Sporonchulus vagabundus Jairajpuri, 1971

Vu, Tam T. T., Nguyen, Anh D., Le, Thi Mai Linh & Pena-Santiago, Reyes, 2024, Updated taxonomy and new insights into the evolutionary relationships of the genus Sporonchulus Cobb, 1917 (Nematoda, Mononchida) after the study of two Vietnamese species, Zoosystematics and Evolution 100 (1), pp. 155-166 : 155

Sporonchulus vagabundus Jairajpuri, 1971

Material examined.

Three females from one location, in good state of preservation.

Morphometrics.

See Table 1 .

Description.

Female. Moderately slender to slender (a = 28-35) of medium size, 1.27-1.41 mm long. Body cylindrical, slightly tapering towards the anterior end and more appreciably towards the posterior extremity as the tail is conical. Upon fixation, habitus strongly curved ventrad, C- to G-shaped. Cuticle smooth, two-layered, 1 µm thick at anterior region, 1-1.5 µm in midbody and 2 µm on tail. Lip region almost continuous with the adjoining body, 2.1-2.5 times as wide as high and hardly more than one-half (53%) of body diameter at neck base, with totally fused lips and weakly protruding papillae. Amphid fovea small, goblet-like, located at 8-10 µm from the anterior end, its aperture a short transverse slit 3 µm long, occupying less than one-sixth (14-15%) of lip region diameter. Vestibulum 5 µm long. Buccal cavity up to twice (1.8-1.9 times) as long as wide, hardly longer (1.1 times) than lip region diameter: vertical (anterior) plates somewhat convergent at their anterior and posterior ends, their walls 1-1.5 µm thick, horizontal (posterior or basal) plates visibly oblique, with foramina, dorsal tooth apex situated at three-fourths of buccal cavity (74-75% from the base), anterior subventral plates bearing each two irregular rows of small teeth with decreasing size from the base till the level of dorsal tooth. Anterior end of pharynx embracing the basal part of buccal cavity, gland nuclei obscure. Nerve ring located at 93-101 µm or ca one-third (34-36%) of the total neck length. Pharyngo-intestinal junction non-tuberculate, 15 × 8-9 µm. Genital system diovarian, with small and equally developed branches occupying 6-7% of body length: ovaries comparatively large, 50-56 µm long, with oocytes first arranged in several rows and then in only one row; genital tract very short: oviduct 40-57 µm long or 1.1-1.4 body diameters, consisting of a small distal part and a well-developed pars dilatata, sphincter hardly perceptible, uterus a simple tube 17-21 µm or 0.4-0.5 body diameters; vagina 11-12 µm long, extending inwards to less than one-third (29-30%) of body diameter, pars proximalis 5.5-6.5 × 1.5-2 µm, pars refringens with two trapezoidal sclerotized pieces 2.5 × 2 µm and a combined width of 4.5-5.5 µm, pars distalis 0.5-1.5 µm, vulva a transverse slit. Rectum as long as anal body diameter long. Tail conical with finely rounded tip, regularly curved ventrad, with distinct caudal glands leading to a visible ampulla with terminal spinneret 2.5 µm long (Figs 3 , 4 ).

Male. Not found.

Locality and habitat.

Vietnam, Quang Ninh Province, Bach Long Vi Island, where the nematodes were collected in soil around the roots of a natural forest.

Voucher specimens.

Permanent slides are stored at the Department of Nematology, Institute of Ecology and Biological Resources, VAST, Hanoi, Vietnam.

Remarks.

As mentioned in the introductory section, these specimens were originally described as A. conoidus by Vu (2017). Nevertheless, their general morphology and morphometrics are almost identical to those provided by Jairajpuri (1971) for the type material of S. vagabundus , with no appreciable difference. This species is very similar to S. ibitiensis , but the study of Vietnamese specimens of both species have revealed some relevant differences. Morphologically, S. vagabundus females show a more developed pars dilatata oviductus and bear distinct caudal glands that, most importantly, lead to appreciable terminal ampulla and spinneret (vs ampulla and spinneret absent). Morphometrically (Table 1 ), S. vagabundus shows a much shorter buccal cavity (22-23 vs 27-28 µm). Although these differences are based on the comparison of only a few specimens, they seem significant enough to separate both species.

Jairajpuri’s (1971) original description and Vietnamese specimens herein studied are regarded as the basic material for the characterization of this species and for comparative purposes. Other references should be taken with more caution due to some uncertainties. Jairajpuri and Khan (1982) provided data of specimens with excessively large ranges of some relevant morphometrics (for instance, L = 1.2-1.8 mm, buccal cavity 22-27 µm), which might belong to more than one species. Tahseen et al. (2013) studied two Indian populations with smaller general size (body length 0.91-1.09 mm), and some inconsistences in their description (for instance, buccal cavity 1.4-1.6 times wider than long according to literal description, but 24-27 × 11-13 µm after the morphometrics provided in their Table 1 , and buccal cavity similar-sized after their morphometrics (25-27 and 24-26 µm long), but appreciably different according to Figs 1A , 2A and their corresponding scales.

Figures

Figure 1. Sporonchulus ibitiensis (Carvalho, 1951) Andrassy, 1958 (Female). A. Entire; B-D. Anterior body region, lateral median (B, C) and lateral submedian (D) view; E. Neck region; F. Anterior genital branch; G. Anterior body region, lateral surface view; H. Caudal region; I. Pharyngo-intestinal junction; J. Vagina. Scale bars: 200 µm (A); 10 µm (B-D, F, H, I); 50 µm (E); 5 µm (G, J).

Figure 2. Sporonchulus ibitiensis (Carvalho, 1951) Andrassy, 1958 (Female, LM). A. Entire; B, C, F, G. Anterior body region, lateral median (B, C) and lateral submedian (F, G) view; C. Lip region (SEM), in face view; E. Neck region; H. Caudal region. I. Vagina; J. Pharyngo-intestinal junction. Scale bars: 200 µm (A); 10 µm (B, C, F, G, H, J); 5 µm (D, I); 50 µm (E).

Figure 3. Sporonchulus vagabundus Jairajpuri, 1971 (Female). A. Entire; B, C. Anterior body region, lateral median view; D. Neck region; E. Posterior genital branch; F. Anterior body region, lateral surface view; G. Caudal region; H. Pharyngo-intestinal junction; I. Vagina. Scale bars: 200 µm (A); 5 µm (B, C, F, G, H); 50 µm (D); 10 µm (E, G).

Figure 4. Sporonchulus vagabundus Jairajpuri, 1971 (Female, LM). A. Entire; B-D. Anterior body region, lateral median view; E. Caudal glands; F-H. Anterior body region, lateral submedian view; I. Vagina; J. Caudal region; K. Posterior genital branch; L, N. Anterior body region, lateral surface view; M. Detail of caudal region tip; O. Pharyngo-intestinal junction. Scale bars: 200 µm (A); 5 µm (B-I, L, N, O); 10 µm (J, K, M).