Pelodera scrofulata, Tahseen & Akram & Mustaqim & Ahlawat, 2014

Tahseen, Qudsia, Akram, Mohd, Mustaqim, Malka & Ahlawat, Shikha, 2014, Descriptions of Pelodera scrofulata sp. nov. and Pelodera aligarhensis sp. nov. (Nematoda: Rhabditidae) with supplementary information on Pelodera teres (Schneider, 1866)., Journal of Natural History 48 (17), pp. 1027-1053 : 1028-1041

Pelodera scrofulata 1 sp. nov.

( Figures 1–3 )

Measurements

See Table 5.

Description

Female. Body medium to large, almost straight or slightly ventrally curved upon fixation; tapering at extremities. Cuticle about 1 μm thick, transversely striated, often with fine longitudinal lines and faint dot-like punctations. Lateral field with six to eight prominent lines along the body length; distinct in a few specimens. Lip region offset, lips well separated, globular with flattened apices; labial sensilla slightly raised. Stoma tubular, c.1.5–1.8 lip diameter, 5.2–7.0 times longer than wide. Cheilostom moderately cuticularized, gymnostom comprising 60–75% of stoma length. Metastegostom relatively expanded, isomorphic. Each metastegostomal swelling bearing three setose denticles. Pharyngeal tissue surrounding basal part of stoma (stegostom) at 20–24% of its length. Pharynx 110–130 μm long, with strongly swollen corpus, 55–68 μm long isthmus and a well-developed, muscular, ovoid (31–39 × 25– 36 μm wide) basal bulb with grinder and double-chambered haustrulum. Pharyngeal corpus c.1.1–1.5 times longer than isthmus and basal bulb together. Nerve ring surrounding isthmus at c.64–74% of pharyngeal length. Secretory–excretory pore cuticularized, located at c.71–92% of pharyngeal length, leading to prominent secretory–excretory glandular cells. Hemizonid visible in few specimens, slightly anterior to excretory pore. Body at level of posterior terminus of pharynx c.2.4–4.0 labial diameter wide. Cardia (pharyngeal–intestinal valve) conoid, 5–10 μm long; often appearing as an extension of the basal bulb. A pair of pseudocoelomocytes 10– 15 × 12–15 μm long or one large pseudocoelomocyte 20–25 × 15–20 μm long located 50–104 μm posterior to base of cardia or close to reflexed part of gonad. Intestine granular, comprising large polygonal cells with prominent nuclei. A portion of the posterior intestinal region equal to about twice the length of the rectum, although not distinctly separated or set off from main part of the intestine is nevertheless slightly demarcated by having relatively larger cells and a constricted lumen. Rectum thinwalled, with length c.0.9–1.5 times the body diameter at the level of the anus and with well-developed rectal glands. Anus a crescent-shaped slit. Reproductive system didelphic, amphidelphic with reflexed ovaries; anterior ovary positioned on right lateral and posterior on left lateral side of intestine. Each ovary bent twice at right angle to form a dorsal flexure. Oocytes arranged in multiple rows at relatively wider distal end and larger oocytes located proximally. Each oviduct connected to round, axial receptaculum seminalis (spermatheca) containing few sperms. Columella comprising prominent glandular cells arranged in three columns, connected to adjacent side of uterus. A pair of dorsal and a pair of ventral elongate, fusiform glandular bodies with defined nuclei and granular inclusions, opening into a kidney-shaped uterine chamber continuous with dilated lumen of vagina uteri having thick walls and wide lumen with some corrugations in the wall. Uterus with smooth-shelled eggs, at most two or three eggs at one time, with dimensions 58–62 × 36–43 μm. Vagina at right angles to longitudinal body axis, thick-walled, about one-third of corresponding body diameter long, and with ovijector and two sets of oblique muscle bands. Vulva a transverse, post-equatorial slit with fringed and protruded lips. Vulva–anus distance about 312–397 μm. Tail conoid with posterior one-third relatively more tapered and terminating as narrow spicate or occasionally cupola-shaped. Cuticle uniformly thick at level of phasmid; in rare instances slightly swollen. Phasmid opening posterior to anus by c.20–25% of tail length.

