Basirotyleptus conicaudatus, Islam & Ahmad, 2022

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 : 24-29

Basirotyleptus conicaudatus sp. nov.

urn:lsid:zoobank.org:act:25B540AE-3BF1-43F8-865C-7342E11514F8

Figs 8–9 , Table 7

Diagnosis

Basirotyleptus conicaudatus sp. nov. is characterized by having robust body, 0.42–0.44 mm long; lip region cap-like, offset by deep constriction, lips rounded, inner part elevated; odontostyle 9.5–10.0 μm long, odontophore 11.0–12.0 μm long and total stylet length 21.0–22.0 μm; pharynx with a slender anterior part, expanding abruptly into a short pear-shaped basal bulb, occupying about 14–15% of total neck length; female genital system monodelphic-opisthodelphic; anterior genital branch a small sac, measuring 15–20 µm or 0.7–0.9 times midbody diameter long; tail convex-conoid with acute terminus, 1.2–1.3 times anal body diameter long; male with 20 µm long spicules, 5.0 µm long lateral guiding pieces and a single ventromedian supplement.

Etymology

The new species is named Basirotyleptus conicaudatus sp. nov. because of its conoid tail.

Material examined

Holotype INDIA • ♀; Kerala State; Thrissur district, Chalakudy ; 10º18′03.6″ N, 76º26′27.6″ E; 5–15 cm depth; 27 Oct. 2017; roots of shrubs (unidentified); slide reference number AMU/ZD/NC/ Basirotyleptus conicaudatus /1.

Paratypes INDIA • 1 ♀, 1 ♂; same collection data as for holotype; slides reference number AMU/ZD/NC/ Basirotyleptus conicaudatus /2 .

Type habitat and locality

Soil samples collected from around the roots of shrubs (unidentified) from Chalakudy, Thrissur, Kerala State.

Description

Female

Small sized nematodes, curved ventrad upon fixation; body cylindrical, tapering gradually towards both extremities but more so towards the anterior end. Cuticle with two distinct layers, 1.0 µm thick at anterior region, 1.5 µm at midbody and 2.0 μm on tail. Outer cuticle thin, smooth to finely transversaly striated; inner layer thick, loose, finely striated, radial refractive elements distinct. Lateral chords occupying about 28–30% of midbody diameter. Lateral, dorsal and ventral body pores indistinct. Lip region caplike, offset by constriction, 2.0–2.1 times as wide as high or about 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 stirrup-shaped, their aperture about three-fifths as wide as lip region diameter. Stoma a long, slender truncate cone, slightly sclerotized in the perioral region. Odontostyle short, slender, solid, needle-like, 1.1–1.2 times the lip region diameter long. Odontophore simple, sclerotized, with basal flanges, about 1.2 times the odontostyle length. Guiding ring simple, refractive, at 0.9–1.0 times the lip region diameter from anterior end. Pharynx consisting of a slender anterior part, expanding abruptly into a short, pear-shaped basal bulb, with a perceptible thickening at the posterior part of its inner lining, occupying about 14–15% of total neck length. Nerve ring at 53–56% of neck length from anterior end. Cardia rounded to conoid, about one-fifth of the corresponding body diameter long.

Genital system monodelphic-opisthodelphic. Ovary reflexed, measuring 49–50 μm; oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 53–60 μm, consisting of a slender distal portion and a well-developed pars dilatata. Oviduct-uterus junction marked by distinct sphincter. Uterus short and wide tubular, measuring 15–17 μm. Anterior genital branch reduced to small sac, 0.7–0.9 times midbody diameter. Vagina cylindrical, extending inwards, 9.0–9.5 μm or about one-half (45–48%) of midbody diameter; pars proximalis vaginae 5.5–6.0 × 4.0–4.5 μm, encircled by circular muscles; pars distalis vaginae 3.0–3.5 μm with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 2.8–3.2 and rectum 1.2 times anal body diameter long. Tail short, convex-conoid with acute terminus, 1.2–1.3 times anal body diameter long, with a pair of caudal pores on each side.

