Dorylaimellus andrassyi Heyns, 1963

Kumar, Sumit & Ahmad, Wasim, 2024, Description of five new and four known species of Dorylaimellus Cobb, 1913 with perioral disc (Nematoda: Belondiroidea) from the Western Ghats of India, European Journal of Taxonomy 925 (1), pp. 1-45 : 3-6

Dorylaimellus andrassyi Heyns, 1963

Fig. 1 , Table 1

Dorylaimellus andrassyi Heyns, 1963: 400–402 .

Dorylaimellus pastura Yeates, 1979: 435–437 .

Dorylaimellus andrassyi — Chaturvedi & Khera 1979: 49–50. — Jordaan & Heyns 1984: 286–288. — De Bruin & Heyns 1993: 22–23.

Material examined

INDIA • 7 ♀♀, 2 ♂♂; Kerala State, Ernakulam district, Thattekad Bird Sanctuary ; 10°7′48″ N, 76°40′48″ E; 5–20 cm deep; 28 Oct. 2017; soil samples collected from around the roots of grasses (unidentified); slide reference number AMU/ZD/NC / Dorylaimellus andrassyi /1–5 .

Description

Female

Body slightly curved ventrad upon fixation, 1.0– 1.2 mm long. Cuticle with distinct transverse striations, about 1 µm at anterior and mid-body, 2–3 µm on tail tip. Lateral chords 5–8 µm wide, or one-fourth to two-fifths (23–40%) of the body diameter at mid-body with weakly developed glandular bodies, about 46–49 in number; 4 in neck region, 16–18 from pharyngeal base to vulva, 23–25 from vulva to anal region and 2 in caudal region. Ventral body pores distinct, about 35–38 in number; 5–6 in pharyngeal region, 12–15 from pharyngeal base to vulva, 18–19 from vulva to anal region; dorsal and lateral body pores indistinct. Lip region cap-like, offset by constriction, 2.3 times as wide as high, or about one-third to two-fifths (33–40%) of body diameter at neck base. Lips rounded, amalgamated, perioral disc distinct. Cheilostome a truncate cone with refractive walls and distinct cuticularized pieces near oral aperture. Amphids fovea stirrup-shaped, their aperture occupying about 0.6–0.7 times lip region diameter, fusus almost at level of odontophore base. Guiding ring distinct, at 0.6 times the lip region diameter from anterior end. Odontostyle short, 4–5 times as long as wide, or about 0.6–0.7 times as long as lip region diameter, its aperture about one-fourth of length. Odontophore with weakly developed basal flanges, 2–3 times as long as odontostyle. Nerve ring encircling anterior slender part of pharynx at 43–50% of neck length from anterior end. Pharyngeal expansion gradual; expanded part 2.9–4.7 times as long as wide, or about 1.6–2.6 times as long as body diameter at neck base, occupying about 25–34% of total neck length, enclosed in thick spiral muscular sheath. Only dorsal pharyngeal gland nucleus and orifice visible: DO =75–78; DN =77–79; DO–DN = 1.5–2.1. Cardia elongate rounded, 1.0–1.4 times as long as wide, occupying about one-fourth to two-fifths (25–40%) of corresponding body diameter.

Genital system amphidelphic, both branches almost equally developed. Ovaries reflexed, rarely reaching oviduct-uterus junction, measuring 41–122 µm (anterior) and 45–65 µm (posterior) long, with squamous shaped oocytes arranged in single row except near tip. Oviduct joining ovary subterminally, anterior 41–65 µm or 1.9–2.7 times, and posterior 41–66 µm or 1.9–2.7 times as long as mid-body diameter, consisting of slender part with prismatic cells and slightly wider pars dilatata with distinct lumen; oviduct-uterus junction marked with sphincter. Uterus simple tube, anterior 30–46 µm or 1.3–2.1 times and posterior 32–43 µm or 1.4–1.9 times as long as corresponding body diameter, mostly containing oval-shaped sperm. Vulva longitudinal with small opening. Vagina extending inwards about two-fifths to three-fifths (42–57%) of corresponding body diameter; pars proximalis longer than wide, 7–10 ×4 µm, with somewhat concave walls, pars refringens absent; pars distalis 3 µm with thickened and slightly rounded walls. Prerectum 3.8–4.7 and rectum 1.2–1.4 times as long as anal body diameter. Tail elongate conoid, ventrally arcuate, with rounded terminus. Caudal pores two on each side.

