Labrys khuzestanensis, Panahandeh & Pourjam & Abolafia & Roshan-Bakhsh & Mojerlou & Afshar & Pedram, 2019

Panahandeh, Yousef, Pourjam, Ebrahim, Abolafia, Joaquín, Roshan-Bakhsh, Ali, Mojerlou, Shideh, Afshar, Farahnaz Jahanshahi & Pedram, Majid, 2019, Labrys khuzestanensis n. sp. (Nematoda, Tylenchidae), a new member of the genus with large labial plate, Zootaxa 4671 (2), pp. 267-276 : 268-272

Labrys khuzestanensis n. sp.

( Figs 1–3 )

Measurements: see Table 1 .

Female: Body straight to slightly ventrally arcuate after heat relaxation. Cuticle finely annulated, annulus ca 1 μm wide at midbody. Lateral field distinct, having two incisures with smooth margins under SEM. Cephalic region smooth, continuous with the adjacent part of body, 4.5 μm wide and 2.1–2.3 μm high, trapezoid under LM, dorsoventrally flattened, with protuberant large and elongate labial plate under SEM. The plate is laterally extended and dorso-ventrally not constricted. In lateral view under LM, the plate seems as a V-shaped piece ( Fig. 2D ; hardly visible due to small size). The oral plate small, laterally elongate, containing labial sensillae, with small and elevated oral opening at the center. Amphidial openings as longitudinal slits, beginning near oral plate, laterally extending to the labial plate corners and confined to it. Stylet delicate, slender, conus shorter than the shaft, comprising ca 33% of its total length, the knobs rounded and small, slightly posteriorly sloping. Dorsal pharyngeal gland orifice (DGO) 1–2 μm from the base of the stylet. Procorpus slender, median bulb moderately developed, elongate fusiform with small valvular apparatus, isthmus narrow, slender, pharyngeal bulb small, pyriform and offset. Cardia small, domeshaped. Nerve ring encircling anterior part of isthmus, 57 to 76 μm from anterior end. Excretory pore wide with sclerotized duct, at the distance between the nerve ring and anterior part of pharyngeal bulb. Reproductive system monodelphic-prodelphic, composed of an outstretched ovary occupying 13–15% of total body length, the oocytes mostly arranged in single row. The border of oviduct, spermatheca and the cell arrangement of crustaformeria indistinct. Vagina with thin wall, perpendicular to body axis and straight or slightly anteriorly sloping. Postvulval uterine sac (PUS) ca 0.6 to 1.0 times corresponding body diameter long. Vulva a small transverse slit with very small lateral flaps. Tail elongate filiform, very gradually narrowing toward end, 1.9 to 3.0 times longer than vulva–anus distance, with finely rounded tip.

Male: Unknown.

Type habitat and locality. The rhizospheric soil of a palm tree ( Phoenix dactylifera L.) in city of Ahvaz, Khuzestan province, southwestern Iran, collected during 2016. GPS coordinates: 31°28.582′N, 48°37.394′E .

Etymology. The specific epithet refers to Khuzestan province, the original geographic point of which the new species was recovered from.

Type material. Holotype female and four paratype females were deposited at Nematode Collection of the Faculty of Agriculture , Tarbiat Modares University , Tehran, Iran (the slide code: TM5043 ). Three paratype females were deposited at Ghent University Museum , Zoology Collections , Ghent , Belgium ( UGMD _104411 and UGMD _ 104412). Two paratype females were deposited at the Nematode Collection of the Department of Animal Biology , Plant Biology and Ecology of the University of Jaén , Jaén, Spain) (Collection ID: Iran 011) (one paratype female was used to prepare SEM photos).

Diagnosis and relationships. Labrys khuzestanensis n. sp. is mainly characterized by large and prominent labial plate as revealed by SEM and trapezoid cephalic region under LM. It is further characterized by 590–675 μm long females having a finely annulated cuticle under LM, lateral field with two incisures, cephalic region dorsoventrally flattened and smooth, labial plate not constricted at middle, elongate, laterally extending and appearing as V-shaped piece in lateral view, amphidial openings long slits confined to the labial plate, stylet 7.5–9.0 μm long, median bulb elongate fusiform with small valvular apparatus, excretory pore wide, with sclerotized duct and tail elongate filiform with finely rounded tip.

