanning electron microscopic (SEM) images, stylet 7.5–9.0 μm long, elongated fusiform median bulb with faint valvular apparatus, excretory pore wide with moderately sclerotized duct and elongate filiform tail with finely rounded tip. Compared to four currently known species under the genus, the new species has a remarkably larger and more prominent labial plate as revealed by SEM and trapezoid cephalic region under LM. The molecular phylogenetic analyses of the new species using partial SSU rDNA revealed it has close affinity with three species of Labrys (L. chinensis, L. fuzhouensis and L. filiformis) in Bayesian inference (BI) and maximum likelihood (ML) methods and occupied a placement inside their clade. L. fujianensis, the other species of the genus, occupied a distant placement to the aforementioned clade. This is the second species of Labrys being originally described from Iran, representing the third species of Labrys occurring in the country.

Data on five known species of the genus Coslenchus are provided. Morphological and morphometric data are given for all studied species. Three of the recovered species were also characterized by molecular phylogenetic data. The species C. leiocephalus was studied for the first time since its original description. Males of the species, C. franklinae and C. oligogyrus were described for the first time and the species C. oligogyrus was reported from Iran for the first time. In molecular phylogenetic studies based on partial sequences of 28S rDNA D2/D3 fragments, all species formed a clade with high Bayesian posterior probability in Bayesian inference, indicating the monophyly of the genus. The clade of Coslenchus spp. formed a highly supported monophyletic group, a sister clade to two species of the genus Aglenchus.