Axonchium vallum Ahmad & Jairajpuri, 1982

Kumar, Sumit & Ahmad, Wasim, 2023, Six new and four known species of the genus Axonchium Cobb, 1920 (Nematoda: Dorylaimida: Belondiroidea) from the Western Ghats of India, European Journal of Taxonomy 857, pp. 1-56 : 13-16

Axonchium vallum Ahmad & Jairajpuri, 1982

Fig. 4 , Table 4

Axonchium vallum Ahmad & Jairajpuri, 1982: 23–25 .

Material examined

INDIA – Kerala State • 4 ♀♀, 1 ♂; Kollam District, Pathananpuram ; 9°5′33.72″ N, 76°51′40.32″ E; 10–15 cm depth; 3 Nov. 2017; soil samples collected around the roots of grasses (unidentified) in Ficus elastica garden; slide reference number AMU/ZD/NC/ Axonchium vallum /1–3. – Thiruvananthapuram District • 3 ♀♀, 3 ♂♂; Ponmudi Hill ; 8°45′37″ N, 77°7′0″ E; 10–15 cm depth; 4 Nov. 2017; soil samples collected around the roots of grasses (unidentified); slide reference number AMU/ZD/NC/ Axonchium vallum /4–6 .

Description

Female

Body slightly curved ventrad upon fixation, 1.7–1.8 mm long. Cuticle with fine transverse striations, about 2 µm thick at anterior region, 2–3 µm at mid-body, 7–9 µm at tail tip in females and 6–8 µm in males. Lateral chords 4–8 µm wide, or about 1/ 13 to 1/ 6 (7–15%) of mid-body diameter, with distinct glandular bodies: 13–14 in pharyngeal region, 5–6 from pharyngeal base to vulva, 4–21 from vulva to anal region and one in caudal region. Lateral, dorsal and ventral body pores indistinct. Lip region rounded, offset by deep constriction, 1.8–2.5 times as wide as high, or about 1/ 6 to 1/ 5 (16–20%) of body diameter at neck base. Amphid fovea cup-shaped, their aperture occupying about 0.7–0.9 times lip region diameter, fusus just opposite odontophore level. Guiding ring single, at 1.0–1.1 times lip region diameter from anterior end. Odontostyle fusiform, 6–7 times as long as wide, or 1.2–1.4 times lip region diameter long, its aperture occupying about ⅓ of its length. Odontophore simple, rod-like, 1.0–1.2 times as long as odontostyle. Nerve ring encircling anterior slender part of pharynx at 17–24% of neck length from anterior end. Anterior slender part of pharynx quite muscular, separated from the posterior expanded part by a deep constriction. Expanded part of pharynx 10.5–17.8 times as long as wide, or 7.1–11 times as long as body diameter at neck base, and occupying about 3/ 5 to ⅔ (60–70%) of total neck length, enclosed in a thick muscular sheath with straight bands. Only dorsal pharyngeal gland and its orifice visible: DO = 30.3–42; DN = 30.5–42.3; DO–DN = 0.3–0.5. Cardia tongue-like, 1.4–2.5 times as long as wide, occupying about ¼ to 2/ 5 (24–37%) of corresponding body diameter. Uninucleated coelomocytes observed near cardia and in post-vulval region, 1–3 between pharyngeal base to vulva, measuring 16–72 × 10–23 µm and 2–4 from vulva to anal region, measuring 16–32 × 6–10 µm, each glandular organ ovoid in shape.

