Dorylaimellus discocephalus Siddiqi, 1964

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 : 7-11

Dorylaimellus discocephalus Siddiqi, 1964

Figs 2–3 , Table 2

Dorylaimellus discocephalus Siddiqi, 1964: 5 . — Dorylaimellus cephalus Jairajpuri, 1964: 182–183 . Dorylaimellus discocephalus Baqri & Jairajpuri 1968: 305–306 .

Material examined

INDIA • 2 ♀♀, 1 ♂; Maharashtra State, Sangli district, Chandoli National Park ; 17°11′30″ N, 73°46′30″ E; 5–20 cm deep; 14 Apr. 2016; soil samples collected from around the roots of Ipomoea carnea plants (morning glory); slide reference number AMU/ZD/NC / Dorylaimellus discocephalus /1–3 .

Description

Female

Body slightly curved ventrad upon fixation, 1.10–1.11 mm long. Cuticle with distinct transverse striations, about 1 µm at anterior and mid-body, 2 µm on tail tip. Lateral chords 4–5 µm or one-fifth (20%) of body diameter at mid-body with weakly developed glandular bodies, about 50 in number; 10 in pharyngeal region, 21 from pharyngeal base to vulva, 18 from vulva to anal region and only one in caudal region. Ventral body pores distinct, about 46 in number; 8 in pharyngeal region, 14 from pharyngeal base to vulva, and 24 from vulva to anal region; lateral body pores about 37 in number; about 5 in pharyngeal region, 7 from pharyngeal base to vulva, and 22 from vulva to anal region; dorsal body pores indistinct. Lip region cap-like, offset by constriction, 2.3 times as wide as high, or about one-third to two-fifths (30–43%) of body diameter at neck base. Lips rounded, amalgamated, perioral disc present. Cheilostome a truncate cone with refractive walls and distinct cuticularized pieces near oral aperture. Amphids fovea cup-shaped, their aperture occupying about 0.7 times lip region diameter, fusus slightly posterior to level of odontophore base. Guiding ring weakly developed, at 0.6 times the lip region diameter from anterior end. Odontostyle short, weakly developed, about three times as long as wide, or about 0.4 times as long as lip region diameter, its aperture occupying about one-third of its length. Odontophore with weakly developed basal flanges, 2.7 times as long as odontostyle. Nerve ring encircling the anterior slender part of pharynx at about 30% of neck length from anterior end. Pharyngeal expansion gradual; expanded part 6.5–8.6 times as long as wide, or about 3.8–4.5 times body diameter at neck base, occupying about 43–47% of total neck length, enclosed in a thick dextrally spiral muscular sheath. Only dorsal pharyngeal gland and orifice visible: DO = 64.6; DN = 66.5; DO–DN =1.9. Cardia elongate rounded, 1.2, 1.4 times as long as wide, occupying about one-fourth to two-sevenths (25–28%) of corresponding body diameter.

Genital system amphidelphic, both branches almost equally developed. Ovaries reflexed, not reaching oviduct-uterus junction, measuring 50 µm (anterior) and 56 µm (posterior) long, with squamous shaped oocytes arrange in single row except near tip. Oviduct joining ovary subterminally, anterior 55 µm or 2.0 times and posterior 60 µm or 2.1 times the mid-body diameter, consisting of a slender part made of prismatic cells and slightly wide pars dilatata with distinct lumen; oviduct-uterus junction marked with a sphincter. Uterus simple tube, anterior 54 µm or 1.9 times and posterior 45 µm or 1.6 times as long as corresponding body diameter; containing oval-shaped sperms. Vulva longitudinal. Vagina extending inwards about two-fifths of corresponding body diameter; pars proximalis vaginae longer than wide, 10 ×5 µm, with somewhat convex walls; pars refringens absent; pars distalis vaginae 2 µm with rounded wall. Prerectum 3.0, 4.2 and rectum 1.4, 1.3 times as long as anal body diameter. Tail cylindroid with broadly rounded terminus. Caudal pores four on each side.

Male Similar to female in general morphology, except for posterior region being more curve ventrad. Genital system diorchic, with oppositely outstretched testes. Sperms oval-shaped, 3–4 ×2 µm. In addition to adcloacal pair, located at 6 µm from cloacal aperture, four irregularly spaced ventromedian supplements, arranged in two groups, first supplement located at 46 µm from adcloacal pair, second at 4 µm from first, third at 23 µm from second and fourth at 10 µm from the third supplement. Copulatory muscles conspicuous, beginning from level of middle of spicules and continues the level of end of supplements. Spicules broad proximally, and sharply ventrally bent at middle, total length along arc equal to chord, 4.7 times maximum width, about 1.1 times body diameter at cloacal aperture. Dorsal contour irregularly convex, ventral contour concave, bearing distinct hump, located at 36.8% of spicules total length from its anterior end; head slightly bent dorsally, occupying about 26.3% of spicule length; median pieces simple, 14 times as long as wide and occupying about 25% of spicules maximum width; posterior end about 2 µm wide. Lateral guiding pieces indistinct. Prerectum 6.4 and rectum 1.5 times as long as cloacal body diameter. Tail dorsally convex-conoid with rounded terminus. Caudal pores three on each side.

Remarks

Siddiqi (1964) described Dorylaimellus discocephalus from the soil around the roots of maize plants (Zea mays) from Aligarh, India and differentiated it from D. projectus Heyns, 1962 on the basis of a longer and slender body, a longer odontostyle aperture, a longer expanded part of the pharynx and a longer tail. In the same year, Jairajpuri described a closely related species, Dorylaimellus cephalus , from roots of Saccharum ravennae in Aligarh and differentiated it from D. projectus based on the long and slender body. Siddiqi (1966) failed to find any reliable differentiating character between D. discocephalus and D. cephalus , therefore, he did not consider D. cephalus a valid species. Baqri & Jairajpuri (1968) redescribed D. discocephalus from various localities of Uttar Pradesh. Andrássy (2009) synonymized D. cephalus with D. discocephalus on the basis of priority. The present population of Maharashtra conforms well with the original and subsequent descriptions.Although, it slightly differs from the original population in having a comparatively robust body (a= 40–43 vs 46–53); a shorter and weak odontostyle (3 µm vs 4–5 µm); a shorter and weakly developed odontophore (8 µm vs 11–12 µm long with well-developed basal flanges), in the presence of body pores (vs not reported) and the presence of males (vs absent). The male of this species is being reported here for the first time.

Figures

Fig. 2. Dorylaimellus discocephalus Siddiqi, 1964. A. Entire female. B. Entire male. C. Anterior region. D. Anterior end showing amphid. E. Neck region. F. Female genital system. G. Vulva region. H. Male posterior region. I. Spicule. J. Female posterior end.

Fig. 3. Dorylaimellusdiscocephalus Siddiqi, 1964(LM photographs).A.Anterior region, arrow indicating basal flanges. B. Arrow indicating perioral disc. C. Anterior end showing amphid. D. Expanded part of pharynx. E. Vulva. F. Arrows indicating ventromedian supplements. G. Male posterior end, arrow indicating spicule. H. Female posterior end. Scale bars: A–H= 10 µm.