Diplogastrellus longipharyngis, Mumtaz & Bashir & Ahmad & Tahseen, 2025

Mumtaz, Sabia, Bashir, Ishrat, Ahmad, Irfan & Tahseen, Qudsia, 2025, New insights into Diplogastrellus Paramonov, 1952 (Nematoda: Rhabditida: Diplogastroidea) with three novel and three known species from India, European Journal of Taxonomy 1008, pp. 1-50 : 9-15

Diplogastrellus longipharyngis sp. nov.

urn:lsid:zoobank.org:act:DC861CBA-FAC5-4440-BC5A-95190CE28528

Figs 3–5 , 17–19 ; Tables 2, 7–8

Diagnosis

The new species Diplogastrellus longipharyngis sp. nov. is characterised by a narrow stoma longer than wide; elliptical amphidial aperture, at the level of dorsal tooth; a medium-sized dorsal tooth with ventrally directed apex; pharynx well-developed, muscular ovoid metacorpal bulb with valve plates, a long isthmus and ovoid basal bulb; posterior pharynx 1.5–1.9 times anterior pharynx; mono-prodelphic reproductive system with a post-uterine sac filled with sperm; spicules separate, heavily cuticularized, slightly curved with small rounded manubrium; a proximally notched, keel-like triangular gubernaculum and nine pairs of genital sensilla.

Etymology

The name of the species is derived from the long isthmus part of pharynx.

Material examined

Holotype

INDIA • ♀; Uttarakhand, District Haldwani ; 29°12′52″ N, 79°31′40″ E; isolated from rotting bark; slide reference number AMU/ZD/NC/ Diplogastrellus longipharyngis /1.

Paratypes

INDIA • 9 ♀♀, 10 ♂♂; same data as for holotype; slide reference number AMU/ZD/NC / Diplogastrellus longipharyngis /2–9 .

Description

Adult

Body slender, about 1 mm long, almost straight after fixation, tapering towards both the extremes. Cuticle with transverse striations. Lip region continuous with body contour. Lips six, amalgamated, each bearing a small papilla. Amphidial apertures elliptical, 5–6 µm from anterior end of stoma, at the level of dorsal tooth. Stoma short, tubular, longer than wide, about 5–6 µm in depth. Cheilostom as long as wide, cheilorhabdions arched inward anteriorly. Gymnostom anisotopic, dorsal wall shorter than subventrals. Stegostom anisotopic and anisomorphic, dorsal metastegostomal wall with a medium-sized tooth, with ventrally directed apex, posterior-ventral aspect strongly cuticularised; subventral walls without armature. Pharynx with slender 42–51 µm long, muscular corpus of uniform diameter; median bulb set off from corpus, ovoid, 11–15 µm long with strong valve plates. Isthmus 65–85 µm long, narrow, conspicuously differentiated from median bulb. Basal bulb bigger than the median bulb, glandular, 25–33 ×13–17 µm, only slightly expanded from isthmus without any valve plate or grinder. Posterior pharynx 1.5–1.9 times anterior pharynx. Dorsal pharyngeal gland nucleus usually prominent, located near base of basal bulb. Nerve ring encircling isthmus in the anterior half, at 46–51% of pharyngeal length. Hemizonid conspicuous, just posterior to the nerve ring, at 51–56% of pharyngeal length. Excretory pore posterior to hemizonid, at 55–59% of pharyngeal length. Cardia well-developed, 5–6 µm long, consisting of three flaps, one dorsal and two ventro-sublateral. Intestine composed of dark granulated cells with prominent nuclei, intestinal lumen uniformly wide, 5–6 µm without any bacterial pouch. Rectum 1.2–1.5 times anal body diameter long; rectal glands distinct.

Female

Reproductive system mono-prodelphic. Ovary reversed on right side of intestine. Oocytes with large nuclei, arranged in multiple rows in germinal zone and single row in maturation zone. Distal tip of ovary not reaching vulva. Oviduct long, narrow, tube-like. Spermatheca expanded, set off from uterus with distinctly narrower walls, containing sperm. Uterus divisible into a distal smaller muscular part and proximally placed longer, glandular part made up of large cells and narrow lumen. Post-uterine sac 35–49 µm long, 2.0–2.5 times vulval body diameter, filled with sperm. Vagina narrow, tubular, slightly inclined anteriorly, 11–16 µm long about one-third of corresponding body diameter long. Vulval opening small, pore-like. Vulva-anus distance 5.5.–7.0 times vulval body diameter. Phasmids located at 1.8–2.4 anal body diameter posterior to anus. Tail long, filiform 1.5–1.9 times vulva-anus distance.

Male

Similar to females in general morphology but smaller in size, curved in posterior region. Reproductive system monorchic, testis reflexed laterally, on right side of intestine. Spermatocytes arranged in two rows distally followed by single row proximally. Vas deferens a long tube containing spermatocytes transforming into spermatozoa, tapering to an ejaculatory duct. Spicules paired, separate, almost straight, heavily cuticularized, 1.4–1.6 times cloacal body diameter long. Manubrium small, rounded, lamina/calamus complex not expanded, smoothly tapering to a pointed distal tip. Gubernaculum 37–44% of spicule length, proximally notched, appearing triangular, keel-like with a pointed distal end. Tail divisible into two parts, a short conoid part and a longer filamentous part. Genital sensilla nine pairs; three pairs precloacal and six pairs postcloacal. Genital sensilla formula: v1, v2, v3d / v4, ad, (v5, v6), ph, v7, pd. v1 located beyond the spicular range, more than one cloacal body diameter anterior to cloaca; v2 less than one cloacal body diameter anterior to cloaca; v3d slightly posterior to v2; v4 just posterior to cloaca; ad one cloacal body diameter posterior to cloaca; v5–7 not grouped, v5 and v6 close to each other while v7 situated more posteriorly at the level of pd. Phasmids pore-like, just posterior to v6, 1.3–1.5 anal body diameter posterior to cloacal opening.

