Doryllium enigmatum, Ahmad & Ahad & Islam & Sturhan, 2018

Ahmad, Wasim, Ahad, Sumaya, Islam, Md. Niraul & Sturhan, Dieter, 2018, Taxonomy of the genus Doryllium Cobb, 1920 (Nematoda: Dorylaimida) with description of two new and a known species, Zootaxa 4441 (2), pp. 261-278 : 267-270

Doryllium enigmatum sp. n.

( Figs. 4 & 5 )

Material examined. Fourteen females in good state of preservation.

Description. Measurements, see Table 2

Female: Small sized nematodes, slightly curved upon fixation; body cylindrical tapering gradually towards both the extremities. Cuticle with two distinct layers, 3–4 µm thick at midbody and 4–5 µm on tail. Outer cuticle finely striated; inner layer smooth. Lateral chords occupying about one-fourth to one-third of the midbody diameter. Lateral, dorsal and ventral body pores indistinct. Lip region continuous, 1.6–2.0 times as wide as high or about one-third of the body diameter at neck base; lips rounded, amalgamated; papillae barely raised. Amphids cup-shaped, their aperture occupying about one-half of lip region diameter. Stoma a truncate cone. Odontostyle asymmetrical, 0.8–1.0 times the lip region diameter in length, with distinct lumen and aperture. Odontophore flanged, 1.8–2.1 times the odontostyle length. Guiding ring simple, refractive, at 0.6 times lip region diameter from anterior end. Pharynx consists of a slender and weakly muscular anterior part, expanding into a slightly constricted pyriform basal bulb, occupying about 16–18% of total neck length. Cardia rounded-conoid, about one-third of the corresponding body diameter long. Nerve ring located at 54–57% of neck length from anterior end.Genital system mono-opisthodelphic. Ovary reflexed, measuring 51–78 µm long, reaching the oviduct-uterus junction (surpassing the oviduct-uterus junction in one specimen); oocytes arranged in single row except near tip. Oviduct joining the ovary subterminally, measuring 65–76 µm, proximal and distal parts not differentiated. Oviduct-uterus junction marked by weak sphincter. Uterus short and tubular, measuring 15–20 µm long.Anterior genital branch small, 0.3– 0.5 times midbody diameter long.Vagina cylindrical; pars proximalis vaginae 5–6 µm long, wall encircled by muscles; pars distalis vaginae short, 3–4 µm long with slightly curved walls; pars refringens absent. Vulva a transverse slit.Prerectum 2.3–2.5 and rectum 0.9–1.2 anal body diameters long. Tail rounded-hemispheroid, 1.2– 1.5 anal body diameters long.

Male: Not found.

Type habitat and locality. Meadow soil, Nienhagen near Kassel, Germany; collected by Dr. Dieter Sturhan on 29.05.1985. GPS Coordinates 51°18'46'' N and 9°28'53'' E.

Type specimens. Holotype female on slide Doryllium enigmatum sp. n. / 1; paratype females on slides Doryllium enigmatum sp. n. / 2–8; deposited with the nematode collection of the Department of Zoology, Aligarh Muslim University, India and on slide Doryllium enigmatum sp. n. / 9; deposited with the German nematode collection.

Etymology. The new species is named D. enigmatum because of its unusual asymmetrical odontostyle and flanged odontophore, which is unique for Doryllium .

Diagnosis and relationships. Doryllium enigmatum sp. n. is characterized by a body length of 0.40–0.52 mm; continuous lip region; rounded lips; asymmetrical odontostyle, 5–6 µm long, flanged odontophore 9–11 µm long (total spear length: 14–17 µm); pharynx with slender anterior part, which expands into a slightly constricted pyriform basal bulb occupying about 16–18% of total neck length; mono-opisthodelphic female genital system, anterior uterine sac 7–9 µm; transverse vulva and rounded-hemispheroidtail.

The new species is distinctive because of its asymmetrical odontostyle which is unusual for a Doyllium species.

In the shape of its lip region and nature of pharyngeal expansion, the new species comes close to D. uniforme Cobb, 1920 but differs in its smaller body size (vs L = 0.78–0.85 mm); more posterior vulva position (vs V= 33– 35); very short anterior uterine sac (vs anterior uterine branch 32 µm); comparatively shorter tail (c= 24–32 vs 38– 41) and in the absence of males (vs present).

D. aestuarii Timm, 1967 also has a continuous lip region and constricted pharyngeal bulb but the new species distinctly differs from it in being smaller in size (vs L= 0.96–1.13 mm); having a more posterior vulva position (vs V= 23.7–24.7) and in tail shape (vs tail bluntly conoid).

In its body size, lip region shape and nature of the anterior uterine sac, the new species is very close to D. jamesi Goseco, Ferris & Ferris, 1975 but differs in having an asymmetrical odontostyle (vs symmetrical); slightly constricted pharyngeal bulb (vs not constricted) and longer tail (vs tail 7–9 µm). The new species is also close to D. flangum Thorne, 1964 but differs in its asymmetrical odontostyle and shorter odontophore (vs odontostyle symmetrical and odontophore three times odontostyle length); slightly constricted pharyngeal bulb (vs not constricted) and in the presence of the short anterior uterine sac (vs anterior uterine sac completely absent).

Figures

FIGURE 4. Dorylllium enigmatum 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 5. Doryllium enigmatum sp. n. A. Anterior region; B. Anterior region showing basal flanges; C. Anterior end showing amphid; D. & E. Pharyngeal bulb; F. Female genital system; G, H, I. Female posterior region. (Scale bar A–E, H, I= 10 µm; F, G = 20 µm).