Pelodera aligarhensis, 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 : 1044-1049

Pelodera aligarhensis 2 sp. nov.

( Figures 5–7 )

Measurements

See Table 5.

Description

Female. Body medium-sized, straight to slightly arcuate with tapering ends. Females are relatively obese with prominent and expanded lip region compared with their male counterparts. Cuticle very finely annulated, with very fine longitudinal lines and inconspicuous punctations. Lateral field with three ridges. Lip region expanded, slightly offset from adjoining body. Lips rounded, separate and distinct, outer labial sensilla slightly raised, inner labials slightly shifted outward. Amphid openings small and rounded, labial. Stoma well developed, fairly long, rhabditoid type 4.8–5 times longer than wide or 13.4–13.8% of pharyngeal length. Cheilostom cuticularized, appearing dot-like in lateral view; gymnostom not markedly conspicuous. Metastegostom strongly cuticularized, widened with each swelling bearing three setose denticles; telostegostom heavily cuticularized. Pharyngeal collar usually surrounding 50–55% of length of stoma as measured from base. Pharynx differentiated into a swollen corpus, slightly narrower isthmus and a muscular, ovoid (27–33 × 22– 25 μm wide) basal bulb with well-developed grinder and a faintly two-chambered haustrulum. Nerve ring encircling anterior half of isthmus at 67.2–68.2% of the pharyngeal length. Secretory–excretory pore in close proximity with the nerve ring at 74.5–79.8% of pharyngeal length; cell bodies located at pharyngeal base 95–103% of pharyngeal length. Cardia (pharyngeal–intestinal valve) 5–9 μm long, often appearing as the extension of basal bulb. Intestine with wide lumen, often anteriorly dilated and distinguishable there as a sac. Posterior intestinal region with dilated lumen bounded by enlarged cells. Rectum 16–22 μm long, about three-quarters of anal body diameter, often with dilated lumen; rectal glands inconspicuous. Reproductive system didelphic, amphidelphic, ovaries well-developed, paired, opposed and lateroventrally reflexed, often with distal end of posterior ovary extending further posterior to the vulva; anterior and posterior ovaries respectively on right and left lateral side of intestine, spermatheca and uterus not differentiated by sphincter. Intrauterine eggs about 42–48 × 30–38 μm with three or four eggs at different stages of embryonation within uterus. Vagina thick-walled, at right angle to longitudinal body axis. Vulva a transverse slit with protruded vulval lips. Vulva–anus distance 9.4–11.6 times that of tail length. Tail conical, often cupola-shaped with a small spike of one-half to one-third of tail length. Phasmid openings positioned at 50– 55% of the broader conical part of the tail.

Male. Similar to female in general morphology except lip region structure, tail shape and greater curvature of the posterior region. Lip region in males narrow, continuous with adjoining body. Lips relatively smaller and amalgamated. Stoma very narrow in most individuals while relatively wider in a few; metacorpal swelling weak; basal bulb relatively smaller than that of female. Secretory–excretory pore located at c.68–75% of the length of pharyngeal region with secretory-excretory gland cells visible near anterior region of isthmus. Cardia very narrow, often appearing as a postbulbar extension continuing into an equally narrow intestine. Testis single, dorsally reflexed, on right lateral side of intestine. Seminal vesicle separated from vas deferens by a constriction. Ejaculatory glands present; right lateral gland slightly anterior to left one. Tail conical, narrowing into a spike with fine terminus. Bursa well-developed peloderan, anteriorly closed, ovoid. Spicules fused up to 20–25% of length from distal end, provided with rounded capitula, narrow necks and slender shafts with velum terminating as a short spur. Gubernaculum slender, trough-shaped, about 40–45% of spicule length. Genital papillae comprising nine pairs in 1/2 + (2 + P) + (3 + 1) configuration. Two precloacal pairs shifted posteriorly: GP1 with base in precloacal region reaches the level of cloaca; GP2 and GP3 slightly posterior to GP1 opening posterior to cloacal level. GP4, GP 5 in close proximity. Region surrounding phasmid openings relatively swollen relative to papillae, located between GP5 and GP6. GP6, GP7 and GP8 basally joined in close proximity to dorsally oriented GP9.

Type habitat and locality

Sample containing Pelodera aligarhensis sp. nov. collected from land fill area of Harduaganj, Aligarh, Uttar Pradesh, India at coordinates 27°56 ′ 39 ″ N, 78°9 ′ 31 ″ E .

Type material

Holotype female, 19 paratype females and 14 paratype males on slide Pelodera aligarhensis sp. nov. No. NOH/1-8 deposited in the Nematode Collection of the Department of Zoology , Aligarh Muslim University, Aligarh, India . One paratype female and one paratype male on slide Pelodera aligarhensis sp. nov. No. NOH/2 deposited at the Wageningen Nematode Collection (WaNeCo), Wageningen, the Netherlands.

Diagnosis and relationships

Pelodera aligarhensis sp. nov. is characterized by gonochoristic individuals having cuticle with fine longitudinal striations and punctations; sexual dimorphism in anterior region with females having conspicuously dilated lips, large stoma; cupolashaped tail; males with stoma smaller than females, an elongated cardia and narrower anterior intestine; slender spicules fused up to 20–25% of length from distal end; anteriorly closed peloderan bursa; three precloacal papillae pairs with two other pairs shifted posterior to cloacal opening.

