Description of Prionchulus girchi sp. nov. (Nematoda: Mononchina) with additional data on two known species of the genus Prionchulus from Lorestan province, Iran

Mononchid nematodes as a group sensitive to habitats disturbances are considered as indicators of ecological changes (Johnson, et al. 1974; Bongers, 1990). The order Mononchida has been proposed by Jairajpuri (1969), which include two superfamily and forty-nine genera (Ahmad & Jairajpuri, 2010). The genus Prionchulus comprises of more than thirty three species, which have been described from various parts of the world (Jana et al., 2010; Vu et al., 2018; Winiszewska & Susulovsky, 2003; Zell, 1985), but only three species of this genus have been described and reported from Iran (Ghaderi et al., 2012; Naghavi et al., 2017). Prionchulus species are characterized by large and barrel-shaped buccal cavity, dorsal tooth stout, situated in anterior half of buccal cavity, opposed subventral denticulate ridges, pharyngo-intestinal junction non-tuberculate, female genital system amphidelphic (Ahmad & Jairajpuri, 2010). In this study P. girchi sp. nov. and two other known species viz. P. fagi and P. muscorum have been collected

and studied using a discriminant analysis based on their most important morphological characters within this genus of Mononchids in Khorramabad County, Lorestan province, Iran.

Nematode surveys were conducted from 2017 to 2018 in natural ecosystem of Khorramabad County, Lorestan province, south west of Iran. Soil samples were collected from the 5 – 30 cm depth of forest soils and processed in the Laboratory of nematology in Lorestan University, Khorramabad, Iran. Nematodes were extracted from 250 cm³ of soil samples, adapting Brown & Boag (1987) modified method. Specimens to be used for light microscopy studies were killed and transferred to dehydrated glycerin, and then permanent microscopic slides of the nematodes were prepared. Morphological and morphometric characters of nematodes were examined and photographed using an Olympus Bx31 light microscope equipped with a Dino-eye microscope eye-piece camera in conjunction with Dino Capture version 2.0 software. Raw photographs were edited using Adobe® Photoshop^® CS. Drawing and photoplate were prepared by Corel DRAW^®, software version 12. Nematodes were identified at specific level using available identification keys (Ahmad & Jairajpuri, 2010 and Jana et al., 2010).

The conducted research is neither related to human nor animals use.

Prionchulus girchi sp. nov.

(Figs. 1, 2)

Fig. 1

Fig. 2

Measurements

See table 1.

The new species collected from Chenar shureh village, Khorramabad County, Lorestan province, Southwest Iran, (GPS coordinates: N 33º 14′ 47′′ E 48º 46′ 59′′, altitude 1790 m a.s.l.), in the rhizosphere of Hawthorn (Crataegus aronia L.) and from Imanabad village, Azna area, Khorramabad County, Lorestan province, Southwest Iran, (GPS coordinates: N 33º 23′ 11′′ E 48º 36′ 16′′, altitude 1661 m a.s.l.), in the rhizosphere of Oak (Quercus libani L.).

Type material

Holotype and paratype females deposited in the Collection of the Nematology Laboratory, Lorestan University.

The new species is characterized by a medium body size, numerous distinct cuticular pores, slightly offset lip region, prominent labial and cephalic papillae, cephalic papillae larger than labial ones, barrel-shaped and spacious (40 – 43 × 22.5 – 24 μm) buccal cavity, lower position of dorsal tooth (22 – 25 % of the buccal cavity length), weakly rounded tail tip and weakly expressed hyaline, pars proximalis vaginae with arcuate walls, pars refringens vaginae with two drop-shaped sclerotizations; pars distalis vaginae short, thick walled. P. girchi sp. nov. is closely related to P. pinophilus Winiszewska & Susulovsky, 2004, P. fistulous Susulovsky & Winiszewska, 2002, P. auritus Andrassy, 1985 and P. muscorum (Dujardin, 1845) Wu & Hoeppli, 1929. The new species is very similar to P. pinophilus (data from Winiszewska & Susulovsky, 2004) are taken for comparative purposes), but P. girchi sp. nov. can be differentiated from P. pinophilus by the position of dorsal tooth apex from base of buccal cavity (75 – 78 % vs 84 %), dorsal tooth length (3 – 3.3 vs 5 μm), number of subventral denticles (8 vs 12), distance between first and last denticle (14.5 – 15.5 vs 18.5 μm), distance of amphidial aperture from anterior end (11 – 12.5 vs 8.6 μm), longer anterior (363 – 476 vs 250 μm) and posterior genital branches (300 – 451 vs 250 μm), posteriorly located vulva (V = 65 – 67 vs 61 %) and caudal gland (absent vs spherical glandular bodies in proximal part). Morever, the new species can be differentiated from P. fistulous (original description by Susulovsky & Winiszewska, 2002) by having narrower lip region (43 – 44.5 vs 46.7 – 51.4 μm), shorter buccal cavity (40 – 43 vs 47.2 – 51μm) and shorter tail (115 – 138 vs 124 – 177 μm). It can also be separated from P. auritus (see detailed description by Orselli & Vinciguerra, 2007) by having narrower lip region (43 – 44.5 vs 47 – 57.5 μm), shorter buccal cavity (40 – 43 vs 43 – 49.5 μm), amphidial position (amphid at the level of apex of dorsal tooth vs anterior of dorsal tooth) and shorter tail (115 – 138 vs 145 – 195 μm). Finally, P. girchi sp. nov. differs from P. muscorum (data from Winiszewska & Susulovsky, 2003) by the size of cephalic and labial papillae (lip region with large conical and prominent labial and cephalic papillae vs lip region rounded with small labial and cephalic papillae), subventral denticle numbers (8 – 10 vs 10 – 14), the size of cuticular pores (cuticle smooth with numerous distinguished body pore vs indistinct pores along the body), shorter buccal cavity (40 – 43 vs 47.6 – 54.3 μm) and shorter tail (115 – 138 vs 140 – 209 μm).

