Axonchium nitidum Jairajpuri, 1964

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 : 3-5

Axonchium nitidum Jairajpuri, 1964

Fig. 1 , Table 1

Axonchium nitidum Jairajpuri, 1964: 178–179 .

Axonchium nitidum – Hechler 1969: 346. — Nair 1973: 529–532. — Dhanachand et al. 1982: 118–119.

Material examined

INDIA • 6 ♀♀; Kerala State, Palakkad District, Mukkali ; 11°3ʹ33ʺ N, 76°32ʹ25ʺ E; 5–20 cm depth; 25 Oct. 2017; soil samples collected around the roots of grasses (unidentified); slide reference number AMU/ZD/NC/ Axonchium nitidum /1–5 .

Description

Female

Body curved ventrad upon fixation, 1.3–1.5 mm long. Cuticle with fine transverse striations, about 1 µm thick at anterior region, 1–2 µm at mid-body and 4–6 µm on tail tip. Lateral chords 3–4 µm wide, about one-eighth to one-seventh (12–15%) of mid-body diameter. Lateral, dorsal and ventral body pores indistinct. Lip region offset by deep constriction, 1.7–2.7 times as wide as high, or about ¼ to ⅓ (26–31%) of body diameter at neck base. Lips bluntly conoid and incompletely separate. Amphids fovea stirrup-shaped, their aperture occupying about 0.6–0.8 times the lip region diameter, fusus slightly posterior to odontophore level. Guiding ring single, at 0.7–1.0 times lip region diameter from anterior end. Odontostyle fusiform, 4–5 times as long as wide, or 1.0–1.1 times lip region diameter long, its aperture occupying about ⅓ of its length. Odontophore simple, rod-like, 1.2–1.4 times as long as odontostyle. Nerve ring encircling anterior slender part of pharynx at 20–21% 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 16–26 times as long as wide, or 10.5–14.3 times longer than body diameter at neck base, and occupying about 3 / 5 to ⅔ (58–65%) of total neck length, enclosed in a thick muscular sheath with straight bands. Only dorsal pharyngeal gland and its orifice visible: DO = 41.4–44.1; DN = 42.3–45.1; DO–DN = 0.8–1.0. Cardia oblong, 1.0–2.2 times as long as wide, occupying about ¼ to ½ (23–50%) of corresponding body diameter.

Genital system mono-opisthodelphic. Anterior genital branch represented by a small sac, measuring 13– 23 µm or 0.5–0.9 times mid-body diameter long. Posterior branch well developed; ovary reflexed, not reaching oviduct-uterus junction, measuring 31–75 µm long with squamous shaped oocytes arranged in a single row except near tip, oviduct joining ovary subterminally, measuring 41–63 µm or 1.6–2.3 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 sphincter; uterus 42–50 µm or 1.5–1.9 times mid-body diameter long, differentiated into a large proximal region with wide lumen, a narrow slightly convoluted intermediate region, and a short spherical pars dilatata with distinct lumen. Vulva transverse. Vagina bent posteriad, extending inwards about 3 / 5 to less than ¾ (57–70%) of corresponding body diameter, vaginal walls not differentiated from body cuticle; pars proximalis vaginae 7–9 × 3–4 µm; pars refringens vaginae absent; pars distalis vaginae 7–10 µm long. Prerectum 6.2–9.7 and rectum 1.3–1.6 times anal body diameter long. Tail short, broadly conoid with rounded terminus. Caudal pores two on each side.

Male

Not found.

Remarks

Jairajpuri (1964) described this species from Jorhat, Assam, India based on females only, and differentiated it from A. bulbosum Williams, 1958 mainly in having ventral body posture, a longer prerectum and the shape and size of tail. Hechler (1969) synonymized A. nitidum with A. bulbosum Williams, 1958 , and mentioned that body posture and prerectum sizes may vary in the same species; hence, it can not be considered a separate species only on bases of these characters. Later, Nair (1973) re-studied the type material of both species, and revalidated A. nitidum . Dhanachand et al. (1982) for the first time reported a male of this species from Manipur, India. The present population conforms well with the original description except in having a slightly shorter odontostyle (8.0 vs 8.5–10 µm), longer vagina (57–70 vs 50% of corresponding body diameter), longer rectum (1.3–1.6 vs less than one anal body width) and from the Manipur population in a having comparatively longer and more slender body (L = 1.3–1.5 vs 1.32–1.34 mm, a = 51–56 vs 42–45), shorter tail (c = 58–67 vs 55–58), and the absence of males (vs male present with 21 µm long spicules).

Figures

Fig. 1. Axonchium nitidum Jairajpuri, 1964 (LM photographs). A. Anterior region. B. Anterior end showing amphid. C. Junction between two parts of pharynx. D. Cardia. E–F. Female vulva and vagina. G. Female genital branch. H. Female posterior region. Scale bars: A–F, H = 10 µm; G = 20 µm.