Genital system mono-opisthodelphic. Anterior genital branch represented by simple uterine sac, measuring 110–154 µm or 2.1–3.0 times mid-body diameter long and occupying about 6.2–8.6% of body length; mostly containing spindle-shaped sperms. Posterior branch well developed; ovary reflexed, rarely reaching oviduct-uterus junction, measuring 47–135 µm long with squamous shaped oocytes arranged in a single row except near tip; oviduct joining ovary subterminally, measuring 67–91 µm or 1.3–1.8 times mid-body diameter long, consisting of a long slender part with prismatic cells and a well developed pars dilatata with distinct lumen; oviduct-uterus junction marked by a sphincter; uterus 90–169 µm or 1.9–3.4 times midbody diameter long, differentiated into a large proximal region with wide lumen, a narrow intermediate region, and a short spherical pars dilatata with distinct lumen. Vulva transverse. Vagina slightly bent posteriad, extending inwards about two-fifths to three-fifths (43–57%) of corresponding body diameter; pars proximalis vaginae longer than wide, 10–17 × 3–4 µm, with somewhat sigmoid walls surrounded by circular musculature; pars refringens vaginae absent; pars distalis vaginae 12–14 µm long, distinctly enlarged at posterior half with rounded walls. Prerectum 4–6 and rectum 1.1–1.4 times anal body diameter long. Tail short, hemispheroid. Caudal pores two on each side.

Male

Similar to female in general morphology, except for posterior region of the body being more curved ventrad. Genital system diorchic, with oppositely outstretched testes; sperms elongate spindle-shaped, measuring 5–6 × 2 µm. In addition to adcloacal pair, located at 6–9 µm from cloacal aperture, only two very widely spaced ventromedian supplements, beginning just in front of proximal end of spicules; first located at 43–61 µm from adcloacal pair, second at 108–136 µm from first supplement. Copulatory muscles conspicuous, beginning from level of middle of spicules and continuing until the level of last supplement. Spicules arcuate with distal and proximal region curved; total length along arc 1.0–1.1 times as long as chord, 5.4–6.1 times maximum width and 1.4–1.6 times body diameter at cloacal aperture. Curvature about 118˚–126˚. Dorsal contour regularly convex; ventral contour concave, bearing weakly developed hump, located at 31–43% of spicule total length from its anterior end; head slender and slightly curved, occupying about 13–18% of spicule total length; median piece 7–12 times as long as wide and occupying about 40–60% of spicule maximum width; posterior end 4–5 µm wide. Lateral guiding pieces sclerotized, slightly curved with bifurcated distal end, about 7–9 times as long as wide or about ⅓ of total spicule length. Prerectum long, 6.0–7.8 and rectum 1.4–1.5 times cloacal body diameter long. Tail short, hemispheroid. Caudal pores two on each side.

Remarks

Ahmad & Jairajpuri (1982) described this species from Silent Valley, India and differentiated it from A. shamimi Baqri & Khera, 1976 and A. siddiqii Coomans & Nair, 1975 in having a longer body and odontostyle, the shape and size of spicules and the number of ventromedian supplements. The morphometrics in the two populations are very similar. However, the Kollam population differs slightly from the Thiruvananthapuram population in having a shorter body in the male (L = 1.6 vs 1.68–1.76 mm); shorter spicules (49 vs 54–55 µm) and lateral guiding pieces (14 vs 15–18 µm). The present population conforms well with the original description except for having distinct lateral glandular bodies (vs indistinct); comparatively narrower lip region (9–10 vs 10–11 µm or 1/ 6 to 1/ 5 vs ¼ body diameter at neck base); longer odontostyle (12–13 vs 10–12 µm or 1.2–1.4 times vs about one lip region diameter long); shorter prerectum (4–6 vs 6–7 anal body diameter in females and 6.0–7.8 vs 8–9 times cloacal body diameter in males); and slightly shorter spicules (49–55 vs 55–57 µm or 1.4–1.6 vs 1.6–1.7 times cloacal body diameter).

Figures

Fig. 4. Axonchium vallum Ahmad & Jairajpuri, 1982 (LM photographs). A. Anterior region. B. Anterior region showing amphid. C. Junction between two parts of pharynx. D. Cardia. E. Vulva and vagina. F–G. Female genital branches. H. Ventromedian supplements. I. Lateral glandular bodies. J. Male posterior end. K. Lateral guiding piece. L. Female posterior end. Scale bars: A–E, I–L = 10 µm; F–G = 50 µm; H = 20 µm.