Pelodera adeeli, 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 : 80-87

Pelodera adeeli sp. nov.

urn:lsid:zoobank.org:act:40B1FCCA-69E5-4C95-957D-3B40DD68E7F2

Figs 4–6 , 13–15 ; Tables 2, 5–6 ; Appendices 1–2

Diagnosis

The new species P. adeeli sp. nov. is characterized by the absence of sexual dimorphism in anterior region; cuticle transversely and longitudinally striated; lips equal, strongly offset with loose cuticular margins; stoma 4.5–5.0 times as long as wide with three well-developed, relatively small setose denticles on each metastegostomal plate; secretory-excretory pore located nearly at level of pharyngo-intestinal junction; distal ends of ovaries crossing each other; vulval lips strongly protruded; tail paedomorphic with retention of juvenile cuticle, conoid, regularly tapering to acute terminus; males with slender spicules, rounded capitulum, long neck, shaft fused distally; gubernaculum ca ⅓–¼ of spicule length; bursa peloderan, anteriorly closed and punctated with serrated margins, anterior rim of bursa distant from cloacal opening; genital papillae nine pairs: two pre cloacal and seven post cloacal pairs arranged in 2/1+2+Ph+3+1 configuration with wide gap between GP2, GP3 and GP4.

Etymology

The species name is given in honour of Mr Mohammad Adeel, the father of Mohammad Mahboob.

Material examined

Holotype INDIA • ♂; Eastern Uttar Pradesh, Terai region, District Gonda ; 27°08′37.38″ N, 82°38′59.65″ E; 309 m a.s.l.; isolated from the elytra (front wing) of dung beetle, Onthophagus ramoss (Wiedeman, 1823) ( Coleoptera : Scarabaeidae ) (the beetle specimens were destroyed due to dissection/excision); AMU/ZD/ NC slide no. Pelodera adeeli sp. nov. /NIT/rpt/1 .

Paratypes INDIA • 3 ♂♂, 5 ♀♀, 5 juvs; same collection data as for holotype; AMU/ZD/NC slide no. Pelodera adeeli sp. nov. /NIT/rpt/2–10 .

Description

Adult

Body medium-sized, obese, stout, almost straight, tapering at both extremities. Cuticle annulated, 2 μm thick with annules 1.0–1.5 μm wide at pharyngeal region and 3–4 μm wide at mid-body. Longitudinal striations relatively prominent, extending up to tail, crossed by transverse striation to form corn cob pattern. Sexual dimorphism indistinct in anterior region with lip region offset from body contour and 2.5–3.0 times as wide as high. Lips six, equal-sized with loose margins, globular in shape, distinctly separated, containing slightly raised labial sensilla. Amphids labial with small, rounded apertures. Stoma well-developed, ca 4.5–5.0 times as long as wide or 13–14% of total pharyngeal length. Cheilostom highly cuticularized; gymnostom relatively narrower than stegostom; stegostom more than half of stoma length, surrounded by pharyngeal tissue at about 56.5–57.4% of stoma length; metastegostom with three prominent setose denticles on each swelling; telostegostom heavily cuticularized. Pharynx well-developed, divided into muscular, 60–66 μm long, slender corpus, well-developed, highly muscular metacorpus of 22–26 ×21–25 μm dimension, and isthmus relatively narrower, 40–45 μm long, expanding posteriorly to form well-developed basal bulb of 27–32×24–26 μm dimension, having a grinder and double-chambered haustrulum. Cardia conoid, 5–7 μm long. Nerve ring encircling posterior region of isthmus at 67.8–68.7% of pharyngeal length from anterior end. Secretory-excretory duct usually opening posterior to pharynx at 96.2–105% from anterior end. Intestine with wide lumen, often anteriorly and posteriorly dilated to form bacterial pouches with intestinal epithelim thinning out in the region; intestinal lumen refractive. Rectum 24–28 μm long, approximately equal to anal body diameter, occasionally with dilated lumen. Tail paedomorphic, retaining larval cuticle, conoid in shape, ca twice of anal body diameter. Phasmids tubular, opening slightly posterior to anus.

Female

Reproductive system didelphic, amphidelphic; ovaries well-developed, paired, opposed, and lateroventrally reflexed, usually distal ends of ovaries extended beyond vulva, crossing each other. Oocytes with prominent nuclei arranged in multiple rows. Usually, two uterine eggs present at different stages of embryonation. Vagina thick-walled. Vulva rounded in shape with strongly protruded vulval lips, situated posterior to the mid-body or at 57.7–60.0% from the anterior end.

