Tylencholaimellus masakii, Ahmad & Ahad, 2018

Ahmad, Wasim & Ahad, Sumaya, 2018, Description of two new and two known species of the Genus Tylencholaimellus Cobb in M. V. Cobb, 1915 (Nematoda: Dorylaimida: Tylencholaimoidea), Zootaxa 4375 (3), pp. 301-324 : 313-323

Tylencholaimellus masakii sp. n.

( Figs. 7 & 8 )

Material examined. Four females in good state of preservation.

Description. Measurements, see Table 4.

Female: Moderately slender nematodes of small size, 0.77–81 mm long, slightly curved ventrad upon fixation, tapering gradually towards the anterior end. Cuticle with two distinct layers, 3 µm thick at midbody and 4–5 µm on tail. Outer cuticle with fine transverse striation; inner layer with distinct radial elements. Dorsal, ventral and lateral body pores indistinct. Lateral chords occupying about 18–22% of the midbody diameter. Lip region slightly offset by a shallow constriction, 1.7–2.3 times as wide as high or more than one-third of body diameter at neck base; lips amalgamated, with rounded contour; its inner portion transformed into a perioral disc. Amphids cup-shaped, their aperture occupying about one-half of the lip region diameter. Stoma a truncate cone. Odontostyle 1.5–1.7 times the lip region diameter long and provided with dorsal accessory piece along the entire dorsal arm; aperture about onesixth of the odontostyle length. Odontophore with basal knobs, 0.5–0.6 times the odontostyle length. Guiding ring simple, refractive, at 1.0–1.1 times lip region diameter from anterior end. Pharynx consisting of a slender and weakly muscular anterior part separated from basal bulb by a constriction. Pharyngeal basal bulb cylindroid, occupying about 15–20% of total neck length. Pharyngeal glands often visible. Cardia rounded to hemispherical. Nerve ring located at 42–53% of neck length. Hemizonid at 74 µm from anterior end. Genital system monoopisthodelphic. Ovary reflexed, measuring 123–181 µm long, oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 181–187 µm, consist of a slender distal part and a poorly developed pars dilatata filled with sperms. Oviduct-uterus junction marked by a distinct sphincter. Uterus short and tubular, measuring 36–42 µm long. Anterior genital branch reduced to a simple sac1.1–1.8 body diameter long, filled with spindle-shaped sperms. Vagina cylindrical, pars proximalis vaginae 9–11 µm long, its walls encircled by muscles; pars distalis vaginae short, 2 µm long with slightly curved walls; pars refringens absent. Vulva apparently a transverse slit. Prerectum 1.9–2.6 anal body diameters long. Intestine-prerectum junction guarded by three cells. Rectum 0.5–1.0 anal body diameter long. Tail rounded conoid, 0.9–1.1 anal body diameters in length; caudal pores two, one on each side.

Male: Not found.

Type habitat and locality. Soil around the roots of unidentified grasses from Koibuchimachi, Mito-shi, Ibaraki, Japan. Collected by Dr. Masaki Araki on December 7, 2011. 36o20’29”N 140o26’48”E. Type specimens. Holotype female onslide Tylencholaimellus masakii sp. n. / 1 ; paratype females on slides Tylencholaimellus masakii sp. n. / 2–4; deposited with the nematode collection of the Department of Zoology , Aligarh Muslim University, India.

TABLE 5. Morphometrics of species belonging to the genus Tylencholaimellus Cobb in M.V. Cobb, 1915 (measurements in µm, except L in mm, anterior uterine sac in body diameter long, 1,2,3,4 in µm).

Character Species n L a b c ć V lrd stylet length ph.bulb length anterior ut. sac tail length spicule length vms geo.distru reference

…Continued on next page TABLE 5. (Continued) …Continued on next page TABLE 5. (Continued) …Continued on next page TABLE 5. (Continued) …Continued on next page TABLE 5. (Continued) …Continued on next page TABLE 5. (Continued) = Lip region diameter ph. bulb = Pharyngeal bulb

Character Species n L a b c ć V lrd stylet length ph.bulb length anterior ut. sac tail length spicule length vms geo.distru reference

anterior ut. sac = Anterior uterine sac vms = Ventromedian supplements

. distru = Geographical distribution *= Calculated values from illustrations Etymology. The new species is named after Dr. Masaki Araki of the National Institute for Agro- Environmental Sciences, Tsukuba, Japan in recognition of his contribution to Nematology in Japan.

Diagnosis and relationships. Tylencholaimellus masakii sp. n. is characterized by having a small-sized body (L= 0.77–0.81 mm); lip region offset by a slight constriction; labial disc present; odontostyle 1 1–12 µm, odontophore 6–7 µm, combined length 18–18.5 µm; female genital system mono-opisthodelphic; anterior uterine sac 1.1–1.8 midbody diameters long; transverse vulva and rounded-conoid tail.

In the presence of labial disc, slightly offset lip region and anterior uterine sac, the new species comes close to T. projectus Siddiqi, 1964 ; T. ozarkensis Goseco, Ferris & Ferris, 1975 and T. amphidius Dhanam & Jairajpuri, 1999 . However, it differs from T. projectus in having a comparatively smaller odontostyle (11–12 vs 13–14 µm); vulva more anteriorly located (V=28–30.9 vs 32–35%); longer prerectum (50–60 vs 48 µm); longer tail (23–25 vs 21–22 µm) and male absent (vs present).

From T. ozarkensis , the new species differs in having lower a (22.7–24.6 vs 28.7–35.4) and b (4.9–5.2 vs 5.2–6.2) ratios; more anterior vulva (28–30.9 vs 39–41.4%); tail rounded-conoid (vs elongate, rounded) and male absent (vs present).

From T. amphidius , it differs in having cup-shaped amphids (vs bell-shaped with angular and thick walled aperture); shorter odontostyle (11–12 vs 14–15 µm); lower a and c values (a = 22.7–24.6 vs 28–34; c =31–33.8 vs 32–47); shorter pharyngeal bulb (vs 31–32 µm); vulva anteriorly located (vs V=31–35%) and male absent (vs present).

Figures

FIGURE 7. Tylencholaimellus masakii sp. n. A. Entire female; B. Anterior region; C. Anterior end showing amphid; D. Pharyngeal region; E. Pharyngeal bulb; F. Female genital system; G. Female posterior region.

FIGURE 8. Tylencholaimellus masakii sp. n. A & B. Anterior region; C. Anterior end showing amphid; D & E. Pharyngeal bulb; F. Female genital system; G. Vulval region; H. Female posterior region.(Scale bar A–C, G = 10 µm; D–F, H = 20µm)