Discotylenchus iranicus, Ghaemi, Razieh, Pourjam, Ebrahim, Atighi, Mohammad Reza, Pedram, Majid & Karssen, Gerrit, 2012

Ghaemi, Razieh, Pourjam, Ebrahim, Atighi, Mohammad Reza, Pedram, Majid & Karssen, Gerrit, 2012, First record of the genus Discotylenchus Siddiqi, 1980 (Nematoda: Tylenchidae) from Iran, with description of one new and data on two known species, Zootaxa 3493, pp. 72-82 : 73-74

Discotylenchus iranicus n. sp.

( Figs. 1 , 2 )

Measurements. See Table 1.

Morphological description.

Female. Body almost straight or slightly ventrally arcuate after heat relaxation. Cuticular annuli fine, 0.8–0.9 μm wide. Lateral field with four incisures, 3.5–4.5 μm wide at mid-body, approximately one-fifth as wide as body diameter. Lip region continuous and smooth, 6.5–7.5 μm broad, 3.5–5.0 μm high, tapering to an offset prominent labial disc, measuring 3.5 μm in diameter. Amphidial aperture minute, appearing as a longitudinal slit in lateral view, originating from the base of labial disc. Stylet long and thin; conus about 32–40 % of total stylet length; knobs rounded, 2.5–3.0 μm wide. Dorsal pharyngeal gland outlet 2–3 μm from base of stylet knobs. Metacorpus elongate, spindle-shaped with distinct central valvular apparatus and located at 37–41 % of total pharynx length. Isthmus elongated, slender. Basal bulb saccate, 41–43 μm long and 13–15 μm wide, not overlapping intestine. Excretory pore located posterior to hemizonid, 89–100 μm from anterior end. Deirids present, a little (five annuli, n=1) behind excretory pore level. Nerve ring enveloping isthmus at mid-point, 76–89 μm from anterior end. Vulva a transverse slit, flaps absent, vagina with thin walls, about one-half times corresponding body diameter, postuterine sac about 0.5–0.9 vulval body width. Reproductive system monodelphic-prodelphic with a single row of oocytes, 31–39 % of body length. Spermatheca almost oval, offset, functional with rounded sperm. Phasmids outside the lateral field, latero-subdorsal in position, 3.5 µm behind the vulval slit (n=1). Tail 6.8–10.0 times longer than anal body width, not filiform, conoid with a rounded tip.

Male. In general morphology similar to female, except for character states associated with sexual differences. Testis single, anteriorly outstretched and 235.6±30.0 (185–265) μm long. Spicules slender, ventrally arcuate. Gubernaculum simple, bursa adanal, 26–30 µm long.

Type habitat and locality. Recovered from the rhizosphere of corn ( Zea mays L.) in Kohgiluyeh and Boyer- Ahmad province, south-western Iran during October 2010.

Type material. Holotype female, one paratype female and four males deposited in the Nematode Collection of the Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran and one female and one male paratypes at Wageningen Nematode Collection, Plant Protection Service, Wageningen, the Netherlands.

Diagnosis and relationships. Discotylenchus iranicus n. sp. is characterized by its continuous and smooth lip region, tapering to an offset prominent labial disc, lateral field with four incisures, stylet length of 14–15 μm, vulva position at 70.8–76.5 %, tail length of 81–100 μm, conoid with a rounded tip tail and presence of functional male in population.

The new species comes close to Discotylenchus brevicaudatus , D. attenuatus and D. discretus . It differs from D. brevicaudatus by having a longer body (0.68–0.74 vs 0.32–0.39 mm), higher a ratio (35–39 vs 27–33), slightly smaller c ratio (7.0–9.2 vs 8.1–9.8), higher c' ratio (6.8–10 vs 4.5–6.0), longer stylet (14–15 vs 7–8 μm), longer tail (81–100 vs 35–47 μm), position of excretory pore (89–100 vs 55–58 μm from anterior end) and presence of functional males in population vs absence. From D. attenuatus , it differs by having longer body (0.6–0.7 vs 0.3–0.4 mm), higher a ratio (35–39 vs 25–33), higher c ratio (7.0–9.2 vs 4.1–5.0), posteriorly located vulva (V = 70.8–76.5 vs 60–64), longer stylet (14–15 vs 6.0–6.5 μm), longer spicules (18–21 vs 11–12 μm), gubernaculum length (5.0–6.5 vs 3.0–4.5 μm) and tail shape (conical with a rounded tip vs attenuated, filiform, with extremely thin end). Finally, the new species differs from D. discretus by having a longer body (0.68–0.74 vs 0.44–0.61 mm), higher c ratio (7.0–9.2 vs 5.0–6.2), posteriorly located vulva (V= 70.8– 76.5 vs 63–67), longer stylet (14–15 vs 7.0–7.5 μm), longer spicules (18–21 vs 11–13 μm), gubernaculum length (5.0–6.5 vs 3.5–4.0 μm) and tail shape (conical with a rounded tip vs gradually tapering, filiform).

Etymology. The specific epithet refers to Iran, the country where the new species was originally found.

TABLE 1. Morphometrics of Discotylenchus iranicus n. sp. All measurements are in μm, and in the form: mean ± s.d. (range). Holotype Paratype females Paratype males

Figures

FIGURE 1. Discotylenchus iranicus n. sp. A: Female entire body; B: Male entire body; C: Anterior end in detail; D, E: Male posterior end; F, G: Female tail; H: Pharyngeal region.

FIGURE 2. Discotylenchus iranicus n. sp. A – D: Morphology of lip region; E: Male posterior end; F: Bursa; G: Female tail; H: Part of pharyngeal region (all scale bars = 10 µm).