Eudorylaimus kahaqensis, Kazemi & Niknam & Jabbari & Peña-Santiago, 2018

Kazemi, E., Niknam, G., Jabbari, H. & Peña-Santiago, R., 2018, Eudorylaimus kahaqensis sp. n. (Nematoda: Dorylaimida: Qudsianematidae), an interesting new species from Iran, Zootaxa 4369 (1), pp. 128-136 : 129-135

Eudorylaimus kahaqensis sp. n.

( Figs 1–6 )

Material examined: Twenty females, twelve males and several juveniles, in acceptable (mostly good) condition. Measurements: See Table 1.

Description. Adult: Slender nematodes (a = 29–39) of medium size, 1.40–1.75 mm long. Body cylindrical, tapering towards both ends as the tail is conical. Habitus regularly curved ventrad, an open ‘C’ or ‘J’ shape in females, ‘J’ or ‘G’ shaped in males. Cuticle 2.0–2.5 µm thick in the anterior region, 2.0–3.5 µm at mid-body and 3.0–4.0 µm on tail; outer layer with fine transverse striation throughout the body, perceptible even under LM; inner layer thicker than the outer one, especially visible at caudal region. Lip region anteriorly truncate, nearly continuous with the adjacent body, 2.8–3.2 times as wide as high, and ca one half (45–50%) of body diameter at neck base; anterior margin visibly corrugated or wrinkled. SEM observations: lips totally amalgamated; labial and cephalic papillae distinct but weakly protruding, button-like; oral field broad, with coarse radial striation—visibly stronger than the transverse striation of the adjacent body, and responsible for the corrugated anterior marginrunning from the oral aperture to the posterior margin of lip region; oral aperture apparently small. A moderately sclerotized but perceptible cephalic framework is present. Amphidial fovea stirrup-shaped, aperture a transverse slit 9–11 µm wide and occupying ca one-half (50–56%) of lip region diameter. Cheilostom wider than usual, with convex walls. Odontostyle equal to lip region diameter long, comparatively slender (9–12 times as long as wide), 1.1–1.3% of total body length, and with aperture 6–8 µm long or occupying less than one-half (33–44%) of total length. Guiding ring simple, somewhat plicate, and located at 8–11 µm or 0.4–0.5 times the lip region diameter from the anterior end. Odontophore rod-like, 1.7–2.0 times the odontostyle in length, its junction with the pharyngeal lining rather inconspicuous. Anterior portion of pharynx slender but muscular, enlarging very gradually into the basal expansion that is 7.4–9.0 times as long as wide, 4.0–4.6 times as long as the body diameter at neck base and occupies 45–53% of total neck length; gland nuclei located as follows: DO = 60–66, DN = 66–70, S1N1 = 78–83, S1N2 = 82–88, S2N = 90–94, S2O = 94; DN remarkably posterior in position, far from pharyngeal enlargement, S1N1 conspicuously longer than wide, with its nucleolus much larger than that of S1N2 and even slightly larger than those of S2N, and S2O visibly behind S 2N. Nerve ring at 128–145 µm or 35–37% of the neck length from the anterior end. One coelomocyte 7.5– 13 x 5.5–10.0 µm is present in dorsal position in all the specimens examined a short distance behind the nerve ring, at 145–162 µm from the anterior end. Cardia cylindroid, 13.5–19.0 x 7.0–8.5 µm. A dorsal cell mass is always present at the pharyngo-intestinal junction. Intestine without any special differentiation.

Female: Genital system didelphic-amphidelphic, with both branches of similar morphology and length, the anterior 192–264 µm or 11–14% of total body length, the posterior 182–273 µm or 12–14% of total body length. Ovaries reflexed, 77–101 µm long, not reaching the oviduct-uterus junction; oocytes in several rows in the germinative zone, then in one row. Oviduct 84–120 µm or 2.0–2.8 times the corresponding body diameter long, consisting of a slender portion made of prismatic cells and an appreciably longer than wide pars dilatata with visible lumen and often containing sperm cells. A marked narrowing surrounded by a weak muscular ring is present separating oviduct and uterus. Uterus a simple tube-like structure 62–125 µm or 1.5–2.3 times the corresponding body diameter long, often containing sperm cells as well. Vagina 26–33 µm long, extending to 63– 70% of body diameter: pars proximalis 18–24 x 16 –22 µm, with somewhat sigmoid walls and surrounded by moderately developed musculature; pars refringens consisting of two trapezoidal pieces 3.0–3.5 x 7.0–7.5 µm and a combined width of 15–18 µm; pars distalis 5.5–6.5 µm long. One gland cell (granular in appearance) is present close the vagina both anteriorly and posteriorly. Vulva a transverse slit. Intestine-prerectum junction especially granular and colored in all the specimens examined. Prerectum 1.4–1.6, rectum 1.1–1.2 times the anal body diameter in length. Caudal region regularly curved ventrad and conical (somewhat) elongate with finely rounded tip; hyaline portion well developed, 17–30 µm or 28–45% of the total tail length.

