Cephaloboides parapapillosus ( Schuurmans Stekhoven, 1951 ) Schuurmans Stekhoven, 1951

Tahseen, Qudsia, Hussain, Ather, Ahlawat, Shikha, Mustaqim, Malka & Khan, Zakaullah, 2017, Description of a new and two known species of Cephaloboides Rahm, 1928 (Nematoda: Rhabditidae) from India, with discussion on the taxonomy of the genus, Zootaxa 4277 (3), pp. 352-368 : 361-365

Cephaloboides parapapillosus ( Schuurmans Stekhoven, 1951) comb. n.

( Figs. 5 , 6 )

Measurements. Table 1

Description. Adult: Body medium-sized, 0.8–0.9 mm, slender, slightly ventrally curved upon fixation, tapering at both extremities, more towards posterior end. Cuticle double, outer smooth, inner faintly striated. Lip region offset from adjoining body. Lips prominent, globular, elevated, provided with inner labial sensilla close to oral aperture; cephalic and outer labials prominent and towards outer border of lips. Amphids small, pore-like on lateral lips. Stoma tubular, 4.5–6.0 times longer than wide or nearly two times lip diameter. Cheilostom not cuticularized, indistinct; gymnostom thickly cuticularized, about 1/4th–1/5th of stomal length; stegostom about 2/ 3rd of stomal length, surrounded by pharyngeal tissue. Metastegostom isotopic and isomorphic. Each metastegostomal swelling provided with a spur-like denticle. Pharynx comprising of a cylindroid or weakly swollen, 120–135 µm long corpus, 38–55 µm long isthmus and a well-developed, oblong, rectangular, valvate basal bulb 37– 43 x 25–31 µm in size. Nerve ring encircling isthmus at 68–70% of pharyngeal length from anterior end. Secretory-excretory pore inconspicuous, observed slightly posterior to nerve ring in few specimens. Hemizonid prominent. Body 2.5–3.5 and 3.2–4.2 times lip diameters at proximal and distal ends of pharynx, respectively. Pharyngeal corpus about 1.2–1.6 times longer than isthmus and basal bulb together. Cardia flattened, 7–15 µm long, with cuticularized lining, hanging into intestinal lumen. Intestine granular; intestinal cells polygonal with defined nuclei; intestinal lumen narrow with irregular outline. Rectum thin-walled, nearly one anal body diameter long; rectal glands present. Anus a crescent-shaped slit.

Female: Reproductive system didelphic, amphidelphic. Ovaries dorsally reflexed, anterior ovary at right side and posterior at left side of intestine. One or two pseudocoelomocytes observed in close proximity with flexures of ovaries. Oocytes in multiple rows at distal end followed by a single row proximally. Oviduct slightly dilated connected with offset, rounded spermatheca filled with sperms. Uterus broad, spacious with usually 1–4 embryonating eggs. Vagina at right angle to longitudinal body axis, thin-walled, 12–15 µm long provided with muscle bands. Vulva a transverse wide slit, located post-equatorially at about 489–580 µm from anterior end; vulval lips protruded, epiptygma present surrounded by vulval flaps. Vulva-anus distance 310–370 µm. Tail short, spicate, narrowing into a whip-like terminus. Phasmidial ducts opening at base of broader part of tail or at beginning of spike.

Male: Similar to female in general morphology except being smaller in size and more arcuate posteriorly. Testis monorchic, ventrally reflexed, at right side of intestine, reflexed portion about 85 µm long. Spicules stout, about 1.2–1.4 anal body diameter long, slightly arcuate with rounded to elliptical capitula. A thin dorsal arm almost reaching up to spicular length and a ventral triangular process present. Distal end of spicules rounded not notched with a thin gelatinous cap. Gubernaculum about half anal body diameter long, bifid proximally expanding into a wider middle part that continues distally into heavily sclerotized, slender dorso-lateral arms surrounded by membranous caps at ends. Bursa leptoderan, greatly reduced, not covering the tail spike. Genital papillae nine pairs in 1+2/1+3+2+P configuration with GP1 far ahead of GP2 and GP3 that appear nearly adcloacal. Of the six postcloacal, GP4 ventro-lateral and protruding from bursal edge; GP5, GP6, GP7 grouped together, subventral; GP8 directed subdorsally, close to subventral GP9. Phasmidial ducts narrower and smaller than papillae opening next to GP9. Copulatory muscles well developed with 6–8 paired bands. Tail similar to that of female, short spicate with pointed tip.

Locality and habitat. Samples containing Cephaloboides parapapillosus were obtained from a ditch behind a forest lodge in Keoladeo National Park, Bharatpur, Rajasthan, India at coordinates 27.1593° N, 77.5232° E.

Voucher specimens. Fourteen females and three males on slide Cephaloboides parapapillosus KNP 2 B/ 1–7 deposited in Nematode Collection , Department of Zoology , Aligarh Muslim University, Aligarh, India.

Emended diagnosis. C. parapapillosus is characterized by a medium-sized body; finely annulated cuticle; prominently raised labial sensilla; small stoma; slightly protruded vulval lips with flaps, epiptygma; males with spicules having rounded to elliptical capitula, dorsal thorn and distinct ventral conoid process, capped distal ends and genital papillae in configuration of 1+2/1+3+2+P with GP1 very distant from GP2 and GP3.

C. parapapillosus can be differentiated from the present population of C. curvicaudatus in having smaller c’ value (0.9–1.5 vs 2.2–4.2); prominent globular, distinctly separated lips (vs lips fused at bases); relatively smaller stoma (22–27 µm vs 27–32 µm long), shorter spicules (30–35 µm vs 42–53 µm long) with round to elliptical capitula (vs with elongate capitula) and GP1 distant from the other precloacal pairs (vs GP1 closer to GP2 and GP3).

C. parapapillosus can be further differentiated from C. musicola Rahm, 1928 in having relatively smaller c’ value (0.9–1.5 vs 1.5–2.0); relatively larger c value (29.7–41.3 vs 17.0–36.0); smaller stoma (22–27 µm vs 33–38 µm long), shorter spicules (30–35 µm vs 42–81 µm long) with round to elliptical capitula (vs hood-shaped capitula); proximally obtuse (vs proximally narrow and acute) gubernaculum and anterior genital papillae relatively more distant from the other precloacal pairs.

C. parapapillosus differs from C. anisospiculus sp. n. in having larger body (0.8–0.9 mm vs 0.5–0.7 mm); greater b (3.8–4.8 vs 2.7–3.6) and c (29.7–41.3 vs 15.4–22.7) values; relatively longer stoma (22–27 µm vs 20–24 µm) and males with larger (30–35 µm vs 19–29 µm), similar and equal (vs dissimilar and unequal spicules in C. anisospiculus sp. n.).

Figures

FIGURE 5. Cephaloboides parapapillosus (Schuurmans Stekhoven, 1951) comb. n. A: Entire female. B: Entire male. C: Female anterior end. D: Female pharyngeal region. E: Female anterior genital branch. F: Female posterior region. G, I: Male posterior region (lateral). H: Male posterior region (ventral).

FIGURE 6. Cephaloboides parapapillosus (Schuurmans Stekhoven, 1951) comb. n. A: En face view (scanning electron microscopy). B, C: Anterior end. D: Posterior pharyngeal region. E: Uterine region. F: Vulval region (scanning electron microscopy). G: Female posterior region. H: Female posterior region (scanning electron microscopy). I – O: Male posterior region (Scale bars = 10 µm).