Butlerius micans Pillai and Taylor, 1968

Butlerius micans Pillai and Taylor, 1968 View in CoL

( Figures 3–8 View Figure 3 View Figure 4 View Figure 5 View Figure 6 View Figure 7 View Figure 8 , Tables 2–4 View Table 2 View Table 3 View Table 4 )

Description

Females. Body slender, medium-sized, less than 1 mm long, almost straight after fixation, tapering towards both extremities. Cuticle with fine transverse and prominent longitudinal striations forming a corn-cob like pattern. Lateral fields with four fine lines (visible in three out of 17 studied specimens). Lip region continuous with body contour. Lips six, amalgamated, with six papilliform inner labial sensilla, small setose outer labial sensilla. Amphidial apertures elliptical, 4–5 µm from anterior end of stoma, at the base of cheilostom. Stoma 1.5 times longer than wide. Cheilostom spacious, barrel-shaped; cheilostomal walls thick, arched anteriorly, cheilostomal flaps eight. Gymnostom broader than long, anisotopic and anisomorphic – with dorsal wall shorter than subventrals. Stegostom anisotopic and anisomorphic. Dorsal metastegostomal wall with a medium-sized movable tooth, subventral walls provided with denticulate ridge. Procorpus muscular, 54–72 µm long with zipper-like lumen; median bulb round or ovoid, 16–21 µm long, strong muscular with thickened lumen, isthmus narrow, 21–37 µm long, conspicuously differentiated from median bulb. Basal bulb small, pyriform, glandular, 18–29 × 16–18 µm in dimension without any valve plate or grinder. Dorsal gland nucleus usually prominent, located near the base of the basal bulb. Nerve ring encircling isthmus in the middle, at 59–71% of pharyngeal length from anterior end. Hemizonid just below the level of nerve ring and anterior to excretory pore, at 66–75% of pharyngeal length. Excretory pore 69–79% of pharyngeal length, at anterior level of basal bulb. Cardia well-developed, 4–5 µm long, consisting of one dorsal and two ventro-sublateral flaps. Intestine composed of dark granulated cells with prominent nuclei, intestinal lumen uniformly wide 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. Oocytes with large nuclei, arranged in multiple rows in germinal zone and single row in maturation zone. Distal tips of ovaries not reaching vulva. Oviduct narrow, tubular and short. Spermatheca thin-walled, not distinctly demarcated, usually containing sperms. Uterus divisible into a longer glandular columella made up of large cells around a narrow lumen and smaller muscular uterus proper. Two pairs of large unicellular glands opening into uterus. Vagina narrow, tubular, 11–17 µm long about one-third of corresponding body diameter. Vulval opening relatively small, elliptical, flush with body contour or sometimes depressed. Vulva–anus distance 6.4–8.0 times vulval body diameter. Rectum 1.2–2.0 times anal body diameter. Anal opening wide, crescent-shaped. Phasmids located at about 1.3–1.9 anal body diameter posterior to anus. Tail filiform 1.2–1.8 times vulva–anus distance long, divided into two parts, a short conoid part and a long filamentous part.

Males. Similar to females in general morphology but smaller in size (572–728 µm). Anterior region with four small cephalic setae present posterior to circlet of six outer labials. Reproductive system monorchic, testis reflexed laterally, on right side of intestine. Spermatocytes arranged in two rows in anterior reflexed part; vas deferens a long tube with spermatocytes in the stage of transformation into immature spermatozoa, tapering to an ejaculatory duct. Spicules paired, cuticularized, arcuate, 1.4–1.6 times cloacal body diameter long. Manubrium oval connecting posteriorly to a calomus/lamina complex, lamina broad with a ventral conoid process, gradually tapering to fine tip with subterminal dorsal protuberance. Gubernaculum 45–65% of spicules length, proximally curved, provided with a small distal sleeve. Tail divided into two parts, a short conoid part and a long filamentous part. Genital sensilla setose in nine pairs constituting two precloacal, one adcloacal 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, more than one cloacal body diameter anterior to cloaca; v2 adcloacal; v3d just anterior and v4 closely posterior to cloaca; ad less than one cloacal body diameter posterior to cloaca. v5 larger than v6 and v7. Phasmids pore-like, at the level of v5, 1.3–1.7 anal body diameter posterior to cloacal opening. pd subdorsal, far posterior to v5–v7 group.

Habitat and locality

The   GoogleMaps present population of Butlerius micans Pillai & Taylor, 1968 was extracted from a sample of rotting banana rhizome collected at Aligarh Fort, Aligarh, Uttar Pradesh, India at geographical coordinates 27°55ʹ47′′N, 78°03ʹ49′′E on 23 September 2019.

