Basiria gracilis ( Thorne, 1949 ) Siddiqi, 1963

Shokoohi, Ebrahim, Abolafia, Joaquín & Mashela, Phatu William, 2020, Redescription of Basiria gracilis (Thorne, 1949) Siddiqi, 1963 (Rhabditida, Tylenchidae) from South Africa, Zootaxa 4758 (2), pp. 387-396 : 388-395

Basiria gracilis ( Thorne, 1949) Siddiqi, 1963

( Figs 1–3 )

Material examined. Ten females and one male, in good condition, were studied. Additionally, one female specimen was used for the SEM study.

Measurements. See Table 1.

Description. Female. Body 692–994 µm, slightly curved ventrad after fixation, in some specimens straight. Cuticular annulation prominent, annuli rounded, annulus width 1.4±0.2 (1.1–1.8) µm. Lateral field a prominent band set off by two longitudinal incisures, 22–30% of body width. Labial region without annuli, more or less rounded, 3–4 µm high and 5–7 µm wide at the base, slightly differentiated by depression from the adjacent part of the body. Labial plate only visible under SEM, squarish, laterally depressed, with four rounded cephalic papillae. Oral plate small, bowtie-shaped, with six labial papillae. Amphidial apertures angular slits, inverted V-shaped. Stoma with fine stylet (stomatostylet): gymnorhabdia with anterior part (conus) ca. half of the posterior part (shaft) in length, ending in three minute rounded knobs (prostegorhabdia), in some specimens knobs are faint; dorsal gland opening (DGO) close to stylet base. Pharynx tylenchoid with median bulb (metacorpus) oval, with small valvular plates; basal bulb pyriform. Nerve ring almost at the middle of isthmus, at 71–73% of neck length. Excretory pore at isthmus level, at 82–92% of neck length. Deirids not visible. Hemizonid anterior to excretory pore. Reproductive system monodelphic-prodelphic, with ovary outstretched and long in some specimens (in one specimen almost reaching the terminal bulb), with oocytes in a single row in all females observed; spermatheca axial and oval to elongated, filled with rounded sperm; vagina straight, extending 35–47% of the corresponding body width; vulva a simple transverse slit without lateral membranes, slightly sunken. Postvulval uterine sac 42–80% of vulval body width. Tail conicalelongated, with rounded or pointed terminus. Vulva-anus distance longer than tail length (1.0–1.6). Phasmids not discernible.

Male. General morphology similar to female, but smaller in size, 448 µm long. Male reproductive system monorchic, with straight testis. Tail conoid-elongate, with acute tip. Bursa poorly developed. Spicules slightly ventrally curved: manubrium having more or less parallel ventral and dorsal walls and anteriorly not refringent; calamus slightly narrower than manubrium; lamina slightly swollen at its middle length and ventrally bent terminus with acute tip. Phasmids not discernible.

Diagnosis based on the South African material. The South African population of B. gracilis is characterised by its body length, 692–994 µm in females and 448 µm in males, lateral field with two longitudinal incisures; cuticle coarsely striated; high and truncated lip region without annuli bearing a bowtie-like oral plate; amphidial apertures inverted V-shape, stomatostylet 8–13 µm long with fine conus and minute knobs, relatively long ovary (12–18 % of the body length), axial spermatheca rounded (18–32 µm long) with small rounded sperm, postvulval uterine sac 0.42–0.80 times the body width, conoid-elongated tail (L= 692–994 µm, c =6.1–7.4, c’= 8.8–12.1 in females; L= 448 µm, c =4.3, c’ = 9.5 in male) with pointed or finely rounded terminus in females, spicules 14 µm long, gubernaculum 5 µm and bursa poorly developed.

Remarks. The South African population of Basiria agrees with B. gracilis in female body length (692–994 µm), stylet length (8–13 µm), lateral field with two incisures, high lip region (3–4 µm), long, axial spermatheca filled with sperm, tail length (103–146 µm) and spicule length (14 µm). The South African population of B. gracilis is similar to previously reported populations ( Table 2) of the same species. In comparison with the Belgian population ( Geraert 1968), they differ in the lower range of the tail length (103 vs 85 µm). From the Iranian material examined by Karegar & Geraert (1997), however, the South African population differs in the lower ranges of the body length (692 vs 475 µm), pharynx (117 vs 87 µm) and tail length (103 vs 72 µm). Although, Karegar and Geraert (1997) reported the tail length of B. gracilis (72–178 µm in the female and 71–177 µm in the male) which the range is high for the specimens. In comparison with the Polish population ( Karegar & Geraert, 1997), it differs in the lower range of the tail length (103 vs 150 µm). This species is reported for the first time from South Africa.

Locality and habitat. Specimens were collected in Potchefstroom (26° 44’ 9.36” S; 27° 6’ 19.7” E) in the North West Province of South Africa from the rhizosphere of the willow tree ( Salix sp. L).

Voucher material. Ten females deposited in the nematode collection of the Nematology Laboratory of Green Biotechnologies Research Centre of Excellence, University of Limpopo, South Africa and four females and one male deposited at Departamento de Biología Animal, Biología Vegetal y Ecología, Universidad de Jaén, Spain.

Figures

FIGURE 1. Basiria gracilis (Thorne, 1949) Siddiqi, 1963. A: Neck of female; B: Anterior end; C: Female reproductive system; D: Entire female; E: Entire male; F: Spicule and gubernaculum; G: Postvulval uterine sac; H: Male posterior end. I: Female posterior end.

FIGURE 2. Basiria gracilis (Thorne, 1949) Siddiqi, 1963 (light microscope). A: Neck; B: Female reproductive system (arrow pointing to spermatheca); C, D: Anterior end (arrow pointing to amphid); E, F: Anal region at spicules and bursa (arrow) level, respectively. G: Entire female; H: Female posterior end; I: Male posterior end; J: Lateral field; K: Vagina region; L: Entire male.

FIGURE 3. Basiria gracilis (Thorne, 1949) Siddiqi, 1963 (scanning electron microscope, female). A, I: Anterior end, in ventral and lateral views, respectively (arrow pointing to excretory pore); B–D: Lip region in lateral, ventral and frontal views, respectively (arrows indicating the amphids); E: Excretory pore (arrow); F, G: Vagina in ventral and right lateral views, respectively; H: Posterior end; J: Lateral field; K: Anus.