(Continued)

G2 37.5 36.4 ± 3.5 – 34.7 32.1 ± 5.4 –

(30.6–43.1) (26.2–41.8) Lip height 7 6.4 ± 0.4 6.2 ± 0.4 8 7.6 ± 0.8 6.6 ± 0.8

(6.0–7.0) (6–7) (7–9) (6–8) Lip diameter 17 15.6 ± 1.4 14.6 ± 1.0 15 16.1 ±1.1 13.4 ± 0.8

(14–18) (13–16) (15–18) (12–14) Stoma length 29 26.2 ± 1.3 23.4 ± 1.3 25 24.8 ± 0.4 20 ± 1

(24–28) (20–25) (24–25) (19–21) Stoma diameter 5 4.2 ± 0.3 4.1 ± 0.3 5 5 ± 0.0 4.4 ± 0.5

(4–5) (4–5) (5–5) (4–5) Pharynx length 225 214 ± 10.3 199 ± 7.9 180 177.5 ± 4.8 142.6 ± 13.7

(202–235) (185–213) (173–186) (119–155) Nerve ring 150 164 ± 20.6 138 ± 8.4 120 120.6 ± 2.8 98 ± 3.3

(144–180) (125–150) (118–125) (93–102) Secretory–excretory pore 180 170 ± 19.2 163.2 ± 12.3 135 133.6 ± 7.5 113.2 ± 6.8

(123–190) (152–185) (129–148) (106–121) Anal body diameter 28 25.8 ± 2.1 35.2 ± 3.8 22 23.3 ± 2.4 22.0 ± 3.3

(23–30) (30–42) (19–25) (18–27)

(Continued)

Male. Similar to females in general morphology except having slightly more slender body, relatively narrower lips and greater posterior curvature. Testis monorchic, laterally reflexed; flexure on right lateral side of intestine. Reflexed portion about 103–141 μm long. A pair of oblong ejaculatory glands present, often at slightly different levels. Spicules with distinct, elongate capitula and tapering toward distal end where it terminates as a slightly curved beak-like structure; 1.4–2.0 anal body diameter long, fused distally up to 60–68% of length. In some specimens capitula tends to be rounded. Gubernaculum length equal to about 64–74% of spicule length, slender, trough-shaped with tapering, often hooked proximal end. Bursa peloderan, slender, anteriorly open with nine pairs of genital papillae (two precloacal and seven postcloacal pairs) in variable configuration of 1 + 1/4 + P + (2 + 1), 1 + 1/ 3 + (1 + P) + (2 + 1) or 1 + 1/(4 + P) + (2 + 1). GP1 and GP2 subventral, spaced, 9–12 μm apart; GP3 dorsally oriented, GP4, GP5 subventral and closely placed with a swollen base while GP6 slightly spaced from the trio; GP7 and GP8, subventral, closely placed along with dorsally oriented smaller GP9. Phasmid opening on a papillum-like structure appearing slightly thicker than other papillae with a swollen base, dorsally oriented, located between GP6 and GP7, close to GP6 or grouping with the four anteriormost postcloacals. Bursal velum very slightly crenate, rod-like cuticular markings as reported in Pelodera cutanea in precloacal region absent. Copulatory muscles well developed with seven or eight paired oblique bands arising from cloacal level. Tail conoid, longer than females.

Type habitat and locality

Samples containing P. scrofulata sp. nov. were collected from a drain at Quarsi, Aligarh, Uttar Pradesh, India located at coordinates 27°53 ′ 37.36 ″ N, 78°05 ′ 16.79 ″ E .

Type material

Holotype female, 14 paratype females and 9 paratype males on slide Pelodera scrofulata sp. nov. No. NOQ/1-14 deposited in the Nematode Collection , Department of Zoology , Aligarh Muslim University, Aligarh, India . One paratype female and one paratype male on slide Pelodera scrofulata sp. nov. No. NOQ/15 deposited at the Wageningen Nematode Collection (WaNeCo), Wageningen, the Netherlands.

