Eudorylaimus saccatus, Liang & Islam & Du & Li & Liang & Ahmad & Zhang & Mahamood & Alhewairini & Li, 2025

Liang, Siwei, Islam, Md Niraul, Du, Xiaofang, Li, Ying bin, Liang, Wenju, Ahmad, Wasim, Zhang, Xiaoke, Mahamood, Mohammad, Alhewairini, Saleh & Li, Qi, 2025, Two new and two known species of the genus Eudorylaimus Andrássy, 1959 (Nematoda, Dorylaimoidea, Qudsianematidae) from Northeast China, ZooKeys 1238, pp. 41-74 : 41-74

Eudorylaimus saccatus sp. nov.

Figs 7 , 8 , 9 , 10 , Tables 5 , 6

Type material.

Holotype • China ( IAE / NC / EU / E. saccatus / 1), Liaoning Province, Dalian City, Wafangdian ; 39.584857°N, 121.803631°E; soil samples collected from around the roots of grasses (unidentified) . Paratypes • China (4 ♀ / 5 ♂; IAE / NC / EU / E. saccatus / 2-9), same data as holotype .

Diagnosis.

Eudorylaimus saccatus sp. nov. is characterized by its 1.1–1.4 mm long slender body; lip region offset by constriction, 15–17.5 μm broad; odontostyle 17.5–18.5 μm with an aperture ~ 37–45 % of its length, odontophore 24.5–27.5 μm, 1.3–1.5 times the odontostyle length, total stylet length 42–45.5 μm; pharynx 332–389 μm long, pharyngeal expansion 148–189 μm or ~ 44–48 % of the total neck length; cardia long 23–37 μm or 0.48–0.67 times corresponding diameter long; female genital system didelphic-amphidelphic, uterus long, well-differentiated; tail short (35–49 μm, c = 24–39, c’ = 1.0–1.6), dorsally convex, conoid, with rounded to sub-acute terminus, hyaline part 21–31 % of its length; males with 44–48 µm long spicules, lateral guiding pieces distinct, rod-like, slightly curved ventrally, bifurcated with claw-like distal end and 9–11 irregularly spaced ventromedian supplements with hiatus.

Description.

Female. Slender nematodes of small-size, 1.1–1.4 mm long body; curved ventrally or open C-shaped upon fixation. Body cylindrical, tapering gradually towards both extremities but more so towards the posterior region. Cuticle with two distinct layers, 1.5–2.0 μm thick at the anterior region, 3.0–4.0 μm at midbody, and 5.0–6.0 μm on tail. Outer cuticle smooth, inner layer thin with distinctly fine transverse striations. Lateral, dorsal and ventral body pores indistinct. Lateral chords 11–14 μm wide at midbody, occupying ~ 1 / 5 (20–22 %) of the corresponding body diameter. Lip region offset from the body by constriction, 2.4–2.5 times as wide as high or ~ 1 / 3 (27–35 %) of the body diameter at the neck base. Lips angular, separated. Amphidial fovea funnel-shaped, aperture slit-like, 8.0–8.5 μm wide or occupying ~ 1 / 2 (50–53 %) of lip region diameter. Cheilostom a truncate cone. Odontostyle typical dorylaimoid, 5.8–6.1 times as long as wide, 1.1–1.2 times the lip region diameter long or 1.2–1.5 % of total body length, its aperture 7.0–8.5 μm or ~ 2 / 5 to 1 / 2 (38–47 %) of its length. Odontophore linear, rod-like, 1.3–1.5 times the odontostyle length. Guiding ring simple, at 0.56–0.62 times lip region diameter from the anterior end. Pharynx consisting of a weakly muscular anterior part, expanding gradually into a cylindroid part, occupying ~ 44–48 % of the total neck length, expanded part of the pharynx 5.7–6.7 times as long as wide, 3.2–3.7 times body diameter at neck base. Pharyngeal gland nuclei and their orifices are located as follows: DO = 56.2–58.4, DN = 60.3–63.4, DO – DN = 3.1–4.9, S 1 N 1 = 74.2–77.8, S 1 N 2 = 80.8–83.8, S 2 N = 89.4–90.9, S 2 O = 90.3–92.2. Nerve ring encircling the pharynx at 36–38 % of pharyngeal length from the anterior end. Cardia long, rounded to conoid, 1.5 – to 2.2 times as long as wide or ~ 1 / 2 to 2 / 3 (52–67 %) of the corresponding body diameter long, its junction with pharyngeal base apparently surrounded by cardiac disc (Fig. 8 H, I ). Genital system didelphic – amphidelphic; both the genital branches almost equally developed. Anterior genital branch 15.8–20.6 % and the posterior branch 14.6–17.3 % of body length. Ovaries reflexed, not reaching the oviduct-uterus junction; measuring 75–170 μm or 1.5–2.6 (anterior) and 85–107 μm or 1.3–1.7 (posterior) times the corresponding body diameter long; oocytes arranged in a single row except near the distal end. Oviduct joining the ovaries sub-terminally, measuring 86–190 μm or 1.7–3.0 (anterior, with one uterine egg inside, egg ovoid, 75 × 36 μm, 2.0 times as long as wide) and 75–136 μm or 1.5–2.1 (posterior) times the corresponding body diameter long; consisting of a slender distal portion and a well-developed pars dilatata. Oviduct-uterus junction marked by a well-developed sphincter. Uterus well-differentiated, tripartite, the proximal part well-developed muscular, the median short, comparatively less muscular, and the distal part long, tube-like, somewhat spheroid at the end, measuring 96–133 μm or 2.0–2.1 (anterior,) and 85–107 μm or 1.3–1.7 (posterior) times the corresponding body diameter long; Vagina extending inwards, 23–27 μm or ~ 2 / 5 to 1 / 2 (38–47 %) midbody diameter; pars proximalis 15–21 × 11–12 μm, with somewhat sigmoid wall encircled by circular muscles; pars refringens with two small trapezoid-shaped sclerotized pieces, measuring 4–5 × 4–5 μm and the combined width 8.5–10 μm; pars distalis 1.5–2.0 μm. Vulva a transverse slit. Sperm cells present (n = 3). Prerectum 1.7–2.8 and rectum 0.83–1.2 times the anal body diameter long, a distinct blind sac extending posteriorly to the prerectum-rectum junction (Fig. 9 G – I ). Tail dorsally convex conoid, its distal end straight to slightly bent ventrally with a rounded to sub-acute terminus, 1.3–1.6 times anal body diameter long; the hyaline part of the tail always perceptible, ~ 1 / 5 to 1 / 3 anal body diameter long with a pair of caudal pores on dorsal side.

