Dorylaimellus attenuatus, 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 : 17-22

Dorylaimellus attenuatus sp. nov.

urn:lsid:zoobank.org:act:195A0EAA–C0AB-449D–ACD9-4D5109715FB2 Figs 6–7 , Table 5

Diagnosis

Dorylaimellus attenuatus sp. nov. is characterized by having a 0.73–0.84 mm long body; lip region distinctly offset, cap-like with prominent perioral disc, cuticularized pieces present around oral opening; odontostyle attenuated with indistinct lumen and aperture, 5.0–5.5 µm long; odontophore with weakly developed basal flanges; amphids with stirrup-shaped fovea; expanded part of pharynx occupying about 39–48% of total neck length; female genital system amphidelphic; vulva longitudinal, and tail elongate-filiform.

Etymology

The new species is named Dorylaimellus attenuatus sp. nov. because of its attenuated odontostyle.

Material examined

Holotype

INDIA • ♀; Kerala State, Palakkad district, Agali Forest Range; 11°06′4.32″ N, 76°38′50.64″ E; 10–15 cm deep; 25 Oct. 2017; roots of grasses (unidentified); slide reference number AMU/ZD/NC/ Dorylaimellus attenuatus /1.

Paratypes

INDIA • 13 ♀♀; same collection data as for holotype; slide reference number AMU/ZD/NC/ Dorylaimellus attenuatus /2–10 .

Type habitat and locality

Soil samples collected from around the roots of grasses (unidentified) from Agali Forest Range, Palakkad district, Kerala State, India.

Description

Female

Body slightly curved ventrad upon fixation, 0.73–0.84 mm long. Cuticle with fine transverse striations, about 1 µm thick throughout the length of body. Lateral chords 4–7 µm, or about one-fifth to two-fifths (22–37%) of mid-body diameter; glandular bodies indistinct. Ventral body pores distinct, about 29–35 in number: 8–9 in pharyngeal region, 8–9 from pharyngeal base to vulva and 15–17 from vulva to anal region; lateral and dorsal body pores indistinct. Lip region cap-like, distinctly offset by constriction, 1.5–2.0 times as wide as high, or about one-third to two-fifths (32–38%) 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, about 0.8 times the lip region diameter, fusus just at level of odontophore base. Guiding ring single and weakly developed, at 0.8 times lip region diameter from anterior end. Odontostyle attenuated with indistinct lumen, 10–11 times as long as wide, or about 0.8–0.9 times lip region diameter, aperture very minute, difficult to measure. Odontophore rod-like with weakly developed basal flanges, 1.6–2.0 times as long as odontostyle. Nerve ring encircling the anterior slender part of pharynx at about 33–37% of neck length from anterior end. Pharyngeal expansion abrupt; expanded part 5.7–8.9 times as long as wide, or about 3.6–5.4 times the body diameter at neck base, occupying about 39–48% of total neck length, enclosed in a thick spiral muscular sheath. Only dorsal pharyngeal gland and orifice visible: DO=62–64; DN =64–65; DO– DN =1.2–2.1. Cardia short, rounded conoid, 1.2–1.8 times as long as wide, occupying about one-fourth to two-fifths (27–40%) of corresponding body diameter.

Genital system amphidelphic; both genital branches almost equally developed. Ovaries reflexed, not reaching oviduct-uterus junction, measuring 21–72 µm (anterior) and 34–96 µm (posterior) long, with oocytes arranged in single row except near tip. Oviduct joining ovary subterminally, anterior 31–41 µm or 1.7–2.4 times, and posterior 35–50 μm or 1.9–2.6 times as long as mid-body diameter, consisting of long slender part of prismatic cells and wider pars dilatata with distinct lumen; oviduct-uterus junction marked with sphincter. Uterus simple tube, anterior 13–21 µm or 0.7–1.1 times, and posterior 13– 18 µm or 0.7–1.0 times as long as corresponding body diameter; sperm not observed. Vulva longitudinal. Vagina extending inwards about one-half to three-fifths (47–59%) of corresponding body diameter; pars proximalis vaginae longer than wide, 5–8 ×3 µm, with convex walls; pars refringens absent; pars distalis 2–3 µm with somewhat rounded walls. Prerectum 5.2–9.0 and rectum 1.5–2.1 times as long as anal body diameter. Tail elongate-filiform with a finely rounded terminus. Caudal pores two on each side.

Male

Not found.

Taxonomic remarks

In having an attenuated odontostyle, an amphidelphic gonad and an elongate filiform tail, Dorylaimellus attenuatus sp. nov. comes close to D. filiformis Jairajpuri, 1964 , D. salvus Siddiqi, 1968 and D. dorylaimoidurus Siddiqi, 1966 , but differs from the former in the shape of the lip region (cap-like with distinct perioral disc vs conoid without perioral disc), in the nature of the odontostyle (attenuated with indistinct lumen and aperture vs slender with distinct lumen and aperture), a longer pharynx (b= 3.9–5.2 vs 5.8); longer expanded part of the pharynx (38–48 vs 33% of total neck length), a posterior vulva position (V= 47–49 vs 43), a longer prerectum (5.2–9.0 vs 5.0 times length of anal body diameter) and the presence of body pores (vs indistinct).

From D. salvus , the new species differs in having a shorter body (L=0.73–0.83 vs 1.17–1.23 mm), a cuticle with fine transverse striations (vs coarsely striated), in the presence of ventral body pores (vs indistinct); indistinct lateral glandular bodies (vs distinct), in the lip region morphology (lip region with distinctly developed perioral disc vs with pseudo-labial disc), in the nature of the odontostyle (attenuated with indistinct lumen and aperture vs robust with distinct lumen and aperture), a longer pharynx (b= 3.9–5.2 vs 6.5–7.5), a longer expanded part of the pharynx (39–48 vs 33% of total neck length) and in the absence of males (vs present).

From D. dorylaimoidurus , it differs in having a slender body (a =41–47 vs 40), in the presence of body pores (vs indistinct), shape of the lip region (cap-like with a prominent perioral disc vs smoothly rounded without a perioral disc), a shorter odontostyle (5.0–5.5 vs 6.5 µm), a shorter odontophore (9–10 vs 12 µm), a longer pharynx (b =3.9–5.2 vs 5.6), the anterior vulva position (V =47–49 vs 42), in the nature of the tail shape (tail not dorsally arcuate vs dorsally arcuate) and in the absence of males (vs present).

Figures

Fig. 6. Dorylaimellus attenuatus sp. nov. A–D, F–G. Paratype 6, ♀ (Slide 7). E. Paratype 11, ♀ (slide 12). A. Entire female. B. Anterior region. C. Anterior end showing amphid. D. Neck region. E. Female genital system. F. Vulva region. G. Posterior region.

Fig. 7. Dorylaimellus attenuatus sp. nov. (LM photographs). A–H. Paratype 6, ♀ (Slide 7). A. Anterior region, arrow indicating basal flanges. B. Arrow indicating odontostyle. C. Anterior end showing amphid. D. Expanded part of pharynx. E. Vulva. F. Female genital system. G. Arrows indicating ventral body pores. H. Female posterior end. Scale bars: A–H=10 µm.