Male

General morphology similar to that of female except for posterior region being more ventrally curved. Genital system diorchic, testes opposed, sperm cell spindle-shaped. In addition to adcloacal pair at 6.5 µm from cloacal aperture, there is single ventromedian supplement located beyond the range of spicules, 25 μm from adcloacal pair. Spicules typically dorylaimoid, curved ventrad, slender, five times as long as wide and 1.4 times as long as cloacal body diameter, dorsal contour regularly convex, ventral contour bearing a moderately developed hump and hollow, curvature 135º, head occupying 22% of total spicules length, median pieces about ten times as long as wide or occupying 37% of the spicules maximum width, reaching the spicules tip, posterior end 2.5 μm wide. Lateral guiding pieces distinct, rod-like, about 5.0 times as long as wide or about one-fourth of the spicules length. Prerectum 3.5 and rectum 1.5 times cloacal body diameter long. Tail short, convex-conoid with acute terminus, 1.2 times cloacal body diameter long, with a pair of caudal pores on each side.

Remarks

In the presence of a flanged odontophore and short anterior uterine sac, the new species comes close to B. syncheilus Siddiqi, 1995 ; B. siremps Siddiqi, 1995 ; B. nindei Siddiqi, 1970 and B. minutus Khan, 1987 but differs from B. syncheilus in having lip region offset by constriction (vs lip region continuous); lips elevated (vs lips not elevated, flat); shorter pharyngeal bulb (14–15 vs 19 µm); differently shaped tail (tail convex-conoid with acute terminus vs convex-rounded with hemispheroid terminus); lower c (25–27 vs 34–53) and slightly higher c’ (1.2–1.3 vs 0.9–1.1) ratios; longer spicules (20 vs 15–16 µm) and presence of ventromedian supplements (vs absent).

From B. siremps , the new species differs in having slightly longer body (L = 0.42–0.44 vs 0.30–0.39 mm); longer total stylet (21–22 vs 15.5–17.5 µm, odontostyle 9.5–10.0 vs 7.5–8.5 µm; odontophore 11.5– 12.0 vs 8.0–9.0 µm); comparatively posterior vulva position (V = 55–58 vs 47–53); lower c (25–27 vs 27–43) ratio; differently shaped tail (tail convex-conoid with acute terminus vs tail with rounded to hemispherical terminus); longer spicules (20 vs 12.5 µm) and presence ventromedian supplements (vs absent).

From B. nindei , the new species differs in having wider lip region (8.0–8.5 vs 6.0–7.0 µm); posterior vulva position (V = 55–58 vs 39–45); presence of longer anterior uterine sac (15–20 vs anterior uterine sac usually absent, rarely present, 4.5–6.0 µm); differently shaped tail (tail conoid with acute terminus vs bluntly rounded to conoid terminus) and presence of male (vs male absent).

From B. minutus , the new species differs in having wider lip region (8.0–8.5 vs 5.0–7.0 µm); amphids simple, stirrup-shaped (vs duplex, stirrup-shape); posterior vulva position (V = 55–58 vs 32–42); differently shaped tail (tail conoid with acute terminus vs rounded to conoid terminus) and presence of male (vs absent).

The new species also comes close to B. discinus Siddiqi, 1995 and B. diminutus Siddiqi, 1995 but differs from the former in having robust body (a = 21–22 vs 28); absence of labial disc (vs labial disc present); odontophore with distinct basal flanges (vs odontophore with poorly developed basal flanges); posterior vulva position (V = 55–58 vs 51) and lower c (25–27 vs 35) ratio.

