Pelodera indica, 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 : 74-80

Pelodera indica sp. nov.

urn:lsid:zoobank.org:act:AE90DC74-C667-4E6B-AE39-D400BF61F43A

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

Diagnosis

The new species Pelodera indica sp. nov. is characterized by transversely and longitudinally striated cuticle; sexual dimorphism in anterior region with females having conspicuously expanded, offset lip region; lips distinctly separated with tapering ends directed towards oral aperture; laterals larger than submedians; stoma wide, having three strong setose denticles on each metastegostomal plate; secretory-excretory pore at level of basal bulb or cardia; distal end of ovaries reaching up to vulva, often crossing each other; bursa peloderan, anteriorly closed; velum punctated with two deep grooves on either side; genital papillae nine pairs, compactly placed arranged in 0/1+1+1+1+1+P+3+1 configuration; without any gap between pre- and post cloacals; GP1 anteriorly directed with base located at level of posterior cloacal lip; GP1, GP4 and GP9 opening dorsally; genital papillae GP6–8 basally fused.

Etymology

The species name is derived from the name of the country ‘India’.

Material examined

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

Paratypes INDIA • 9 ♂♂, 9 ♀♀, 5 juvs; same collection data as for holotype; AMU/ZD/NC slide no. Pelodera indica sp. nov. /NIT/ctrs/2–15 .

Description

Adult

Body medium-sized, almost straight to slightly ventrally arcuate, tapering at both extremities. Cuticle 1 μm thick, finely annulated, with fine longitudinal lines and inconspicuous punctations. Lip region showing sexual dimorphism, with females having 2.5–3.0 times as wide as high, offset lip region more expanded than in males. Lips six, globular, distinctly separated with tapering ends projecting into stomal cavity; lateral lips larger than submedians. Labial sensilla papilliform. Amphids labial with small openings indiscernible under LM. Stoma well-developed, posteriorly widened, ca 3–4 times as long as wide or 13.1–13.4% of pharyngeal length. Cheilostom small, rod-shaped, cuticularized. Gymnostom with parallel walls, strongly cuticularized. Stegostom covering about 45–46% of stoma from its base. Metastegostom anisoglottoid, relatively widened with three strongly developed, thorn-like setose denticles on each plate. Telostegostom heavily cuticularized. Pharynx well-developed, highly muscular, divided into 65–70 μm long corpus with prominent metacorpal swelling, a slightly narrower 39–49 μm long isthmus, and a muscular, rounded to ovoid basal bulb of 26–31 μm×25–28 μm dimension with a well-developed grinder and two-chambered haustrulum. Nerve ring encircling posterior region of isthmus at ca 71–82% of pharyngeal length. Secretory-excretory duct opening at level of basal bulb, at ca 82.8–98.2% of pharyngeal length. Intestine with wide lumen, often dilated at anterior and posterior ends to form bacterial pouches with intestinal epithelium thinning out in the region; intestinal lumen refractive. Rectum 20–26 μm long, shorter than anal body diameter often with dilated lumen; rectal glands distinct. A thick-walled, conspicuous pre-rectal pouch observed in one specimen.

Female

Reproductive system didelphic, amphidelphic; ovaries paired, lateroventrally reflexed with distal parts often crossing each other. Oocytes with prominent nuclei, arranged in multiple rows around rachis towards distal end. Spermathecae filled with stacked spermatozoa. Each uterus divided into well-developed glandular and muscular parts; two pairs of glandular cells opening at proximal end of vagina. Intra-uterine eggs about 6–10, linearly arranged end to end or obliquely placed. Vagina thick-walled. Vulva transverse slit with protruded vulval lips. Tail cupola-shaped with a moderately developed spike of ca ½ of tail length. Phasmids opening laterally at level or just posterior to anus.

Male

Similar to female in general morphology except for relatively narrower lip region and body having greater ventral curvature posteriorly. Lip region narrow, continuous, or slightly offset from body contour. Lips relatively smaller than those of female, laterals larger than submedians. Testis single, dorsally or laterally reflexed, on right side of intestine. Spermatocytes arranged in multiple rows; seminal vesicle separated from vas deferens by a deep constriction. Tail conoid, tapering posteriorly to an acute terminus. Spicules with rounded capitulum, narrow neck and slender shaft, fused distally up to 24–28% of total length. Gubernaculum slender, trough-shaped, 37–51% of spicule length. Genital papillae nine pairs, evenly spaced and arranged in 0/1+1+1+1+1+P+3+1 configuration, without any gap in between. GP1 slender, directed towards anterior edge of bursa, with base located at posterior cloacal lip or beyond. GP2 relatively plump. GP1, GP4 and GP9 opening dorsally. Bursa well-developed, anteriorly closed, transversely and longitudinally striated with dot-like punctations. Anterior bursal rim close to cloacal opening, bursal velum appearing lobed under LM, forming two deep grooves at GP2 and GP5. Phasmids relatively plump and shorter, located in between GP5 and group of GP6–8. Genital papillae GP6–8 basally fused.