Male. General morphology similar to that of female except for the posterior region being more ventrally curved. Genital system diorchic, testes opposed, sperm cells spindle-shaped, 5.0–7.5 μm long. In addition to the adcloacal pair, situated at 7–8 µm from the cloacal aperture, there are 9–11 irregularly spaced ventromedian supplements, the first ventromedian supplement located outside the range of spicules, 44–48 μm from the adcloacal pair. Spicules typically dorylaimoid, curved ventrad, relatively robust, 4.0–4.6 times as long as wide and 1.2–1.5 times as long as body diameter at the level of cloacal aperture, dorsal contour regularly convex, ventral contour bearing a moderately developed hump, curvature of 124–130 °. Head occupying 16.6 % of total spicules length, its dorsal side longer than ventral side, both sides slightly curved. Median pieces 10.6–12.3 times as long as wide or occupying ~ 27.2–35 % of the spicules’ maximum width, reaching the spicules tip, posterior end 3.5–4.0 μm wide. Lateral guiding pieces distinct, rod-like, slightly curved ventrally, bifurcated with claw-like distal end, ~ 4.8–5.6 times as long as wide or ~ 1 / 4 to 1 / 3 of the spicules’ length. Prerectum 2.6–4.4 and rectum 1.0–1.5 cloacal body diameter long. Tail dorsally convex, conoid, tapering gradually, its distal end slightly bent ventrally with rounded to sub-acute terminus, 1.0–1.3 times cloacal body diameter long, the hyaline part of the tail always perceptible, ~ 1 / 4 to 1 / 3 anal body diameter long with a pair of caudal pores on dorsal side.

Etymology.

The new species is named Eudorylaimus saccatus because of the pre-rectal blind sac.

Remarks.

