Proleptonchus prerectus, Ahad, Sumaya & Ahmad, Wasim, 2016

Ahad, Sumaya & Ahmad, Wasim, 2016, Three new and a known species of the genus Proleptonchus Lordello, 1955 (Nematoda: Leptonchidae) with a diagnostic compendium of the genus, Zootaxa 4189 (1), pp. 115-133 : 122-126

Proleptonchus prerectus n. sp.

(Figs. 4, 5)

Measurements. See Table 2 .

Description. Female: Medium sized nematodes, 1.1–1.4 mm long; body cylindrical, tapering slightly towards both extremeties, generally striaght or sligthly curved ventrally. Cuticle with two distinct layers, 2–3 µm thick at midbody and 3–4 µm on tail. Outer layer thin; inner layer with irregular outline and loose; radial refractive elements abundant. Lateral chords occupying about 30–35% of the midbody diameter. Lateral body pores distinct, 3 to 4 in the phargyngeal region, 6 to 8 between pharyngeal bulb to vulva and six to eight between vulva to anus; dorsal and ventral body pores indistinct.

Lip region cap-like, offset by slight constriction, 2.3–2.5 times as wide as high or about one-third of the body diameter at neck base; lips rounded and amalgamated. Amphids cup-shaped with aperture located at the level of cephalic constriction and occupying about two-thirds of lip region diameter. Stoma inverted flask-shaped with sclerotized walls. Odontostyle attenuated, 0.7–0.8 times the lip region diameter long, with narrow lumen and fine aperture. Odontophore slightly sclerotized, arcuate, 1.1–1.5 times the odontostyle length. Guiding ring simple, refractive, at 0.7 times the lip region diameter from anterior end. Pharynx consists of a slender and weakly muscular anterior part, separated from basal bulb by a constriction. Pharyngeal bulb short, cylindroid, occupying about 16–20% of total neck length. Cardia short, rounded to hemispherical, about one-sixth of the corresponding body diameter long. Nerve ring at 42–48% of neck length from the anterior end.

Genital system monodelphic-prodelphic. Ovary reflexed, measuring 80–105 µm long, not reaching the oviduct-uterus junction; oocytes arranged in a single row except near tip. Oviduct joining the ovary subterminally, measuring 160–186 µm, consisting of a slender portion and a well developed par dilatata. Oviduct-uterus junction marked by well developed sphincter. Uterus tubular, measuring 67–73 µm long; distal portion of uterus with distinctly sclerotized central lumen containing refringent apophyses (Figs. 4G, 5F). Posterior genital branch 0.7–1.0 times the midbody diameter long. Vagina cylindrical; pars proximalis vaginae 7–13 µm long, its wall encircled by muscles; pars distalis vaginae short, 1–2 µm long with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 2.0–4.4 anal body diameters long, a small prerectal chamber (Figs 4H, 5H) present between the prerectum and the intestine proper. Rectum 1.0–1.3 anal body diameter long. Tail short, rounded-hemispheroid, 0.6–0.8 anal body diameter long, with distinct terminal caudal pore. A single female specimen with a very small tail (c’ = 0.3).

Male: General morphology similar to female except for the posterior body region being comparatively more ventrally curved. Sperms spindle-shaped. In addition to ad-cloacal pair situated at 16 µm from cloacal aperture, there is a series of six ventromedian supplements, located outside the range of spicule, first ventromedian at 55 µm from ad-claocal pair. Spicules 1.4 times cloacal body diameter long. Lateral guiding pieces very prominent, about one-third of the spicules length. Tail short, rounded, 0.8 times anal body diameter long.

Type habitat and locality. Soil around the roots of grasses (unidentified) from Koibuchimachi, Mito C., Ibaraki, Japan. Collected by Dr. M. Araki on December 7, 2011.

Type specimens. Holotype female on slide Proleptonchus prerectus n. sp. / 1; paratype females on slides Proleptonchus prerectus n. sp. / 2–9 and a paratype male on slide Proleptonchus prerectus n. sp. / 10; deposited with the nematode collection of the Department of Zoology, Aligarh Muslim University, India .

Etymology. The new species is named P. prerectus because of its characteristic prerectal chamber.

