Metaxonchium persicum, Peña-Santiago, R., Niknam, G., Álvarez-Ortega, S. & Jabbari, H., 2014

Peña-Santiago, R., Niknam, G., Álvarez-Ortega, S. & Jabbari, H., 2014, Metaxonchium persicum sp. n. from Iran (Nematoda, Dorylaimida, Belondiridae), with an updated taxonomy of the genus, Zootaxa 3785 (4), pp. 501-517 : 502-504

Metaxonchium persicum sp. n.

( Figs 1–4 )

Morphometrics. See Table 1 .

Description. Type population from Azarbaijan rangelands (6♀♀ + 3♂♂). Adult: Slender to very slender nematodes of medium to large size, 2.46–3.12 mm long. Body cylindrical, visibly tapering towards the anterior end, less so towards the posterior end since the caudal region is short and conoid. Habitus curved ventrad upon fixation, C- or G-shaped. Cuticle three-layered, consisting of inner layer thicker than the others, especially obvious at caudal region where it bears distinct radial striation, an intermediate and more transparent layer, and a thinner outer layer nearly smooth under LM but bearing very fine transverse striation under SEM; cuticle thickness 2–3 Μm in anterior region, 4–6 Μm at mid-body and 8–15 Μm on dorsal side of tail. Cervical lacunae often clearly visible. Lateral chord comparatively narrow, 5–7 Μm wide or up to one-tenth (7–10%) of mid-body diameter, of granular nature and lacking any other differentiation. Lip region rounded to slightly truncate anteriorly, offset by constriction, 2.2–2.8 times as broad as high or less than one-sixth (11–15%) of body diameter at neck base; lips separate, under SEM appearing conoid, tapering toward the oral aperture, and with deep radial incisures in between; labial and cephalic papillae very low, not interfering the labial contour. Amphid fovea cup-like, its aperture 7–9 µm wide or occupying about four-fifths (75–82%) of lip region diameter. Cheilostom a truncate cone, lacking any differentiation. Odontostyle small, somewhat fusiform, as thick as the cuticle at its level, equal to or hardly longer (1.0–1.2 times) than lip region diameter, 5.8–6.8 times as long as wide and 0.36–0.40% of body length; aperture 3.0–3.5 µm long, occupying one-fourth to one-third (25–35%) of total length. Guiding ring thin, simple but visibly refractive, at 11–14 µm or 0.8–0.9 times the lip region diameter from the anterior end. Odontophore rod-like, 1.8–2.2 times the odontostyle length, bearing a very slight thickening at its approximate midpoint. Pharynx consisting of a slender and weakly muscular anterior portion, which is separated from the basal expansion by a short isthmus-like narrowing, and bearing a well developed, spindle-shaped thickening with valvelike structures, situated at 117–155 Μm from anterior end; basal expansion 13–20 times as long as broad, 7.5–9.9 times longer than body diameter at neck base, and occupying up to three-fourths (68–73%) of total neck length; a very distinct spiral muscular sheath, with nearly straight muscular bands, envelops the whole basal expansion. Cardia tongue-like, 22–25 Μm long x 13–14 Μm wide, surrounded by intestinal tissue. Caudal region conoid with broadly rounded terminus, ventrally straighter, dorsally more convex; caudal pores two pairs at the posterior half of tail, one lateral, another subdorsal.

Female: Genital system monodelphic-opisthodelphic. Anterior branch 117–324 Μm long or 6–11% of body length, and consisting of a long uterine sac often devoid of sperm cells, and a small solid terminal mass probably representing oviduct and/or ovary remnants. Posterior branch very long and impossible to measure as its tract always appears strongly convoluted: reflexed ovary large, 170–370 µm long, with oocytes arranged first in several rows and then in a single row; oviduct joining the ovary subterminally, 135–142 Μm long or 1.4–2.1 body diameters, and consisting of a tubular part made of prismatic cells and a well developed pars dilatata with distinct lumen and occasionally containing sperm cells. A strong sphincter separates oviduct and uterus. Uterus very long and tripartite, i.e., provided with a proximal region with very wide lumen, a convoluted long intermediate region with narrow lumen and containing numerous refractive, irregular elements (apophyses), and a large spherical distal pars dilatata. One female bearing a uterine egg, 145 x 52 µm. Vagina 32–42 µm long, extending inwards about one-half (43–55%) of the corresponding body diameter; pars proximalis longer than wide, 21–24 x 15 –20 Μm, with convergent walls and surrounded by moderately developed, circular musculature; pars refringens (in lateral view) consisting of two trapezoidal pieces measuring 4– 5 x 7–8 µm and with a combined width of 9–11 µm; pars distalis 3–7 Μm long. Vulva a somewhat posterior transverse slit, about 10 µm long. Prerectum 4–10, rectum 1.0–1.4 anal body diameters long. Anus a straight transverse slit about 8 µm long.

Male: Genital system diorchic, with opposite testes. In addition to the adcloacal pair, situated at 15–17 Μm from cloacal aperture, there is a series of 7–10 ventromedian supplements 17–34 Μm apart, the posteriormost of which is situated at 38–50 Μm from the adcloacal pair; hiatus lacking as at least two ventromedian supplements lie within the range of spicules. Spicules dorylaimoid, curved ventrad, relatively slender (7.8–8.3 times as long as wide) and long (1.8–2.2 times the cloacal body diameter), and with a rather narrow anterior part. Lateral guiding pieces 19–20 Μm long, 9–10 six times as long as wide.

