Mesodorylaimus khasianus, Tauheed, Uzma & Ahmad, Wasim, 2010

Tauheed, Uzma & Ahmad, Wasim, 2010, Four new species of the genus Mesodorylaimus Andrássy, 1959 (Nematoda: Dorylaimida) from India, Zootaxa 2642, pp. 19-35 : 20-22

Mesodorylaimus khasianus n. sp.

( Figs. 1 , 2 )

Measurements: Table 1 .

Description. Female: Body slightly curved ventrad upon fixation, tapering towards both extremities but more so towards the posterior end. Cuticle with fine transverse striations, 1.5–2.0 µm thick at mid body and 3–4 µm on tail. Lateral chords about one-third of body width at mid body. Lateral, dorsal and ventral body pores indistinct.

Lip region offset by shallow constriction, about 2.5–3.0 times as wide as high or about one-third as wide as body width at neck base. Lips truncate; labial and cephalic papillae slightly raised. Amphids stirrup-shaped, their aperture occupying about half of the lip region width. Odontostyle 1.0–1.2 times the lip region width long, its aperture about one-third of its length. Guiding ring single, at 0.7–0.8 times lip region width from anterior end. Odontophore simple, rod-like, 1.27–1.5 times the odontostyle length. Nerve ring encircling the anterior slender part of pharynx, at about 39–43% of neck length from anterior end. Pharyngeal expansion gradual; expanded portion occupying about 36.5–39.5% of total neck length. Cardia elongate conoid, about half of the corresponding body width long. A pair of ovoid bodies (probably coelomocytes), measuring 28–31 µm present near the base of cardia. Pharyngeal gland nuclei located as follows: D = 66–68%; AS 1 = 26–28%; AS 2 = 42–44%; PS1 = 72–75%; PS2 = 79–81%.

Genital system didelphic-amphidelphic; with both branches almost equally developed. Ovaries reflexed, short, not reaching or surpassing the oviduct-uterus junction, measuring 60–93 µm (anterior) and 58–76 µm (posterior); oocytes arranged in single row except near the tip. Oviduct joining the ovary subterminally, measuring 90–100 µm (anterior) and 88–99 µm (posterior); consisting of a long slender part with prismatic cells and a well developed pars dilatata with clear lumen. Sphincter distinct at oviduct-uterus junction, its inner part more refractive, being encircled by a muscular ring. Sperms visible only in one specimen. Uterus a simple tube with clear lumen, measuring 61–76 µm (anterior) and 65–78 µm (posterior) with no clear demarcation of proximal and distal parts. Vulva transverse, slit-like. Vagina extending inwards, about half of the corresponding body width deep; pars proximalis vaginae 8–10 µm long, with convex walls, encircled by circular musculature; pars refringens vaginae with two divergent usually well separated trapezoidal sclerotizations, each measuring 5– 6 x 3 µm and with a combined width (cw) 8.0–9.5 µm; two additional, drop-shaped sclerotized pieces present between pars refringens vaginae and pars distalis vaginae; pars distalis vaginae short, 2–4 µm long with slightly curved walls. Prerectum 2.4–4.3 anal body widths long. Rectum 1.4–2.0 times anal body width long. Tail elongate, gradually tapering on both sides, its terminus slightly dorsally bent in only one specimen, 6.1–7.1 times anal body width long; hyaline part occupying about 15–16% of tail length. Caudal pores two pairs, one on each side.

Male: Supplements an adcloacal pair and 7–11 regularly spaced ventromedians. Spicules dorylaimoid, slightly ventrally curved, 1.3–1.6 times anal body widths long; lateral guiding pieces rod-like, about onefifth of spicule length. Prerectum length 2.5–4.1 times the anal body width, terminating within the range of supplements. Tail short conoid, with blunt terminus, about as long as cloacal body width, with two caudal pores on each side.

Type habitat and locality: Soil around the roots of paddy ( Oryza sativa L.) from Moujarung east, Khasi hills, Meghalaya State, India.

Type material. Holotype female on slide Mesodorylaimus khasianus n. sp. /1; paratype males and females on slide Mesodorylaimus khasianus n. sp. /2–8; deposited with the nematode collection of the Department of Zoology, Aligarh Muslim University, Aligarh. A paratype female and a male deposited with the nematode collection of the Universidad de Jaen, Spain.

Diagnosis and relationships: Mesodorylaimus khasianus n. sp. is characterized by having 0.94–1.14 mm long body; lip region offset by a slight constriction; 10–12 µm long odontostyle; amphidelphic female genital system, transverse vulva, presence of an additional pair of sclerotized pieces at vagina and female tail 6–7 anal body widths long with rounded terminus.

Mesodorylaimus khasianus n. sp. differs from all known species of the genus in having its characteristic, additional pair of sclerotized pieces between pars refringens vaginae and pars distalis vaginae.

On the basis of shape of lip region and tail length, the new species comes close to M. kowyni Basson and Heyns, 1974 ; M. transkeiensis Basson and Heyns, 1974 ; M. derni Loof, 1969 and M. parapotus Ahmad and Ahmad, 2001 , but differs from the former in having a wider lip region (vs one-fourth as wide as body width at neck base); absence of lateral body pores (vs presence); more posterior vulva position (vs V = 43–46); differently shaped pars refringens vaginae (vs triangular); tail shape (vs dorsally bent tail); shorter prerectum in males (vs 131–156 µm, extending beyond the range of supplement); smaller spicules and lateral guiding pieces (vs spicules 36–41 µm, lateral guiding pieces 7.6–9.7 µm); arrangement and number of supplements (vs 10–15, contiguous) and differently shaped male tail (vs bluntly rounded).

