Cephaloboides anisospiculus, Tahseen & Hussain & Ahlawat & Mustaqim & Khan, 2017

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 : 353-358

Cephaloboides anisospiculus sp. n.

( Figs. 1 , 2 )

Measurements. Table 1.

Description. Adult: Body small to medium-sized, slender, almost straight or slightly ventrally curved upon fixation. Cuticle double, about 1.5–2.0 µm thick, faintly punctated, with fine transverse and longitudinal striations. Lateral fields indistinct. Lip region expanded, 11–13 µm in diameter, set off from adjoining body. Lips six, prominent, globular with smooth margins, fused at bases. Inner labial sensilla close to oral aperture; cephalic and outer labial sensilla slightly raised and towards outer border of lips. Amphids small, on lateral lips. Stoma tubular, 4.6–6.5 times longer than wide or 1.6–2.0 labial diameters in length. Cheilostom weakly cuticularized. Gymnostom tubular, with parallel walls, thickly cuticularized about 1/4th–1/3rd of stomal length. Pharyngeal tissue surrounding about 50-55% of stoma. Metastegostom isotopic and slightly anisomorphic with a fine wart on each plate. Pharyngeal corpus swollen, 97–120 µm long or 2.6–3.3 times isthmus length. Basal bulb 36–50 µm x 22–25 µm in size having a grinder and single-chambered haustrulum. Nerve ring surrounding isthmus at 59.4–64.8% of pharyngeal length from anterior end. Secretory-excretory pore located posterior to nerve ring at 71.7–72.8% of pharyngeal length from anterior end. Body at pharyngeal end 2.3–3.0 times labial diameter in width. Cardia with conical flaps, 4–6 µm long. Intestine granular with wide lumen. Rectum thin-walled, 0.7–1.0 anal body diameter long with three rectal glands. Anal opening crescentic slit.

Female: Reproductive system didelphic, amphidelphic. Ovaries weakly-developed, dorsally reflexed, flexure small, often convoluted, never reaching vulva; anterior ovary on right, posterior ovary on left side of intestine. Proximal part of oviduct prominently dilated, separated from spermatheca by a prominent sphincter, with another strong sphincter lying between spermatheca and uterus. Uterus often with 2– 8 eggs, 37–42 µm long x 20–24 µm wide, at different stages of embryonation. Intra-uterine development usually observed in older females with juveniles hatched inside the body. Vagina 13–23 µm long occupying about 2/3rd of the corresponding body diameter and perpendicular to the main body axis with distal folds appearing as internal epiptygma. Vulva a transverse slit surrounded by cuticular flaps. Distance between vulva and anus 268–315 µm or 4.4–7.1 times tail length. Tail cupola-shaped, about 1.3–1.5 times of anal body diameter long with 26–34 µm long anterior conical part and a posterior narrow, 20–24 µm long spike. Phasmidial ducts opening at base of broader part of tail or at beginning of spike.

Male: Similar to female in general morphology except in shorter body length and greater posterior curvature. Testis single, ventrally reflexed; reflexed part 57–95 µm long, at right side of intestine. Spicules visibly unequal, well-built, stout, about 1.1–1.4 times anal body diameter long, slightly arcuate with hood-like capitula. Each spicule with a ventral conoid process and a dorsal thorn. Left one more robust and shorter with bilobed or hood-like capitulum. Right one slender and longer with globose capitulum. Distal end of spicule usually surrounded by an extending velar cap. Gubernaculum about 51.7–52.1% of spicule length. Bursa leptoderan, rudimentary, not covering the spike and hardly differentiated from the body cuticle. Genital papillae nine pairs with one precloacal, two nearly adcloacal and six postcloacal pairs in 1/2/(1+3)+2+P configuration. Of the genital papillae, GP1, GP4 and GP8 are the longest extending beyond bursal edge. GP1 subventral, precloacal slightly spaced from nearly adcloacal, subventral GP2, GP3. Of six postcloacal papillae, GP4 forms a group with subventral GP5, GP6 and GP7; GP8 dorsally-oriented and close to GP9. Phasmidial ducts narrower and smaller than papillae opening next to GP9 at base of tail spike. Copulatory muscle bands 6 pairs, weakly developed, often indiscernible.