Male

Similar to female in general morphology except prominently curved posterior region. Testis single, dorsally reflexed, on right lateral side of intestine. Spermatocytes arranged in multiple rows. Seminal vesicle filled with spermatids continuing into vas deferens. Vas deferens narrowing posteriorly to form a narrow ejaculatory duct. A pair of ejaculatory glands present. Tail conical, ending in an acute terminus. Bursa well-developed, anteriorly closed, oval in shape, transversally and longitudinally striated with dot-like punctations. Bursal margins crenate. Anterior bursal velum distant from cloacal opening. Spicules slightly ventrally curved, slender with rounded capitulum, narrow necks and conspicuous ventral conoid process, fused distally up to 20–22% of total length. Gubernaculum slender, trough-shaped, ca 22–25% of spicule length. Genital papillae nine pairs in 2/1+2+P+3+1 configuration. Pre cloacals GP1 and GP2 similar in shape and size, directed towards anterior velum of bursa. GP3 situated just posterior to cloaca. GP4, GP5 and phasmid closely placed while GP4 far from GP3. Phasmid relatively shorter and plump, GP6–8 basally fused, equal in shape and size. GP9 open dorsally, close to group of GP6–8.

Dauer/phoretic juvenile

Body straight, tapering at both extremities, more towards posterior region. Cuticle thin, ca 0.1–0.3 μm. Lateral field with single line or incisor. Lip region continuous. Stoma long, narrow, ca 6–7 times as long as wide. Metastegostomal swellings weakly-developed with faintly visible small denticles. Pharynx well-developed with slender procorpus 38–45 μm long, a swollen metacorpus of 12–15 μm× 11–12μm dimension and a narrow, long isthmus of 28–32 μm, expanded posteriorly to an oval basal bulb of 15– 17 μm ×12–12 μm dimension, having weakly-developed grinder. Nerve ring encircling mid-region of isthmus. Secretory-excretory duct inconspicuous. Bacterial chamber present. Rectum shorter than anal body diameter. Rectal glands prominent. Tail long, conoid, ending with filiform tip.

Remarks

Pelodera adeeli sp. nov. comes closer to P. cylindrica ( Cobb, 1898) in most morphometric and morphological characteristics but differs in sexual dimorphism absent (vs present); females having smaller c (12.5–17.2 vs 38.6–70.5) and greater c’ (1.7–2.1 vs 0.5–0.6) values; labial sensilla slightly raised (vs minute); metastegostomal denticles relatively smaller (vs larger); lip margins loose (vs defined); posteriorly located secretory-excretory pore 96.2–105.0% (vs 53–75%) of pharyngeal length; tail conoid (vs hemispheroid); males with pre cloacal genital papillae not shifted posteriorly (vs shifted posteriorly in P. cylindrica fide Sachs (1950) and Völk (1950)).

The new species differs from P. par Andrássy, 1962 in having females with smaller a (11.6–13.9 vs 18.5), b (4.2–5.4 vs 7.1) and c (12.5–17.2 vs 27.5) values; labial sensilla raised (vs minute); stegostom slightly (vs strongly) expanded; tail conoid (vs cupola-shaped); males with smaller a (13.4–16.8 vs 22.7) and c (15.6–19.4 vs 21.0) values; gubernaculum ca ⅓–¼ of spicule length (vs half of spicule length); pre cloacal genital papillae 2 pairs (vs 3 pairs in P. par ).

The new species resembles P. cystilarva ( Völk, 1950) but differs in having females with smaller body size (678–934 μm vs 1224–1744 μm); smaller b (4.2–5.4 vs 6.2–7.6) and c’ (1.7–2.1 vs 2.6–6.7) values; greater c (12.5–17.2 vs 7.5–9.1) value; stoma 4.5–5.0 times (vs 6–7 times) as long as wide; rectum approximately equal to (vs half or less than) anal body diameter; tail conoid (vs dome-shaped); males with smaller body (577–722 μm vs 880–1072 μm); greater a (13.4–16.8 vs 11.5–12.0) value; smaller b (4.0–4.8 vs 5.0–5.4) and c (15.6–19.4 vs 26.1–46.3) values; bursal velum expanded (vs relatively converging type in P. cystilarva fide Völk (1950)).