Dauer/phoretic juvenile

Body often straight or slightly ventrally arcuate upon fixation. Cuticle thin, ca 0.1–0.5 μm. Lateral field inconspicuous. Lip region continuous. Lips amalgamated, not differentiated into six separate lips. Oral aperture covered by a highly sclerotized cuticular plug. Stoma long, narrow, ca 5–6 times as long as wide. Metastegostomal swellings with faintly visible denticles. Pharynx weakly developed with slender procorpus 42–56 μm long; a swelling metacorpus 11–15 ×10–12 μm in dimension and a narrow, long, isthmus of 25–36 μm, expanded posteriorly to an oval basal bulb 15–25 ×12–17 μm in dimension, having weakly-developed grinder. Nerve ring encircling mid or posterior region of isthmus. Secretory-excretory duct inconspicuous. Cardia short, conoid. Rectum shorter than anal body diameter. Rectal glands inconspicuous. Phasmidial aperture inconspicuous. Tail long, conoid, ending with a sharp, pointed tip.

Remarks

Pelodera indica sp. nov. comes closer to P. cylindrica ( Cobb, 1898) in most of the morphometric and morphological characters but differs in having females with smaller c (14.7–21.1 vs 38.6–70.9) and greater c’ (1.1–1.8 vs 0.5–0.6) values; tail cupola-shaped (vs hemispheroid) with (vs without) spike and males with spicules having rounded (vs elongated) capitula, fused up to 24–28% (vs 15–20%) at distal end; bursa lobed (vs not lobed in P. cylindrica fide Sachs (1950), Völk (1950) and Osche (1952)).

The new species resembles P. isociensis ( Maupas, 1916) in most morphometric characters but differs in having smaller females (849–1065 μm vs 1214–1830 μm); smaller c (14.7–21.1 vs 30.3–57.3) value; tail spike as long as (vs one third) of anal body diameter; males with GP2 and GP3 relatively closer (vs spaced in P. isociensis fide Sachs (1950)).

The new species also differs from P. tretzeli ( Sachs, 1950) in having females with smaller body (849– 1065 μm vs 1543–3327 μm); smaller b (5.1–6.2 vs 8.1–11.9) and c (14.7–21.1 vs 28.4–33.1) values; phasmids present at level of (vs posterior to) anus; males with smaller c (13.8–18.1 vs 28.4–35.6) value; larger spicules (45–57 μm vs 32–39 μm); pre cloacal genital papillae absent (vs present); GP3 close to (vs distant from) GP4; bursa with two notches (vs one notch) and anterior rim of bursa close to (vs distant from cloacal opening in P. tretzeli fide Sachs (1950)).

Pelodera indica sp. nov. differs from P. voelki ( Sachs, 1950) in having females with smaller body (849– 1065 μm vs 1470–3610 μm), smaller b (5.1–6.2 vs 7.6–9.6) and c (14.7–21.1 vs 25.8–36.3) values; males having smaller body (591–727 μm vs 885–1625 μm), and relatively smaller b (4.1–5.3 vs 5.3–6.1) and c (13.8–18.1 vs 21.6–26.7) values; smaller spicules (45–47 μm vs 51–70 μm); genital papillae compactly placed (vs spaced); pre cloacals absent (vs present); GP2 relatively plump (vs slender); GP2 and GP3 closely (vs distantly) placed; anterior bursal rim just ahead of cloaca (vs distant from cloaca in P. voelki fide Sachs (1950)).

The new species differs from P. aligarhensis Tahseen et al., 2014 in having females with relatively larger body length (849–1065 μm vs 688–841μm); greater b (5.1–6.2 vs 3.9–4.6) and relatively smaller c (14.7–21.1 vs 22.1–41.2) values; longer tail spike (20–31 μm vs 5.9 μm); males with larger spicules (45–57 μm vs 30–38 μm); anterior bursal rim just anterior to (vs distant from) cloacal opening; pre cloacal genital papillae shifted (vs not shifted) posterior to cloaca; genital papillae not arranged in groups (vs arranged in three groups in P. aligarhensis ).

Figures

Fig. 1. Pelodera indica sp. nov., paratypes (AMU/ZD/NC slide no. Pelodera indica sp. nov./NIT/ ctrs/2–15). A. Entire female. B. Entire male. C. Female anterior region. D. Female pharyngeal region. E. Female reproductive system. F. Female posterior region. G. Male posterior region (lateral view). H. Male posterior region (ventral view). I. Spicule (lateral view). Scale bars = 25 μm.

Fig. 2. Pelodera indica sp. nov., paratype, ♀ (AMU/ZD/NC slide no. Pelodera indica sp. nov./NIT/ ctrs/2–15). A–B. En face view (scanning electron microscopy). C. Anterior end.D. Posterior pharyngeal region. E. Vulval region with anterior genital branch (lateral view). F. Anterior genital branch. G. Posterior genital branch. H. Vulval region. I–J. Tail. Scale bars = 10 μm.

Fig. 3. Pelodera indica sp. nov., paratype, ♂ (AMU/ZD/NC slide no. Pelodera indica sp. nov./NIT/ ctrs/2–15). A. Anterior region (scanning electron microscopy). B. Anterior end. C. Anterior pharyngeal region. D. Posterior pharyngeal region. E. Ovarian flexure of anterior genital branch. F–H. Posterior region showing spicules and gubernaculum. I–L. Tail region showing bursa and genital papillae (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.