Other material examined (9♀♀ from three locations). These nine females are nearly identical to those of type population. They have slightly smaller general size, but largely overlap in their morphometric ranges. In many of these females the pars refringens vaginae is variably developed, often with weaker sclerotization than usual. It is also remarkable that no male has been collected together with the females and that these do not contain sperm cells.

Diagnosis. The new species is characterized by its body length of 2.46–3.12 mm, lip region offset by constriction and 8–11 µm wide, odontostyle fusiform and 10–12 µm long, neck 773–1150 µm long, anterior portion of pharynx bearing a spindle-shaped thickening with valve-like structures inside, both parts of the pharynx separated by a short isthmus-like narrowing, pharyngeal expansion 531–825 µm long and occupying up to threefourths of total neck length, female genital system monodelphic-opisthodelphic, anterior genital branch reduced to a large uterine sac and a small terminal mass, posterior uterus long and tripartite with a intermediate region bearing apophyses, V = 53–57, caudal region conoid with broadly rounded terminus (24–35 µm, c = 79–105, c’ = 0.6–0.9), spicules 93–102 µm long and 7–10 spaced ventromedian supplements, at least two of them within the range of spicules.

Relationships. In having comparatively large general size (body length more than 2 mm), echinophorous uterus (i.e., bearing abundant, refractive, spine-like elements or apophyses) and posterior vulva position (V more than 50), the new species is very similar to M. bihariense ( Popovici, 1990) Andrássy, 1996 , M. giennense Peña- Santiago & Coomans, 1990 and M. paravalvulatum Peña-Santiago & Coomans, 1990 . It differs from M. bihariense in its wider lip region (8–11 vs 7–8 µm, n= 14 in Romanian material), longer neck (773–1000 vs 600–775 µm; b = 2.8–3.4 vs b = 3.2–4.0), presence of a valvate swelling at the anterior section of pharynx (vs absent or overlooked), an isthmus-like narrowing separating both pharyngeal sections (vs apparently no special differentiation marking this separation), pars refringens vaginae readily perceptible (vs weakly sclerotized if present), and male known (vs unknown). From M. giennense in the presence (vs absence) of valves at the spindle-shaped swelling in the anterior slender portion of pharynx, larger spicules (93–102 vs 71–87 µm long, n=9), and lower number of ventromedian supplements (7–10 vs 10–14) with different arrangement (two vs at least three of them within the spicules range, with the last two somewhat shifted from the midventral position, one on the left, the other on the right in M. giennense ). And from M. paravalvulatum in its longer male tail (37–43 vs 30 µm), larger spicules (93–102 vs 71 µm long) with different shape (more slender and having a long slender anterior part vs more robust and lacking an especially narrow anterior part), and lower number of ventromedian supplements (7–10 vs 11) with different arrangement (two vs only one distinctly lying within the range of spicules).

Type locality and habitat. The new species was collected from northwest Iran, Mahmood Abad region, East Azarbaijan province (GPS coordinates: N 38° 48′ 43.5 E 46° 51 59.6″), in Arasbaran rangelands, during 2012.

Other localities and habitats. Dolat Abad district, Marand, in an orchard with fruit trees; Ass district, Arasbaran, in a natural pasture; and Hervi district, around Tabriz, in an orchard with fruit trees.

Type material. Female holotype, two female and two male paratypes deposited in the Collection of Nematology Lab., University of Tabriz, Tabriz, Iran. Two female and one male paratypes deposited in the Nematode Collection of the University of Jaén, Spain.

Etymology. The specific epithet refers to the geographical origin of this species in Persia, the former name of Iran.

Remarks. Metaxonchium persicum sp. n. is morphometrically very similar to M. giennense and M. paravalvulatum , making the identification of their respective females especially problematic. Nevertheless, the morphology of the spicules and the number and arrangement of the ventromedian supplements seem to be sufficiently different to support a provisionally separate status for these three species.

Holotype Paratypes

Character n ♀ 5♀♀ 3♂♂ 4♀♀ 4♀♀ ♀ 15♀♀

Figures

FIGURE 1. Metaxonchium persicum sp. n. A: Anterior region in median lateral view. B: Lip region in lateral, surface view. C: Detail of spindle-shaped thickening at the anterior portion of pharynx. D: Vagina. E: Detail of the uterus showing apophyses. F: Female, Genital system. G: Isthmus-like junction of both pharyngeal sections. H: Neck. I: Pharyngo-intestinal junction. J: Female, entire body. K: Male, posterior body region. L: Female, caudal region. M: Spicule and lateral guiding piece.

FIGURE 2. Metaxonchium persicum sp. n. (Female, LM). A: Entire. B: Anterior region in lateral median view. C: Slender portion of pharynx, showing the spindle-shaped thickening. D: Detail of spindle-shaped thickening at the anterior portion of pharynx. E: Genital system. F: Detail of the uterus showing apophyses. G: Isthmus-like junction of both pharyngeal sections. H: Vagina. I: Vagina and tripartite uterus. J: Caudal region. K: Pharyngo-intestinal junction. (Scale bars: A = 500 µm; B, F, G, J, K = 20 µm; C, I = 50 µm; D, H = 10 µm; E = 100 µm.)

FIGURE 3. Metaxonchium persicum sp. n. (Male, LM). A: Entire. B-D: Posterior body region showing the location of ventromedian supplements. E: Detail of three ventromedian supplements. F, G: Spicules. H: Caudal region. (Scale bars: A = 500 µm; B = 100 µm; C, D = 50 µm; E-H = 20 µm.)

FIGURE 4. Metaxonchium persicum sp. n. (Female, SEM). A: Lip region in frontal view. B: Vulva in ventral view. C: Caudal region in latero-ventral view. (Scale bars: A = 2 µm; B, C = 5 µm.)