Male: Genital system diorchic, with opposite testes. In addition to the ad-cloacal pair situated at 11–15 µm from the cloacal aperture, there is a series of 7–9 irregularly spaced (12–15 µm apart), ventromedian supplements, the most posterior of which is located at 22–28 µm from the ad-cloacal pair, at the level of or a short distance behind the anterior end of spicules. A distinct pre-cloacal space (hiatus) is therefore not present. Spicules dorylaimid, 1.7–1.9 times longer than the body diameter at level of cloacal aperture, 3.9–4.2 times longer than wide, and curved ventrad 124–130º; head 12–16 µm long, occupying 23–30% of total spicule length, 2.0–2.3 times as long as wide, with its dorsal side distinctly longer than the ventral one and slightly curved; median piece 35–41 µm long, 6.4–7.6 times longer than wide, occupying 37–46% of spicule width, and reaching the spicule posterior tip. Lateral guiding piece 13–17 µm long, 5.2–6.8 times longer than wide, with slightly bifid end. Prerectum 1.8– 2.5, cloaca 1.4–1.7 times the body diameter at level of cloacal aperture. Caudal region similar to that of female, its hyaline portion 22–25 (11.5 in one specimen, probably aberrant) µm long, occupying 39–40 (26)% of total tail length.

Diagnosis. The new species is characterized by its 1.40–1.75 mm long body, lip region nearly continuous and 17–21 µm wide and bearing a weakly sclerotized but distinct cephalic framework, cheilostom broad and with convex walls, odontostyle 21–23 µm long with aperture occupying 33–44% of its length, presence of a dorsal coelomocyte a short distance behind the nerve ring, neck 347–397 µm long, DN rather posterior (66–70%), pharyngeal expansion 162–205 µm or occupying 45–53% of total neck length, presence a dorsal cell mass at level of pharyngo-intestinal junction, V = 48–52, caudal region conical (somewhat) elongate (50–73 µm, c = 24–30, c’ = 1.9–2.6 in females, 45–68 µm, c = 22–32, c’ = 1.7–2.3 in males) and regularly curved ventrad with large hyaline portion, spicules 48–55 µm long and 7–9 irregularly spaced ventromedian supplements lacking hiatus.

Relationships. Eudorylaimus kahaqensis sp. n. is easily recognizable by an unusual combination of features, but its conical, somewhat elongate, caudal region in both sexes and the position of its most posterior ventromedian supplement at the level of the anterior end of the spicules and not too far anterior to the pre-cloacal pair (i. e., lacking a distinct hiatus) raise doubts about its true generic identity (see further discussion below), since it possesses characteristics of the genera Eudorylaimus Andrássy, 1959 , Allodorylaimus Andrássy, 1986 and Epidorylaimus Andrássy, 1986 .

Within Eudorylaimus , it resembles several species (some without known males), in particular E. altherri Tjepkema et al., (1971) , E. nudicaudatus Heyns, 1993 and E. unicus Khan & Araki, 2000 . It differs from E. altherri in its nearly continuous (vs offset by constriction and visibly wider than the adjacent body) lip region, longer odontostyle (21–23 vs 19.3 ± 1.2 µm), shorter female prerectum (43–50 vs 90 ± 22 µm), pars refringens vaginae with trapezoidal (vs triangular) pieces, and male as frequent as female (vs male absent). From E. nudicaudatus , it differs in its nearly continuous (vs offset by constriction) lip region, longer odontostyle (21–23 vs 13–15 µm, equal to vs distinctly shorter than lip region diameter), more posterior vulva (V = 48–52 vs V = 43–48), comparatively longer female tail (c = 24–30 vs c = 32–46) with long (vs very short) hyaline portion, and male lacking (vs having) hiatus. It can be distinguished from E. unicus by its nearly continuous (vs offset by constriction) lip region, more posterior DN (vs close the pharyngeal expansion), longer vagina (extending to 63–70% vs up to one-half of body diameter), longer female tail (c’ = 1.9–2.6 vs c’ = 1.6–1.8) with different morphology (ending in a finely rounded vs relatively coarse tip), and male present (vs absent). The new species also resembles E. rugosus ( Andrássy, 1957) Andrássy, 1959 in several aspects (general morphology and morphometry, lip region nearly truncate and visibly slender odontostyle) but differs in its longer tail (c = 24–30, c’ = 1.9–2.6 vs c = 30–33, c’ = 1.5–1.6). It can also be compared to E. pseudobokori Zell, 1986 in its general morphology and morphometry as well its comparatively long caudal region, but can be distinguished by the morphology of lip region (truncate and continuous vs angular and offset) and odontostyle (slender vs more robust), and the number (7–9 vs 5) and arrangement of ventromedian supplements (most posterior of them at level of or slightly posterior to vs visibly anterior to the end of spicules).