Remarks

Diplogastrellus longipharyngis sp. nov. comes close to D. heynsi ( Kiontke & Sudhaus, 1996) in most morphometric and morphological characteristics but differs in the size of stoma (5–6 µm vs 11–13 µm), size of dorsal tooth (medium-sized, ventrally directed vs massive, ventrally directed), position of amphids (at the base of dorsal tooth vs posterior to the base of stoma), median bulb (ovoid vs oblong), isthmus (longer that procorpus vs shorter than procorpus), shape of spicules (strongly built, almost straight vs stout, strongly arcuate at the distal end), shape of gubernaculum (triangular, proximally notched vs short, keel-like, caudally projected loop) and in the arrangement of genital sensilla (v4 just posterior to cloaca, v5–7 not grouped vs v4 more than one cloacal diameter posterior to cloaca, v5–7 grouped).

The new species resembles D. sikorai and D. stammeri Weingärtner, 1955 in general morphometric values. However, it can be easily distinguished from both species by its short tubular stoma, long isthmus and in the structure of gubernaculum without sleeve. It further differs from D. sikorai in having larger body size (L= 865–1091 µm vs 492–657 µm in females; 597–752 µm vs 395–470 µm in males), by structure of dorsal tooth (ventrally directed vs anteriorly directed), size of post-uterine sac (35–49 µm vs 19–31 µm), length of spicules (25–27 µm vs 17–19 µm) and arrangement of genital papillae (v1 anterior to spicule head, v7 more posterior at the level of pd vs v1 within the spicule range, v5–v7 grouped).

From D. stammeri , it can be further differentiated in the shape of dorsal tooth (ventrally directed vs anteriorly directed), position of amphids (at the base of dorsal tooth vs at the base of gymnostom), subventral armature (absent vs small tooth in both walls), size of post-uterine sac (more than twice vulval body diameter long vs less than one vulval body diameter) and structure of spicules (almost straight with rounded manubrium, anteriorly flattened, merging with shaft vs arcuate with ovoid manubrium separated from shaft by neck).

The new species differs from D. thoubalicus in having shorter stoma (5–6 µm vs 12–15 µm), by position of amphids (at the base of dorsal tooth vs posterior to the base of stoma), median bulb (ovoid vs oblong), isthmus (longer that procorpus vs shorter than procorpus), shape of spicules (strongly built, almost straight vs slender, distally more curved), shape of gubernaculum (triangular, proximally notched vs posterio–dorsally directed loop with a small sleeve) and in the arrangement of genital sensilla (v4 just posterior to cloaca, v5–7 not grouped vs v4 more than one cloacal diameter posterior to cloaca, v5–7 grouped).

Figures

Fig. 3. Diplogastrellus longipharyngis sp. nov. A, C–F. Holotype, ♀ (AMU/ZD/NC/Diplogastrellus longipharyngis sp. nov./1). B, G. Paratype, ♂ (AMU/ZD/NC/Diplogastrellus longipharyngis sp. nov. /2–9). A. Entire female. B. Entire male. C. Anterior region showing stoma. D. Pharyngeal region. E. Female reproductive system. F. Female posterior region. G. Male posterior region showing spicules and gubernaculum.

Fig. 4. Diplogastrellus longipharyngis sp. nov. A–E, G–H. Holotype, ♀ (AMU/ZD/NC/Diplogastrellus longipharyngis sp. nov./1). F, I. Paratype, ♂ (AMU/ZD/NC/Diplogastrellus longipharyngis sp. nov./2– 9). A. Anterior part of pharynx. B. Posterior part of pharynx. C. Anterior region showing stoma. D. Anterior region showing amphid. E. Female reproductive system showing anterior branch. F. Male posterior region showing spicules and gubernaculum. G. Post-uterine sac. H. Female posterior region. I. Male posterior region showing genital papillae. The arrowheads in D, F–G and I indicate amphidial aperture, distal part of keeled gubernaculum, sperm-filled post-uterine sac and genital papillae, respectively. Scale bars: A–B, E, G–I = 20 μm; C–D, F = 10 μm.

Fig. 5. Diplogastrellus longipharyngis sp. nov. A–F. Holotype, ♀ (AMU/ZD/NC/Diplogastrellus longipharyngis sp. nov./1). G–H. Paratype, ♂ (AMU/ZD/NC/Diplogastrellus longipharyngis sp. nov./2– 9). A–B. Enface view. C. Anterior region showing amphid. D. Vulval opening. E. Anal opening. F. Female posterior region showing phasmid. G–H. Male posterior region showing genital papillae. The arrowheads in C, F and H indicate amphidial aperture, phasmid and genital papillae, respectively. Scale bars: A, C–G = 5 μm; B, H = 2 μm.

Fig. 17. Map showing the worldwide geographical locations of the holotypes of species of Diplogastrellus Paramonov, 1952.

Fig. 18. Cladogram (constructed manually) showing the relationships of the species of Diplogastrellus Paramonov, 1952. Apomorphic morphological traits are designated by black squares and plesiomorphic traits by white squares.

Fig. 19. Cladistic analysis of the species of the genus Diplogastrellus Paramonov, 1952, indicating the position of the new species D. didelphis sp. nov., D. longipharyngis sp. nov., and D. robustus sp. nov. The phylogenetic tree was constructed for nineteen species using PAUP ver. 4.0. (Swofford 2002).