Type locality and habitat. Samples containing Cephaloboides anisospiculus sp. n. were obtained from green manure at Lado Saray, New Delhi, India at coordinates 28.5245° N, 77.1919° E.

Type material. Holotype female, ten paratype females and seven paratype males on slides Cephaloboides anisospiculus sp. n. SA2/1–5 deposited in Nematode Collection , Department of Zoology , Aligarh Muslim University, Aligarh, Uttar Pradesh, India.

Diagnosis and relationships. Cephaloboides anisospiculus sp. n. is characterized by small- to medium-sized body; double, finely striated, faintly punctated cuticle; slightly raised labial papillae; stoma with slightly anisomorphic metastegostom; pharyngeal bulb with single-chambered haustrulum; presence of epiptygma; slightly protruded vulval lips with flaps; and males with dimorphic, small, stout, slightly arcuate spicules with hood-like capitula and genital papillae in 1/2/(1+3)+2+P configuration.

Cephaloboides anisospiculus sp. n. differs from C. curvicaudatus in having relatively smaller body (0.5–0.7 mm vs 0.6–1.8 mm); finely punctated and striated (vs smooth) cuticle; relatively smaller b (2.7–3.6 vs 3.4–6.0) and c' (1.0–1.8 vs 2.0–4.2) values; globular, prominent (vs amalgamated) lips; relatively smaller stoma (20–24 µm vs 19–32 µm) and males with relatively smaller (19–29 µm vs 30–54 µm) and unequal (vs equal) spicules with hoodshaped (vs elongate) capitulum and a trough-shaped gubernaculum with narrow acute (vs wide angular) proximal end in C. curvicaudatus apud ( Schneider, 1866) Zullini, 1982 .

The new species differs from C. dimorphus Sudhaus, 1976 in having a smaller body (0.5–0.7 mm vs 0.8–0.9 mm); relatively smaller b (2.7–3.6 vs 3.7–4.6), c (15.4–22.7 vs 26–30) and V (51.2–60.9 vs 61–64) values; similar labial sensilla in both sexes (vs labial sensilla dimorphic, lateral labials longer and tentacle-like in females); smaller stoma (20–24 µm vs 28–34 µm) and males with smaller spicules (19–29 µm vs 32–37 µm) and relatively smaller gubernaculum (10–15 µm vs 15–21 µm in C. dimorphus apud Sudhaus, 1976 ).

The new species differs from C. musicola Rahm, 1928 in having smaller body (0.5–0.7 mm vs 0.9–1.9 mm); relatively smaller b (2.7–3.6 vs 3.5–5.0) and c (15.4–22.7 vs 17–36) values; smaller stoma (20–24 µm vs 33–38 µm) and males with smaller (19–29 µm vs 42–81 µm), dissimilar and unequal (vs similar and equal) spicules in C. musicola Rahm, 1928 .

The new species resembles the original population of C. parapapillosus Schuurmans Stekhoven, 1951 in having similar lengths of stoma and spicules but markedly differs in having smaller body (0.5–0.7 mm vs 1.4 mm); significantly smaller b (2.7–3.6 vs 6.8) and c values (15.4–22.7 vs 51.5 in C. parapapillosus ( Schuurmans Stekhoven, 1951) .

Etymology. The species name ‘ anisospiculus ’ denotes its unidentical or dissimilar spicules.

Remarks. The new species is unique in several features when compared with other congeners. It has a very small stoma and dimorphic spicules. Another unusual feature is the presence of a single-chambered haustrulum in the basal bulb which in most rhabditid species remains double chambered. The shifting of GP4 to form a group with GP5, GP6 and GP7 is another diagnostic feature of this new species.

Figures

FIGURE 1. Cephaloboides anisospiculus sp. 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: Male posterior region. H: Dimorphic spicules.

FIGURE 2. Cephaloboides anisospiculus sp. n. A: En face view (scanning electron microscopy). B, C: Anterior end. D: Posterior pharyngeal region. E: Female anterior genital branch. F: Female posterior genital branch. G: Female posterior region. H, I, K: Male cloacal region showing variation in spicules. J: Male cloacal region showing gubernaculum. L: Male cloacal region showing bursa and associated papillae (Scale bars = 10 µm).