Prodontorhabditis robustus, 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 : 176-180

Prodontorhabditis robustus sp. n.

( Fig. 1–3 )

Measurements See Table.1

Females. Body small, always less than 1mm; slender, almost straight upon fixation. Cuticle thin with fine transverse striations. Lateral fields with two incisures, approx. 1/7 th of maximum body diameter. Lip region continuous with body contour. Lips low, fused; labial sensilla small, papilliform. Amphids distinct, 3 µm from anterior end. Stoma long, narrow, 2.3–3.2 labial diameters long. Cheilostom uniformly concave, wider than gymnostom, with lightly sclerotised cheilorhabdions. Three bluntly-rounded denticles basal to the cheilostom, at the same level. Gymnostom long, heavily-sclerotised 73–81% stoma length. Stegostom simple, lacking glottoid apparatus. Pharyngeal collar absent. Procorpus 42–61 µm long, muscular and cylindrical. Metacorpus swollen, ovoid with inner wall more refractive. Isthmus narrow, 14–28 µm long, basal bulb ovoid, 13–18 µm long, 12–14 µm in diameter with a grinder. Haustrulum single-chambered. Length of the procorpus plus metacorpus 1.3–1.7 times the length of the isthmus and postcorpus. Nerve ring encircling middle of isthmus, located at 62–84% of the pharyngeal length. Excretory pore at level of the anterior end of basal bulb, 88–94% of the pharyngeal length. Hemizonid distinct, just below the level of nerve ring. Cardia small, about 2–3 µm long. Intestine composed of flat, granulated cells with wide lumen.

Reproductive system amphidelphic, anterior branch on right and posterior on left side of intestine. Ovary reflexed, oocytes with large nuclei, arranged in double row in germinal zone and single row in maturation zone. Oviduct very short. Spermatheca usually set off from the uterus by a constriction. Uterus differentiated into a small muscular and a large glandular part. Uterus usually with a single egg, 33 x 15 µm. Vagina short, narrow, at right angle to longitudinal axis. Vulval opening transverse slit-like, pre-equatorial, short flaps at lateral edge of vulva. Rectum length 1.0–1.2 times anal body diameter. Rectal glands absent. Phasmids about 2.6 times anal body diameter posterior to anus. Tail long filiform, whip-like, length 1.2–1.9 times vulva-anus distance.

Males. Similar to female in general morphology but smaller in size. Reproductive system monorchic, testis reflexed ventrally, on right side of intestine. Vas deferens filled with sperms. Spicules free, robust, 1.4–1.8 times anal body diameter long. Capitulum triangular, lamina broad with well-developed middorsal hump, tips bifurcate with a lateral spur. Gubernaculum boat-shaped in lateral view, about half of spicule length, with an attenuated proximal end. Bursa peloderan, anteriorly closed, 23–29 µm long. Cleft observed at 6 th pair of genital papillae. Genital papillae nine pairs: two pairs precloacal and seven pairs postcloacal; GP1 short, subventral, immediately anterior to bursa, GP2 precloacal, located at bursal edge; GP3, GP4 and GP5 subventral, equidistant from each other. GP5 and GP7 short, turn outward, GP8 turn inward. Phasmids located slightly anterior to GP6. Tail short and conoid.

Type habitat and locality: Collected from rotting banana rhizome near Aligarh fort, Aligarh, Uttar Pradesh, India.

Type specimens: Holotype female on slide Prodontorhabditis robustus sp. n. /1, twelve female and twelve male paratypes on slides Prodontorhabditis robustus sp. n. /2 to 9, deposited in the nematode collection of Department of Zoology, Aligarh Muslim University, Aligarh, Uttar Pradesh, India.

Etymology: The name of the species is based on the robust spicules.

Diagnosis and relationships. Prodontorhabditis robustus sp. n. is characterised by a small slender body; two ridges in lateral fields; cheilostom uniformly concave with three denticles at the base; spicules free, robust having triangular capitulum, lamina broad at its middle with well-developed dorsal hump, tips bifurcated with a lateral spur; nine pairs of genital papillae, the anterior most pair prebursal; bursa with cleft at 6 th GP.

The new species resembles P. pluvialis Timm, 1961 , P. prodontis Sudhaus, 1974 and P. wirthi Sudhaus, 1974 in general morphometric values. However, it is easily distinguished from the afore mentioned species by its robust spicules with bifid tips. It can be further differentiated from P. pluvialis by the position of subventral denticles (at the base of cheilostom vs slightly anterior in the cheilostom) and the number of genital papillae (one prebursal, eight bursal pairs vs one prebursal, seven bursal pairs). From P. prodontis and P. wirthi , it can be further differentiated by the position of denticles (at the base of cheilostom vs anterior end of gymnostom), length of stoma (more than twice head diameter vs less than twice head diameter), shape of gubernaculum (proximal part attenuated vs bent, reduced) and by the cleft in the bursa (present vs absent).