Diagnosis and relationships

Pelodera scrofulata sp. nov. is a gonochoristic species with females having more expanded lips than males; moderately developed cheilostom; reflexed part of ovary conspicuously bent at right angle; few (one to three) intrauterine eggs; glandular bodies associated with uterus; prerectum inconspicuously separated from intestine; tail conoid with acutely pointed spicate tip; cuticle uniformly thick in the region of phasmids; males with slender spicules fused up to 60–68% from distal end; open, peloderan bursa with smooth velum; GP1 and GP2 9–12 μm apart and GP4, GP5 and phasmids with swollen bases.

Pelodera scrofulata sp. nov. differs from P. strongyloides Schneider, 1860 in having relatively shorter body length (0.8–1.0 mm vs 1.0– 2.3 mm) with presence (vs absence) of longitudinal lines and punctations; smaller “b” (3.8–4.8 vs 4.9–7.6) and “c” (17.7–25.7 vs 26.3–37.9) values; moderately developed cheilostom (vs inconspicuous cheilostom); relatively smaller stoma (24–28 vs 33–38 μm); reflexed part of ovary conspicuously bent at right angle (vs rounded); smaller gubernaculum (40–44 vs 45–60 μm) and cuticle uniformly thick (vs greatly thickened) in the region of phasmids in P. strongyloides Schneider, 1860 apud Sudhaus and Schulte (1988).

The new species further resembles Pelodera termitis Carta et al., 2010 but differs in females showing presence (vs absence) of longitudinal lines and punctations; lateral lines (6–8 vs 4); relatively greater “V” (56.7–63.5 vs 55–58); relatively smaller stoma (24–28 vs 26.2–33.3 μm); cheilostom moderately developed (vs indistinct); reflexed part of ovary conspicuously bent at right angle (vs curved); glandular bodies associated with uterus present (vs absent); prerectum inconspicuously (vs conspicuously) separated from rest of intestine; smaller spicules (56–65 vs 70–77 μm); smaller gubernaculum (40–44 vs 45.2–53.6 μm); smooth (vs ornamented) bursal velum in P.termitis apud Carta et al., 2010 .

The new species is similar to Pelodera orbitalis Sudhaus and Schulte, 1986 in most morphometric characteristics but differs in having cheilostom moderately cuticularized (vs not cuticularized); metastegostomal teeth conspicuous (vs less conspicuous); conoid (vs cupola-shaped) tail; proximally wider (vs narrow) spicules; bursal velum not crenate (vs proximally crenate); and greater distance between precloacal papillae GP1 and GP2 (9–12 μm vs 4–6 μm apart in P. orbitalis Sudhaus and Schulte, 1986 ).

The new species differs from another closely related species, Pelodera nidicolis Sudhaus and Schulte, 1986 , in having cheilostom moderately cuticularized (vs strongly cuticularized); glandular bodies associated with uterus (vs not reported); spicules proximally wider (vs narrower); bursal velum not crenate (vs prominently crenate); greater distance between precloacal papillae GP1 and GP2 (9–12 μm vs 4–6 μm); conoid (vs cupola-shaped) tail with tail spine straight (vs bent ventrad); cuticle of uniform thickness (vs thickened in the region of phasmids in P. nidicolis apud Sudhaus and Schulte, 1986 ).

The new species further differs from P.cutanea Sudhaus et al., 1987 by its relatively smaller body length (0.8–1.0 vs 1.0– 1.7 mm); smaller b (3.8–4.8 vs 5.2– 7.3) and greater V (56.7–63.5 vs 55–58) values; relatively smaller stoma (24–28 vs 26–34 μm); cheilostom moderately developed (vs indistinct); seminal receptacle axial (vs adaxial); glandular bodies associated with uterus present (vs not reported); lesser number of eggs in uterus (up to three vs up to eight); tail conoid (vs dome-shaped with a spike); larger gubernaculum (40–44 vs 29–40 μm); rod-like cuticular structure in the region of precloacal papillae absent (vs present) and base of GP4, GP5 and region surrounding phasmid opening swollen (vs base of GP2 swollen while that associated with phasmid opening slender in P. cutanea apud Sudhaus et al., 1987 ).

