Basirotyleptus acus Goseco, Ferris & Ferris, 1974

Islam, Md Niraul & Ahmad, Wasim, 2022, Description of five new and six known species of the genus Basirotyleptus Jairajpuri, 1964 (Nematoda: Dorylaimida: Tylencholaimoidea) from the Western Ghats, India, European Journal of Taxonomy 791 (1), pp. 1-57 : 16-19

Basirotyleptus acus Goseco, Ferris & Ferris, 1974

Fig. 5 , Table 5

Basirotyleptus acus Goseco et al., 1974: 12 , 14.

Basirotyleptus pini – Furstenberg 1980: 153–155.

Material examined

INDIA – Kerala State • 11 ♀♀; Palakkad district, Silent Valley National Park ; 11º03′49.6″ N, 76º32′17.4″ E; 5–15 cm depth; 26 Oct. 2017; soil samples collected from around the roots of forest trees (unidentified); slides reference number AMU/ZD/NC/ Basirotyleptus acus /1–4 . – Tamil Nadu State • 7 ♀♀; Nilgiris district, Mudumalai National Park ; 11º32′35.4″ N, 76º31′24.1″ E; 5–15 cm depth; 14 Nov. 2016; soil samples collected from around the roots of shrubs (unidentified); slides reference number AMU/ZD/NC/ Basirotyleptus acus /5–8 .

.

Description

Female

Small sized nematodes, slightly curved ventrad or open C-shaped upon fixation; body cylindrical, tapering gradually towards both extremities but more so towards the anterior end. Cuticle with two distinct layers, 1.0–1.5 µm thick at anterior region, 1.5–2.0 µm at midbody and 2.0–2.5 μm on tail. Outer cuticle thin, with fine transverse striations; inner layer thick, striated, loose, its outline irregular, with distinct radial refractive elements. Lateral chords occupying about 28–35% of midbody diameter. Lateral body pores distinct; 1–3 in neck region; 1–2 from pharyngeal base to vulva and 3–8 post-vulval region. Dorsal and ventral body pores indistinct. Lip region cap-like, offset by constriction, 2.0–2.3 times as wide as high or about one-third to two-fifths of the body diameter at neck base. Lips rounded, amalgamated; inner part slightly elevated. Labial and cephalic papillae distinct but not interfering with labial contour. Amphids duplex, stirrup-shaped, their aperture about one-half to three-fifths as wide as lip region diameter. Stoma a long, slender truncate cone, slightly sclerotized in the perioral region. Odontostyle very slender, solid, thin needle-like, sometimes slightly dorsally bent, 1.2–1.6 times the lip region diameter long. Odontophore simple, sclerotized, about 1.0–1.1 times the odontostyle length. Guiding ring simple, refractive, at 1.2–1.4 times the lip region diameter from anterior end. Pharynx consisting of a slender and slightly muscular anterior part, expanding gradually into a short pear-shaped basal bulb, with a perceptible thickening at the posterior part of its inner lining, occupying about 14– 18% of total neck length. Nerve ring at 51–60% of neck length from anterior end. Cardia rounded to conoid, about one-fifth to one-fourth of the corresponding body diameter long.

Genital system monodelphic-opisthodelphic. Ovary reflexed, measuring 42–89 μm; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 44–63 μm, consisting of a slender distal portion and a well-developed pars dilatata. Oviduct-uterus junction marked by weak sphincter. Uterus short and slender tube without any specialization, measuring 17–30 μm.Anterior genital branch usually absent or reduced to a very small sac, about one-fifth to one-third midbody diameter long. Sperm cell absent. Vagina cylindrical, extending slight posteriorly, 8.5–11.5 μm or about two-fifths to one-half (40–52%) of midbody diameter; pars proximalis vaginae 5.5–7.5 × 4.0–6.0 μm, encircled by circular muscles; pars distalis vaginae 3.5–4.5 μm with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 2.5–3.8 and rectum 0.9–1.3 times anal body diameter long. Tail short, rounded to conoid, 0.6–0.8 times anal body diameter long, with a pair of caudal pores on each side, a distinct terminal pore also present.

Male

Not found.

Remarks

Goseco et al. (1974) described this species from the Indiana. The morphometrics of present populations conform well with the type population except in having a slightly longer odontostyle (10.0–11.5 vs 8 µm), slightly shorter odontophore (11–13 vs 14.4 µm); shorter pharyngeal bulb (15–20 vs 22 µm); longer vagina (8.5–11.5 vs 13 µm) and presence of anterior uterine sac in some specimens (vs anterior uterine sac absent). This species is reported here for the first time from India.

During the present study, two populations representing eighteen specimens were collected from the Western Ghats, India. Although in some specimens of the present populations a very small anterior uterine sac was present, other morphometric values completely overlapped to with those in B. acus , and therefore these specimens are considered as B. acus .

