Dorylaimellus cylindricaudatus, Kumar & Ahmad, 2024

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 : 22-26

Dorylaimellus cylindricaudatus sp. nov.

urn:lsid:zoobank.org:act:B689B655-0FC9-4084-8013-7AF11DF4489D

Figs 8–9 , Table 6

Diagnosis

Dorylaimellus cylindricaudatus sp. nov. is characterized by having a 1.0– 1.15 mm long body; lip region offset, cap-like with prominent perioral disc, perioral sclerotization distinct; odontostyle slender 4 µm long; odontophore 11–12 µm long with moderately developed basal flanges; expanded part of pharynx occupying about 47–56% of total neck length; female genital system amphidelphic; vulva longitudinal, post-equatorial, located at 55–60% of total body length; prerectum 4.8–6.4 times as long as anal body diameter; tail arcuate, elongate-cylindrical with rounded terminus.

Etymology

The new species is named Dorylaimellus cylindricaudatus sp. nov. because of its cylindrical tail shape.

Material examined

Holotype

INDIA • ♀; Karnataka State, Shimoga district, village Thirtha ; 14°07′10.0″ N, 75°03′26.5″ E; 10–15 cm deep; 27 Oct. 2018; roots of grasses (unidentified); slide reference number AMU/ZD/NC / Dorylaimellus cylindricaudatus /1.

Paratypes

INDIA • 3 ♀♀; same collection data as for holotype; slide reference number AMU/ZD/NC / Dorylaimellus cylindricaudatus /2–3 .

Type habitat and locality

Soil samples collected from around the roots of grasses (unidentified) from village Thirtha, Shimoga district, Karnataka State, India.

Description

Body curved ventrad upon fixation, 1.0– 1.15 mm long, Cuticle with fine transverse striations, more pronounced on tail, about 1 µm at anterior and mid-body, 1–2 µm on tail tip. Lateral chords 5–6 µm wide, one-fifth to one-fourth (21–24%) of mid-body diameter with distinct glandular bodies, about 39–51 in number; 5 in neck region but weakly developed, 16–20 from pharyngeal base to vulva, 22– 29 from vulva to anal region and 1–2 in caudal region. Ventral body pores distinct, about 35–42 in number; 7–8 in neck region, 11–15 from pharyngeal base to vulva and 14–19 from vulva to anal region; dorsal and lateral body pores indistinct. Lip region cap-like, distinctly offset by constriction, 2.3 times as wide as high, or about two-sevenths to one-third (28–33%) 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 cup-shaped, their aperture occupying about 0.7 times lip region diameter, fusus slightly posterior to odontophore base. Guiding ring weakly developed, at 0.6 times lip region diameter from anterior end. Odontostyle slightly fusiform, slender with distinct lumen, four times as long as wide, or about 0.6 times as long as lip region diameter, its aperture occupying about one-fourth of its length. Odontophore with moderately developed basal flanges, 2.7–3.0 times as long as odontostyle. Nerve ring encircling anterior slender part of pharynx at 29–32% of neck length from anterior end. Pharyngeal expansion gradual; expanded part 8.2–12 times as long as wide, or about 5.1–6.7 times as long as body diameter at neck base, occupying about 47–56% of total neck length, enclosed in a thick spiral muscular sheath. Only dorsal pharyngeal gland and orifice visible: DO =50.6–56.2; DN =51.7–7.4; DO–DN =1.2. Cardia elongate conoid, 1.2–2.0 times as long as wide, occupying about two-sevenths to one-half (28–51%) of corresponding body diameter.