Male

Similar to female in general morphology, except for posterior region being more curved ventrally. Genital system diorchic, with oppositely outstretched testes. Sperm oval-shaped, 4–5 × 1–2 µm. In addition to adcloacal pair, located at 6–7 µm from cloacal aperture, there are five ventromedian supplements, located above range of spicules; first ventromedian supplement at 17–26 µm from adcloacal pair, second at 5–22 µm from first, third at 6–15 µm from second, fourth at 10–20 µm from the third and fifth at 8–12 µm from the fourth ventromedian supplement. Copulatory muscles weak, beginning from level of middle of spicules and continues till level of last supplement. Spicules dorylaimoid, slightly bent ventrally, total length along arc as long as chord, 3.2–5.7 times maximum width or 1.2–1.3 times body diameter at cloacal aperture. Curvature estimated about 137–140°. Dorsal contour regularly convex, ventral contour concave with prominent hump, located at 47–48% of spicules total length from anterior end; head occupying about 31% of spicule length; median pieces simple, 13 times as long as wide and occupying about 17% of spicule maximum width; posterior end about 2 µm wide. Lateral guiding pieces indistinct. Prerectum 3.9–4.7 and rectum 1.2–1.4 times as long as cloacal body diameter. Tail elongate conoid, ventrally arcuate with rounded terminus. Caudal pores two on each side.

Remarks

Heyns (1963) described D. andrassyi from Transvaal, South Africa and differentiated it from D. bambesae de Coninck, 1962 and D. imitator Heyns, 1963 , in having a shorter expanded part of the pharynx and a ventrally arcuate tail. Chaturvedi & Khera (1979) redescribed it from the rhizosphere of jute plants ( Corchorus capsularis ) from West Bengal, India. Yeates (1979) described a closely related species, D. pastura , from New Zealand and differentiated it from D. andrassyi , in the nature of the glandular bodies in the lateral hypodermal chords and absence of male. Later, Jordaan & Heyns (1984) made a detailed study of this species based on the type material, as well as fresh specimens (161 females and 8 males) collected from several localities of South Africa, and recorded variations in body size, number of glandular bodies in the lateral chords, absence of male in some populations, in the shape of spicules and tail.As a results of this, they did not find any conclusive difference between D. pastura and D. andrassyi , and hence they synonymized D. pastura Yeates, 1979 with D. andrassyi . Further, it was reported from Botswana by De Bruin & Heyns (1993). The present population of Kerala generally conforms well to the original one, although it differs from this in its slightly wider lip region (one-third to two-fifths vs one-fourth of body diameter at neck base) and slightly longer prerectum (3.9–4.7 vs 2.0–3.5 times as long as anal body diameter). It differs from the West Bengal population, in having a shorter odontostyle (4–5 vs 6 µm long) and a slightly longer odontophore (10–12 vs 9 µm). From the material described by Jordaan & Heyns (op. cit.) from South Africa, it differs in its shorter odontostyle (4–5 vs 5.2–10 µm), lower number of glandular bodies in lateral hypodermal chords (46–49 vs 54–108), and shorter body length in males (0.9–1.0 vs 1.2–1.6 mm). From the material described by De Bruin & Heyns (1993) from Botswana, it differs in its shorter body size (1.0–1.2 vs 1.64 mm), narrower lip region (7 vs 9 µm wide), shorter expanded part of pharynx (25–34% vs 39% of total neck length) and posterior located vulva (V= 50–53 vs 49). The specimens from various localities of South Africa reported by Jordaan & Heyns (op. cit.) display a wide range of morphological variations in body length (0.87–2.3 mm), odontostyle length (5–10 µm) and tail length (36–67 µm). As a results of this, they regarded it as a single highly variable species (cf. Jordaan & Heyns, 1984).

Figures

Fig. 1. Dorylaimellus andrassyi Heyns, 1963 (LM photographs). A–B. Anterior region, arrow indicating perioral disc. C. Anterior end showing amphid. D. Expanded part of pharynx, arrows indicating ventral body pores. E. Vulva. F–G. Female genital branches. H–I. Spicules. J. Arrows indicating ventromedian supplements. K–L. Male posterior end. M. Female posterior end. Scale bars: A–M =10 µm.