Dorylaimellus karnatakensis, 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 : 27-31

Dorylaimellus karnatakensis sp. nov.

urn:lsid:zoobank.org:act:32155AE3-FE8E-40FE–B67C-93FB53646399 Figs 10–11 , Table 7

Diagnosis

Dorylaimellus karnatakensis sp. nov. is characterized by having a 1.2–1.3 mm long body; lip region rounded, offset with perioral disc, cuticularized pieces distinct; odontostyle slender, 5 µm long, odontophore 12–13 µm long with weakly developed basal flanges; expanded part of pharynx occupying about 45–53% of total neck length; female genital system amphidelphic; vulva at 48–52% of total body length; male with 22 µm long spicules; ventromedian supplements four, arranged in two groups, and tail elongate-conoid, dorsally convex, ending with a rounded terminus similar in both sexes.

Etymology

The new species is named after its type locality.

Material Examined

Holotype

INDIA • ♀; Karnataka State, Uttara Kannada district, Yellapur village ; 14°58′12″ N, 74°43′12″ E; 10–15 cm deep; 28 Oct. 2018; roots of grasses (unidentified); slide reference number AMU/ ZD/NC / Dorylaimellus karnatakensis /1.

Paratypes

INDIA • 2 ♀♀, 1 ♂; same collection data as for holotype; slide reference number AMU/ZD/NC / Dorylaimellus karnatakensis /2–4 .

Type habitat and locality

Soil samples collected from around the roots of the grasses (unidentified) from village Yellapur, Uttara Kannada district, Karnataka State of India.

Description

Female

Body curved ventrad upon fixation, 1.2–1.3 mm long. Cuticle with distinct transverse striations, about 1 µm at anterior and mid-body, 2 µm on tail tip. Lateral chords 6–7 µm wide, about one-fourth to two-sevenths (25–28%) of body diameter at mid-body with distinct glandular bodies, about 43–46 in number; 4–12 in pharyngeal region weakly developed, 11–16 from pharyngeal base to vulva, 21–25 from vulva to anal region and 2 in caudal region. Body pores observed on ventral and dorsal side of body, about 61–74 on ventral side; 14–18 in pharyngeal region, 19–23 from pharyngeal base to vulva and 28–33 from vulva to anal region; about 59–61 on dorsal side; 16 in pharyngeal region, 17 from pharyngeal base to vulva, 26–61 from vulva to anal region. Lip region rounded, offset by constriction, 1.7–2.3 times as wide as high, or about one-third (30–33%) of body diameter at neck base. Lips amalgamated, inner lips elevated forming perioral disc. 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 as long as lip region diameter, fusus slightly posterior to level of odontophore base. Guiding ring weakly developed, at 0.7–0.9 times as long as lip region diameter from anterior end. Odontostyle weak, slender, about five times as long as wide, or about 0.7 times as long as lip region diameter, its aperture occupying about one-third of length. Odontophore with weakly developed basal flanges, 2.4–2.6 times as long as odontostyle. Nerve ring encircling anterior slender part of pharynx at 27–31% of neck length from anterior end. Pharyngeal expansion gradual; expanded part 7.5–12.2 times as long as wide, or about 4.9–6.7 times longer than body diameter at neck base, occupying about 45–53% of total neck length, enclosed in thick dextrally spiral muscular sheath. Only dorsal pharyngeal gland and orifice visible: DO =55.8–59.7; DN =56.6–60.4; DO–DN = 0.8–1.1. Cardia elongate-conoid, 1.2–2.0 times as long as wide, occupying about one-third to one-half (31–54%) of corresponding body diameter.