From M. transkeiensis , the new species differs in having lip region offset by shallow constriction (vs offset by deep constriction); larger odontostyle (vs 7.0–9.2 µm); wider amphid aperture (vs 3.2–3.8 µm); posterior vulva position (vs V = 36–47); in the shape of tail (vs dorsally bent tail); shorter prerectum in males (vs 130–135 µm, extending beyond the range of supplement); arrangement of supplements (vs contiguous) and longer male tail (vs 17.5–20 µm).

From M. derni , the new species differs in having slightly smaller body (vs L = 1.4–1.8 mm); slightly shorter odontostyle and odontophore (vs odontostyle 13–15 µm; odontophore twice the odontostyle length); transverse vulva (vs longitudinal); smaller spicules and lateral guiding pieces (vs spicules 39–48 µm; lateral guiding pieces 12–13 µm); number and arrangement of supplements (vs supplements 11–20, contiguous). The new species differs from M. parapotus , in having lip region offset by shallow constriction (vs offset by deep constriction); slightly wider amphid aperture (vs 3–4 µm); longer pharynx and pharyngeal expansion (vs pharynx 175–191 µm long, b = 5.7–6.5, expanded part of pharynx 25–34%); more posterior vulva position (vs V= 41–46); lesser number of ventromedian supplements (vs 15–17); smaller lateral guiding pieces (vs 9–10 µm).

Etymology: The new species is named after the type locality, Khasi hills.

Figures

FIGURE 1. Mesodorylaimus khasianus n. sp. A: Entire female. B: Entire male. C: Anterior region. D: Anterior end showing amphid. E: Expanded part of pharynx. F: Coelomocytes. G: Female genital branch (posterior). H: Vulval region. I: Female posterior region. J: Male posterior region. K: Male tail.

FIGURE 2. Mesodorylaimus khasianus n. sp. A: Anterior region. B: Pharyngo-intestinal junction. C-D: Vulval region. E: Female prerectum. F: Female posterior region. G: Male posterior region. H: Male tail.

Tables

TABLE 1. Morphometrics of Mesodorylaimus khasianus n. sp. All measurements in µm (except L) and in the form: mean standard deviation (range).

Characters	Holotype	Paratype females	Paratype males
n		6	6
L (mm) a	1.14 32.5	1.11±33.73 (1.05–1.14) 32.06±0.68 (30.97–32.75)	1.02±43.79 (0.94–1.09) 30.6±0.71 (29.5–31.5)
b	4.6	4.7±0.14 (4.56–4.87)	4.4±0.21 (4.14–4.73)
c c`	8.1 6.7	8.41± 0.25 (8.07–8.77) 6.45±0.21 (6.18–6.71)	41.6±2.3 (38.7–45.0) 1.04± 0.05 (0.96–1.1)
V	50.1	49.9±0.73 (48.7–50.8)	–
G1 G2 Lip region width	13.3 13.4 9.5	14.2±0.72(13.3–15.0) 14.5±0.91 (13.4–15.6) 9.7±0.25 (9.5–10)	– – 10
Lip region height	3.5	3.5±0.29 (3–4)	4.08±0.18 (4–4.5)
Amphid aperture Odontostyle length	5 11	5.0 10.8±0.47 (10.0–11.5)	6 10.5±0.71 (10–12)
Odontophore length	15	14.3±0.74 (13–15)	13.8±0.37 (13–14)
Guiding ring from ant. end Nerve ring from ant. end	8 98	7.8±0.4 (7–8) 91.7±3.7 (87–98)	7.6±0.49 (7–8) 90.4±0.8 (90–92)
Neck length	249	227±13.6 (208–249)	232±5.8 (225–241)
Expanded part of pharynx Cardia length	95 20	87±4.7 (80–95) 17.6±1.53 (15–20)	86±3.06 (81–89) 19.25±0.43 (19–20)
Body width at neck base	33	31.6±1.49 (30–34)	31.6±1.34 (30–34)
Body width at mid body Body width at anus/cloaca	35 21	34.6±0.79 (33.5–36.0) 20±1.07 (19–22)	33.3±1.03 (31.5–34.5) 23.6±1.36 (21.5–26.0)
Anterior genital branch	151	164±14.15 (150–184)	–
Posterior genital branch Vaginal depth	153 19	168±15.83 (152–189) 18.25±0.56 (17.5–19.0)	– –
Vulva from anterior end	570	545± 20.4 (512–570)	–
Prerectum length Rectum length	80 33	68±11.8 (54–86) 32±2.92 (29–37)	76.7 ± 10.8 (60–94) 39 ± 3.3 (35–46)
Tail length	141	132±7.7 (120–141)	24.5 ± 0.9 (23–26)
Spicule length Lateral guiding pieces	– –	– –	33 ± 0.9 (32–34) 7.0 ± 0.29 (6.5–7.5)
Ventromedian supplements	–	–	7–11