Axonchium saccatum 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 : 6-9

Axonchium saccatum Jairajpuri, 1964

Fig. 2 , Table 2

Axonchium saccatum Jairajpuri, 1964: 179 .

Axonchium saccatum – Hechler 1969: 346. — Nair 1973: 535–540.

Material examined

INDIA • 5 ♀♀, 2 ♂♂; Kerala State, Palakkad District, Mukkali ; 11°3ʹ33ʺ N, 76°32ʹ25ʺ E; 10–15 cm depth; 25 Oct. 2017; soil samples collected around the roots of grasses (unidentified); slide reference number AMU/ZD/NC/ Axonchium saccatum /1–5 .

Description

Female

Body slightly curved ventrad upon fixation, 1.85–1.9 mm long. Cuticle with fine transverse striations, about 1–2 µm thick at anterior region, 2–3 µm at mid-body, 7–8 µm on tail tip in females and 6 µm in males. Lateral chords 5–10 µm wide, or about 1/ 10 to 1/ 5 (9–18%) of mid-body diameter with weakly developed glandular bodies, 36–44 in number: 10–16 in pharyngeal region, 5–12 from pharyngeal base to vulva, 15–21 from vulva to anal region and one in caudal region. Lateral, dorsal and ventral body pores indistinct. Lip region offset by deep constriction, 2.2–2.5 times as wide as high, or about 1/ 7 to 1/ 5 (14–19%) of body diameter at neck base. Lips rounded, separate, outer and inner portions demarcated by weak depression. Amphid fovea stirrup-shaped, their aperture occupying about 0.6– 0.7 times lip region diameter, fusus slightly anterior to or at level of odontophore base. Guiding ring single, at 0.8–1.0 times lip region diameter from anterior end. Odontostyle fusiform, 4–5 times as long as wide, or 0.9–1.0 times lip region diameter long, its aperture occupying about ⅓ of its length. Odontophore simple, rod-like, 1.3–1.5 times as long as odontostyle. Nerve ring encircling the anterior slender part of pharynx at 21–29% 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 7.2–12 times as long as wide, or 4.3–7.4 times longer than body diameter at neck base, occupying about ½ to two-thirds (50–63%) of total neck length, enclosed in a distinct muscular sheath with straight muscular bands. Only dorsal pharyngeal gland and its orifice visible: DO = 37–54; DN = 38–55; DO–DN = 0.3–0.7. Cardia tongue-like, 1.3–2.3 times as long as wide, occupying about 1/ 5 to ⅓ (20–35%) of corresponding body diameter.

Genital system mono-opisthodelphic.Anterior genital branch represented by simple uterine sac,measuring 111–161 µm or 1.9–3.0 times mid-body diameter long, and occupying about 5.9–8.4% of total body length; mostly containing spindle-shaped sperms. Posterior branch well developed; ovary reflexed, not reaching oviduct-uterus junction, measuring 59–99 µm long with squamous-shaped oocytes arranged in a single row except near tip; oviduct joining ovary subterminally, 81–126 µm or 1.5–2.3 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 98–145 µm or 1.8–2.4 times the mid-body diameter long, differentiated into a relatively large proximal region with wide lumen, a narrow intermediate region, and a short spherical distal pars dilatata. Vulva transverse. Vagina almost straight, narrowing within sphincter, extending inwards about ½ (45–51%) of corresponding body diameter; vaginal wall thick, distinctly differentiated from body cuticle; pars proximalis vaginae longer than wide, 12–16 × 4–6 µm, somewhat sigmoid, surrounded by well-developed circular musculature; pars refringens vaginae absent; pars distalis vaginae 11–13 µm long. Prerectum 6–9 and rectum 0.9–1.3 times anal body diameter long. Tail short, hemispheroid. Caudal pores three 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 spindle-shaped, measuring 3–4 × 1–2 µm. In addition to adcloacal pair, located at 9 µm from cloacal aperture, 5–6 irregularly spaced ventromedian supplements, beginning at 13 µm from adcloacal pair, or slightly posterior to proximal end of spicules. Copulatory muscles conspicuous, beginning from level of middle of spicules and continuing until level of last supplement. Spicules well developed, arcuate, proximal region slender with curved ends and broad and truncate distal ends; total length along arc 1.3 times as long as chord, 5.0–5.4 times maximum width or 1.3–1.4 times body diameter at cloacal aperture. Curvature about 132˚–136˚. Dorsal contour regularly convex, comparatively thick at distal end; ventral contour concave without a distinct hump; head slender with curved ends, occupying about 37–38% of total spicules length; median piece simple, 8–9 times as long as wide, occupying about 37% of spicules maximum width; posterior ends 6–7 µm wide. Lateral guiding pieces sclerotized, slightly curved with bifid distal end, about 5.0–5.5 times as long as wide or about ¼ of total spicule length. Prerectum long, 9.1–9.3 and rectum 0.8–1.3 times cloacal body diameter long. Tail hemispheroid with bluntly truncated terminus. Caudal pores two on each side.

Remarks

Jairajpuri (1964) described A. saccatum from Trivandrum, Kerala, India, and differentiated it from A. gossypii De Coninck, 1962 by the presence of a longer body, longer pharynx and prerectum. Hechler (1969) synonymized A. saccatum with A. gossypii De Coninck, 1962 . Nair & Coomans (1973) synonymized A. gossypii with A. metobtusicaudatum Schuurmans-Stekhoven & Teunissen, 1938 . Nair (1973) redescribed this species based on two paratype females and two paratype males loaned from the original author, and differentiated it from A. metobtusicaudatum , in having a relatively wider lip region with conoid lips, in the shape of the lateral guiding pieces and the presence of two caudal pores on each side, and concluded that both species are distinctly different. The two male specimens observed showed variation in the shape of spicules and arrangements of ventromedian supplements, i.e., a robust spicule in combination with ventromedian supplements beginning just opposite to the proximal end of the spicule ( Nair 1973: 539, fig. 10c, h) vs a comparatively slender spicule with a strongly curved head region and ventromedian supplements beginning the spicule range ( Nair 1973: 539, fig. 10c, h). Probably the males were from two different species; however, she (l.c.) left it for further observation on additional specimens. In the present population both the male specimens have slender spicules with a curved head region and ventromedian supplements beginning within the range of the spicules; however, the females conform well to the original and subsequent descriptions except in having a slightly shorter prerectum in females (6–9 vs 11 times anal body diameter).

Figures

Fig. 2. Axonchium saccatum Jairajpuri, 1964 (LM photographs). A. Anterior region. B. Anterior region showing amphid. C. Junction between two parts of the pharynx. D. Cardia. E–F. Vulva and vagina. G–H. Female genital branches. I. Ventromedian supplements. J. Spicule. K. Male posterior region, arrow indicating lateral guiding piece. L. Arrow indicating beginning of ventromedian supplements. M. Female posterior end. Scale bars: A–F, I–M = 10 µm; G–H = 20 µm.