Pelodera paratretzeli, Mahboob & Jahan & Tahseen, 2023

Mahboob, Mohammad, Jahan, Rehmat & Tahseen, Qudsia, 2023, Comparative and cladistic analyses of the species of the genus Pelodera Schneider, 1866 (Rhabditidae: Nematoda) belonging to the coarctata group, European Journal of Taxonomy 890 (1), pp. 71-114 : 87-93

Pelodera paratretzeli sp. nov.

urn:lsid:zoobank.org:act:C4B7FC68-5CD4-4A07-8B72-E4B32459F209

Figs 7–9 , 13–15 ; Tables 3 , 5–6 ; Appendices 1–2

Diagnosis

Pelodera paratretzeli sp. nov. is characterized by conspicuous sexual dimorphism in anterior region with females having lip region strongly offset with well-developed, globular lips and males having lip region dome-shaped, continuous, with low, amalgamated lips; stoma 2.5–3.8 times as long as wide; metastegostom anisomorphic with three well-developed setose denticles on each sector; vulval lips not protruded, flanked by cuticular flaps; tail cupola-shaped with a long spike; spicules with rounded capitulum, long neck, fused up to 12–14% of spicule length; bursa peloderan, anteriorly closed and punctated; anterior bursal rim distant from cloacal opening; bursal velum lobed with a shallow groove at cloaca; genital papillae nine pairs: three pre cloacal and six post cloacals arranged in 3/2+Ph+3+1 configuration. GP1-3 closely placed. GP3 shorter than others. GP4, GP5 and relatively shorter and thickened phasmid forming a group, quite posterior to cloaca; GP6–8 basally fused, equal in shape and size.

Etymology

The species epithet ‘ paratretzeli ’ indicates its close similarity with P. tretzeli ( Sachs, 1950) .

Material examined

Holotype INDIA • ♀; Uttar Pradesh, District Aligarh; 27°08′37.38″ N, 82°38′59.65″ E; 309 m a.s.l.; isolated from the elytra (front wing) of dung beetle, Digitonthophagus bonasus ( Coleoptera : Scarabaeidae ) (the beetle specimens were destroyed due to dissection/excision); AMU/ZD/NC slide no. Pelodera paratretzeli sp. nov. /HS/AL/ST/BS/1.

Paratypes INDIA • 5 ♀♀, 5 ♂♂, 5 juvs; same collection data as for holotype; AMU/ZD/NC slide no. Pelodera paratretzeli sp. nov. /HS/AL/ST/BS/2–12 .

Description

Adult

Body medium-sized, plump, almost straight, with tapering ends. Sexual dimorphism conspicuous in anterior region. Cuticle with transverse and longitudinal striations and fine punctations. Lip region strongly offset from body contour and dilated, ca 2.6–3.2 times as wide as high. Lips globular, distinctly separated, with slightly raised labial sensilla. Amphids labial with small, elliptical apertures. Stoma well-developed, 2.5–3.8 times as long as wide or 11–14% of total pharyngeal length. Cheilostom highly cuticularized. Gymnostom with parallel walls. Stegostom surrounded by pharyngeal tissue up to half of stoma length. Metastegostom anisomorphic and most widened part of stoma, armed with three prominent setose denticles on each plate. Telostegostom heavily cuticularized. Pharynx well-developed, divided into 58–68 μm long corpus, a well-developed, muscular, strongly swollen metacorpus of 18–28 ×20–26 μm; a relatively narrower, 40–53 μm long isthmus, and a well-developed basal bulb of 18–28 μm ×18–24 μm, with a grinder and cuticularized double-chambered haustrulum. Cardia conoid, 5–7 μm long. Nerve ring encircling anterior region of isthmus, just posterior to median bulb at 62.7– 67.1% of pharyngeal length. Secretory-excretory pore located posterior to nerve ring, at mid-level of isthmus or at 79.6–82.8% of total pharyngeal length from anterior end. Intestine showing a bacterial pouch just posterior to pharyngo-intestinal junction. In some individuals, an intestinal diverticulum representing shifted bacterial pouch was observed. Rectum, 0.5–0.7 times anal body diameter. Tail cupola-shaped, ca 1.5–1.7 times as long as anal body diameter. Spike covering more than half of total tail length. Phasmids opening at level of anus.

Female

Reproductive system didelphic, amphidelphic, ovaries well-developed, opposed and dorsally reflexed, distal ends reaching up to vulva. A coelomocyte present close to distal tip of each ovary, while another found close to reflexed part. Oocytes with prominent nuclei arranged in multiple rows distally. Oviducts not distinctly separated. Spermathecae elongated, filled with sperm. Uteri spacious, accommodating two to ten eggs at a time. Vagina cuticularized, thick-walled. Vulva equatorial, a transverse slit, with lips not protruded. Lateral cuticular vulval flaps present.