Remarks

Cluster analysis ( Figure 4 ) based on 21 morphological characters ( Tables 1 and 3) indicates a close affinity of P. cutanea with P. nidicolis . In fact, these two species have previously been identified as sibling species ( Sudhaus and Schulte 1988). Likewise, two other species of the group, P. strongyloides and P. orbitalis , showed a close relationship. These four species formed a more inclusive cluster from which P. termitis is excluded, at least at low distance values (<0.6). In addition, P. scrofulata sp. nov. clearly stands out as the most morphologically divergent species considered in the cluster analysis.

The species of Pelodera constituting the ‘ strongyloides ’ group have largely been reported to be parasitic with third-stage juveniles (J3) having association with vertebrate or invertebrate hosts, namely chicken, wood mice, voles, horses and termites. The present species was collected from the muddy sample of a ditch. Unfortunately, juvenile specimens were not recorded from this sample and only the adults were preserved for morphological evaluation. The locality apparently indicates any association with termites, mice or voles to be unlikely. The new species is morphologically similar to P. strongyloides , P. termitis and P. punctata , but not convincingly enough to place it in any of the corresponding species. Table 6 gives a comparative account of the differences between P. scrofulata and other congeners of the strongyloides group. The species apparently resembles P. punctata with respect to the freshwater type habitat as well as the longitudinally striated and punctated body cuticle; however, a short conoid tail, and more slender spicules (including an angular dorsal profile), and widely spaced precloacal papillae are features that clearly differentiate the two species. With P. termitis , the species shows similarity with respect to lip morphology, female tail shape and spacing of precloacal papillae; however, the presence of longitudinal cuticular lines and punctations, as well as the shape and length of spicules and their trapezoid capitulum, the length of the gubernaculum and the continuous prerectum region are some of the prominent distinguishing features. Another interesting feature is their putative association with termites that were not found and were unlikely to be found in the ditch with mud and slurry around. Hence it is perhaps another sibling species in the group such as P. cutanea , P. nidicolis and P. orbitalis that have had its status confirmed through cross-breeding tests with P. strongyloides (Sudhaus and Schulte 1986). It appears that the process of speciation in the group has led to different species adaptations for parasitism and switching over to a variety of hosts with very little change in morphology. This would have given rise to several cryptic sibling species. The present species seems to form one such example.

Figures

Figure 1. Pelodera scrofulata sp. nov. (all lateral) (A) Entire female; (B) entire male; (C) female anterior end; (D) female pharyngeal region; (E) female reproductive system; (F) female tail region; (G) male tail region.

Figure 2. Pelodera scrofulata sp. nov. female. (A–D) Anterior end; (E) anterior pharyngeal region; (F) posterior pharyngeal region; (G) anterior genital branch; (H, I) uterine region with glandular bodies (lateral); (J) uterus with thick muscular walls (lateral); (K, L) bean-shaped central chamber of uterus; (M–O) uterine region (ventral); (P) posterior intestinal region; (Q–S) caudal region (lateral). Scale bars: 10 μm.

Figure 3. Pelodera scrofulata sp. nov. male. (A) Anterior pharyngeal region; (B) posterior pharyngeal region; (C, D) cuticular surface pattern showing longitudinal lines and punctations; (E) pseudocoelomocytes close to reflexed testis; (F) male genital tract at level of ejaculatory gland (lateral); (G) posterior body region with copulatory muscle bands; (H–N) Posterior region (lateral); (O, P) posterior region (ventral). Scale bars: 10 μm.

Figure 4. Cluster analysis (complete linkage) showing relationship between species of Pelodera (strongyloides-group) based on morphological data.