Labronemella major n. sp.

Measurements

For measurements of L. major n. sp., see table 1.

Table 1

Morphometric data of Labronemella major n. sp. All measurements are in the form: mean ± SD (range), and in μm (except for ‘L’ and ‘Vulva from anterior end’ in mm).

n, number of specimens observed; L, body length; a= L/maximum width; b= L/pharyngeal length; c= L/tail length; c′ = tail length/body diameter at anus; V= distance of vulva from anterior end ×  100/L; G1 = anterior genital branch reflection end to vulva ×  100/L; G2 = posterior genital branch reflection end to vulva ×  100/L.

Description

Female

Body moderately slender, ‘C’-shaped following heat relaxation and fixation (figs 1–3). Cuticle two-layered, 4–5 μm thick in anterior body, 6–7.5 μm at mid-body and 10–11.5 μm on tail; the outer layer thin with fine transverse striations, the inner one bearing distinct radial striations. Lateral chord 21–27 μm wide at mid-body, about one-fifth to three-tenths of the body diameter at mid-body. Lip region well offset by a distinct constriction, about three times as wide as high or about 0.3 times as wide as body diameter at neck base. Under SEM, lip region completely amalgamated, forming a disc-like structure, with an almost regular hexagonal outer margin and rounded inner margin; six separated inner liplets protruding on oral field; lateral liplets trapezoidal, larger than the triangular subdorsal and subventral ones. Labial papillae slightly protruding, inner labial papillae located on inner margin of labial disc, outer labial papillae and cephalic papillae located on six angles of outer margin of labial disc. Amphid fovea funnel-shaped, bulging distinctly on body surface under SEM; aperture located at the labial constriction, about 0.4 times as wide as lip region width. Odontostyle straight with distinct lumen and opening, about 1.2–1.3 times longer than lip region width and its aperture about 39–47% of its length. Odontophore rod-like, 1.4–1.7 times as long as the odontostyle. Guiding ring double. Nerve ring situated at 25.7–32.8% of the neck length from the anterior end. Anterior part of pharynx slender and muscular, basal expanded part of pharynx up to half (48–50%) of the total neck length. Pharyngeal gland nuclei located as follows: D = 54–56, AS1 = 55–62, AS2 = 56–64, PS1 = 64–80, PS2 = 72–83. Cardia conoid to ligulate. Genital system amphidelphic, with both well-developed branches. Ovary reflexed, anterior 138.5–295 μm long and posterior 140.5–237 μm long, usually surpassing the junction of oviduct and uterus. Oocytes arranged in a single row, except within the germination zone. Oviduct consists of a long slender part and a well-developed pars dilatata which is usually filled with sperm; anterior 162–187 μm long and posterior 170–187 μm long. Sphincter present at the junction of oviduct and uterus. Uterus differentiated into three parts; with one slender and twisting proximal region, one shorter intermediate region with thick walls and one distal portion with thinner walls and distinct lumen; anterior 322–397 μm long, posterior 307–450 μm long. Vulva transverse, vagina extending inwards about one-third of the corresponding body diameter. Pars proximalis vaginae 28–31 × 19–22 μm with convex walls; pars refringens with two well-developed drop-shaped sclerotized pieces that are close to each other, measuring about 9 × 6 μm and with a combined width of about 15 μm; pars distalis relatively short, 3–5 μm long. One egg observed, measuring 124 × 50.5 μm. Prerectum 1.8–2.6 times and rectum 1.0–1.4 times in length compared to the body diameter at anus. Tail short, rounded to conoid.

Fig. 1

Labronemella major n. sp. Female: (B) entire body; (C) anterior end; (D) amphid; (E) vulva; (G) posterior genital branch; (I) posterior end; (J) anterior region showing pharynx. Male: (A) entire body; (F) spicules; (H) posterior end.