Furstenberg (1980) redescribed B. pini Siddiqi & Khan, 1965 based on two populations comprising twenty eight females from Australia and mentioned that Australian specimens correspond well with type population of B. pini except for the absence of anterior uterine sac in some specimens. Some doubt exists on the correct identity of the Australian population as it shows some morphological differences i.e., differently shaped odontostyle (odontostyle very slender, thin needle-like vs slender, simple needle-like); differently shaped lip region (lip region low, flat, offset by slight constriction vs lip region comparatively higher, angular, offset by deep constriction), labial papillae not interfering with labial contour (vs labial papillae interfering with labial contour, forming a liplets-like structure), and absence of anterior uterine sac in some specimens (vs anterior uterine present in every specimen). The morphometrics of Furstenberg (1980) population is quite comparable to B. acus except in the presence of anterior uterine sac in some specimens (vs absent in the type population). With the addition of present populations, which have specimens both with or without sac, B. pini apud Furstenberg, 1980 is considered here as B. acus .

Figures

Fig. 5. Basirotyleptus acus Goseco, Ferris & Ferris, 1974, ♀ (AMU/ZD/NC/Basirotyleptus acus/1–4) (LM photographs). A–C. Anterior region. D. Anterior region showing amphid. E. Pharyngeal region. F–G. Pharyngeal bulb. H. Genital system. I. Vulval region. J–K. Posterior region. L. Posterior end. Scale bars = 10 µm.

Tables

Table 5. Measurements ofBasirotyleptus acus Goseco, Ferris & Ferris, 1974. All measurements are in μm and in the form: mean ± s.d. (range)

Localities	Mukkali population	Modumalai population
Characters	Females	Females
n	11	7
L	486.1 ± 50.5 (391–552)	530.0 ± 40.6 (471–594)
Body diameter at neck base	18.9 ± 0.98 (17.5–20.5)	18.9 ± 0.68 (18.5–20.5)
Body diameter at mid body	20.9 ± 1.1 (19.5–23.5)	21.0 ± 0.98 (19.5–22.5)
Body diameter at anus	13.9 ± 1.5 (11.5–16.5)	13.5 ± 0.58 (12.5–14.5)
a	23.1 ± 1.7 (20.0–25.6)	24.7 ± 2.2 (21.3–28.7)
b	4.8 ± 0.38 (4.2–5.4)	4.7 ± 0.18 (4.5–5.0)
c	48.9 ± 4.5 (40.5–54.7)	48.3 ± 2.6 (44.5–53.4)
c’	0.72 ± 0.07 (0.61–0.84)	0.79 ± 0.06 (0.64–0.85)
V	36.9 ± 1.2 (35.5–39.8)	36.9 ± 1.6 (35.7–41.0)
G2	20.5 ± 3.1 (13.3–24.5)	18.2 ±2.4 (14.6–21.5)
Lip region diameter	7.2 ± 0.32 (7.0–8.0)	7.6 ± 0.34 (7.0–8.0)
Lip region height	3.3 ± 0.20 (3.0–3.5)	3.6 ± 0.24 (3.5–4.0)
Amphidial aperture	3.5 ± 0.22 (3.5–4.0)	3.8 ± 0.18 (3.5–4.0)
Odontostyle length	11.5 ± 0.26 (10–11)	11.0 ± 0.54 (10.5–11.5)
Odontophore length	11.4 ± 0.58 (11–12)	12.0 ± 0.88 (11–13)
Total stylet length	22.2 ± 0.73 (21–23)	23.0 ± 1.3 (21.5–24.5)
Guiding ring from anterior end	9.0 ± 0.39 (8.5–9.5)	9.6 ± 0.21 (9.0–10)
Nerve ring from anterior end	57.8 ± 2.0 (54–61)	62.8 ± 1.6 (60–65)
Neck length	99.6 ± 4.4 (93–106)	111.3 ± 4.6 (102–119)
Expanded part of pharynx	15.5 ± 0.92 (15–18)	18.9 ± 0.83 (17–20)
Cardia length	4.8 ± 0.14 (4.5–5.0)	4.4 ± 0.71 (3.0–5.0)
Anterior genital branch	4.9 ± 0.61 (4.0–6.0)	5.8 ± 0.42 (5.0–6.5)
Posterior genital branch	100.8 ± 13.5 (70–117)	97.7 ± 9.1 (84–112)
Vaginal length	10.0 ± 0.76 (8.5–10.5)	10.8 ± 0.57 (10.0–11.5)
Vulva from anterior end	179.4 ± 19.1 (139–201)	199.6 ± 12.1 (179–213)
Prerectum length	42.7 ± 5.0 (38–53)	42.7 ± 3.1 (39–49)
Rectum length	15.1 ± 1.7 (13.5–17.5)	17.0 ± 0.97 (15.5–18.5)
Tail length	9.9 ± 1.2 (8.0–11.5)	10.7 ± 0.98 (9.0–12)