Butlerius indicus, Mumtaz & Ahmad & Tahseen, 2025

Butlerius indicus sp. n.

( Figures 1 View Figure 1 , 2 View Figure 2 , 7 View Figure 7 , 8 View Figure 8 , Tables 1 View Table 1 , 3 View Table 3 , 4 View Table 4 )

Description

Female. Body slender, medium–sized, less than 1 mm; almost straight after fixation, tapering only very slightly anteriorly, but more posteriorly towards a filiform tail. Cuticle with fine transverse striations. Longitudinal striations fine with equally spaced dot-like punctations ( Figure 2 View Figure 2 (F)). Lip region more or less flat, continuous with body contour. Lips six, amalgamated with six small papilliform inner labial and six setose outer labial sensilla. Amphidial apertures large, elliptical to square-shaped ( Figure 2 View Figure 2 (B)), 12–13 µm from anterior end of stoma, at the level of dorsal tooth. Stoma 2.5 times longer than wide. Cheilostom longer than wide, spacious, barrel-shaped, cheilorhabdions arched inward anteriorly, cheilorhabdial flaps eight, arched outwards to reveal an open stoma; gymnostom broader than long, isotopic, isomorphic, lacking armature ( Figure 1 View Figure 1 (D)). Stegostom anisotopic and anisomorphic, dorsal metastegostomal wall with a medium-sized, triangular, anteriorly directed, movable tooth, subventral walls without armature ( Figure 1 View Figure 1 (D)). Pharynx with slender 56–95 µm long, muscular corpus of uniform diameter, expanding slightly into a 12–20 µm long median bulb. Corpus lumen prominently sclerotised. Isthmus relatively muscular, 20–30 µm long, continuing posteriorly into a basal bulb of 17–27 µm × 13–15 µm dimension without any valve plate or grinder. Dorsal pharyngeal gland nucleus usually prominent, located near base of basal bulb ( Figure 1 View Figure 1 (F)). Nerve ring encircling isthmus immediately posterior to median bulb, at 68–78% of pharyngeal length. Hemizonid located near the expanding part of basal bulb, about 74–80% of pharyngeal length. Secretory–excretory pore faintly visible. Cardia well-developed, 3–4 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, 7– 8 µm without any bacterial pouch.

Reproductive system amphidelphic, anterior gonad on right side and posterior on left side of intestine. Both branches almost identical. Ovaries reversed with distal part of ovaries not reaching the level of vulva ( Figure 2 View Figure 2 (D)). Oocytes arranged in double row in germinal zone and single row in maturation zone ( Figure 1 View Figure 1 (E)). Oviduct narrow, tubular. Spermatheca thin-walled, without distinct demarcation, filled with rounded to ovoid sperms. Uterus divisible into a distal smaller muscular part and a proximally placed longer, glandular part made up of large cells and narrow lumen. Columella distinct from spermatheca. Vagina narrow, tubular, 5–6 µm long about one-fourth of corresponding body diameter. Vulval opening small, elliptical, flushing with body contour. Vulva–anus distance 8.0–12.5 times vulval body diameter. Rectum 1.1–1.7 times anal body diameter ( Figure 2 View Figure 2 (I)). Phasmids located at a level, 1.4–2.5 anal body diameter posterior to anus. Tail long, filiform 0.6–1.7 times vulva–anus distance, divided into two parts, an anterior short conoid part and a posterior longer filamentous part.

Male. Similar to female in general morphology but smaller in size (625–823 µm). Lip region with four cephalic papillae posterior to outer labial sensilla. 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, slender, arcuate, 1.2–1.7 times cloacal body diameter long. Manubrium round connected to calomus/lamina complex – that is slightly expanded just posterior to manubrium, and then smoothly tapering to prominent bifid distal tips constituting a fine ventral spur ( Figure 2 View Figure 2 (H)). Gubernaculum slender, boat-shaped, 56–75% of spicules length, proximally curved and distally with a sleeve ( Figure 1 View Figure 1 (G)). Tail divided into two parts, an anterior short conoid part and a posterior longer filamentous part. Genital sensilla nine pairs – constituting three precloacal and six postcloacal pairs in the configuration of v1, v2, v3d/v4, ad, (v5, v6, v7), ph, pd. Precloacal pair v1 located above the spicule range, about twice cloacal body diameter anterior to cloaca; v2 and v3d almost at the same level, just anterior to cloacal opening. ad about one cloacal body diameter posterior to cloaca. v7 larger than v5 and v6. Phasmids pore-like, at the level of v5, 1.7–2.1 anal body diameter posterior to cloacal opening. pd subdorsal, far posterior to the v5–v7 group ( Figure 1 View Figure 1 (G)).