Male

Sexually dimorphic with lip region dome-shaped, continuous with body contour. Lips weak, amalgamated, without a discernible identity. Pharynx relatively weak with moderately swollen metacorpus. Anterior region of intestine showing a small bacterial pouch. Testis single, dorsally reflexed, on right lateral side of intestine. Spermatocytes arranged in multiple rows. Seminal vesicle filled with spermatocytes leading to vas deferens.A pair of well-developed ejaculatory glands present.A coelomocyte present close to distal end of testis while another found close to reflexed part. Tail conoid, ending in an acute terminus. Bursa well-developed, anteriorly closed, transversally and longitudinally striated with dot-like punctations. Bursal velum lobed with a shallow groove at cloaca. Anterior bursal rim distant from cloacal opening. Spicules almost straight, slender with rounded capitulum, narrow neck and shaft fused distally up to 12–14% of total length. Gubernaculum trough-shaped, ca 42.5–46.6% of spicule length. Genital papillae nine pairs, arranged in 3/2+Ph+3+1 configuration with pre cloacals GP1 and GP2 forming a group along with very short GP3, nearly half the length of others. GP1, GP4 and GP9 opening dorsally outside bursa; GP4, GP5 and phasmid forming a group; phasmids relatively shorter and thickened, located in between GP5 and group of GP6. GP6–8 basally fused, equal in shape and size. GP9 dorsally oriented.

Dauer/phoretic juvenile

Body almost straight, abruptly tapering posterior to anus. Cuticle with fine transverse striations. Lateral field inconspicuous. Lip region continuous with amalgamated lips. Oral aperture covered with a cuticular plug. Stoma long, narrow, ca 5 times as long as wide. Metastegostomal swelling weakly developed, with faintly visible small denticles. Pharynx with a slender procorpus ca 40–52 μm long, an oblong, ca 12–13 μm×9–12 μm metacorpus, a narrow, ca 22–32 μm long isthmus and a pyriform, ca 14–17 μm ×10–14 μm basal bulb, lacking valvular plate. Nerve ring encircling mid-region of isthmus. Secretory-excretory duct inconspicuous. Rectum faintly visible, ca equal to anal body diameter. Phasmidial aperture inconspicuous. Tail long, conoid, covered with hyaline sheath and ended with a sharp, pointed tip.

Remarks

Pelodera paratretzeli sp. nov. comes close to P. tretzeli ( Sachs, 1950) in most morphological characters but differs in females having small-sized body (644–866 μm vs 1543–3327 μm); smaller b (4.8–5.5 vs 8.1–11.9) and c (15.9–21.5 vs 28.4–33.1) values; metastegostom anisomorphic (vs isomorphic); rectum 0.5–0.7 times (vs 0.3–0.4 times) anal body diameter; phasmids at level of anus (vs at base of wider part of tail); males with smaller body length (483–639 μm vs 636–758 μm); smaller b (3.7–4.6 vs 4.9–5.9), c (17.2–21.3 vs 28.4–35.6) and greater c’ (1.2–1.5 vs 0.7–0.8) values; spicules slender (vs slightly plump), having distinct neck (vs neck not demarcated); bursa with shallow groove (vs deep indentation) laterally at level of cloaca; genital papillae with slender bases (vs swollen bases in P. tretzeli fide Sachs (1950)).

Figures

Fig. 7. Pelodera paratretzeli sp. nov., paratypes (AMU/ZD/NC slide no. Pelodera paratretzeli sp. nov./ HS/AL/ST/BS/2–12). A. Entire female.B. Entire male.C. Female pharyngeal region.D. Female anterior end. E. Male anterior end. F. Female reproductive system. G. Female posterior region (lateral view). H. Male posterior region (lateral view).

Fig. 8. Pelodera paratretzelisp. nov., paratype, ♀ (AMU/ZD/NC slide no. Pelodera paratretzeli sp. nov./ HS/AL/ST/BS/2–12). A. En face view (scanning electron microscopy). B. Anterior region (scanning electron microscopy).C–D. Anterior end.E. Anterior pharyngeal region. F. Posterior pharyngeal region. G–H. Female genital branch. I. Vulval region (scanning electron microscopy). J. Tail region (scanning electron microscopy). K. Posterior region. Scale bars = 10 μm.

Fig. 9. Pelodera paratretzeli sp. nov., paratype, ♂ (AMU/ZD/NC slide no. Pelodera paratretzeli sp. nov./ HS/AL/ST/BS/2–12). A. En face view (scanning electron microscopy). B. Anterior region (scanning electron microscopy). C. Anterior end. D. Anterior pharyngeal region. E–F. Posterior pharyngeal region. G. Reflexed testis. H–J. Posterior region (lateral view). K. Posterior region (scanning electron microscopy). Scale bars = 10 μm.

Fig. 13. Map showing worldwide distribution of the species of genus Pelodera Schneider, 1866 (coarctata goup) in countries like Algeria, Australia, Germany, Georgia, Hungary, India, Lithuania, Russia, United Kingdom, Uzbekistan, etc.

Fig. 14. Pictorial key for the comparison of the species of genus Pelodera Schneider, 1866 (coarctata group) based on the female anterior region, tail region, male tail region (lateral and ventral views) and spicules (distally fused). Scale bars = 20 μm.

Fig. 15. Cladistic analysis of the species of genus Pelodera Schneider, 1866 (coarctata goup) indicating the position of the new species P. indica sp. nov., P. adeeli sp. nov. and P. paratretzeli sp. nov. within the genus. The evolutionary history was inferred in MrBayes ver. 3.1.2 (Huelsenbeck & Ronquist 2001) by using the Jukes Cantor (JC) model. The phylogenetic tree is supported by posterior probability values with minimum 50% majority rules.