Pelodera adeeli sp. nov. comes close to P. serrata (Körner in Osche, 1952) but differs in having females with smaller body size (678–934 μm vs 1148–1409 μm); smaller c (12.5–17.2 vs 37.0–50.7) value; secretory-excretory pore located at level of pharyngo-intestinal junction (vs at mid-level of isthmus); tail conoid (vs cupola-shaped); males with body shorter (577–722 μm vs 1067–1242 μm); relatively smaller b (4.0–4.8 vs 4.8–5.9) and c (15.6–19.4 vs 29.3–41.0) values; smaller spicules (37–50 μm vs 68–80 μm) and genital papillae GP3 and GP4 distantly positioned (vs closely placed in P. serrata fide Körner in Osche (1952)).

The new species differs from P. voelki ( Sachs, 1950) in having no sexual dimorphism (vs sexual dimorphism present); females with smaller body size (678–934 μm vs 1470–3610 μm); smaller b (4.2– 5.4 vs 7.6–9.6) and c (12.5–17.2 vs 25.8–36.3) values; metastegostomal denticles relatively small (vs long); stoma 4.5–5.0 times (vs 2.5–3.0 times) as long as wide; tail conoid (vs cupola-shaped); males shorter (577–722 μm vs 885–1625 μm), with relatively smaller a (13.4–16.8 vs 16.3–20.0), b (4.0–4.8 vs 5.3–6.1) and c (15.6–19.4 vs 21.6–26.7) values; smaller spicules (37–50 μm vs 51–70 μm); genital papillae GP1 and GP2 distant (vs close) to cloaca and GP3 distant from GP4 (vs close to GP 4 in P. voelki fide Sachs (1950)).

The new species also differs from P. kolbi ( Sachs, 1950) in not showing (vs showing) sexual dimorphism; females with smaller body length (678–934 μm vs 1185–1326 μm); smaller b (4.2–5.4 vs 5.9–7.9) and c (12.5–17.2 vs 21.9–27.9) values; greater c’ (1.7–2.1 vs 0.9–1.0) value; tail conoid (vs cupola-shaped); males with relatively smaller a (13.4–16.8 vs 16.1–18.1) value; genital papillae GP1 inside (vs outside) bursa; pre cloacal genital papillae (two pairs vs single pair); GP2 distantly ahead of cloaca (vs at level of cloaca) and GP4–5+P and GP6–8 arranged in groups (vs not arranged in groups in P. kolbi fide Sachs (1950)).

Pelodera adeeli sp. nov. differs from the Indian species, P. aligarhensis Tahseen et al., 2014 , in having sexual dimorphism absent (vs present); smaller a (11.6–13.9 vs 16.3–20.0) and c (12.5–17.2 vs 22.1– 41.2) values; relatively greater c’ (1.7–2.1 vs 0.8–1.4) value; labial margins wavy (vs compact); denticles relatively small (vs large); tail conoid (vs cupola-shaped); males with smaller a (13.4–16.8 vs 17.5–18.4) value; adcloacal papilla absent (vs present); GP3 distant (vs close to GP 2 in P. aligarhensis ).

Figures

Fig. 4. Pelodera adeeli sp. nov., paratypes (AMU/ZD/NC slide no. Pelodera adeeli sp. nov./NIT/ rpt/2–10). A. Entire female. B. Entire male. C–D. Female anterior end. E. Male lip region. F. Female pharyngeal region. G. Female reproductive system. H. Female posterior region. I. Male posterior region (lateral view). J. Male posterior region (ventral view). Scale bars = 25 μm.

Fig. 5. Pelodera adeeli sp. nov., paratype, ♀ (AMU/ZD/NC slide no. Pelodera adeeli sp. nov./NIT/ rpt/2–10). A–B. En face view (scanning electron microscopy). C. Anterior end. D. Anterior pharyngeal region. E–F. Posterior pharyngeal region. G. Reproductive system. H. Distal parts of ovaries. I. Vulval region (scanning electron microscopy). J. Tail region (scanning electron microscopy). K. Tail with old cuticle. L. Cuticular markings (scanning electron microscopy). Scale bars = 10 μm.

Fig. 6. Pelodera adeeli sp. nov., paratype, ♂ (AMU/ZD/NC slide no. Pelodera adeeli sp. nov./NIT/ rpt/2–10). A. Anterior end. B. En face view (scanning electron microscopy). C. Pharyngeal region. D. Reflexed part of testis. E. Ejaculatory gland. F–H. Posterior region (lateral view). I. Posterior region (ventral view). J–L. 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.