Diagnosis and relationship. Proleptonchus prerectus n. sp. is characterized by having 1.18–1.43 mm long body; lip region cap-like, offset by a slight constriction; odontostyle 8 µm, odontophore 9–10 µm; pharynx consists of a slender and weakly muscular anterior part, separated from a short cylindroid basal bulb by a constriction, basal bulb 16–20% of total neck length; female genital system mono-prodelphic; distal portion of uterus with sclerotized refringent apophyses; posterior uterine sac small, 27–36 µm; transverse vulva; a prerectal chamber; short, roundedhemispheroid tail and male with 37 µm long spicules, lateral guiding pieces and six, regularly spaced ventromedian supplements.

In the presence of refringent apophyses in the distal part of uterus and a prerectal chamber, the new species is most closely related to P. orientalis Ahmad et al. 2009 . However, it differs from it, in having larger body size (L = 1.18–1.43 vs 0.86–0.97 mm); comparatively stronger refringent apophyses (vs weak refringent apophyses); small posterior uterine sac, without rudimentary oviduct (posterior uterine sac 27–36 vs 92–185 µm long, with rudimentary oviduct); higher c ratio (c = 66.5–84.9 vs 45–55.3); longer spicules (37 vs 29–32 µm) and more ventromedian supplements (6 vs 4–5).

In the presence of refringent apophyses, the new species is also close to P. sclerouterinus Mushtaq et al., 2007 but differs in the shape of lip region (vs low lip region); odontophore not thickened (vs thickened odontophore); in having cylindroid basal bulb (vs pyriform); small posterior uterine sac, without rudimentary oviduct (posterior uterine sac 27–36 vs 85–110 µm long, with rudimentary oviduct); presence of prerectal chamber (vs absent) and in the presence of male (vs absence).

In having a prerectal chamber and a short posterior uterine sac, the new species also resemble P. parkerus Choi & Jairajpuri, 1998 from same region ( Korea), but differs in having longer odontostyle (8 vs 5–6 µm); cylindroid basal bulb (vs pyriform); presence of refringent apophyses (vs absent); much smaller posterior uterine sac (27–36 vs 55.8–75.6 µm); in the position of prerectal chamber (vs between rectum and prerectum) and presence of male (vs absence).

Tables

TABLE 2. Measurements of Proleptonchus prerectus n. sp. (All measurements in µm)

Characters	Holotype female Paratype females, n= 8	Paratype male
L	1288 1328.8±81.0(1180–1434)	1372
Body diameter at neck base	32 33.2±2.1 (29–35)	35
Body diameter at mid body	34 36.2±2.1 (32–39)	39
Body diameter at anus	23 23.5±1.2 (22–25)	25
a	37.8 36.6±1.4 (34.9–39.8)	35.1
b	6.5 6.8±0.3 (6.4–7.4)	7.7
c	71.5 74.3±7.5 (66.5–84.9)	65.3
c`	0.7 0.7±0.07 (0.6–0.8)	0.8
V	57.3 57.6±1.7 (53.9–59.4)	-
G1	19 18.4±1.7 (14.8–20.7)	-
G2	2.4 2.2±0.1 (2.1–2.5)	-
Lip region diameter	10 9.7±0.2 (9.5–10)	9
Lip region height	4 3.9±0.1 (3.5–4)	3.5
Amphid aperture	7 6.8±0.6 (6–8)	6
Odontostyle length	8 8	8
Odontophore length	10 9.4±0.6 (9–10)	10
Guiding ring from anterior end	7 7	7
Nerve ring from anterior end	84 86.8±2.7 (82–90)	83
Neck length	196 195±12.3 (169–211)	178
Expanded part of Pharynx	38 36.2±2.2 (32–39)	31
Cardia length	5 5.4±1.9 (3–9)	7
Anterior genital branch	245 246±28.6 (205–298)	-
Posterior genital branch	31 30.8±2.7 (27–36)	-
Vaginal length	16 17±1.9 (15–20)	-
Vulva from anterior end	739 766.1±48.3 (695–842)	-
Prerectum length	94 74.3±19.6 (50–98)	?
Rectum length	27 29.1±2.1 (25–32)	38
Tail length	18 18.3±1.3 (16–20)	21
Spicule length	- -	37
Lateral guiding pieces	- -	12
Ventromedian supplements	- -	6