Cobbonchus vulvastriatus, Nusrat, Tabinda, Anjum, Ashher & Ahmad, Wasim, 2013

Nusrat, Tabinda, Anjum, Ashher & Ahmad, Wasim, 2013, Mononchida (Nematoda) from Silent Valley National Park, India, Zootaxa 3635 (3), pp. 224-236 : 225-229

Cobbonchus vulvastriatus n. sp.

( Figs. 1 & 2 )

Material examined. Four females and three males, in good state of preservation.

Measurements: Table1.

Description: Female: Medium sized nematodes with cylindroid body, ventrally curved, becoming J-shaped upon fixation. Cuticle smooth, 1–2 μm thick along the body. Lateral hypodermal chords occupying about onefourth of the mid-body diameter. Lateral, dorsal and ventral body pores indistinct. Lip region slightly offset, wider than the adjoining body, about 3–4 times as wide as high. Labial papillae distinct, projecting slightly above the labial contour. Amphid aperture slit-like, 5 μm wide, at level with dorsal tooth apex. Buccal cavity cylindrical, tapering at base, twice or slightly more than twice as long as wide; dorsal tooth large, its apex at 72–81% from base of stoma, its tip slightly elevated making a concave depression at its front edge; subventral teeth comparatively smaller but of similar shape, at 40–41% from the base of stoma. A pair of ventrosublateral foramina present near the oblique basal plate of stoma. Nerve ring at 23–27% of neck length from anterior end. Excretory pore indistinct. Pharyngo-intestinal junction non-tuberculate. Genital system didelphic-amphidelphic; both the sexual branches almost equally developed; ovaries reflexed, 34–56 μm long, its distal end not reaching oviduct-uterus junction with oocytes arranged in a single row except near tip; oviduct 55–87 μm long with a well developed pars dilatata; sphincter present at oviduct uterus junction; uterus a convoluted tube, 62–97 μm long. Vagina thick-walled extending inwards about one-half of the corresponding body width; pars proximalis vaginae 9–11 μm long with parallel walls surrounded by circular muscles; pars refringens vaginae with rather moderately developed, slightly triangular sclerotized pieces, each measuring 2–3×1–1.5 μm, cw 3–4 μm; pars distalis vaginae 1.5–2.5 μm. Vulva a transverse slit with 1–3 pre- and 2–4 post-vulval cuticular infoldings (with weak indication of nerve endings). Tail conoid, curved ventrad with a strong angular bending, slightly bulged at the ventral side before tapering, slender portion of tail about twice the anterior part; caudal glands well developed, arranged in tandem, spinneret terminal.

Male: Similar to female in general morphology except for the posterior region being more ventrally curved due to the presence of copulatory muscles. Genital system diorchic, each testis thin walled, filled with ovoid spermatozoa. The two testes join to form a common vas deferens which leads to the ejaculatory duct. Four pairs of ejaculatory glands. Rectal glands indistinct. Spicules robust, distal part aligned ventrally, ventral arm convex, 1.2–1.4 times the body diameter long. Gubernaculum trough-shaped, about two-fifths of spicule length, distal half distinctly thickened. Lateral guiding pieces about one-sixth of spicule length, with a flat tip. Ventromedian supplements almost regularly spaced, six in number. Tail similar in shape as female.

Type habitat and locality: Soil around the roots of forest trees from Mukkali, Silent Valley National Park, Palakkat, Kerala State, India.

Type specimens: Holotype female on slide Cobbonchus vulvastriatus n. sp. /1; paratype females and males on slides Cobbonchus vulvastriatus n. sp. /2–4; deposited with the nematode collection of the Department of Zoology, Aligarh Muslim University, India.

Etymology: The new species is named vulvastriatus because of its cuticular infoldings near the vulva.

Diagnosis and relationships: Cobbonchus vulvastriatus n. sp. is characterized by its 0.92– 0.11 mm long body; buccal cavity 25–27×12–13 μm, dorsal tooth comparatively large with its apex at 72–81% from base of stoma; subventral teeth slightly smaller with their apices at 40–41% from the base of stoma; female genital system amphidelphic with both branches almost equally developed, 1–3 pre-vulval and 2–4 post-vulval cuticular infoldings present (with weak indication of nerve endings); spicules 1.2–1.4 times the cloacal body diameter long; TABLE I. Cobbonchus vulvastriatus n. sp. All measurements in µm.

gubernaculum trough-shaped with distal thickening; lateral guiding pieces small; ventromedian supplements six, spaced; tail conoid, curved ventrad, tapering, beak-shaped; caudal glands well developed, arranged in tandem, spinneret terminal.