In the presence pre-rectal blind sac, the new species is similar to E. productus ; E. bombilectus Andrássy, 1962 and E. blisterocaudatus sp. nov., but differs from the former in having comparatively broader and differently shaped lip region (15–17.5 vs 13–15 µm, lip region offset by constriction, lips more angular vs lip region almost continuous, lip comparatively less angular); longer and broader odontostyle (17.5–18.5 vs 14–15 µm, 5.8–6.1 vs 6.3–7.5 times as long as wide), comparatively longer odontophore and total stylet (24.5–27.5 vs 19.5–24.0; 43.5–45.5 vs 33.5–38.5 µm); long and slender expanded part of pharynx (148–189 vs 115–141 µm or 5.7–6.7 µm vs 3.7–5.0 times as long as wide), anteriorly located dorsal pharyngeal gland nuclei (DN = 60–63 vs 63–68); more posterior vulval position (V = 61–63 vs 52–54 %) and differently shaped tail (tail dorsally convex, conoid, straight to continuously curved ventrad vs tail conoid, first ventrally straight two-thirds then curved ventrad). The new species differs from E. bombilectus in having a comparatively shorter body size (L = 1.1–1.4 vs 1.3–1.7 mm); longer odontostyle (17.5–18.5 vs 14 µm) and expanded part of pharynx (44–48 vs 38–40 % of the total pharyngeal length); more posteriorly vulval position (V = 61–63 vs 52–54 %) and differently shaped tail terminus (tail tip rounded to sub-acute vs tail tip acute, pointed). From E. blisterocaudatus sp. nov. in having differently shaped lip region (lips separated, moderately angular vs lips well-separated, strongly angular) and amphid (funnel-shaped vs cup-shaped); comparatively longer pharynx and its expanded part (332–389 vs 300–339 µm, 148–189 vs 129–156 µm); longer spicules (44–48 vs 39–45 µm) and more ventromedian supplements (9–11 vs 6–8); differently shaped tail (tail conoid with rounded to subacute terminus vs tail conoid with sub-clavate to rounded terminus) and absence of blisters on the ventral side of the tail (vs blisters present).

Based on the body size and pattern of the tail the new species also resembles E. opisthohystera Altherr, 1953 ; E. subdigitalis Tjepkema et al. 1971 and E. piecea Wu et al. 2018 but differs from the former in having comparatively shorter male body size (L = 1.1–1.4 vs 1.5 mm) and odontostyle (17.5–18.5 vs 18–20 µm); shorter tail length (35–47 vs 58–73 µm); presence of pre-rectal blind sac (vs blind sac absent); comparatively smaller spicules (44–48 vs 55) and fewer ventromedian supplements (9–11 vs 12). The new species differs from E. subdigitalis in having shorter pharyngeal expansion (44–48 vs 50 % of pharyngeal length) and presence of cardiac disc at the pharyngo-intestinal junction (vs absent); comparatively more posterior vulval position (V = 61–63 vs 56–60), longer prerectum (61–84 vs 60 µm), presence of pre-rectal blind sac (vs blind sac absent) and presence of male (vs male not known). From E. piecea in its comparatively slender body (a = 22–24 vs 15–21.6) and shorter odontostyle (17.5–18.5 vs 20–22 µm); longer pharyngeal expansion (157–189 vs 140–156) and cardia (23–36 vs 13–20 µm), presence of cardiac disc at the pharyngeal-intestinal junction (vs absent); comparatively more posterior vulva position (V = 61–63 vs 59–61), presence of pre-rectal blind sac (vs absent) and presence of male (vs absent).

Figures

Figure 7. Eudorylaimus saccatus sp. nov. A entire female B entire male C anterior region showing amphid D, E anterior region F pharyngeal region G pharyngo-intestinal junction H female genital system I vulval region J, K female posterior region L male posterior region M spicule.

Figure 8. Eudorylaimus saccatus sp. nov. female: A entire B – D anterior region E anterior region showing amphid F pharyngeal region G pharyngeal expansion (arrow showing DN) H, I pharyngo-intestinal junction (arrow showing S 2 N and cardiac disc). Scale bars: 100 µm (A); 10 µm (B – E, G – I); 20 µm (F).

Figure 9. Eudorylaimus saccatus sp. nov. female: A, B genital system (arrow showing sphincter) C – E vulval region F oviduct and ovary (arrow showing sphincter) G, H. posterior region (arrow showing blind sac) I posterior end (arrow showing blind sac and caudal pores). Scale bars: 20 µm (A, B, G, H); 10 µm (C – F, I).

Figure 10. Eudorylaimus saccatus sp. nov. male: A entire B anterior region C pharyngeal region D pharyngo-intestinal junction (arrow showing cardiac disc) E, F posterior region (arrow showing series of supplements) G, H posterior end I – K spicules. Scale bars: 100 µm (A); 10 µm (B, D, G – K); 20 µm (C, E, F).