Proleptonchus orientalis, Ahmad & Park & Lee & Choi, 2009

Ahmad, Wasim, Park, Byeong-Yong, Lee, Jae-Kook & Choi, Dong-Ro, 2009, Some new and known species of Tylencholaimoidea (Nematoda: Dorylaimida) from Korea, Journal of Natural History 43 (37 - 38), pp. 2329-2356 : 2347-2352

Proleptonchus orientalis sp. nov.

( Figures 7 and 8 ; Table 6)

Description

Female. Body slightly curved ventrad upon fixation, slender, tapering slightly towards anterior extremity. Cuticle with fine transverse striations; inner layer with irregular outline and often detached from the outer layer. Radial refractive elements abundant along entire body length. Lateral hypodermal chords about one-quarter to one-third as wide as body width at mid-body. Lateral, dorsal and ventral body pores indistinct. Lip region cap-like, offset by slight constriction; labial and cephalic papillae not projecting above labial contour. Amphids large, stirrup-shaped, fovea simple; its aperture occupying slightly more than two-thirds of the corresponding body width; fusus large, 19–21 µm behind aperture. Stoma flask-shaped, its wall slightly sclerotized. Odontostyle slender, attenuated, about as long as lip region width. Guiding ring 0.66–0.70 times lip region width from anterior end. Odontophore almost straight with slightly thickened base, about as long as the odontostyle. Combined odontostyle and odontophore length about 15–17 µm. Pharynx with very slender, weak anterior part separated from the posterior cylindrical bulb by an abrupt expansion. Pharyngeal bulb about two and a half times as long as wide and occupying about 18–20% of total neck length. Nerve ring encircling the anterior slender part of pharynx at 45–50% of neck length from anterior end. Cardia rather short conoid. DN 7–8 µm behind beginning of pharyngeal enlargement while S2N 10–11 µm anterior to base of pharynx. Genital system pseudo-mono-prodelphic. Anterior genital tract well developed; ovary reflexed, measuring 90–127 µm with oocytes arranged in a single row except near its tip. Oviduct joining ovary subterminally, 106–123 µm long with well-developed pars dilatata. Uterus 60–73 µm long; pars dilatata of uterus containing weak refringent apophyses. Posterior branch 3.0–6.3 times mid-body width long, comprising a long sac-like uterine part and a small appendix representing rudiments of oviduct; a distinct sphincter present between the two parts. Vulva a transverse slit. Vagina muscular, 17–18 µm or about half of the corresponding body width deep. Pars proximalis vaginae 10–12 µm long with straight walls encircled by circular musculature; pars refringens vaginae absent; pars distalis vaginae spindle-shaped, 5–6 µm long. Prerectum five to eight anal body widths long, a small prerectal chamber present between the prerectum and intestine proper. Rectum 1.1–1.3 times anal body width long. Tail short, conoid with bluntly rounded terminus, 0.9–1.0 times anal body width long with a pair of caudal pores on each side.

Male. Similar to females in general morphology except for posterior region being curved strongly because of the presence of copulatory muscles. Supplements, an adanal pair and four to five spaced ventromedians. Spicules dorylaimoid, slightly arcuate, 1.45–1.58 times anal body widths long. Lateral guiding pieces about onethird of spicule length. Prerectum 6.5–9.5 times anal body width long, terminating beyond the range of supplements. Rectum about 1.4–1.6 times anal body width long. Tail short conoid, with bluntly rounded terminus, 1.1–1.2 times anal body width long. Caudal pores two on each side.

Type habitat and locality

Soil around roots of forest trees from Jungmisan Mt, Yangpyeong-gun, Gyeongi-do, South Korea.

Type specimens

Holotype female and a paratype male on slide Proleptonchus orientalis sp. nov. /1; paratypes females and males on slides Proleptonchus orientalis sp. nov. /2–3; deposited with the nematode collection of National Institute of Agricultural Sciences and Technology, Suwon, Korea. Two paratype females and males deposited with the nematode collection of the Department of Zoology, Aligarh Muslim University, India.

Diagnosis and relationships

Proleptonchus orientalis sp. nov. is characterized by having a small (0.86–0.97 mm in female and 0.99–1.13 mm in male), comparatively slender body; lip region slightly offset, low; 6–8 µm long, slender odontostyle; almost straight odontophore with slightly thickened base; pharyngeal bulb cylindrical, occupying about 18–20% of neck length; posterior genital branch with reduced terminal oviduct; a small prerectal chamber between intestine proper and prerectum; short conoid tail; 29–32 µm long spicules and four or five ventromedian supplements.

The new species is distinctive in the presence of refringent apophyses in the pars dilatata of the uterus and a prerectal chamber. Mushtaq et al. (2007) described a new species, P. sclerouterinus from India, characterized by the presence of very strong refringent apophyses in the pars dilatata of uterus. Although our new species has refringent apophyses, they are weak. The new species further differs from P. sclerouterinus in having a smaller body size (versus 1.2–1.3 mm); almost straight odontophore (versus arcuate); in the presence of a prerectal chamber (versus absence) and in the shape and size of the tail (versus tail hemispherical with thick cuticle at terminus, c = 68.5–94, c′ = 0.6–0.8). By having a prerectal chamber, the new species resembles P. parkerus Choi and Jairajpuri, 1998 , a species described from Korea, but differs in having a smaller body size (versus 1.33–1.37 mm), in the position of the prerectal chamber (versus between prerectum and rectum) and in having a much longer post-uterine sac with rudiments of oviduct (versus post-uterine sac 56–75 µm long without rudiments of oviduct).

The new species is also similar to P. shamimi Bajaj and Bhatti, 1980 ; P. saccatus ( Clark, 1962) Andrássy, 1963 and P. fagi Jiménez Guirado and Arcos, 1994 (see Bajaj and Bhatti 1980; Clark 1962; Andrássy 1963; Jiménez Guirado and Arcos 1994). However, it differs from the former in having comparatively smaller body size (versus 1.10–1.50 mm); in the nature of its odontophore, which is almost straight with thickened base (versus odontophore arcuate without thickened base); comparatively posterior vulva (versus V = 54–60); in the presence of prerectal chamber (versus absence) and longer tail (versus 11–18 µm).

From P. saccatus , the new species differs in having a smaller body size (versus 1.56–1.68 mm); smaller stoma (versus 10 µm); in the nature of its odontophore (versus arcuate and base not thickened); relatively shorter expanded part of the pharynx (versus 22–26%); posterior genital branch with different morphology (versus apparently without sphincter between reduced oviduct and uterine region) and shorter spicules (versus 48–49 µm).

From P. fagi , the new species differs in having a shorter body size (versus 1.69–2.23 mm); in the shape of the lip region (versus lip region with a disc-like perioral area); in the size of the tail (versus c = 69–109; c′ = 0.45–0.80), and smaller spicules (versus 41.5–49.5 µm).

Figures

Figure 7. Proleptonchus orientalis sp. nov. (A) Entire female; (B) entire male; (C) anterior region; (D) anterior end showing amphid; (E) pharyngeal region; (F) expanded part of pharynx; (G) vulval region; (H) female genital branch (anterior); (I,J) female genital branch (posterior); (K) intestine– prerectum junction; (L) female posterior region; (M) female posteriorend; (N) male posterior region.

Figure 8. Proleptonchus orientalis sp. nov. (A,B) Anterior region; (C) anterior end showing amphid; (D) expanded part of pharynx; (E) vulval region; (F) end of posterior genital branch showing vestigial oviduct and sphincter; (G) intestine–prerectum junction; (H) female posterior half; (I,J) female posterior ends; (K) male posterior end.