Fig. 2

Labronemella major n. sp. Female: (A) entire body; (C) posterior region, (D) amphid; (E, F) anterior ends; (G) anterior region showing pharynx; (H) genital system; (I, J) vulvas in lateral view. Male: (B) entire body; (K) posterior region showing ventromedial supplements; (L) spicules. Scale bars: A, B = 500 μm; C–L = 20 μm.

Fig. 3

Labronemella major n. sp. Female: (A–C) anterior regions showing lip regions and amphids; (D) vulva; (E) posterior region. Male: (F, G) posterior regions. IL, inner labial papillae; LL, lateral liplet. Scale bars: A, C = 10 μm; B, D = 5 μm; E, G = 20 μm; F = 50 μm.

Male

Body similar to that of female, except that the posterior region of the body is more ventrally curved (figs 1–3). Ventromedial supplements 19–23, contiguous, the most posterior one lying 80–94.5 μm from the adanal one. Spicules dorylaimoid, slender with lateral guiding pieces, length 1.7–1.8 times the body diameter at anus. Prerectum relatively longer, 3.0–4.3 times, and rectum length 1.5–1.7 times the anal body width. Tail similar to that of female.

Diagnosis and relationships

Labronemella major n. sp. is characterized by a body length of 3.03–3.34 mm; lip region wide, offset by a distinct depression, disc-like with six separated inner liplets; amphid fovea funnel-shaped, distinctly bulged on body surface in SEM; long and straight odontostyle with distinct lumen, aperture 39–47% of its length; odontophore rod-like and long; guiding ring double; pharyngeal basal expansion about half of the total neck length; uterus relatively long and tripartite; vulva transverse and sclerotized; spicules 81–90 μm long; ventromedial supplements 19–23; tail short, rounded to conoid.

The new species can be differentiated from all other species of the genus (Peña-Santiago et al., Reference Peña-Santiago, Abolafia and Pedram2012) by its relatively longer body (3.03–3.34 mm), odontostyle (35–39 μm), spicules (81–90 μm), and wider lip region (29–31 μm). Due to the distinct offset lip region and long (three or more times body diameter at mid-body) tripartite uterus, the new species is close to L. czernowitzensis (Micoletzky, 1922) Andrássy, 2002 and L. labiata Andrássy, Reference Andrássy1985. In addition to the morphological differences described here, the new species can also be distinguished from these species by the following characters. It differs from L. czernowitzensis (Andrássy, Reference Andrássy2009) by having a transverse vulva (vs. longitudinal) and lower a value (a= 30.8–37.2 vs. 40–43 in female; 34.1–38.4 vs. 43–47 in male). From L. labiata (Peña-Santiago et al., Reference Peña-Santiago, Abolafia and Pedram2012), it mainly differs by the amphid distinctly bulging from the body surface (vs. not bulging on body surface); longer rectum (50–68 μm vs. 41–48 μm) in female and more ventromedial supplements (19–23 vs. 14–17) in male.

Key to species of Labronemella (after Peña-Santiago et al., Reference Peña-Santiago, Abolafia and Pedram2012)

In the key to the species of the genus provided by Peña-Santiago et al. (Reference Peña-Santiago, Abolafia and Pedram2012), L. andrassyi was classified into the group having a body less than 2.00 mm long. As described by Choi (Reference Choi1999), the Korean populations of L. andrassyi have a body length that is more than 2.00 mm long (1.98–2.28 mm). As a result, the key provided by Peña-Santiago et al. (Reference Peña-Santiago, Abolafia and Pedram2012) needs to be revised. A new key to the species is presented in fig. 4.

Fig. 4

Key to species of Labronemella (after Peña-Santiago et al., Reference Peña-Santiago, Abolafia and Pedram2012). References: *, (1) Thorne (Reference Thorne1939), (2) Andrássy (Reference Andrássy1985), (3) Peña-Santiago et al. (Reference Peña-Santiago, Abolafia and Pedram2012); **, (1) Choi (Reference Choi1999), (2) Peña-Santiago et al. (Reference Peña-Santiago, Abolafia and Pedram2012).