Pelodera cylindrica ( Cobb, 1898 ), 1972

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 : 93-99

Pelodera cylindrica ( Cobb, 1898)

Figs 10–15 ; Tables 4–6 ; Appendices 1–2

Rhabditis cylindrica Cobb, 1898: 296–321 .

Rhabditis neuhausi Sachs, 1950: 323–366 , fig. 4.

Coarctadera cylindrica – Andrássy 1983: 113.

Pelodera serrata – Ali et al. 1973: 169–188 [not P. serrata (Körner in Osche, 1952)].

Pelodera icosiensis – Hussain et al. 2006: 55–62 [not P. icosiensis Maupas, 1916 ].

Emended diagnosis

Pelodera cylindrica ( Cobb, 1898) is characterized by an obese, stout and almost straight body, tapering at anterior region; sexual dimorphism present in anterior region; cuticle finely annulated; lip region strongly offset from body contour and dilated approximately twice of its height; lips with small labial sensilla; stoma ca 2.5–3.0 times as long as its height; metastegostom with three setose denticles on each sector; rectum shorter than anal body diameter; tail short, hemispheroid, shorter than anal body diameter, lacking spike, often with a small mammellate peg or protrusion terminally; spicules with rounded capitulum, short, narrow neck and slender shaft, fused distally up to 24–25% of spicule length; gubernaculum ca 44.0–47.5% of spicule length; bursa peloderan, anteriorly closed, punctated; bursal velum lobed with three deep grooves at GP2, GP3 and GP5; anterior bursal rim close to cloacal opening; genital papillae nine pairs, arranged in 0/1+1+1+1+1+P+3+1 configuration; pre cloacals shifted posterior to cloaca; GP1, GP4 and GP9 open dorsally outside the bursa; GP3–5 relatively close to each other, GP6–8 basally fused and phasmids shorter and thickened between GP5 and GP6.

Material examined

INDIA • 5 ♂♂, 5 ♀♀, 6 juvs; Uttar Pradesh, Aligarh, Satha ; 27°58′52″ N, 78°06′10″ E; extracted from soil samples contaminated by the discharges of sugar industry; AMU/ZD/NC slide no. Pelodera cylindrica /HL/AL/ST/SM/1–10 .

Description

Adult

Body medium-sized, obese, stout, almost straight with tapering anterior region. Sexual dimorphism observed in anterior body region. Cuticle 1.0–1.5 μm thick, transversely annulated, interspersed with longitudinal striations and punctation. Lip region dilated, strongly offset from body contour, approximately more than twice its height. Lips six, globular in shape, distinctly separated, with minute papilliform labial sensilla.Amphids labial with small, ovoid apertures. Stoma well-developed, expanding posteriorly, 2.5–3.0 times as long as wide or 13–15% of total pharyngeal length. Cheilostom not cuticularized. Gymnostom constituting 40–45% of stoma length. Stegostom surrounded by pharyngeal tissue, constituting 56–58% of stoma length; metastegostom wide, armed with three well-developed setose denticles on each sector. Telostegostom heavily cuticularized. Pharynx well-developed, divided into 55–77 μm long, slender corpus, a well-developed, highly muscular, approximately 20–30 μm×22– 32 μm metacorpus, a relatively narrower, 35–50 μm long isthmus and a well-developed, rounded to oval-shaped basal bulb of 28–39 μm×24–35 μm having a highly cuticularized grinder with double-chambered haustrulum. Cardia conoid, 5–10 μm long. Nerve ring usually encircling posterior region of isthmus at ca 65.2–73.4% of pharyngeal length. Secretory-excretory pore located posterior to nerve ring, or at 72.4–78.7% of total pharyngeal length. Bacterial chamber present posterior to pharyngo-intestinal junction. Rectum 0.5–0.6 times anal body diameter.