Voucher specimens

Fifteen females and 12 males on slides AMU/ZD/NC/ Butlerius micans /1–9 deposited in the nematode collection of Department of Zoology , Aligarh Muslim University, Aligarh, Uttar Pradesh, India .

Remarks

The original population of B. micans , 1968 was collected from sludge drying bed of the Champaign– Urbana Sanitary sewage treatment plant at Urbana, Illinois, USA. In the type slides of B. micans, Pillai and Taylor (1968) described a large cheilostom divisible into two parts; anterior composed of eight movable plates and a more strongly cuticularised posterior part. They mentioned a large dorsal tooth on dorsal stegostomal wall but did not give any information about the subventral wall. Later; Mahamood (2014) collected another population of B. micans from farmyard manure at Aligarh , India. He reported a pointed tooth on the right and a denticulate plate on the left subventral stegostomal wall. In our study, SEM observations ( Figure 5 View Figure 5 (C)), provided for the first time, revealed the morphology of stoma with denticulate ridges on both subventral walls.

On comparing the loaned type specimens ( Figure 6 View Figure 6 ) with our specimens, sufficient evidence of similarity could be noticed. The morphological characteristics viz., structure of stoma, zipper-like structure in the pharyngeal lumen, shape of spicules, and gubernaculum of our specimens conform well with those studied by Pillai and Taylor (1968). Despite the opacity and flattening of type specimens in the loaned slide, the similarity of stomal armature indicated towards possibility of denticulate ridges on subventral walls. Conspicuous uterine glands ( Figure 6 View Figure 6 (E)) and the adcloacal male genital sensilla ( Figure 6 View Figure 6 (F)) could be observed, though not reported by Pillai and Taylor (1968) in the original description and also by Mahamood (2014). However, our population showed minor morphometric differences from the original population in having smaller individuals (L = 667–864 µm vs 980–1,250 µm in females and 572–728 µm vs 790–1,100 µm in males) and smaller b value (5.5–6.0 vs 6.7–8.1) in females. Compared with the population reported by Mahamood (2014), our specimens differ considerably in having thicker bodies (a = 22–29 µm vs 34–43 µm in females;17–20 µm vs 28– 34 µm in males), smaller males (L = 572–728 µm vs 803–997 µm), relatively shorter stoma (10– 13 µm vs 16–20 µm), smaller spicules (23–26 µm vs 31–35 µm) and adcloacal genital sensilla (present vs absent). The comparative study of the two populations reveal interesting results where their status as cryptic species cannot be overruled considering the geographic distance. However, a thorough testing is required at molecular level to ascertain the status of both our specimen and those from the type locality in USA. We, therefore, intend to take up this task in the future.

The present population of B. micans differs markedly from the newly described population of B. indicus sp. n. in having transverse and longitudinal cuticular striations forming a corncob pattern (vs cuticle finely-striated and punctated); amphidial aperture elliptical (vs large square-shaped); stoma with dorsal tooth and subventral serrated ridge (vs dorsal tooth and no subventral armature);males with slender,arcuate spicules with conspicuous ventral triangular process ( Figure 3 View Figure 3 (h)) (vs spicules plump with ventral conoid process inconspicuous, Figure 1 View Figure 1 (g)); lamina gradually terminating into a pointed distal tip provided with a dorsal subterminal protuberance (vs distal end with fine ventral subterminal spur); and nine pairs of genital sensilla (constituting two precloacal,one adcloacal and six postcloacal pairs vs three precloacal and six postcloacal pairs in B. indicus sp. n.).

Some outstanding differences between B. micans Pillai and Taylor, 1968 , B. butleri ; Goodey, 1929 and B. degrissei ; Grootaert and Jaques, 1979 in general morphology and morphometric values have been given hereunder. It can be easily differentiated from the closely related species by zipper-like lumen of corpus, structure of stoma and arrangement of genital papillae. It further differs from B. butleri in the number of cheilostomal flaps (8 vs 6), size of stoma (10–13 µm vs 21–29 µm), shape of dorsal tooth (anteriorly-directed vs ventrally-directed), armature on subventral stegostomal walls (both walls provided with serrated ridge vs right subventral with a small tooth; left a smooth-edged plate) and arrangement of genital sensilla (both v5–7 cluster at the same level vs v5–7 cluster greatly separated, right subventral group at the level of pd). From B. degrissei , it differs in the number of cheilostomal plates (8 vs 6), size of stoma (10–13 µm vs 22.4–24.5 µm), armature on subventral stegostomal walls (both walls provided with serrated ridge vs lacking armature), female reproductive system (amphidelphic vs monodelphic with a post–uterine sac), shape of spicules (broad lamina vs narrow lamina) and arrangement of genital sensilla (v2 adcloacal vs v2 above the spicule range).