Genital system amphidelphic, both branches almost equally developed. Ovaries reflexed, not reaching oviduct-uterus junction, measuring 34–61 µm (anterior), and 56–57 µm (posterior) long, with squamous shaped oocytes arranged in single row except near tip. Oviduct joining ovary subterminally, anterior 55–67 µm or 2.3–2.7 times and posterior 65–72 µm or 2.7–3.0 times as long as mid-body diameter, consisting of a slender part with prismatic cells and wide pars dilatata with distinct lumen; oviduct-uterus junction marked with sphincter. Uterus simple tube, anterior 43–45 µm or 1.8–1.9 times and posterior 40–48 µm or 1.7–2.0 times as long as corresponding body diameter; mostly containing oval-shaped sperm. Vulva longitudinal. Vagina extending inwards about one-half (50–54%) of corresponding body diameter; pars proximalis vaginae longer than wide, 8–10 ×4–5 µm, with convex walls surrounded by weakly circular muscles; pars refringens vaginae absent; pars distalis vaginae 2–3 µm with rounded walls. Prerectum 6.9–8.0 and rectum 1.3–1.6 times as long as anal body diameter. Tail elongate-conoid, dorsally convex, ending with bluntly rounded terminus. Caudal pores three 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. In addition to adcloacal pair, located at 4 µm from cloacal aperture, there are four ventromedian supplements, first supplement located at a distance of 46 µm from adcloacal pair, second at 4 µm from first, third at 23 µm from the second and fourth supplement at 10 µm from third ventromedian supplement; arranged in two groups. Copulatory muscles conspicuous, beginning from level of middle of spicules and continues till level of last supplements. Spicules stout, relatively broad in proximal half and strongly ventrally bent near middle, total length along arc 1.2 times as long as chord, 5.5 times maximum width or 1.3 times body diameter at cloacal aperture. Dorsal contour irregularly convex; ventral contour concave, with prominent hump, located at 32% of spicules total length from anterior end; head short with rounded end, occupying about 20.7% of spicule length; median piece simple, 17 times as long as wide and occupying about 25% of spicule maximum width; posterior end slightly less than 2 µm wide. Lateral guiding pieces absent. Prerectum 5.1 and rectum 1.2 times as long as cloacal body diameter. Tail arcuate-conoid with sharply rounded terminus. Caudal pores two on each side.

Taxonomic remarks

Dorylaimellus karnatakensis sp. nov. comes close to D. discocephalus Siddiqi, 1964 , D. vexator Heyns, 1963 , and D. graminis Kruger, 1965 in general morphology and measurements, but differs from the former in having a comparatively weak perioral disc (vs prominent), in the nature of the lip region (offset by weak constriction vs deeply constricted), of the odontophore (odontophore with weak flanges vs prominent flanged), longer prerectum (7–8 vs 6 times as long as anal body diameter), a longer tail (c= 28–32 vs 34–39), a differently shaped tail (elongate-conoid, dorsally convex, ending with sharply rounded terminus vs elongate-cylindroid with broadly rounded terminus) and in the presence of males (vs absent).

From D. vexator Heyns, 1963 , the new species differs in having longer and slender body (L=1.2–1.3 vs 0.8–0.9; a =51–54 vs 36–44), a comparatively weak and slender odontostyle (vs well developed and relatively robust), a longer odontophore with weak basal flanges (2.4–2.6 vs 2.0 times odontostyle length with prominent basal flanges), a shorter pharynx (b= 4.5–5.2 vs 2.9–3.6), a longer prerectum (7–8 vs 6 times as long as anal body diameter), a differently shaped tail (vs dorsally convex, ventrally straight with bluntly rounded terminus) and in the presence of males (vs absent).

From D. graminis Kruger, 1965 , it differs in having a longer and slender body (L=1.2–1.3 vs 0.88– 0.9 mm; a =51–54 vs 36–40), in the presence of body pores (vs not reported) and lateral glandular bodies (vs inconspicuous), a distinct perioral disc (vs indistinct), a shorter and slender odontostyle (5.0 µm vs 6.5 µm or almost equal to the lip region diameter, and robust comparatively thick walled), a slightly shorter pharynx (b= 4.5–5.2 vs 4.0–4.1), an anterior vulva position (V =48–52 vs 54–56) and in the tail shape (vs dorsally convex, arcuate-conoid ending with sharply rounded terminus).

Figures

Fig. 10. Dorylaimellus karnatakensis sp. nov. A, C–D. Paratype 1,♀ (slide 2). E–G, J. Paratype 2, ♀ (slide 3). B, H–I. Paratype 4, ♂ (slide 4). 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 showing ventromedian supplements. I. Male posterior end showing spicule. J. Female posterior end.

Fig. 11. Dorylaimellus karnatakensis sp. nov. (KM photographs). A–C. Paratype 1,♀ (slide 2). D– G, J–K. Paratype 2, ♀ (slide 3). H–I. Paratype 4, ♂ (slide 4). A–B. Anterior region. C. Amphid. D. Expanded part of pharynx. E. Vulva. F–G. Female genital branches. H. Ventromedian supplements. I. Male posterior end. J–K. Female posterior end. Scale bars:10 µm.