The new species is distinctive in having its dorsal tooth larger than the subventral teeth and in the presence of cuticular infoldings near vulva. In its tail shape, it closely resembles C. inclinatus Dhanam & Jairajpuri, 1998 and C. citri Dhanam & Jairajpuri, 1999 but differs from the former in having smaller body size (0.92–1.16 vs 1.3–1.6 mm), narrower lip region (18–19 vs 24–26 µm), comparatively smaller buccal cavity (25– 27 x 12–13 vs 29–34 vs 15–17 µm), dorsal tooth larger than the subventral teeth and comparatively anterior (dorsal tooth apex 72–81% vs 67–74%), vagina not inclined (vs vagina characteristically inclined), in the presence of cuticular infoldings near vulva (vs cuticular infolding absent), and in the presence of males (vs males absent). From C. citri Dhanam & Jairajpuri, 1999 , it differs in the presence of vulval cuticular infoldings (vs cuticular infoldings absence), anterior position of dorsal tooth (vs dorsal tooth apex at 67%), subventral teeth far behind dorsal (vs subventral teeth slightly behind dorsal), longer female tail (30–35 vs 24.5 µm), arrangement of caudal glands (tandem vs grouped), in shape and size of spicules and lateral guiding pieces (spicules 32–33 vs 37–40 µm, lateral guiding pieces 5–6 vs 12 µm).

The new species also resembles C. indicus Baqri, Baqri & Jairajpuri, 1978 but distinctly differs in the presence of vulval cuticular infoldings (vs absence) and the shape and size of tail. The tail in C. indicus is short-conoid, rather bulbous, slightly ventrally curved, with the slender portion of tail almost equal to the anterior part (female tail 30–35 vs 22 µm; c = 30.9–34.6 vs 49 in females; 30.4–37.4 vs 43 in males). It further differs in having a larger buccal cavity (25– 27 x 12–13 vs 23 x 11 µm), in the position of amphid (at the level of dorsal tooth vs near anterior end of buccal cavity), arrangement of caudal glands (tandem vs grouped), shape and size of spicules and gubernaculum (spicules 32–33 vs 36 µm; gubernaculums13–14 vs 7 µm).

Among the two Indian species having vulval papillae, C. paraindicus Rahman & Jairajpuri, 1984 and C. papillatus Dhanam & Jairajpuri, 1998 , the new species distinctly differs from the former in the shape and size of tail (tail bulbous conoid with subterminal spinneret, c= 48–53 in C. paraindicus ). If further differs from C. paraindicus in the position of amphid (anterior to dorsal tooth apex vs posterior to dorsal tooth apex), in the presence of vulval cuticular infoldings (vs presence of vulval papillae); smaller spicules and gubernaculum (vs spicules 58 µm; gubernaculum 26 µm) and in the number of ventromedian supplements (6 vs 16).

From C. papillatus Dhanam & Jairajpuri, 1998 the new species differs in having smaller body size (0.92–1.16 vs 1.6–2.3 mm), smaller buccal cavity (25– 27 x 12–13 vs 34– 47 x 17–20 µm) with quite anteriorly placed dorsal tooth (dorsal tooth apex at 72–81 vs 58–65% from base of stoma), position of amphid (at the level of dorsal tooth vs much anterior to dorsal tooth apex), smaller c value (30.9–34.7 vs 44–69), smaller spicules and lateral guiding pieces (spicules 32–33 vs 41–52 µm, lateral guiding pieces 5–6 vs 13–15 µm). C. papillatus has distinct vulval papillae both anterior and posterior to vulva, whereas, in C. vulvastriatus n. sp. all the females have cuticular infolding on both sides of vulva with slight indication of nerve endings.

Figures

FIGURE 1. Cobbonchus vulvastriatus n. sp. A: Anterior end. B: Anterior region. C: Female genital branch (posterior). D – E: Vulval region. F: Female posterior end. G: Male posterior region. H: Male copulatory apparatus.

FIGURE 2. Cobbonchus vulvastriatus n. sp. A – B: Anterior end. C: Female genital system. D: Vulval region. E: Female posterior end. F – G: Male posterior region (scale bars A, B = 20 µm; C – G = 10 µm).