Mesodorylaimus noreasus, 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 : 23-27

Mesodorylaimus noreasus n. sp.

( Fig. 3 , 4 )

Measurements: Table 2 .

Description. Female: Body slightly curved ventrad upon fixation, tapering towards both extremities but more so towards the posterior end. Cuticle with fine transverse striations, 2–3 µm thick at mid body and 2.5– 4.0 µm on tail. Lateral chords about one-fourth of body width at mid body. Lateral, dorsal and ventral body pores indistinct.

Lip region truncate, offset by slight depression, about three times as wide as high or about one-third as wide as body width at neck base. Lips amalgamated; labial and cephalic papillae slightly protruding above the labial contour. Amphids cup-shaped, their aperture occupying about half or slightly more than half of lip region width. Odontostyle 1.2–1.3 times the lip region width long, its aperture about one-third of its length. Guiding ring single, at 0.64–0.75 times lip region width from anterior end. Odontophore simple, rod-like, 1.1– 1.3 times the odontostyle length. Nerve ring encircling the anterior slender part of pharynx, at 34–37% of neck length from anterior end. Pharyngeal expansion gradual; expanded portion occupying about 38–42% of total neck length. Cardia elongate conoid, three-fourths of the corresponding body width long. Pharyngeal gland nuclei located as follows: D = 61–62%; AS 1 = 35–39%; AS 2 = 54–55%; PS1 = 79–80%; PS2 = 81%.

Genital system didelphic-amphidelphic; both branches almost equally developed. Ovaries reflexed, short, not reaching or surpassing the oviduct-uterus junction, measuring 74–106 µm (anterior) and 83–111 µm (posterior); oocytes arranged in single row except near the tip. Oviduct joining the ovary subterminally, measuring 137–168 µm (anterior) and 115–177 µm (posterior), consisting of a long slender part with prismatic cells and a slightly wider pars dilatata with obscure lumen. Sphincter distinct at oviduct-uterus junction, its inner part more refractive, being encircled by a muscular ring. Sperms present both in uterus and oviduct. Uterus a short tube with obscure lumen, measuring 87–110 µm (anterior) and 69–105 µm (posterior) long. Vulva transverse slit-like. Vagina extending inwards for slightly more than half of the corresponding body width; pars proximalis vaginae 16–17 µm long, with almost straight walls, encircled by circular musculature; pars refringens vaginae with two well separated rectangular sclerotizations, each measuring 6– 7 x 2 µm and with a combined width (cw) 9.0–10 µm; pars distalis vaginae short, 2–3.5 µm long with slightly curved walls. Prerectum 2.4–2.8 anal body widths long. Rectum about 1.6–1.8 times anal body width long. Tail elongate, gradually tapering on both sides to a rounded terminus, 4.6–5.6 times anal body width long, with a small distinct hyaline part. Caudal pores two pairs, one on each side.

Male: Supplements an adcloacal pair and nine spaced ventromedians. Spicules dorylaimoid, slightly ventrally curved, 1.27–1.34 times anal body widths long; lateral guiding pieces rod-like, about one-fifth to one-sixth of spicules length. Prerectum 4.4–4.9 times anal body widths long, extending far beyond the range of supplements. Tail short convex-conoid with rounded terminus, 0.7–0.8 times anal body width long. Two caudal pores on each side.

Type habitat and locality. Soil around the roots of unidentified trees from the evergreen forest, Bomdilla, district West Kameng, Arunachal Pradesh, India.

Type material. Holotype female on slide Mesodorylaimus noreasus n. sp. /1; paratype males and females on slide Mesodorylaimus noreasus n. sp. /2–5; deposited with the nematode collection of the Department of Zoology, Aligarh Muslim University, Aligarh. A paratype female deposited with the nematode collection of the Universidad de Jaén, Spain.

Diagnosis and relationships: Mesodorylaimus noreasus n. sp. is characterized by having 1.42–1.74 mm long body; lip region truncate, offset by slight depression; 14–16 µm long odontostyle; amphidelphic female genital system; transverse vulva; elongate attenuated tail with rounded terminus in females, and, males with nine regularly spaced ventromedian supplements and short conoid tail with rounded terminus.