Compared to four currently known species of the genus, the new species has a remarkably large and prominent labial plate and trapezoid cephalic region under LM (vs. rounded). The detailed morphological comparisons of the new species with Labrys members are as follows:

From L. chinensis Qing & Bert, 2018 by distinctly annulated cuticle under LM (vs. smooth), greater a ratio (53.6– 74.8 vs. 37.7–48.7), lower c ratio (2.6–3.2 vs. 3.5–4.4), greater cʹ ratio (23.5–32.9 vs. 13.3–20.3), more anteriorly located vulva (V = 48.0–54.3 vs. 54–60), greater tail length/vulva to anus distance ratio (1.9–3.0 vs. 1.3–1.7), longer tail (188–237 vs. 132–171 μm) and difference in tail end morphology (finely rounded tip vs. broadly rounded).

From L. fujianensis Qiao, Bai, Wang, Hou, Chen, Xiao, Liu, Bert & Qing, 2019a by laterally elongate oral plate (vs. dorsoventrally, after its SEM data) and slightly longer body (590–675 vs. 524–599 μm).

From L. filiformis Panahandeh, Abolafia, Pourjam, Jahanshahi Afshar, Giblin-Davis & Pedram, 2018 by its distinct annulated cuticle under LM (vs. smooth), longer body (590–675 vs. 425–463 μm), greater a ratio (53.6–74.8 vs. 38.7–46.2), greater b ratio (5.7–7.4 vs. 4.9–5.7), lower c ratio (2.6–3.2 vs. 3.5–4.0), greater cʹ ratio (23.5– 32.9 vs. 13.2–15.9), more anteriorly located vulva (V = 48.0–54.3 vs. 57.7–61.5), lower Uʹ ratio (74.6–79.8 vs. 79.9–84.1) and longer tail (188–237 vs. 106–127 μm).

From L. fuzhouensis Qiao, Bai, He, Chen, Xiao, Cheng, Liu, Braun-Miyara & Qing, 2019b by longer body (590–675 vs. 495–564 μm), greater a ratio (53.6–74.8 vs. 40.6–53.1), longer neck (86–108 vs. 72–80 μm) and lacking male (vs. present).

Phylogenetic analyses. To study of the phylogenetic affinities of the new species with other genera/species of the family Tylenchidae , its partial SSU rDNA was used in corresponding phylogenetic analysis. A total number of 75 species/isolates (including the newly obtained SSU sequence of the new species and three aphelenchid+a phelenchoidid outgroups) were selected for these analyses (Bayesian inference and ML trees). The alignment of SSU dataset had 1824 total characters with 981 variable characters. The average nucleotide composition was as follows: 24.5% A, 22.9% C, 28.3% G, and 24.3% T. Figure 4 represents the Bayesian phylogenetic tree inferred using the abovementioned dataset. In this tree, the new species and three previously described species viz. Labrys chinensis ( KY776630 , KY776631 , KY776632 , KY776633 ), L. fuzhouensis ( MK039731 , MK039732 ), and L. filiformis ( MG686086 ) formed a clade and Discotylencus lorestanensis Mehrabian, Azizi, Bazgir & Darvishnia, 2017 ( KU878152 , KU878153 ) is the closest taxon to these species. The other species of Labrys , L. fujianensis occupied a distant placement to them.

Figures

FIGURE 1. Labrys khuzestanensis n. sp. (line drawing, female). A: Entire body; B: Anterior region; C: Amphidial opening; D, E: Neck (stoma + pharynx); F: Cuticular annuli at mid-body; G: Reproductive system; H, I: Tail.

FIGURE 2. Labrys khuzestanensis n. sp. (light microscopy, female). A: Pharyngeal region; B: Reproductive system; C: Part of neck; D: Anterior region; E: Amphidial opening; F: Cuticular annuli at mid-body; G: Distal part of tail showing its tip; H: Excretory pore; I: Vulva region. All scale bars =10 µm.

FIGURE 3. Labrys khuzestanensis n. sp. (scanning electron microscopy, female). A: Anterior region; B–D: Cephalic region in dorsal, lateral and frontal views, respectively; E, I: Excretory pore in ventral and sublateral view, respectively; F: Tail; G, H: Vulva in ventral and lateral view, respectively; J: Lateral field; K: Cuticular annuli at mid-body; L: Anus.

FIGURE 4. Bayesian 50% majority rule consensus tree inferred using SSU rDNA of Labrys khuzestanensis n. sp. under the GTR+G+I model. Bayesian posterior probabilities and maximum likelihood bootstrap values are given for appropriate clades in the shape BPP/ML BS. The newly obtained sequence is in bold font.