Female

Reproductive system didelphic, amphidelphic. Ovaries well-developed, paired, opposed, and dorsally reflexed, usually distal end extending beyond vulva. Oocytes with prominent nuclei arranged in multiple rows. Spermathecae ovoid filled with sperm. Uteri with 2– 15 eggs ca 50–70 × 37–45 μm in dimension. Vulva without protruded lips, slightly post equatorial. Tail short, hemispheroid, often with a small peg or mammellate tip, shorter than anal body diameter. Phasmids opening slightly posterior to anus.

Male

Similar to female in general morphology except narrower lip region, smaller body size, smaller metastegostomal denticles and slight curvature in posterior region. Testis single, dorsally conoid, ending in a pointed terminus. Spicules almost straight, slender with rounded capitulum, narrow neck and slender shaft, fused distally up to 24–25% of total spicule length. Gubernaculum slender, trough-shaped, ca 44.0–47.5% of spicule length. Bursa well-developed, anteriorly closed, transversely and longitudinally striated with dot-like punctations. Bursal velum lobed, forming three deep grooves at GP1, GP2 and GP3. Anterior bursal rim close to cloacal opening. Nine pairs of genital papillae arranged in 0/1+1+1+1+1+P+3+1 configuration with pre-cloacal genital papillae GP1 and GP2 shifted posterior to cloaca. GP3–5 relatively closely placed. Phasmid relatively shorter and thickened, located in between GP5 and GP6. GP6–8 basally fused. GP1, GP4 and GP9 open dorsally outside bursa.

Dauer/phoretic juvenile

Body slightly arcuate ventrally, tapering at both extremities. Cuticle with fine transverse striations. Lateral field with a single ridge. Lip region continuous with six separated lips, each containing setose sensilla. Stoma long, narrow, ca 4–5 times as long as wide. Metastegostomal swelling with faintly visible small denticles. Pharynx well-developed with ca 40–43 μm, long, slender procorpus, a highly muscular metacorpus 15–17 μm×13–16 μm in dimension, a narrow, ca 20–34 μm long isthmus and a basal bulb ca 18–22 μm ×15–17 μm in dimension, having a cuticularized grinder. Nerve ring encircling mid of isthmus. Secretory-excretory pore inconspicuous. Pre-rectum-like structure present in posterior region. Rectum ca equal to anal body diameter in length. Phasmidial aperture inconspicuous. Tail short and conoid.

Remarks

The present population showed conformity with P. cylindrica ( Cobb, 1898) in most characteristics except a few minor differences from the originally described population viz., metastegostom with strongly developed (vs moderately developed) denticles and males with genital papillae GP1 and GP2 distant (vs closely placed). The females in the present population also show a small terminal peg or mammellate protrusion in the tail not reported in the original population.

Figures

Fig. 10. Pelodera cylindrica Cobb, 1898 (AMU/ZD/NC slide no. Pelodera cylindrica/HL/AL/ST/ SM/1–10). A. Entire female. B. Entire male. C–F. Female anterior end. G. Male anterior end. H. Female reproductive system. I. Female tail (lateral view). J. Male tail (lateral view). K. Male tail (ventral view).

Fig. 11. Pelodera cylindrica Cobb, 1898, female (AMU/ZD/NC slide no. Pelodera cylindrica/HL/AL/ ST/SM/1–10). A–B. En face view (scanning electron microscopy). C–E. Anterior end. F–G. Anterior pharyngeal region. H–I. Posterior pharyngeal region. J. Distal end of anterior and posterior genital branches. K. Vulval region (scanning electron microscopy). L. Uterine region. M–O. Tail end. Scale bars = 10 μm.

Fig. 12. Pelodera cylindrica Cobb, 1898, male (AMU/ZD/NC slide no. Pelodera cylindrica/HL/AL/ ST/SM/1–10). A–C. En face view (scanning electron microscopy). D. Anterior end. E–F. Anterior pharyngeal region. G. Posterior pharyngeal region. H. Body region showing large excretory gland cell. I. Reflexed testis. J–L. Posterior region (lateral view).M. Posterior region (ventral view).N–Q. 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.