Dorylaimoides micoletzkyi ( de Man, 1921 ) Thorne and Swanger 1936

Islam, Md Niraul & Ahmad, Wasim, 2022, Description of two new and six known amphidelphic species of the genus Dorylaimoides Thorne and Swanger, 1936 (Nematoda: Dorylaimida: Tylencholaimoidea) from the Tropical Rainforest, Western Ghats, India, Journal of Natural History 56 (5 - 8), pp. 311-347 : 317-321

Dorylaimoides micoletzkyi ( de Man, 1921) Thorne and Swanger 1936

( Figure 3 ; Table 2 )

Description

Female. Small-sized nematodes, slightly curved ventrad to open C-shaped upon fixation; tapering gradually towards the anterior end and posteriorly narrowing to form an elongate tail. Cuticle with two distinct layers, 1.0–1.5 μm thick at anterior region, 2.0 μm at midbody and 3.5–4.0 μm at tail. Outer cuticle thin, with fine transverse striations; inner layer thick, finely striated. Lateral chords 6.0–7.5 μm at midbody, occupying about onefifth (21–23%) of corresponding body diameter. Lateral, ventral and dorsal body pores indistinct. Lip region cap-like, offset by depression, twice as wide as high or about onethird of the body diameter at neck base. Under SEM ( Figure 3 (c)), lips rounded, low, amalgamated; labial and cephalic papillae button-like, but not protruding over the lip surface; oral aperture small slit-like. Amphids large, cup-shaped, with slit-like aperture, occupying an area about two-thirds as wide as lip region diameter. Stoma a truncate cone. Odontostyle asymmetrical, 1.1–1.2 times the lip region diameter long, ventral arm 6.0– 6.5 μm, dorsal arm 6.5–7.5 μm, its aperture about one-fifth to one-fourth of the odontostyle length. Odontophore arcuate, about 1.3–1.4 times the odontostyle length. Guiding ring simple, refractive, at 0.8 times lip region diameter from anterior end. Pharynx consisting of a slender and slightly muscular anterior part, expanding gradually into a short, cylindrical basal bulb, 4.2–4.8 times as long as wide, 2.0–2.3 times as long as corresponding body diameter, occupying about 29–30% of total neck length. Pharyngeal gland nuclei barely visible. Nerve ring located at 44–46% of neck length from anterior end. Cardia rounded to conoid, about one-fourth to one-third of the corresponding body diameter long. Genital system didelphic-amphidelphic. Ovaries reflexed, measuring 59– 63 μm (anterior) and 56–70 μm (posterior) long; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 55–88 μm (anterior) and 46– 68 μm (posterior), consisting of a slender distal part and a well-developed pars dilatata. Oviduct-uterus junction marked by well-developed sphincter. Uterus long and tubular with wide lumen, filled with sperm cells, measuring 42–69 μm (anterior) and 45–71 μm (posterior). Vagina cylindrical, extending inwards, 16.5–17.5 μm or about one-half (52– 57%) of midbody diameter; pars proximalis vaginae 11–12 × 8.0–9.0 μm, encircled by circular muscles; pars distalis vaginae 5.0–6.0 μm with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 5.3–6.0 and rectum 1.2–1.3 times anal body diameter long. Tail elongate, tapering gradually to a subacute terminus, its distal part slightly bent dorsally, 2.8–2.9 times anal body diameter long, with a pair of caudal pores on each side.

Male. General morphology similar to that of female except for posterior region being more ventrally curved. Genital system diorchic, testes opposed, sperm cells spindleshaped, 4.0–5.0 μm long. In addition to adcloacal pair, situated at 6.0–8.0 µm from cloacal aperture, there are seven to eight irregularly spaced ventromedian supplements, first ventromedian supplement located within the range of spicules, 13–15 μm from adcloacal pair. Spicules typically dorylaimoid, curved ventrad, relatively robust, 4.0–4.1 times as long as wide and 1.3–1.4 times as long as body diameter at level of cloacal aperture, dorsal contour regularly convex, ventral contour bearing a moderately developed hump and hollow, curvature 126–130°, head occupying 13–18% of total spicule length, median pieces 8.3–10.4 times as long as wide or occupying about 31–42% of the spicules’ maximum width, reaching the spicule tip, posterior end 3 μm wide. Lateral guiding pieces distinct, rod-like, about 6.0–6.5 times as long as wide or about one-third of the spicules’ length. Prerectum 5.0–5.3 and rectum 1.3–1.4 cloacal body diameter long. Tail elongate with subacute terminus, tapering gradually, its distal end slightly bent dorsally, 1.8 times cloacal body diameter long, with a pair of caudal pores on each side.