The specific epithet is derived from the Lori word Girch meaning howthorn (Crataegus aronia L), the plant which the P. girchi sp. nov. was collected from its rhizosphere for the first time.

Measrements

See Table 2.

Description:

Female

Body medium sized, open ‘C’-shaped upon fixation, more curved in tail region. Cuticle smooth, 3 – 4 μm thick in mid body, Cuticular small pores, arranged along the body (excluding tail). Lip region rounded, 43 – 49.5 μm wide, offset by a slightly depression, small labial and cephalic papillae, slightly raised, labial papillae are the same size as head papillae. Buccal cavity barrel-shaped, 43 – 48 × 24 – 27 μm. Dorsal tooth 9 – 10.2 μm long, its apex located at 11 – 13.8 μm from the anterior end of the buccal cavity, subventral ridges with 10 – 12 well-developed denticles each. Amphidial aperture 5.5 – 6 μm wide, located at the level of anterior end of buccal cavity, 14 – 16 μm from anterior end. Pharynx cylindroid and muscular, 23 – 25 % of the body length, nerve ring at 30 – 38 % of the neck length. Reproductive system didelphic, amphidelphic, ovaries reflexed. Vulva post-equatorial, a transverse slit with sclerotized pars refringens. Tail conical, ventrally bent, tail tip weakly rounded, caudal glands and spinneret absent.

Male: Not found.

Robat Namaki village, Robat area, Khorramabad County, Lorestan province, Iran, (GPS coordinates: N 33º 36′ 31′′ E 48º 18′ 16′′, altitude 1332 m a.s.l.), in the rhizosphere of Hawthorn (Crataegus aronia L.), and Imanabad village, Azna area, Khorramabad County, Lorestan province, Iran, (GPS coordinates: N 33º 23′ 11′′ E 48º 36′ 16′′, altitude 1661 m a.s.l.), in the rhizosphere of Oak (Quercus libani L.).

Prionchulus muscorum is a very well-known species with worldwide distribution reported from many countries of Europe, Africa, America, Asia and Australia (Andrassy, 2009). In Iran, this species was first observed by Loof et al. (1990) in the rhizosphere of Oak; later on, this species obtained from different localities in the country from the rhizosphere of different plants. The present Iranian females fit well with described population by Jiménez Guirado et al. (1997) except for having smaller c ratio (13 – 16 vs 16 – 18) and shorter tail (117 – 168 vs 142 – 211.5 μm). The main features of the specimens, also fit perfectly to those populations described by Winiszewska & Susulovsky (2003) except for shorter buccal cavity (43 – 48 vs 47.6 – 54.3 μm) and shorter tail (117 – 168 vs 140 – 209μm).

(Fig. 2)

Measurements

See Table 2.

Hamvar-e Kulivand village , Bastam area, Selseleh County, Lorestan province, Iran, (GPS coordinates: N 33º 44′ 34′′ E 48º 10′ 04′′, altitude 1875 m a.s.l.), in the rhizosphere of Hawthorn (Crataegus aronia L.).

P. fagi was first described by Zell, 1985. It was later redescribed based on the type material by Winiszewska & Susulovsky, 2003. In Iran, this species was first observed by Naghavi et al. (2016) from Lorestan and Ardabil provinces. The present survey lorestanian population perfectly fit with described specimens by Winiszewska & Susulovsky, 2003.