Summary Synonchium iranicum sp. n. and Richtersia bispinata sp. n. are described from the Persian Gulf and their relationships investigated using SSU phylogenetic analyses. Synonchium iranicum sp. n. is characterised by a buccal cavity with three equally sized mandibles, each with five small teeth, a rounded tail with three distinct caudal glands and distinct duct, males without gubernaculum and supplements, and short spicules. Richtersia bispinata sp. n. is characterised by multispiral amphids with 3.0-3.5 turns in males and 2.0-2.5 turns in females, cuticle with numerous, irregularly arranged, simple spines in the cervical region, 20-25 longitudinal rows of double spines in the mid-body region, 15-25 longitudinal rows of simple spines in the tail region, and the left spicule markedly longer than the right one. We provided the first near-full-length small subunit ribosomal DNA (SSU rDNA) sequences for both newly described species, as well as cytochrome c oxidase I (COI), and provided D2-D3 expansion segments of large subunit ribosomal DNA (LSU rDNA) sequence for the new species of Richtersia. Our SSU phylogenetic analyses confirmed the placement of Synonchium iranicum sp. n. within the Selachinematidae, and suggested that the selachinematids may form a distinct clade from other chromadorids Our phylogenetic analyses indicated that Richtersia should not be classified within the Selachinematidae as suggested by some authors. Instead, we propose that Richtersia should be placed within the Desmodorida. Although Richtersia differs from Desmodorida in the arrangement of cephalic sensilla, it shares the golden body colouration characteristic of desmodorids in glycerin preparations, the same structure of genital branches in both males and females, and similar cuticular ornamentation to some desmodorid genera (notably Desmodorella).

Summary Sigmolenchus n. gen., is proposed as a new member of the Tylenchidae. The new genus is proposed based upon light and scanning electron microscopic (LM and SEM) observations and phylogenetic analyses based upon small, large and internal transcribed spacer sequences of ribosomal DNA (SSU, LSU D2-D3, ITS rDNA) and mitochondrial cytochrome c oxidase I gene (COI mtDNA) sequences. It is characterised partly by its slender body, but mainly by having a dorso-ventrally flattened, smooth and elevated cephalic region, unique elongate sinuous amphidial openings, each appearing as a wavy slit with three peaks, originating from the vicinity of the labial plate, extending posteriorly and reaching and passing the first body annulus, and a spacious amphidial fovea. It has an anteriorly rounded outline under LM, knobbed stylet, its conus comprising about one-third of the total length, lateral field with a single band, metacorpus with a distinct valve, vulva with small lateral flaps, and males common with tylenchoidiform spicules. The new genus is morphologically compared with seven tylenchid genera, viz., Chilenchus, Ecphyadophoroides, Filenchus, Labrys, Lelenchus, Sakia, and Tenunemellus, mainly by having small slender body and dorso-ventrally flat cephalic region, and is placed under the subfamily Ecphyadophorinae because of its slender body, elevated smooth cephalic region, long amphidial openings and spacious amphidial fovea. It was recovered from marine muddy sediments taken 2 m deep in mangrove forests off southern Iran. Currently S. sinuosus n. gen., n. sp. is monotypic. In SSU phylogeny, the new genus formed an unsupported sister relationship with Filenchus discrepans, and in LSU phylogeny it occupied a placement inside a major clade including several Tylenchinae genera.

Summary The Desmodoridae is a diverse and widespread family of free-living nematodes. Here, we provide the first record of the group in the Persian Gulf and describe three new species: Metachromadoroides sinuspersici sp. n., Zalonema iranicum sp. n. and Z. supplementorum sp. n. Metachromadoroides sinuspersici sp. n. is characterised by finely annulated cuticle, short and stout cephalic sensilla, amphidial fovea on cuticular thickening, pharyngeal bulb well developed and partitioned into three sections, absence of precloacal supplements, and presence of 6-8 pairs of rounded postcloacal papillae. Zalonema iranicum sp. n. is characterised by papilliform subcephalic sensilla (best observed with SEM), convex cephalic capsule, large multispiral amphidial fovea with 4-5 turns in both males and females, buccal cavity with one ventrosublateral and two dorsal teeth and posterior body of males with lateral alae extending from the last third of the body to the cloacal aperture and ventral alae extending 1395-2250 μm anterior to the cloacal aperture, and no precloacal supplements. Zalonema supplementorum sp. n. is characterised by four subcephalic sensilla 1-2 μm long, multispiral amphidial fovea with three turns in both males and females, buccal cavity with one dorsal and two ventrosublateral teeth, males with lateral alae present on each side of body from posterior half of body to cloacal aperture, ventral alae extending 942-1257 μm anterior to cloacal aperture, strongly cuticularised spicules 41-43 μm long, and 12-16 precloacal supplements. Near full length SSU and partial D2-D3 LSU sequences are provided for M. sinuspersici sp. n. and Z. iranicum sp. n., and the COI sequence is provided for Z. iranicum. The SSU phylogeny suggests a close relationship between M. sinuspersici sp. n. and Metachromadora and Metachromadoroides species and the monophyly of Zalonema (after currently available data). The LSU phylogeny suggests an affinity between Metachromadoroides and Zalonema with Spirinia and Acanthopharynx, respectively.