Figures

FIGURE 1. Prodontorhabditis robustus sp. n. A. Entire female B. Entire male, C. Pharyngeal region. D, E. Anterior region showing stoma with denticles, F. Lateral lines, G. Female reproductive system showing anterior branch, H. Female posterior region, I. Male posterior region showing spicules and gubernaculum, J. Male posterior region showing genital papillae (dorsoventral), K. Spicule.

FIGURE 2. Prodontorhabditis robustus sp. n. A. Pharyngeal region, B. Anterior region showing stoma with denticles, C. Lateral lines, D. Female reproductive system showing posterior branch, E. Female posterior region, F. Male posterior region showing genital papillae, G, H, I. Male posterior region showing spicules and gubernaculum, J. Closed bursa (Scale bars: A–J= 20 μm).

FIGURE 3. Prodontorhabditis robustus sp. n. (SEM images) A.Anterior region, B. Excretory pore, C. Lateral lines, D. Female posterior region, E. Vulva, F, I. Male posterior region showing spicules, G, H. Bursal papillae (Scale bars: A, B, D–H = 5 μm, C, I = 2 μm).

Tables

TABLE 1. Morphometric of Prodontorhabditis robustus 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	12	12
L	511	559.8 ± 41.0 (490–625)	323.0 ± 42.0 (219–406)
a	26.5	30.5 ± 2.4 (25.8–34.7)	19.3 ± 2.4 (12.9–22.6)
b	5.0	5.7 ± 0.4 (4.9–6.4)	4.0 ± 0.5 (2.7–4.7)
c	3.2	2.8 ± 0.3 (2.4–3.7)	13.3 ± 1.7 (9.5–15.6)
c’	15.6	20.2 ± 2.7 (12.0–22.8)	1.9 ± 0.1 (1.6–2.1)
V	39.9	40.3 ± 2.9 (34.9–46.1)	–
Maximum body diameter	19	18.4 ± 5.1 (17.0–21.0)	16.8 ± 4.5 (16.0–18.0)
Body diameter at lips	6	5.8 ± 0.6 (5.0–6.5)	5.4 ± 0.5 (5.0 – 6.0)
Length of stoma	16	15.2 ± 0.4 (15.0–16.0)	13.4 ± 1.0 (11.0–14.0)
Corpus length	50	49.4 ± 4.6 (42.0–61.0)	24.6 ± 2.7 (21.0–29.0)
Median bulb length	17	15.9 ± 2.3 (12.0–21.0)	14.0 ± 1.0 (12.0–16.0)
Isthmus length	19	19.5 ± 2.3 (14.0–28.0)	16.7 ± 2.5 (12.0–22.0)
Basal bulb length	18	15.1 ± 1.1 (13.0–18.0)	13.1 ± 1.0 (11.0–14.0)
Pharynx length	104	99.3 ± 7.5 (85.0–113)	81.8 ± 5.6 (69.0–89.0)
Excretory pore from anterior end	86	88.6 ± 4.6 (79.0–93.0)	75.0 ± 6.1 (64.0–83.0)
Nerve ring from anterior end	78	74.3 ± 4.4 (68.0–83.0)	62.3 ± 4.1 (56.0– 67.0)
Hemizonid from anterior end	83	78.6 ± 4.7 (73.0–90.0)	66.2 ± 5.1 (58.0–73.0)
Cardia length	2	2.6 ± 0.5 (2.0–3.0)	2.4 ± 0.5 (2.0–3.0)
Anterior gonad length	116	120.8 ± 13.4 (100–145)	–
Posterior gonad length	104	116.1 ± 17.3 (82–147)	–
Body diameter at vulva	19	18.8 ± 1.2 (18–22)	–
Distance from vulva to anus	119	119.5 ± 10.8 (110–149)	–
Rectum length	10	10.8 ± 0.4 (10.0–11.0)	12.5 ± 0.8 (11.0–13.0)
Tail length	156	200.3 ± 22.9 (132–223)	24.3 ± 1.3 (23.0–26.0)
Body diameter at anus/cloaca	10	10.0 ± 0.8 (9.0–11.0)	11.6 ± 1.3 (10.0–14.0)
Phasmid from anus	20	20	11
Testis length	–	–	184.3 ± 36.6 (132–270)
Spicules length	–	–	20.7 ± 0.9 (20.0–23.0)
Gubernaculum length	–	–	10.7 ± 0.5 (10.0–11.0)
Bursa length	–	–	26.2 ± 2.1 (23.0–29.0)
Number of genital-papillae	–	–	9