Genital system amphidelphic, both genital branches almost equally developed. Ovaries reflexed, not reaching oviduct-uterus junction, measuring 35–40 µm (anterior), and 35–39 µm (posterior) long, with squamous shaped oocytes arranged in single row except near tip. Oviduct joining ovary subterminally, anterior 45–50 µm or 2.0 times and posterior 62–63 µm or 2.5–2.8 times as long as mid-body diameter, consisting of a slender part made of prismatic cells and wide pars dilatata with distinct lumen; oviduct-uterus junction marked by sphincter. Uterus simple tube, anterior 35–40 µm or 1.4–1.8 times and posterior 38–43 µm or 1.5–2.0 times as long as corresponding body diameter; sperms not observed. Vulva longitudinal. Vagina extending more than one-half (56–64%) as long as corresponding body diameter; pars proximalis vaginae longer than wide, 7–10×4–5 µm, with convex walls, pars refringens absent; pars distalis 3 μm with slightly rounded wall. Prerectum 4.8–6.4 and rectum 1.1–1.5 times as long as anal body diameter. Tail arcuate, elongate cylindrical with rounded terminus. Caudal pores three on each side.

Male

Not found.

Taxonomic remarks

In the presence of a perioral disc, elongate cylindrical tail and amphidelphic gonad, Dorylaimellus cylindricaudatus sp. nov. comes close to D. afer Andrássy, 1969 , D. globatus Yeates, 1970 and D. jonsoni Jordaan & Heyns, 1984 , but it differs from the former in having a longer and slender body (L= 1.0–1.15 vs 0.84–0.88 mm; a= 38–52 vs 31–33), a wider and comparatively weakly offset lip region (7.0 vs 5.5 µm wide, offset by deep constriction), a shorter odontostyle with narrower lumen (4 µm vs 5 µm long, with comparatively wider lumen), a shorter pharynx (b =3.8–5.0 vs 3.3–3.5), a longer expanded part (46–56 vs 45% of total neck length), a posterior vulval position (V=55–60 vs 52), in the tail shape (elongate cylindrical with broad rounded terminus vs quickly narrow like finger and curve slightly dorsally with finely rounded terminus) and differs in the absence of males (vs present).

From D. globatus , the new species differs mainly in the absence of globules in the anterior region of the expanded part of the pharynx (vs large and small sizes globules present in anterior portion of expanded part of pharynx), a shorter body (L=1.0–1.15 vs 1.2–1.4 mm), a shorter odontostyle (4 µm vs 5–7 µm or 0.6 vs 0.7–0.8 times as long as lip region diameter), a slightly shorter odontophore (11–12 vs 12.5– 13.0 µm), a shorter expanded part of the pharynx (46–56 vs 57–69% of total neck length), a shorter tail (43–58 vs 61–75 µm), and a very short hyaline part of the tail (1–2 µm vs 6.5–12 µm long).

From D. jonsoni , the new species differs in having a shorter tail (43–58 µm vs 59–84 µm long), a higher c and a lower c′-value (c=19–26 vs 12–15 and c′=2.7–3.5 vs 3.6–5.1), a narrower lip region (about one-third vs one-half of body diameter at neck base), in the presence of well-developed perioral disc (vs weak), a shorter odontostyle (4.0 vs 4.8–7.4 µm or 0.6 times vs 0.8 times the lip region diameter), a larger expanded part of the pharynx (46–56 vs 43% of total neck length), in the tail shape (elongate cylindroid vs conoid with a more or less cylindroid distal portion) and in the absence of males (vs presence).

Figures

Fig. 8. Dorylaimellus cylindricaudatus sp. nov. A–G. Paratype 2, ♀ (Slide 3). H. Holotype, ♀ (slide 1). A. Entire female. B. Anterior region. C. Anterior end showing amphid. D. Neck region. E. Female genital system. F. Vulva region. G–H. Posterior regions showing prerectums and tails.

Fig. 9. Dorylaimellus cylindricaudatus sp. nov. (LM photographs), paratype 2, ♀ (Slide 3). A. Anterior region, arrow indicating basal flanges. B. Anterior end showing amphid. C. Expanded part of pharynx. D. Vulva region. E–F. Female genital branches. G. Lateral glandular bodies. H–I. Posterior end. Scale bars: 10 µm.