Prodontorhabditis grandistoma, Mumtaz & Fatima & Jamal & Ahlawat & Tahseen & Ahmad, 2020

Mumtaz, Sabia, Fatima, Hiba, Jamal, Wajih, Ahlawat, Shikha, Tahseen, Qudsia & Ahmad, Irfan, 2020, Description of two new species of Prodontorhabditis Timm, 1961 (Nematoda: Rhabditidae) from India, Zootaxa 4763 (2), pp. 175-188 : 180-182

Prodontorhabditis grandistoma sp. n.

( Fig. 4 , 5 )

Measurements See Table. 2

Females. Body small, almost straight upon fixation, tapering at both extremities. Cuticle with fine transverse striations. Lateral fields with two spaced ridges. Lip region continuous with body contour. Lips low amalgamated, with smooth margins; labial sensilla papilliform. Stoma long, narrow, length 3.0–4.3 labial diameters or 8.0–11.8 times its own diameter. Cheilostom cuticularised, straight tubular or slightly narrowing posteriorly. Three wartlike stomal denticles: subventrals on cheilostomal walls while relatively larger dorsal one present at the base of cheilostom. Gymnostom 6–7 times longer than cheilostom, heavily cuticularised; arcades of pro-, meso- and metastegostom distinctly differentiated in few speciemens. Metastegostomal walls slightly diverging with terminal ends swollen; glottoid apparatus absent. Pharynx with corpus 45–52 µm long, swollen, ovoid median bulb 12-15 µm long with inner wall more refractive than rest of pharynx, narrow isthmus 21–25 µm long and rounded basal bulb, 14–16 µm long and 11–13 µm in diameter with a grinder. Haustrulum single-chambered. Anterior pharynx length 1.5 times posterior pharynx. Nerve ring encircling anterior region of isthmus, at 67–72 % of pharyngeal length. Excretory pore inconspicuous; a faint excretory duct often observed. Hemizonid distinct just posterior to the nerve ring. Hemizonion posterior to hemizonid near basal bulb. Body diameter at posterior end of pharynx 3.3–4.7 times labial diameter. Cardia conoid, about 2–3 µm long. Intestinal cells with prominent nuclei; intestinal lumen cuticularised and wide.

Reproductive system didelphic, amphidelphic; ovaries dorsally reflexed; anterior ovary on right and posterior on the left side of intestine. A small round pseudocoelomocyte observed in close proximity to flexure of each ovary. Oocytes with large nuclei, arranged in double rows in germinal zone and single row in maturation zone. Oviduct dilated proximally, set off spermatheca containing rounded sperm, continued with tricolumella. Uterus differentiated into a small muscular and large glandular part, often with a single, spinose-shelled egg 31–35 x 15–16 µm. Vagina at right angle to longitudinal body axis, narrow, 1/3 rd of corresponding body diameter without sclerotization. Vulva a wide transverse slit, pre-equatorial. Vulval lips constricted. Vulva-anus distance 107–125 µm. Rectum thin-walled, rectal lumen dilated, about one anal body diameter long. Rectal glands absent. Anus a crescent-shaped slit. Tail long, filiform, length 1.2–1.4 times vulva-anus distance. Phasmids obscure.

Males. Similar to female in general morphology but smaller with slightly ventral curvature. Testis monorchic, reflexed ventrally, on right side of intestine. Vas deferens narrow, filled with sperms. Ejaculatory glands absent. Spicules free, stout with distinct more or less triangular capitula, lamina with thick cuticularised rib, distally notched with a subterminal spur. Gubernaculum appearing boat-shaped in lateral view, length about half that of spicule with proximal end tapering. Cloacal chamber well demarcated. Bursa peloderan, anteriorly closed, 26–28 µm long. Indentation or cleft at 6 th pair of genital papillae (GP) and at terminal end. Nine pairs of genital papillae (two pairs precloacal and seven pairs postcloacal); GP1 subventral, prebursal, GP2 subventral, equal and close to GP1, located at bursal edge; GP3, GP4, GP5, subventral, equidistant from each other, GP5 and GP8 dorsally directed; closely placed to GP7 and GP9. Tail short and conoid.

Type habitat and locality: Collected from small ditch, rich in decaying organic matter at Harduaganj, Aligarh, Uttar Pradesh, India.

Type specimens: Holotype female on slide Prodontorhabditis grandistoma sp. n. /1, nine females and ten male paratypes on slide Prodontorhabditis grandistoma sp. n. /2 to 6 deposited in the nematode Collection, Department of Zoology, Aligarh Muslim University, Aligarh, Uttar Pradesh, India.

Etymology: The name of the species is derived from the latin word ‘ grandis ’= large, denoting its relatively larger stoma in relation to its small body size.

Diagnosis and relationships. Prodontorhabditis grandistoma sp. n. is characterised by a small, slender body; finely transversely annulated cuticle; ridges in lateral fields; a narrow lip region; amalgamated lips; small papilloid labial sensilla; a long narrow stoma having a tubular, non-arched, lightly cuticularised cheilostom with a dorsal denticle at its base and subventral denticles slightly anterior; a long filiform tail 11–20 times anal body diameter and males with free, stout spicules having triangular capitula and a subterminal spur; a gubernaculum with a tapering proximal end, nine pairs of genital papillae with GP2 located at anterior bursal edges and a reduced tail spike.

