Mesodorylaimus spicatus, 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 : 27-31

Mesodorylaimus spicatus n. sp.

( Fig. 5 , 6 )

Measurements: Table 3 .

Description. Female. Body slightly curved ventrad upon fixation, tapering towards both the extremities but more so towards the posterior end. Cuticle with fine transverse striations, 1.5–2.5 µm thick at mid body and 3–4 µm on tail. Lateral chords about one-fourth of body width at mid body. Lateral, dorsal and ventral body pores indistinct.

Lip region offset by slight depression, about two and a half to three times as wide as high or about onethird as wide as body width at neck base. Lips slightly angular; 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 0.6–0.7 times lip region width from anterior end. Odontophore simple, rod-like, 1.2–1.5 times the odontostyle length. Nerve ring encircling the anterior slender part of pharynx, at 39.5–44% of neck length from anterior end. Pharyngeal expansion gradual; expanded portion occupying about 36–41%, of total neck length. Cardia elongate conoid, more than half of the corresponding body width long. Pharyngeal gland nuclei located as follows: D = 66– 67%; AS 1 = 29–35%; AS 2 = 45–50%; PS1 = 70–71%; PS2 = 73–74%.

Genital system didelphic-amphidelphic; both branches almost equally developed. Ovaries reflexed, short, not reaching or surpassing the oviduct-uterus junction, measuring 60–90 µm (anterior) and 70–98 µm (posterior); oocytes arranged in a single row except near the tip. Oviduct joining the ovary subterminally, measuring 87–118 µm (anterior) and 80–122 µm (posterior). It consists of a long slender part with prismatic cells and a pars dilatata distalis with distinct lumen. Sphincter poorly developed as a slight demarcation at oviduct-uterus junction. In some specimens sperm cells present either in uterus or oviduct. Uterus a simple tube with no clear demarcation of pars proximalis and pars dilatata distalis, measuring 59–69 µm (anterior) and 58–74 µm (posterior). Vulva transverse, slit-like. Vagina extending inwards for about half of the corresponding body width; pars proximalis vaginae 6–12 µm, with convex walls, encircled by circular musculature; pars refringens vaginae with two divergent, usually well separated triangular to drop-shaped sclerotizations, each measuring 1.5–2.0 x 3–4 µm and with a combined width (cw) = 5.0–7.5 µm; pars distalis vaginae short, 3–4 µm long with slightly curved walls. Prerectum 2.1–2.9 anal body widths long. Rectum about 1.3–1.6 times anal body width long. Tail conical, with a short digitate terminal portion, 1.4–1.7 times anal body width long. Caudal pores two pairs, one on each side.

Male: Supplements an adcloacal pair and 6–9 spaced ventromedians. Spicules dorylaimoid, slightly ventrally curved, 1.3–1.5 times anal body width long; lateral guiding pieces rod-like, about one-fourth of spicules length. Prerectum 1.8–3.1 cloacal body widths long, terminating within the range of supplements. Tail short conoid with rounded terminus, 0.6–0.8 cloacal body width long, and with two caudal pores on each side.

Type habitat and locality. Soil around the periphery of a nalla, near Aligarh-Mathura Ring road, Aligarh district, Uttar Pradesh, India.

Type material. Holotype female on slide Mesodorylaimus spicatus n. sp. /1; paratype males and females on slide Mesodorylaimus spicatus n. sp. / 2–9; 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 Jaén, Spain.

Diagnosis and relationships: Mesodorylaimus spicatus n. sp. is characterized by having 0.82–1.14 mm long body; lip region offset by slight depression; 10.0–12.5 µm long odontostyle; amphidelphic female genital system; transverse vulva, short spicate tail with rounded terminus.

The new species comes close to M. brevicaudatus Abolafia & Peña Santiago, 1996 ; M. pseudorecurvus Abolafia & Peña Santiago, 1996 and M. nodicaudatus ( Dey & Baqri, 1986) Ahmad, 1993 , but differs from the former in having slightly shorter body (vs L = 1.3–1.6 mm); narrower lip region width (vs lip region width 12– 13.5 µm); longer and differently shaped female tail (vs. c’ = 0.9–1.4, tail short with digitate terminus) and smaller spicules (vs 46.5–54 µm).

