Stegelletina lingulata, Abolafia & Shokoohi, 2017

Abolafia, Joaquín & Shokoohi, Ebrahim, 2017, Description of Stegelletina lingulata sp. n. (Nematoda, Rhabditida, Cephalobidae) from xeric environments in Iran, Zootaxa 4358 (3) : -

Stegelletina lingulata sp. n.

= Zeldia spannata apud Mehdizadeh & Shookohi (2013), nec Waceke et al. (2005). ( Figs 1–3 )

Material examined. Five females and two males.

Type locality and habitat. Gharyatolarab (province of Kerman, Iran; 29°54'23.6"N, 56°58'24.2"E), collected in the rhizosphere of Haloxylon persicum Bunge ex Boiss. & Buhse.

Type material. One female (holotype) deposited in the Departamento de Biología Animal , Biología Vegetal y Ecología, Universidad de Jaén, Spain ; four females and two males (paratypes) deposited in the Nematology Laboratory (Plant Protection Department, Shahid Bahonar University of Kerman, Iran) .

Morphometrics. See Table 1.

Description. Adult: Small body, 0.50–0.69 mm long, habitus curved ventrad after fixation. Cuticle annulated by transverse incisures, slightly tessellated in the anterior end, more pronounced near the lip region; annuli 2.5–4.0 mm wide. Lateral field with two alae or three longitudinal incisures, occupying 17% of midbody diameter, fading out to tail terminus; on each side, the cuticle appears longitudinally slightly elevated, resembling a further two alae when observed under light microscope. Lips six, grouped in pairs, bearing six labial and four cephalic papillae; primary axils deep, U-shaped, bearing one triangular guard process; secondary axils V-shaped, bearing four tines per lip, one elongate triangular close to the primary axil followed by one rounded and two short triangular. Amphids rounded. Three labial probolae snake-tongue-like, bifurcated at about half of their length, lacking tines; base straight and smooth, lacking adaxial expansions or ridges; prongs curved toward each other. Stoma cephaloboid; cheilostom short, with well-developed oval rhabdia; gymnostom very reduced; stegostom robust, slightly longer than the lip region width. Pharynx cephaloboid; pharyngeal corpus cylindrical, 2.7–3.6 times isthmus length, with metacorpus one third of the corpus length, narrower towards the isthmus; isthmus narrow; basal bulb pyriform. Cardia conoid, surrounded by intestinal tissue. Intestine without differentiation, continuing from the cardiac area with narrower walls. Nerve ring at 62–79% of neck length, anteriorly surrounding the isthmus. Excretory pore at isthmus level: 68–87% of neck length or 33–34 annuli from anterior end. Deirid at basal bulb level: 80–99% of neck length or 40–41 annuli from anterior end.

Female: Reproductive system monodelphic-prodelphic, dextral; ovary straight; oviduct very short; spermatheca 1.1–1.4 times the corresponding body diameter in length; uterus c.a. 2.0–2.5 times the corresponding body diameter, with a long tubular distal part and a swollen proximal part with thinner walls; post-vulval sac 0.9– 1.2 times the corresponding body diameter long; vagina extending inwards one third of the body diameter. Rectum 0.6–0.8 times anal body diameter, with three rectal glands. Tail conical with rounded terminus, with 14–15 ventral annuli. Phasmid at 32–48% of tail length.

Male: Reproductive system monorchic, anteriorly testis reflexed ventrally. Tail conical, distally curved ventrad, with rounded tip. Genital papillae three pairs pre-cloacal and five pairs post-cloacal, comprising: one subventral pair at mid-tail, one lateral pair, one dorsal pair near the posterior end, and two pairs near the tail terminus. Spicules almost straight and slightly ventrally curved at distal part, with straight manubrium and slender, conoid calamus with dorsal hump, and lamina distally curved, having a ventral anteriorly expanded wing. Gubernaculum slightly curved ventrally.

