Three populations of Xiphinema primum n. sp. and two populations of X . pachtaicum were recovered from natural forests and cultural regions of northern Iran. Both species belong to the X . americanum -group and were characterized by their morphological, morphometric and molecular data. The new species, which was recovered in three locations, belongs to the X . brevicolle -complex and is characterized by 2124–2981 μm long females with a widely rounded lip region separated from the rest of the body by a depression, 103–125 μm long odontostyle, two equally developed genital branches with endosymbiont bacteria inside the ovary, which are visible under light microscope (LM), vulva located at 51.8–58.0%, the tail is 26–37 μm long with a bluntly rounded end and four juvenile developmental stages. It was morphologically compared with nine similar species viz . X . brevicolle , X . diffusum , X . incognitum , X . himalayense , X . luci , X . parabrevicolle , X . paramonovi , X . parataylori and X . taylori . The second species, X . pachtaicum , was recovered in two geographically distant points close to city of Amol. Molecular phylogenetic studies of the new species were performed using partial sequences of the D2-D3 expansion segments of the large subunit ribosomal RNA gene (LSU rDNA D2-D3), the internal-transcribed spacer rDNA (ITS = ITS1+5.8S+ITS2), and the mitochondrial cytochrome c oxidase I gene ( COI mtDNA) regions. The Iranian population of X . pachtaicum was also phylogenetically studied based upon its LSU rDNA D2-D3 sequences. Both species were also inspected for their putative endosymbiont bacteria. Candidatus Xiphinematobacter sp. was detected from two examined populations of the new species, whereas the second endosymbiont bacterium, detected from three examined isolates of X . pachtaicum , was related to the plant and fungal endosymbionts of the family Burkholderiaceae. The phylogenetic analyses of the two endosymbiont bacteria were performed using partial sequences of 16S rDNA. In cophylogenetic analyses, significant levels of cophylogenetic signal were observed using both LSU rDNA D2-D3 and COI mtDNA markers of the host nematodes and 16S rDNA marker of the endosymbiont bacteria.

Aphelenchoides primadentusn. sp. is described and illustrated based on its morphological, morphometric and molecular characters. It was recovered from natural forests of northern Iran in association with mosses. The new species is characterised by its body length of 502-613μm in females and 461-564μm in males, presence of three lines in the lateral fields, a low lip region slightly offset by a shallow depression, 11.1-13.8μm long stylet in females, its conus being longer than the shaft (m = 53.0-68.5) and bearing well-developed, rounded basal knobs, the excretory pore located atcaone body diam. posterior to the metacorpus, a conical tail with a multipapillate terminus or with a single, warty, wide mucron-like structure at the tip, and males with 19-22μm long arcuate spicules that lack a well-developed condylus and rostrum. The new species was morphologically compared with species of the genus having three lines in the lateral field and a multipapillate tail tip or tail with warty mucron, namelyA. iranicusandA. heidelbergi. Compared toA. ensete,A. huntensisandA. gorganensis, three species with a multipapillate tail tip or warty mucron at the tail tip, the new species has a basic difference in the number of lines in the lateral field and, compared to two species,A. composticolaandA. petersi, which have three lines in the lateral field and a similar overall morphology, the new species has basic differences in tail tip morphology. The results of phylogenetic analyses using partial sequences of ribosomal small subunit RNA (SSU) and mitochondrial cytochrome c oxidase 1 (COImtDNA) genes revealed there is currently no sequenced species of the genus phylogenetically close to the new species being sequenced for these two genomic and non-genomic regions. The new species forms a clade withA. ritzemabosiin SSU, and three other species,A. besseyi,A. ritzemabosiandA. fujianensis, in theCOItree.

Malenchus geraerti n. sp., recovered from natural regions of northern Iran, is described and illustrated based on morphological, morphometric and molecular data. The new species is characterized by having females with a short body, an anteriorly wide S-shaped amphidial opening narrowing posteriorly, cuticle with prominent annuli, lateral field a plain band with smooth margins, muscular metacorpus with well-developed valve and corresponding plates, spermatheca filled with small spheroid sperm cells, vulva sunken in body with large epiptygma and no flap, and conical tail tapering gradually to a more or less pointed tip. Males of the new species are characterized by having a short body, tylenchoid spicules, adcloacal bursa with smooth margin and tail similar to that of the female. Morphologically, the new species is similar to five known species of the genus: M. fusiformis, M. machadoi, M. pachycephalus, M. solovjovae and M. undulatus. It most closely resembles M. pachycephalus, but as a cryptic species it can be differentiated using morphological and molecular characteristics. Comparisons with the four other aforementioned species are also discussed. Molecular phylogenetic studies using partial sequences of small and large subunit ribosomal DNA fragments reveal that the new species forms a clade with the species M. neosulcus in the small subunit (SSU) rDNA, and two species of Lelenchus in the large subunit (LSU) rDNA tree.

Anguillonema amolensis n. sp. is described and illustrated based on its morphological, morphometric, and molecular characters. The new species is characterized by its 575 to 820 mm long and wide body (body width at vulva = 30 to 59 mm), irregularly ventrally curved after fixation, five to six lines in lateral fields, 6.0 to 7.5 mm long stylet with small rounded knobs, pharynx lacking a median bulb, pharyngo-intestinal junction anterior to nerve ring and excretory pore, females with monodelphic-prodelphic reproductive system, 15 to 19 mm long conical tail with broad rounded tip, and males absent. The new species is compared with two known species of the genus, Anguillonema poligraphi and A. crenati. Molecular phylogenetic studies of the new species using partial sequences of small subunit (SSU) rDNA revealed that it forms a clade with an unidentified nematode species and two species of the genus Howardula. In phylogenetic analyses using partial sequences of the 28S rDNA (D2-D3 segment), the new species formed a monophyletic group with species belonging to two genera Howardula and Parasitylenchus.

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