The new species resembles Pelodera tretzeli ( Sachs 1950) in most morphometric characteristics as well as by the presence of three pairs of precloacal papillae in males but differs in females by the smaller body (0.6–0.8 mm vs 1.1–1.3 mm) with presence (vs absence) of fine longitudinal lines and punctations; smaller b (3.9–4.6 vs 5.9–7.9) and relatively greater V (56.7–63.5 vs 56.2–57.7) values; intestine not overlapping (vs overlapping) the basal pharyngeal region; tail spike smaller (vs larger) than cupolashaped part of tail; males having relatively smaller (30–38 vs 35–47 μm) spicules and precloacal papillae positioned posterior (vs anterior) to cloacal opening in P.tretzeli apud Sachs (1950) .

The new species resembles Pelodera par Andrássy, 1962 in most morphometric characteristics as well as by the presence of three pairs of precloacal papillae in males but differs in having (vs lacking) sexual dimorphism in lip region; presence (vs absence) of fine longitudinal lines and punctations on the cuticle; smaller b (3.9–4.6 vs 7.1) and relatively greater V (56.7–63.5 vs 59) values; presence of small-sized eggs (42–48 vs 58–64 μm); tail spike smaller (vs larger) than cupola-shaped part; males having smaller (30–38 vs 40–44 μm) spicules and two precloacal papillae pairs positioned posteriorly (vs anteriorly) in P. par apud Andrássy (1962).

Remarks

Sudhaus (2011) identified 10 species under the coarctata -group. The species of the group have been reported from dung, cow pats, moulds, horse droppings and in most cases, associated with beetles or mites. Pelodera aligarhensis sp. nov. was, however, reared in the laboratory on an E.coli culture at a temperature of 25 ± 2°C; the development was found to be normal without any dauer stage.

The species of the coarctata -group are characterized by obese females and relatively slender, smaller males. Most of them show sexual dimorphism in the lip region with lips more prominent, wide and offset in females and they have a wide stoma with heavily cuticularized metastegostom bearing conspicuous teeth compared with their male counterparts. The only species lacking sexual dimorphism in the group is stated to be P. par apud Andrássy (2006). The species P. tretzeli , P. voelki and P. kolbi in particular have males with an extremely reduced anterior region. In the present species males were observed to have a slightly reduced or extremely reduced labial region with amalgamated lips as well as a narrower stoma. Even the pharynx was found to be relatively cylindrical and the anterior intestinal region was considerably narrowed. On the contrary, the anterior end of the intestinal lumen was widened in the female similar to the bacterial pouch found in many entomopathogenic nematodes. The excretory cells in males were small and confined to the level of the middle of the isthmus in males while the females possessed relatively larger cells. Females of all the species of the coarctata group have a cupola-shaped tail with a terminal spike except in Pelodera cylindrica where the female tail is bluntly rounded. As a rule the males have an anteriorly closed peloderan bursa that appears sucker-shaped and often indented and lobed, however, variation has been observed in the number of precloacal genital papillae. Most of them possess two pairs of precloacals with the exception of P. tretzeli and P. par, which possess three precloacal pairs.

Cluster analysis ( Figure 8 ) based on 20 morphological characters ( Tables 2 and 4) indicates a close affinity of P. aligarhensis with P. tretzeli compared with other existing species of the group. Both species appears to form a more inclusive cluster with P. par and P. voelki . This larger cluster is related to two other species, Pelodera cystilarva and Pelodera serrata , and the resulting cluster is itself related to a cluster containing a sister relationship between P. cylindrica and P. isociensis which together are distantly related to P. kolbi . Pelodera coarctata maintains a separate identity and clearly stands out as the most morphologically divergent species showing an overall affinity with other species of the group. The species Pelodera operosa has not been included in the analysis because the species is represented by females only.

Figures

Figure 5. Pelodera aligarhensis sp. nov. (all lateral) (A) Entire female; (B) entire male; (C) female anterior end; (D) male anterior end; (E) female pharyngeal region; (F) female reproductive system; (G) female tail region; (H) male tail region.

Figure 6. Pelodera aligarhensis sp. nov. female. (A, B) En face view (scanning electron microscopy); (C) anterior end (lateral); (D) anterior pharyngeal region (lateral); (E, F) posterior pharyngeal region (lateral); (G) lateral field; (H) anterior genital branch; (I) vulval region (lateral); (J) vulval region (ventral); (K, L) posterior intestinal region (lateral); (M–O) caudal region (lateral). Scale bars: 10 μm.

Figure 7. Pelodera aligarhensis sp. nov. male. (A–C) Anterior end (A is scanning electron micrograph); (D) anterior pharyngeal region (lateral); (E) posterior pharyngeal region (lateral); (F) male genital tract at level of ejaculatory gland (ventral); (G) posterior region (lateral); (H–J) tail end showing bursa and genital papillae (lateral) (J is scanning electron micrograph); (K–N) Tail end showing bursa and genital papillae (ventral) (K is scanning electron micrograph). Scale bars: 10 μm.

Figure 8. Cluster analysis (complete linkage) showing relationship between species of Pelodera (coarctata-group) based on morphological data.