Remarks. Mehdizadeh & Shokoohi (2013) described this species as Zeldia spannata , misinterpreting the nature of its lateral field as apparently having five longitudinal incisures as observed under LM. Molecular analysis provided by Mehdizadeh et al. (2013) with one specimen of this Iranian material (GenBank accession number KC509906 ) shows that this species is not closely related to members of the genus Zeldia Thorne, 1937 . SEM study reveals the presence of only three longitudinal incisures plus another two accessory lateral lines (“pseudolines”) created by the fold of the cuticle at its edges. In addition, the absence of an adaxial basal ridge on the labial probolae refers this material to the genus Stegelletina and not to other related genera such as Chiloplacus Thorne, 1937 and Zeldia .

Locality Gharyatolarab

Province Kerman

Habitat Haloxylon persicum Diagnosis. Stegelletina lingulata sp. n. is characterized by its small body (0.51–0.69 mm long in females and 0.45–0.64 mm long in males), cuticle slightly tessellated especially at anterior end, lateral field with three longitudinal incisures, lips with long acute processes at primary axils and three more dentate processes at secondary axils, primary axils with one triangular axillar guard process and secondary axils lacking axillar processes, labial probolae 9–11 µm long, with slender peduncle lacking adaxial expansion and with convergent smooth prongs, stoma, pharynx and reproductive systems cephaloboid, excretory pore at isthmus level, spermatheca 1.1–1.4 times, and post-vulval sac 0.9–1.2 times the corresponding body diameters in length, female rectum 0.6–0.8 times anal body diameter long, female tail conoid (35–47 µm long, c = 14.0–15.6, c' = 2.1–2.7) with fine rounded terminus, male tail conoid, curved ventrad (53–59 µm long, c = 11.0–12.0, c' = 1.9–2.5) with rounded terminus, spicules 31–33 µm long with ventrally straight manubrium, and gubernaculum 14–17 µm long.

Relationship. The new species resembles S. argentinica ( Andrássy, 1963) Andrássy, 1984 and S. coprophila Abolafia & Peña-Santiago, 2006 in having acute primary axils (see Fig. 5). However, it can be distinguished from S. argentinica by having a weakly tessellated cuticle, more developed at anterior end (vs well developed along the entire body), primary axils with very long acute tips (vs very short), labial probolae with convergent curved prongs (vs T-shaped prongs). It differs from S. coprophila by having longer labial probolae (9–11 µm vs 4–6 µm long), excretory pore at isthmus level (vs at basal bulb level), longer post-vulval sac (as long as the corresponding body diameter vs ca. a half of the body diameter), spicules with manubrium having its ventral side straight (vs slightly ventrally curved).

On the other hand, it also resembles Chiloplacus tauricus Holovachov & Boström, 2010 and Zeldia spannata Waceke, Bumbarger, Mundo-Ocampo, Subbotin & Baldwin, 2005 in the general morphology of the lip region, distinguished from both species by lacking a basal ridge on the labial probolae (vs bearing small basal ridge), and lateral field with two alae (vs four).

Etymology. The specific name (Latin word meaning "bearing tongues") refers to the particular morphology of the labial probolae resembling a snake’s tongue.

Figures

FIGURE 1. Stegelletina lingulata sp. n. A: Neck. B: Lip region. C: Female reproductive system. D: Entire female. E: Entire male. F: Female posterior end.G: Male posterior end. H:Lateral field.

FIGURE 2. Stegelletina lingulata sp. n. (light microscopy). A: Neck. B, C, E: Lip region (I = primary axil, II = secondary axil). D: Anterior end. F: Cuticle showing the slightly tessellated surface. G, H: Lateral field at deirid (arrow) and midbody levels, respectively. I: Femaleposterior end (arrow points the phasmid). J: Male posterior end.

FIGURE3. Stegelletina lingulatasp. n. (juvenile, scanning electron microscopy). A: Anterior end.B–E: Lip region in frontal, dorsal, ventral and lateral views, respectively. F: Cuticle. G, H: Posterior end in left lateral and ventral views, respectively. I. Lateral field.