In the presence of its large sized body, comparatively long odontostyle and shape and size of tail, the new species comes close to M. shamimi Ahmad and Araki, 2003 ; M. nevadensis Pêna Santiago and Abolafia, 2000 ; M. palustris Andrássy, 1991 and M. baqrii ( Dey and Baqri, 1986) Ahmad, 1993 ; but differs from the former, in having slightly longer and slender body (vs. L = 1.4–1.5 mm; a = 35–39); coelomocytes absent at the base of pharynx (vs coelomocytes present); differently shaped vagina and pars refringens vaginae (vs walls of pars proximalis convex; pars refringens triangular-shaped); slightly longer tail (vs c = 9.8–10.8 µm; c’ = 5.5–6.2); prerectum longer and extending far beyond the range of supplements (vs 105 µm; prerectum terminating just in front of first ventromedian supplements); smaller spicules (vs 49 µm).

From M. nevadensis , it differs in having slightly longer odontostyle (vs odontostyle 12.5–14 µm); stirrupshaped amphids (vs cup-shaped); differently shaped pars refringens vaginae (vs pars refringens vaginae triangular to drop-shaped); differently shaped female tail (vs tail with a sudden dorsal depression after about one anal body with and then tapering gradually); absence of tongue-like structure in the intestine (vs presence) and in males prerectum extending much beyond the range of supplements (vs prerectum termination at level with the last supplement).

The new species differs from M. palustris in having slightly longer body (vs L = 1.41 mm); slightly offset lip region (vs well offset); slightly longer odontostyle (vs 14 µm); longer pharynx (vs 270–292 µm); transverse vulva (vs pore-like vulva), absence of cuticular irregularities at perivulval region (vs cuticular irregularities at perivulval region present); longer tail (vs tail 93 µm long) and slightly longer spicules (vs 40 µm).

From M. baqrii , it differs in having slightly longer and robust body (vs L = 1.2–1.4 mm, a = 29.3–33.6); longer pharynx (vs b = 5.6–6.2); longer odontostyle (vs 11–13 µm); longer prerectum in males, extending beyond the range of ventromedians (vs prerectum = 98–101 µm and terminating within the range of ventromedians supplements); slightly longer spicule (vs 36–40 µm) and lesser number of ventromedian supplements (vs 12–14).

Etymology: The new species is named after the Nor th- Eas tern states of India from where it was collected.

Figures

FIGURE 3. Mesodorylaimus noreasus n. sp. A: Entire female. B: Entire male. C: Anterior region. D: Anterior end showing amphid. E: Expanded part of pharynx. F: Female genital branch (posterior). G: Vulval region. H: Female posterior region. I: Male posterior region.

FIGURE 4. Mesodorylaimus noreasus n. sp. A: Anterior region. B: Pharyngo-intestinal junction. C: Female genital branch (anterior). D: Vulval region. E: Female posterior region. F: Male posterior region. G-H: Male tail.

Tables

TABLE 2. Morphometrics of Mesodorylaimus noreasus n. sp. All measurements in µm (except L) and in the form: mean standard deviation (range).

Characters	Holotype Paratype females	Paratype males
n	5	2
L (mm) a	1.72 1.69±0.03 (1.65–1.74) 42.8 42.14±1.37 (40.2–43.4)	1.42, 1.61 38.2, 40.5
b	5.2 5.2±0.15 (5.04–5.49)	4.2, 4.7
c c`	11.8 13.02±0.78 (11.8–14.0) 5.57 5.1±0.31 (4.6–5.6)	56.7, 64.2 0.75, 0.78
V	50.96 49±1.6 (47–51)	–
G1 G2 Lip region width	14.9 15.02±1.15 (13.7–16.8) 13.6 14±0.53 (13.3–14.5) 12 12.1±0.2 (12.0–12.5)	– – 12.5
Lip region height	4 4.1±0.2 (4–4.5)	4.0, 4.5
Amphid aperture Odontostyle length	6 6.5±0.45 (6–7) 15.5 15.4±0.37 (15–16)	7 14
Odontophore length	18 18.4±1.02 (17–20)	19, 20
Guiding ring from ant. end Nerve ring from ant. end	8 8.25±0.43 (8–9) 119 116±3.5 (110–120)	8 115, 116
Neck length	332 324±13.0 (300–336)	334, 338
Expanded part of pharynx Cardia length	136 131±10.3 (115–142) 31 30±2.5 (27–35)	132, 133 28, 33
Body width at neck base	36 37±1.3 (36.0–39.5)	34, 40
Body width at mid body Body width at anus/cloaca	40 40±0.8 (39.0–41.5) 26 25.6±0.49 (25–26)	35, 42 32, 33
Vulva from anterior end	874 832±32.3 (790–874)	–
Prerectum length Rectum length	68 68±3.7 (62–72) 41 42.7±2.7 (40–47)	140, 162 42, 45
Tail length	145 131±7.9 (121–145)	25
Spicule length Lateral guiding pieces	– – – –	42, 43 9
Ventromedian supplements	– –	9