Axonchium indicum, Kumar & Ahmad, 2023

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 : 17-21

Axonchium indicum sp. nov.

urn:lsid:zoobank.org:act:116B7509-1BE9-4315-A6D7-5B819B4C2789

Figs 5–6 , Table 5

Diagnosis

Axonchium indicum sp. nov. is characterized by having a 1.2–1.4 mm long body; lip region angular and offset; odontostyle fusiform, 8–9 µm long; the two parts of the pharynx separated by a deep constriction; expanded part of pharynx short, occupying about 39–49% of total neck length; vagina lumen narrow with thickened walls, slightly bent posteriorly; vulva transverse and pre-equatorial; anterior uterine sac short, 0.9–1.6 times the mid-body diameter; tail bluntly conoid.

Etymology

The new species is named after its country of origin, India.

Material examined

Holotype INDIA • ♀; Kerala State, Kollam District, Pathanampuram ; 9°5ʹ27.5136ʺ N, 76°53ʹ22.6702ʺ E; 10–15 cm depth; 3 Nov. 2017; roots of grasses (unidentified); slide reference number AMU/ZD/NC/ Axonchium indicum /1.

Paratypes INDIA • 6 ♀♀; same collection data as for holotype; slide reference number AMU/ZD/NC/ Axonchium indicum /2–3 • 2 ♀♀; same collection data as for holotype; slide reference number AMU/ZD/ NC/ Axonchium indicum /4, nematode collection of the Zoological Survey of India, Kolkata, India .

Type habitat and locality

Soil samples collected around the roots of grasses (unidentified) from Pathanampuram, Kollam District, Kerala State, India.

Description

Female

Body curved ventrad upon fixation, 1.2–1.4 mm long. Cuticle with fine transverse striations, about 1–2 µm thick at the anterior, 1–2 µm at mid-body, and 4–5 µm on tail tip. Lateral chords 5–7 µm wide, or 1/ 7 to 1/ 5 (14–20%) of mid-body diameter with indistinct glandular bodies. Lateral, dorsal and ventral body pores indistinct. Lip region angular, offset by deep constriction, 2.0–2.5 times as wide as high, or about 1/ 5 to ¼ (22– 25%) of body diameter at neck base. Lips incompletely separate.Amphid fovea stirrup-shaped, their aperture occupying about 0.7–0.8 times lip region diameter, fusus just opposite or slightly posterior to odontophore level. Guiding ring single, at 0.9–1.1 times lip region diameter from anterior end. Odontostyle fusiform, 4.0–4.5 times as long as wide, or 0.9–1.1 times lip region diameter long, its aperture occupying about ⅓ of its length. Odontophore simple, rod-like, 1.2–1.6 times as long as odontostyle. Nerve ring encircling anterior slender part of pharynx at 28–33% of neck length from anterior end. Anterior slender part of pharynx quite muscular, separated from posterior expanded part by a deep constriction. Expanded part of pharynx 6.0–10 times as long as wide, or 3.7–5.6 times as long as body diameter at neck base, and occupying about 2/ 5 to ½ (39–49%) of total neck length, enclosed in a thick muscular sheath with straight bands. Only dorsal pharyngeal gland and its orifice visible: DO = 53–62; DN = 55–64; DO–DN = 0.3–1.9. Cardia oblong, 1.1–2.0 times as long as wide, and occupying about 2/ 7 to 2/ 5 (28–37%) of corresponding body diameter.

Genital system mono-opisthodelphic. Anterior genital branch represented by a small sac, measuring 35–59 µm or 0.9–1.6 times mid-body diameter long, and occupying about 2.6–4.7% of total body length. Posterior branch well developed; ovary reflexed, measuring 43–71 µm long with squamous shaped oocytes arranged in a single row except near tip; oviduct joining ovary subterminally, measuring 35–70 µm or 1.0–1.9 times mid-body diameter long, consisting of a long slender part with prismatic cells and a wide pars dilatata; oviduct-uterus junction marked by sphincter; uterus 46–68 µm or 1.2– 1.9 times mid-body diameter long, differentiated into a large proximal part with distinct lumen, and a short spherical pars dilatata with clear lumen; sperms not observed. Vulva transverse. Vagina slightly bent posteriad, extending inwards about ½ to three-fifths (52–60%) of corresponding body diameter long, vaginal lumen slender with thickened distal region but not differentiated from body cuticle; pars proximalis vaginae slender, surrounded by well-developed circular musculature; pars refringens vaginae absent; pars distalis vaginae 7–9 µm long. Prerectum 5.2–9.0 and rectum 1.2–1.5 times anal body diameter long. Tail short, bluntly conoid. Caudal pores two on each side.

Male

Not found.

Taxonomic remarks

The new species differs from all known species of Axonchium in its comparatively short posterior expanded part of the pharynx. However, it comes close to A. nitidum Jairajpuri, 1964 in its body size and tail shape, but differs from it in having a shorter pharynx (b = 3.3–3.7 vs 2.2–3.0); anterior vulva position (V = 45–48 vs 52–53); longer anterior uterine sac (G1 = 2.5–4.7 vs 0.8–1.3 or 0.9–1.6 vs 0.5 times the corresponding body diameter long) and male not found (vs known).

In the body size and vaginal character, the new species also resembles A. perplexans Siddiqi, 1995 but differs in having a robust body (a = 34–38 vs 49–57); shape of lip region (angular vs hemispheroid); shorter pharynx (b = 3.3–3.7 vs 2.8–3.0); anterior vulva position (V = 45–48 vs 54–56); longer anterior uterine sac (0.9–1.6 times vs less than corresponding body diameter long); and tail shape (conoid vs hemispherical to clavate).

The new species also resembles A. bulbosum Williams, 1958 but differs in the shape of the lip region (angular lips vs with rounded outer and inner portion); shorter pharynx (b = 3.3–3.7 vs 2.4–2.9); anterior vulva position (V = 45–48 vs 55–57); slightly longer anterior uterine sac (G1 = 2.5–4.7 vs 1.7–2.3 or 0.9–1.6 times vs shorter than corresponding body diameter long); the nature of the vagina (vaginal lumen slender, not enlarged vs distinctly enlarged with rounded or spheroid walls); and tail shape (conoid vs bulboid with extremely thick cuticle at terminus).

Figures

Fig. 5. Axonchium indicum sp. nov. A–C. Paratype 2, ♀ (slide 2). D–H. Paratype 6, ♀ (slide 4). A. Entire body. B. Anterior region. C. Anterior end showing amphid. D. Junction between anterior slender and posterior expanded part of pharynx.E. Cardia. F. Female genital system. G. Vulva. H. Female posterior region.

Fig. 6. Axonchium indicum sp. nov. (LM photographs). A–B. Paratype 2, ♀ (slide 2). C–I. Paratype 6, ♀ (slide 4). A. Anterior region. B. Anterior end showing amphid. C. Pharynx. D. Junction between two parts of the pharynx. E. Cardia. F. Vulva. G. Anterior uterine sac. H. Posterior genital branch. I. Posterior region. Scale bars: A–B, D–I = 10 µm; C = 20 µm.