Prodontorhabditis grandistoma sp. n. most closely resembles P. pluvialis Timm, 1961 in most morphometric and morphological characters, but differs in the structure of the cheilostom (straight vs arched), size of eggs (31–35 x 14–16 µm vs 60 x 18 µm), structure of the rectum (lumen dilated, bladder-like vs normal), shape and length of the spicules (plump, 17–20 µm vs slender, 21 µm), shape and length of the gubernaculum (proximal part tapering, 7–10 µm vs hair-like, 12 µm), number of genital papillae (nine pairs: one prebursal, eight bursal pairs vs eight pairs: one prebursal, seven bursal pairs), and bursa indentation (terminally indented vs non-indented).

The new species resembles P. robustus sp. n. in most morphometric characteristics but differs in the structure of chielostom (straight vs arched), position of denticles (dorsal denticle basal to the cheilostom and subventrals being slightly anterior vs all denticles basal to the cheilostom at the same level), width of stoma (>8 times vs <5 times longer than wide), structure of rectum (lumen dilated vs normal), structure of spicules (without vs with dorsal hump) and bursa (with vs without terminal indentation).

Figures

FIGURE 4. Prodontorhabditis grandistoma sp. n. A. Entire female, B. Entire male, C. Anterior region showing stoma with denticles, D. Pharyngeal region, E. Female reproductive system showing anterior branch, F. Female posterior region, G. Male posterior region showing spicules and gubernaculum, H. Spicule.

FIGURE 5. Prodontorhabditis grandistoma sp. n. A, B, D. Anterior region showing stoma with denticles, C. Anterior region (Scanning Electron Microscopy), E. Pharyngeal region, F. Female reproductive system showing anterior branch, G. Egg, H. Vulval region, I. Lateral lines, J. Female posterior region, K, L, M & N. Male posterior region showing spicules and gubernaculum, O. Bursal papillae (Scanning Electron Microscopy), P & Q. Male posterior region showing genital papillae, R. Closed bursa (Scale bars: A–R= 5 μm).

Tables

TABLE 2. Morphometric of Prodontorhabditis grandistoma sp. n. from India. All measurements are in μm and in the form: mean ± standard deviation (range).

Characters	Holotype female	Paratype female	Paratype male
N	1	9	10
L	509	502.3 ± 46.3 (440–552)	336.5 ± 35.7 (288–372)
a	25.5	23.9 ± 1.1 (23.9–25.5)	19.8 ± 1.3 (18.0–20.7)
b	5.0	5.1 ± 0.6 (4.4–5.7)	3.7 ± 0.5 (3.0–4.0)
c	2.9	3.3 ± 0.6 (2.9–4.2)	14.2 ± 1.8 (12.0–16.0)
c’	19.0	14.2 ± 3.6 (10.2–19.0)	1.7 ± 0.1 (1.6–1.8)
V	41	43.3 ± 2.8 (39.5–45.9)	–
Maximum body diameter	20	21.0 ± 1.8 (19.0–23.0)	17.0 ± 1.4 (16.0–19.0)
Body diameter at lips	5	4.8 ± 0.95 (4.0–6.0)	4.8 ± 0.9 (4.0 – 6.0)
Length of stoma	15	16.3 ± 0.6 (15.0–18.0)	14.8 ± 1.5 (13.0–15.0)
Corpus length	46	48.5 ± 2.9 (45.0–52.0)	42.3 ± 1.1 (41.0–45.0)
Median bulb length	15	13 ± 0.8 (12.0–15.0)	14.0 ± 1.2 (13.0–15.0)
Isthmus length	25	22.5 ± 1.3 (21.0–25.0)	21.8 ± 3.6 (17.0–25.0)
Basal bulb length	15	15.3 ± 1.0 (14.0–16.0)	13.5 ± 0.6 (13.0–14.0)
Pharynx length	101	99.3 ± 3.6 (96.0–104)	91.5 ± 4.5 (85.0–95.0)
Nerve ring from anterior end	70	67.8 ± 1.0 (67.0–70.0)	64.3 ± 2.1 (62.0– 66.0)
Cardia length	3	2.5 ± 0.5 (2.0–3.0)	2.4 ± 0.5 (2.0–3.0)
Anterior gonad length	103	101.5 ± 7.5 (93–110)	–
Posterior gonad length	97	100.5 ± 11.8 (89–115)	–
Body diameter at vulva	20	21.3 ± 2.4 (18–23)	–
Distance from vulva to anus	110	120.0 ± 8.7 (107–125)	–
Rectum length	10	10.3 ± 0.5 (10.0–11.0)	13.5 ± 0.6 (13.0–15.0)
Tail length	190	154.3 ± 29.9 (122–190)	23.8 ± 2.1 (21.0–26.0)
Body diameter at anus/cloaca	10	11.1 ± 0.9 (10.0–13.0)	14.0 ± 1.4 (13.0–15.0)
Testis length	_	–	184.3 ± 36.6 (132–270)
Spicules length	_	–	18.0 ± 0.8 (17.0–20.0)
Gubernaculum length	_	–	9.8 ± 1.0 (9.0–12.0)
Bursa length	_	–	27.3 ± 0.5 (26.0–28.0)
Number of genital-papillae	_	–	9