From B. diminutus , the new species differs in having slightly longer and slender body (L = 0.42–0.44 vs 0.29–0.36 mm, a = 21–22 vs 17–20); longer total stylet (21–22 vs 16.0–18.5 µm) and odontostyle (9.5–10 vs 7.5–8.5 µm), odontophore with well developed basal flanges (vs poorly developed flanges); posterior vulva position (V = 55–58 vs 37–42); presence of anterior uterine sac (vs absent) and differently shaped tail (conoid with acute terminus vs hemispherical to rounded).

In the presence of a conoid tail the new species comes close to B. caudatus Jairajpuri, 1966 ; B. lieberi Goseco et al., 1974 and B. westralis Siddiqi, 1970 , but differs from B. caudatus in having odontophore with basal flanges (vs odontophore without flanges); posterior vulva position (V = 55–58 vs 40–48); presence of anterior uterine sac (vs anterior uterine sac absent) and presence of male (vs male absent).

From B. lieberi , the new species differs in having shorter body (L = 0.42–0.44 vs 0.67–0.90 mm); female genital system mono-opisthodelphic (vs mono-prodelphic) and smaller spicules (20 vs 24–28 µm).

From B. westralis , the new species differs in having shorter body (L = 0.42–0.44 vs 0.55–0.75 mm); female genital system mono-opisthodelphic (vs amphidelphic) and smaller spicules (20 vs 22– 25 µm).

Figures

Fig. 8. Basirotyleptus conicaudatus sp. nov. A, C–G. Holotype, ♀ (AMU/ZD/NC/Basirotyleptus conicaudatus/1). B, H. Paratype, ♂ (AMU/ZD/NC/Basirotyleptus conicaudatus/2). A. Entire female. B. Entire male. C. Female, anterior region. D. Female, anterior region showing amphid. E. Female, pharyngeal region. F. Female, genital system. G. Female, posterior region. H. Male, posterior region.

Fig. 9. Basirotyleptus conicaudatus sp. nov. (LM photographs). A, C–I. Holotype, ♀ (AMU/ZD/ NC/Basirotyleptus conicaudatus/1). B. Paratype 1, ♀ (AMU/ZD/NC/Basirotyleptus conicaudatus/2). J–K. Paratype 2, ♂ (AMU/ZD/NC/Basirotyleptus conicaudatus/2). A–B. Female, anterior region. C. Female, anterior region showing amphid. D. Female, pharyngeal region. E. Female, pharyngeal bulb. F–G. Female, genital system. H. Female, posterior region. I. Female, posterior end. J–K. Male, posterior end. Scale bars = 10 µm.

Tables

Table 7. Measurements of Basirotyleptus conicaudatus sp. nov. All measurements are in μm.

Characters	Holotype ♀	Paratype ♀	Paratype ♂
n		1	1
L	442	427	423
Body diameter at neck base	18	18.5	16.5
Body diameter at mid body	19.5	19.5	18.5
Body diameter at anus	13.5	13.0	13.5
a	22.6	21.8	24.0
b	4.3	4.4	4.0
c	25.1	27.3	25.4
c’	1.3	1.2	1.2
V	55.3	58.0	–
G1	4.2	3.4	–
G2	21.0	20.4	–
Lip region diameter	8.0	8.5	8.0
Lip region height	4.0	4.0	4.0
Amphidial aperture	5.0	5.0	5.0
Odontostyle length	10	9.5	10
Odontophore length	12	11.5	11
Total stylet length	22	21	21
Guiding ring from anterior end	8.5	8.0	8.5
Nerve ring from anterior end	56	50	58
Neck length	101	97	105
Expanded part of pharynx	15	14	15
Cardia length	4.0	4.0	4.0
Anterior genital branch	20	15	–
Posterior genital branch	87	93	–
Vagina length	9.0	9.5	–
Vulva from anterior end	245	247	–
Prerectum length	37	41	48
Rectum length	14	13	20
Tail length	17	15.5	16.5
Spicules length	–	–	20
Lateral guiding pieces	–	–	5
Ventromedian supplements	–	–	1