Habitat and locality. Soil sample collected around the roots of grasses (unidentified) from Yaraganalu, Shivamoga district, Karnataka State, India; coordinates 13.801208°N, 75.573151°E .

Remarks. De Man (1921) described Dorylaimus micoletzkyi from the Netherlands, which was later transferred to Dorylaimoides by Thorne and Swanger (1936) in their monograph when they proposed the genus Dorylaimoides . Thorne (1974) redescribed this species from the USA. Goseco et al. (1976) made a detailed study of this species based on the type population as well as specimens from several localities in the USA. They also synonymised Dorylaimoides pakistanensis Siddiqi, 1964 with this species. Dorylaimoides micoletzkyi has a wide distribution and has been redescribed from India ( Ahmad and Jairajpuri 1979; Jana and Baqri 1981; Baqri 1991), Hungary ( Andrássy 1991) and Spain (Peralta and Peña-Santiago 1995). The morphometrics of the present population conforms well with the type population except in having a shorter body (L = 1.0–1.1 vs 1.2–1.4 mm) and slightly lower c ratio (18.1–18.8 vs 19–26). It also conforms well with the USA populations described by Thorne (1974) and Goseco et al. (1976). The present specimens conform well with all the Indian populations except for differing from Ahmad and Jairajpuri’s (1979) population in having a slightly less slender body (a = 32–36 vs 38–41) and a lower c ratio (18 vs 20–22); from Jana and Baqri’s (1981) population in having a slightly shorter body (L = 1.0–1.1 vs 1.2–1.3 mm), lower c ratio (18 vs 21–23), slightly smaller spicules (29–32 vs 36 μm) and more ventromedian supplements (7–8 vs 5); and from Baqri’s (1991) population in having an anterior vulva position (V = 40–41 vs 44–46), lower c’ ratio (2.8–2.9 vs 3.5–4.0), smaller spicules (29–32 vs 36 μm) and more ventromedian supplements (7.0–8.0 vs 5.0). The present population also conforms well with the Hungarian population except in having a slightly shorter body (L = 1.0–1.1 vs 1.1–1.4 mm), and differs from the Spanish population in having a slightly less slender body (a = 32–36 vs 37–45).

The present population conforms well with all the earlier described populations, except for differing from the Pakistan population described by Siddiqi (1964) in having a slightly less slender body (a = 32–36 vs 36–46); shorter tail (56–59 vs 80); higher c (18.1– 18.8 vs 12.5–16) and lower c’ (2.8–2.9 vs 4.5) ratios and more ventromedian supplements (7–8 vs 5–6). Peña-Santiago and Peralta (1997) did not consider the Siddiqi (1964) population similar to D. micoletzkyi due to the presence of a longer tail (84 vs 48–80) lower c ratio (12.5–16 vs 16–29) and shorter spicules (29–30 vs 32–38). These differences are also distinct in the present specimens; hence we agree with Peña-Santiago and Peralta (1997) and do not consider the Pakistan population conspecific with D. micoletzkyi .

Figures

Figure 3. Dorylaimoides micoletzkyi (de Man, 1921) Thorne and Swanger 1936 (LM photographs unless otherwise specified). (a, b) anterior region; (c) en face view (SEM); (d) anterior region showing amphid; (e) pharyngeal region; (f) expanded part of pharynx; (g) vulval region; (h, i) female genital system; (j) female posterior region; (k) female posterior end; (l) male posterior region (SEM); (m, n) male posterior end. Scale bars: a, b, d, g–i, k–n = 10 μm; c = 2 μm; e, j = 20 μm.