From M. pseudorecurvus , it differs in the shape of lip region (vs lip region with slightly raised papillae); smaller pharynx (vs pharynx 250–294 µm long); posteriorly situated vulva (vs V = 51–53); absence of cuticular irregularities near vulva (vs presence) and presence of males (vs absent).

From M. nodicaudatus , it differs in having slightly longer expanded part of pharynx (vs 33–34%); absence of cardiac disc (vs present); more posteriorly situated vulva (vs V = 50–53); smaller female tail (vs tail = 50– 55 µm, c = 16.8–21.6 & c’= 2.6–3.0), and smaller spicules (vs 36–38 µm).

Figures

FIGURE 5. Mesodorylaimus spicatus 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 6. Mesodorylaimus spicatus n. sp. A: Anterior end showing amphid. B: Anterior region. C: Expanded part of pharynx. D: Vulval region. E: Female genital branch (anterior). F: Female posterior region. G: Female tail. H: Male posterior region showing ventromedian supplements. I: Male tail.

Tables

TABLE 3. Morphometrics of Mesodorylaimus spicatus n. sp. All measurements in µm (except L) and in the form: mean standard deviation (range).

Characters	Holotype Paratype females	Paratype males
n	8	7
L (mm) a	0.97 0.96 ±0.10 (0.81–1.14) 30.4 29.4 ±1.5 (26.7–31.3)	0.96±0.08(0.86–1.1) 32.5±1.2 (30.9–34.5)
b	4.6 4.5±0.23 (4.2–4.9)	4.5±0.13 (4.3–4.7)
c c`	30.4 31.8±2.2 (28.1–35.8) 1.68 1.6±0.11 (1.45–1.73)	57.3 ± 2.7 (54–62) 0.73 ± 0.04 (0.66–0.81)
V	56.6 56.7±1.4 (54.9–60.1)	–
G1 G2 Lip region width	15.7 16.7±0.8 (15.7–18.4) 16.9 17.1±1.3 (14.5–18.4) 10 10±0.3 (10–11)	– – 10.14 ± 0.3 (10–11)
Lip region height	4 3.9 ±0.5 (3.0–4.5)	3.6±0.22(3.5–4)
Amphid aperture Odontostyle length	5 5.25±0.35 (5–6) 11 11.6 ±05 (10.5–12.5)	4.6±0.47 (4–5) 11.2±0.6 (10–12)
Odontophore length	15 15.4±0.5 (15–16)	15±0.5 (14–16)
Guiding ring from ant. end Nerve ring from ant. end	7 7.0 89 87.25±5.4 (81–95)	7.7±0.45 (7–8) 85.7±4.03 (81–92)
Neck length	212 211±12.4 (193–228)	213±12.3 (193–237)
Expanded part of pharynx Cardia length	78 80.5±6.2 (70–88) 20 19.7±1.2 (17–21)	79±7.8 (70–94) 19±2.1 (17–24)
Body width at neck base	29 29.7±2.3 (27–34)	28.5±0.7 (28–30)
Body width at mid body Body width at anus/cloaca	32 32.8±2.2 (30–37) 19 18.5±1.2 (17–20)	30±2.7 (28–36) 23± 0.9 (21–24)
Anterior genital branch	153 162±15 (150–183)	–
Posterior genital branch Vaginal depth	165 165±14 (150–196) 20 17.5±1.7 (16–20)	– –
Vulva from anterior end	552 528±44.4 (457–600)	–
Prerectum length Rectum length	55 46.3±4.6 (40–55) 29 29.4±2.5 (26–35)	61.8±10.4 (42–72) 35.8±1.81 (32–38)
Tail length	32 30± 2.8 (25–34)	16.7±0.69 (16–18)
Spicule length Lateral guiding pieces	– –	31±1.69 (28–33) 7.3±0.47 (7–8)
Ventromedian supplements	–	7–9