Axonchium transkeiense Nair, 1973

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 : 9-13

Axonchium transkeiense Nair, 1973

Fig. 3 , Table 3

Axonchium transkeiense Nair, 1973: 545–548 .

Material examined

INDIA – Kerala State • 8 ♀♀, 4 ♂♂; Palakkad District, Silent Valley National Park ; 11°08ʹ0ʺ N, 76°28ʹ0ʺ E; 10–15 cm depth; 25 Oct. 2017; soil samples collected around the roots of grasses (unidentified); slide reference number AMU/ZD/NC/ Axonchium transkeiense /4–8. – Kozhikode District • 1 ♀, 3 ♂♂; village Mukkali ; 11°40′10.38″ N, 75°33′26.64″ E; 10–15 cm depth; 25 Oct. 2017; soil samples collected around the roots of shrubs plants (unidentified); slide reference number AMU/ ZD/NC/ Axonchium transkeiense /1–3 .

Description

Female

Body curved ventrad upon fixation, 1.4–1.6 mm long. Cuticle with fine transverse striations, about 1–2 µm thick at anterior and mid-body, 8–10 µm on tail tip in females and 5–7 µm in males. Lateral chords 4–6 µm wide, or one-tenth to one-seventh (9–14%) of mid-body diameter, with weakly developed glandular bodies, 34–45 in number: 10–15 in pharyngeal region, 4–6 from pharyngeal base to vulva, 19–23 from vulva to anal region and one in caudal region. Lip region offset, marked by deep constriction, 1.8–2.5 times as wide as high, or about 1/ 6 to ¼ (17–23%) of body diameter at neck base. Lips conoid, separate, outer and inner portions demarcated by shallow depression. Amphid fovea stirrup-shaped, their aperture occupying about 0.6–0.7 times lip region diameter, fusus lying opposite or slightly above 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 1.0–1.3 times lip region diameter long; 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 19–23% 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 11–18 times as long as wide, or 7.1–10.2 times as long as body diameter at neck base, occupying about 3/ 5 to ⅔ (61–70%) of total neck length, enclosed in a thick muscular sheath with straight bands. Only dorsal pharyngeal gland and its orifice visible: DO = 31.7–41.2; DN = 32.2–41.6; DO–DN = 0.4–0.8. Cardia oblong, 0.9–1.3 times as long as wide, occupying about 1/ 7 to ¼ (15–25%) of corresponding body diameter.

Genital system mono-opisthodelphic. Anterior genital branch represented by a simple uterine sac, with slight proximal constriction, measuring 77–111 µm or 1.8–2.5 times mid-body diameter long, and occupying about 5.2–7.3% of total body length; mostly containing spindle-shaped sperms. Posterior genital branch well developed; ovary reflexed, not reaching oviduct-uterus junction, measuring 74– 128 µm long with squamous-shaped oocytes arranged in a single row except near tip; oviduct joining ovary subterminally, 85–107 µm or 1.6–2.5 times mid-body diameter long, consisting of a long slender part with prismatic cells and well developed pars dilatata with distinct lumen; oviduct-uterus junction marked by sphincter; uterus 70–127 µm or 1.7–3.0 times mid-body diameter long, differentiated into a long proximal region with distinct lumen, and a short spherical distal pars dilatata. Vulva transverse. Vagina almost straight, or slightly bent posteriorly, extending inwards about 2/ 5 to ½ (42–52%) of corresponding body diameter; vaginal walls thick, not differentiated from body cuticle, widening toward uterus with anchor-shaped ends, posterior half encircled by well developed circular musculature; pars proximalis vaginae 10–12 × 5–6 µm; pars refringens vaginae absent; pars distalis vaginae 15–18 µm long. Prerectum 4.5–6.2 and rectum 1.1–1.3 times anal body diameter long. Tail broadly conoid to hemispherical. Caudal pores two on each side.

Male

Similar to female in general morphology, except for posterior region of body being more curved ventrad. Genital system diorchic, with oppositely outstretched testes, enclosed in a conspicuous muscular sheath, sperms spindle-shaped, measuring 4–5 × 1–2 µm. In addition to adcloacal pair, located at 7–9 µm from cloacal aperture, a series of 6–8 irregularly spaced ventromedian supplements, beginning at 27–40 µm from adcloacal pair, or slightly above range of spicules. Copulatory muscles conspicuous, beginning from level of middle of spicules and continuing until the level of last supplement. Spicules arcuate, proximal part slender with slightly curved ends, distal part unusually wide; total length along arc 1.0– 1.1 times as long as chord, 4.1–4.7 times maximum width, or 1.3–1.4 times body diameter at cloacal aperture. Curvature about 139–149°. Dorsal contour regularly convex with curved distal end; ventral contour concave with weakly developed hump, located at 50–54% of spicule total length from its anterior end; head slender, curved, occupying about 13–28% of spicule total length; median piece simple with or without fine projection in head region, 9–15 times as long as wide, or occupying about 25–37% of spicule maximum width; posterior region with blunt ends, 5–6 µm wide; a sac-like structure filled with small granules, located at level of middle part of spicules. Lateral guiding pieces with slightly bifurcated distal end, about 4.5–6.6 times as long as wide or about 1/ 5 to ⅓ (21–30%) of total spicule length. Prerectum 5.9–7.3 and rectum 1.3–1.5 times cloacal body diameter long. Tail with bluntly rounded terminus. Caudal pores two on each side.

Remarks

Nair (1973) described this species from the Transkei, South Africa, and differentiated it from A. heynsi Nair, 1973 and A. metobtusicaudatum (Schuurmans Stekhoven & Teunissen, 1938) on the basis of its shorter and less curved body, longer vagina, shape of spicules, shape of lateral guiding pieces and arrangements of ventromedian supplements. The present population from Kerala, India, conforms well with the type description except for having a shorter body (1.3–1.6 vs 1.8–2.0 mm); comparatively thinner cuticle at mid-body (1–2 vs 3–4 µm); presence of lateral glandular bodies (vs indistinct glandular bodies); narrower amphid aperture (two-thirds vs fourth-fifths of lip region diameter); shorter cardia (15–25 vs 33% of corresponding body diameter); shorter prerectum (4.5–5.2 vs 6.5–8.0 times the anal body diameter long); shorter spicules (35–38 vs 43–46 µm); shorter and simple rod-like lateral guiding pieces with poorly bifurcated distal end (8–10 vs 16–17 µm long with prominent bifurcate distal end and its proximal end slightly expanded); sac-like structure filled with small granules present at the level of spicules (vs absent) and longer tail (c = 51–61 vs 64–81). This is the first record of this species from India and first ever report since its original description.

Figures

Fig. 3. Axonchium transkeiense Nair, 1973 (LM photographs). A. Anterior region. B. Anterior end showing amphid. C. Junction between two parts of pharynx. D. Cardia. E. Vulva and vagina. F. Female genital branches. G. Ventromedian supplement series. H. Male posterior end. I. Lateral guiding piece. J. Arrow indicating sac-like structure in the male posterior region. K. Female posterior end. Scale bars: A–E, H–K =10 µm; F = 50 µm; G = 20 µm.