Summary Members of the family Leptolaimidae are reported for the first time from Iran with description of two new species of Leptolaimus from the Persian Gulf in the south of the country. Leptolaimus hormozganensis sp. n. is described based upon three populations. It differs from other Leptolaimus species in the position of the pharyngeal supplement and the number of precloacal tubular supplements and has a single sickle-shaped tubular pharyngeal supplement at mid-pharynx level in both sexes, 9-12 male precloacal supplements and one female preanal supplement. Leptolaimus dimorphus sp. n. is characterised by the presence of a pharyngeal tubular supplement only in some adults, one female preanal supplement and four male precloacal supplements. It differs from other species in that the pharyngeal supplement is only present in some specimens, presence of four male precloacal supplements, tail 50-59 μm long and ventrosublateral position of vulva on either the right or left side of the body. Near full length SSU rDNA sequences are provided for L. hormozganensis sp. n. and two different males (one with, and one without, a pharyngeal supplement) of L. dimorphus sp. n. COI sequences for three populations of L. hormozganensis sp. n. from different regions of the Persian Gulf are also obtained. New sequences of two Leptolaimus species formed a clade with other sequenced Leptolaimus spp. and representatives of two genera of Leptolaimidae, i.e., Aphanolaimus and Paraplectonema in a phylogeny based on SSU rDNA gene with 1.00/81 Bayesian posterior probability/maximum likelihood bootstrap (BPP/BS) values. Molecular phylogeny confirmed the synonymy of Leptolaimus and Halaphanolaimus that was formerly proposed based only on morphology. Based on SSU sequences and morphological characters, the presence of a pharyngeal supplement may not be a species-specific character and should not be used to differentiate genera.

An infestation of mangrove forests with Neodolichodorus persiangulfus n. sp. in southern Iran is reported. This paper is the first to report a representative species of the genus in the country. The new species was characterized by 2,120 (1795-2400) µm long females, and 1755 (1533-2019) µm long males, a continuous to slightly offset cephalic region separated from the rest of the body by a shallow depression, having 5-7 annuli and a distinct labial plate, a lateral field with four lines, the outer ones crenate, irregularly areolated in anterior and posterior body region, 79 (66-85) μm long female stylet, a didelphic-amphidelphic female reproductive system with asymmetric sclerotized vaginae, phasmids 5-10 annuli behind the anus, female tail elongate conoid, suddenly narrowing at 5-12 annuli posterior to anus and males with trilobed bursa, 52.5 (47-58) μm long spicules and 21.5 (18-27) μm gubernaculum. With the elongate-conoid female tail and cʹ >1.2, the new species is close to five known species of the genus: N. brevistylus, N. leiocephalus, N. paralongicaudatus, N. rageshi and N. sinensis, but is distinguished from them by the morphology of the female tail, areolation type of the lateral field, position of hemizonid and phasmid and morphometric data. Molecular phylogenetic analyses using sequences of the near full-length fragment of the small and the D2-D3 expansion segments of the large subunit ribosomal DNA (SSU and LSU rDNA D2-D3) revealed the new species placed in a clade including one isolate of Neodolichodorus sp. and some species of Globodera, Heterodera and Rotylenchulus with 0.89 Bayesian posterior probability (BPP) in SSU phylogeny. The only available SSU sequence of the genus was the tentative closest relative to the new species in the inferred SSU tree. In the reconstructed LSU phylogenetic tree, N. persiangulfus n. sp. formed a poorly supported clade with Rotylenchulus spp. in Bayesian inference (BI), and the only other available D2-D3 sequence of the genus occupied a distant placement to the new species. K E Y W O R D S Bayesian inference, description, LSU rDNA D2-D3, mangrove forests, phylogenetic analyses, SSU rDNA | INTRODUC TI ONMangroves are woody plants growing in tidal zones between land and sea in tropical and subtropical latitudes. They include many associated prokaryotes, fungi, plants and animals that constitute the term of "mangrove forest community" or "mangal." The mangal and its associated abiotic factors constitute the mangrove ecosystem (Kathiresan & Bingam, 2001). According to Rise, Prabhu,