Trischistoma abharensis n. sp.

(Figs 1‒3)

Measurements. See Table 1.

Material examined. Holotype female and two paratype females deposited in Nematode Collection of the Faculty of Agriculture, University of Zanjan, Zanjan, Iran (slide no, N4–1, N4–2). Two paratype females deposited at the National Nematode Collection, New Zealand (NNCNZ).

Description. Female (n = 9). Body slender, bent dorsad mainly in the posterior part after heat relaxation (Fig. 1 E). Cuticle very thin, 1–2 Μm thick, apparently smooth under light microscopy (LM) but fine transverse striations seen with SEM, with sparse somatic setae on the sublateral body. Labial region broadly rounded, slightly offset, 12.3 ± 0.5 (12–13) Μm diameter. SEM and LM micrographs (Figs 2 A,B; 3A‒C) show: three triangular lips, labial papillae short and conical, outer labial and cephalic setae in two whorls, six longer setae (outer labial) 6.7 ± 0.4 (6.0–7.5) Μm long, 50–58% of head diameter long, more or less arcuate and directed anteriorly, four shorter setae (cephalic setae) 5.2 ± 0.3 (4.5–6) Μm, 38–46% of head diameter long, thinner than the outer labial setae, more or less arcuate. Ventral cervical setae absent but a pair of thin sublateral setae placed at about half (51–59%) the pharynx length (Fig. 1 C), 144 ± 7.4 (135–153) Μm from anterior end. Amphid small, calyciform, 18.5 ± 0.9 (18– 20) Μm from anterior end. Mouth cavity narrow, dorsal tooth distinct, 17.6 ± 1.1 (16–19) Μm from anterior end of body, subventral tooth not seen or difficult to observe. (Figs 1 A,B; 2C). Pharynx cylindrical, strongly muscular. Cardia small, disc-like (Fig. 2 D). No glands between pharynx and intestine observed. Coelomocytes not seen.

Genital tract mono-prodelphic, 332–397 Μm long, reflexed anteriorly, tip not reaching vulva. Distance between posterior end of pharynx and vulva 2.7–3.0 times longer than pharynx. Vulval lips not sclerotized, vagina short, less than one third body diameter and surrounded by muscular tube (Fig. 2 F). Post-vulval uterine sac absent. Vulvaanus distance 2.6 ± 0.2 (1.9–4.0) tail lengths. Rectum almost as long as anal body diameter (Fig. 2 G). Tail 74 ± 3.5 (60–87) Μm long, conoid, and dorsally bent, with one pair subdorsal caudal setae (Fig. 3 G). Three caudal glands, spinneret small.

Male. Not found.

Type habitat and locality. The new species was extracted from the rhizosphere of grapevines, in Abhar, Zanjan province, Iran (GPS coordinates: 36° 6ʹ 22.03" N, 49° 16ʹ 28.65" E). All specimens were collected by the last author during July-August 2013.

Diagnosis and Relationships. Trischistoma abharensis n. sp. is characterised by having females with body length of 1069–1322 Μm; sparse somatic setae on the sublateral body; absence of ventromedian cervical setae; a distinct dorsal tooth directed anteriorly; absence of post-vulval uterine sac (PVS); and a pair of caudal setae on the tail. Males were not found, suggesting that they are either rare or absent.

The species in the genus Trischistoma are divided into two groups with or without a PVS (Table 2). Trischistoma abharensis n. sp. belongs to the second group (i. e. without a PVS), containing T. waiotama, T. pellucidum, T. tukorehe and T. gracile .

Trischistoma abharensis n. sp. is morphologically similar to T. gracile, but it can be separated by having slightly longer body length (1069–1322 vs 1000–1100 Μm), more slender body (a = 53.5–62.6 vs 49–53), longer pharynx (240–266 vs 205–216 Μm), the location of the dorsal tooth: (posterior to cephalic setae and 16–19 Μm from the anterior end vs opposite to cephalic setae and 12 Μm from the anterior end), distinct dorsal tooth vs indistinct or minute dorsal tooth, having sparse somatic setae on the body vs absent; and a pair of caudal setae on the tail vs absent.

The new species differs from T. waiotama by having a longer body length (1069–1322 vs 675–908 Μm) and more slender body shape (a = 53.5–62.6 vs 32–41), longer pharynx (240–266 vs 171–198 Μm), posterior position of dorsal tooth (16–19 vs 13–15 Μm from anterior end), tail length (60–87 vs 50–64 Μm), ventral cervical seta (absent vs present), lateral cervical seta (or somatic seta) in the cervical region (present vs absent). It can be separated from T. pellucidum by its longer body length (1069–1322 vs 600–800 Μm) and more slender body (a = 53.5–62.6 vs 36– 43), longer pharynx (240–266 vs 155 Μm), having a distinct dorsal tooth vs a minute dorsal tooth, lateral cervical seta (or somatic seta) in the cervical region (present vs unknown) and tail length (78–87 vs 50–60 Μm). It also differs from T. tukorehe by having a more slender body (a = 53.5–62.6 vs 38.5–47.1), number of dorsal tooth (one vs two), lateral cervical seta (or somatic seta) in the cervical region (present vs absent).

The new species lacks a post-vulval uterine sac and differs from the species possessing this character viz: T. monohystera, T. equatoriale, T. otaika, T. subtilissimum, T. tenuissimum and T. veracruzense .

Etymology. Species epithet refers to the city of Abhar, where the type specimen was collected.