Type habitat and locality

The wet collection of the present population of Butlerius indicus sp. n. was collected from rotting bark in Haldwani, Uttarakhand, India on 12 February 2019 at geographical coordinates 29°12ʹ52′′N, 79°31ʹ40′′E.

Type material

Holotype: Female on slide AMU/ZD/NC/ Butlerius indicus sp. n. /1 deposited in the nematode collection of the Department of Zoology, Aligarh Muslim University, Aligarh, Uttar Pradesh, India. GoogleMaps

Paratypes: Sixteen females and 13 males on slides AMU/ZD/NC/ Butlerius indicus sp. n. /2–14 deposited in the nematode collection of Department of Zoology, Aligarh Muslim University, Aligarh, Uttar Pradesh, India GoogleMaps .

Diagnosis and relationships

Butlerius indicus sp. n. is characterised by finely-striated and punctated cuticle; large barrel-shaped, anteriorly arched cheilostom; isotopic and isomorphic gymnostom; anisotopic and anisomorphic stegostom, dorsal stegostomal wall with medium-sized, anteriorly directed tooth; female reproductive system amphidelphic; males with slender, arcuate spicules having a bifid distal tip constituting a fine ventral spur; boat-shaped gubernaculum, proximally curved, distal end provided with a sleeve, and nine pairs of genital sensilla.

The new species closely resembles B. canadensis Ebsary, 1986 , B. degressei Grootaert and Jaques, 1979 , B. longipyge Khera, 1969 , B. butleri Goodey, 1929 and B. gerlachi Meyl, 1957 in general morphology and morphometric values. However, it differs from B. canadensis in the number of cheilostomal plates (8 vs 12), shape of cheilostom (anteriorly curved vs linear), subventral tooth (absent vs present on left wall), distal end of spicules (bifid vs blunt), sleeve of gubernaculum (present vs absent) and number and arrangement of genital sensilla (nine pairs with six postcloacal pairs vs eight pairs with five postcloacal pairs in B. canadensis ).

From B. degressei , the new species differs in having smaller females (671–970 µm vs 1,076 –1,311 µm), length of stoma (11–17 µm vs 22.4–24.5 µm), position of amphids (anterior to dorsal tooth vs at the level of dorsal tooth), female reproductive system (amphidelphic vs prodelphic with post-uterine sac), shape of spicules (lamina broad, distal tips bifid or with a spur vs lamina narrow, distally hooked) and arrangement of genital sensilla (v2 just anterior to cloaca vs v2 above the spicule range).

The new species comes close to B. longipyge but differs in having smaller body size in females (671–970 µm vs 1,000 –1,200 µm), more slender body (a = 32.0–43.4 vs 25–28 in females; 35.4–45.6 vs 26–28 in males), subventral tooth (absent vs present on both walls), size of spicules (20–25 µm vs 30–32 µm) and rudimentary bursa (absent vs present).

B. indicus sp. n. also resembles B. butleri in most allometric ratios but differs from it in having smaller body size (671–970 µm vs 1,335 –1,857 µm in females; 625–823 µm vs 1,197 –1,641 µm in males), length of stoma (11–17 µm vs 24.5–27.5 µm), position of amphids (at the level of dorsal tooth vs at the base of dorsal tooth), uterine glands (absent vs present), size of spicules (20–25 µm vs 38.5–48.5 µm), size of gubernaculum (12–15 µm vs 24.5–32.5 µm) and arrangement of genital sensilla (v5–7 cluster at the same level vs v5– 7 cluster separated from each other).

From B. gerlachi , the new species differs in having smaller female (L = 671–970 µm vs 1,000 –1,140 µm), size of cheilostom (longer than gymnostom, as long as head diameter vs as long as gymnostom, half of head diameter), median bulb (oval, as long as corresponding body diameter vs elongate, almost twice the corresponding body diameter), shape of amphid (broad, elliptical to square-shaped vs stirrup-shaped), shorter pharynx (b = 5.5–6.8 vs 4.4–4.9), longer tail (c = 2.5–5.0 vs 5.9–7.6), posterior position of vulva (V = 38–49% vs 51–54%), males having spicules (with bifid distal tip constituting a fine ventral spur vs pointed distal tip), gubernaculum slender (boat-shaped vs broad, keel-shaped) and genital sensilla (9 pairs vs 11 pairs in B. gerlachi ).

Etymology

The name of the species is based on its country of origin, ie India.