In lacking a distinct precloacal space in males, the new species also resembles members of Allodorylaimus , especially A. aljabaranus Quijano et al., (1991) and A. digiturus ( Thorne, 1939) Andrássy, 1986 . It differs from A. aljabaranus in its broader (17.0–21 vs 14–16 µm) and amalgamated (vs lips separated and angular) lip region, and fewer ventromedian supplements (7–9 vs 10–15) with different arrangement (only the most posterior ventromedian supplement located at the level of the anterior end of the spicules or a short distance posterior vs two or three ventromedian supplements well within the range of the spicules). From A. digiturus , a poorly known species described on the basis of only one male, it differs in its larger general size (body length 1.40–1.75 vs 1.30 mm), broader lip region (17.0–21 vs ca 12 µm), longer (21–23 vs ca 12 µm) and more slender (9–12 vs ca 6 times as long as wide) odontostyle, and fewer ventromedian supplements (7–9 vs 11) with different arrangement (only the most posterior ventromedian supplement located at the level of the anterior end of the spicules or a short distance behind it vs two ventromedian supplements well within the range of the spicules).

In its general morphology, and in particular in its comparatively long tail in both females and males, and males lacking hiatus, the new species resembles some Epidorylaimus representatives (see the updated diagnosis and compendium by Ahmad et al., 2016), especially E. consobrinus (de Man, 1880) Andrássy, 1986 and E. filicaudatus ( Tjepkema et al., 1971) Andrássy, 1986 . The new species differs from E. consobrinus , a poorly characterized species, in its weakly (vs distinctly) angular lip region, and shorter caudal region (c’ = 1.9–2.6 vs c’ = 2.7–4.3 in females) with different morphology (with finely rounded vs acute tip, large vs no hyaline portion). It can be distinguished from E. filicaudatus by having weakly (vs distinctly) angular lip region, more attenuated odontostyle (9–12 vs up to 7 times as long as wide), shorter caudal region (50–73 vs 81–123 µm), and frequent males (vs male unknown).

Finally, some traits (continuous lip region, broad cheilostom) of the new species resemble those found in species of the genus Chrysonema Thorne, 1929, but it does not fit at all the very peculiar morphological pattern of this taxon (see Andrássy, 2009), which is characterized by, among other diagnostic features, a very slender body (a - ratio very usually over 50), comparatively small and attenuate odontostyle, absence of pars refringens vaginae, tail conical elongate (c’> 4), tapering very gradually, and male bearing subventral caudal papillae.

Type locality and habitat. The new species has been collected from Iran, East Azarbaijan province, north of Maragheh, Kahaq region (GPS coordinate 47º13´35.7´´E, 37º28´12.1´´ N), where it was found in the rhizosphere soil of walnut, spruce and willow.

Type material. Female holotype, 10 female and eight male paratypes deposited in the Nematode Collection of Nematology Laboratory, Department of Plant Protection, Faculty of Agriculture, University of Tabriz, Tabriz, Iran. Two female and two male paratypes with the Nematode Collection, University of Jaén, Spain.

Etymology. The specific epithet refers to the geographical origin of the new species in Kahaq region, Iran.

Remarks. The new species herein described is an excellent example of the problematic taxonomy of the conical-tailed species of the family Qudsianematidae . It is characterized by a combination of features that allows its relatively easy identification but that, at the same time, raises doubt about its generic identity. Its conical, somewhat elongate caudal region is intermediate between those observed in species of Eudorylaimus , which tend to be shorter, and those of Epidorylaimus species, which tend to be longer, but there is no distinct borderline between the two genera. The location of the posteriormost ventromedian supplement is also notable: situated at approximately the level of the anterior end of the spicules, it is not too much farther from the adcloacal pair than from the penultimate ventromedian supplement of the series, so that a pre-cloacal space (hiatus) is not distinctly perceptible, again representing an intermediate condition between Eudorylaimus (males with distinct hiatus) and Allodorylaimus and Epidorylaimus (both with males lacking hiatus, i.e. with one or more ventromedian supplements within the range of the spicules). With due caution, the new species has been provisionally classified under Eudorylaimus because its general morphology fits better the pattern of that genus. Nevertheless, leaving aside the tail length and the presence/absence of a hiatus, it should be emphasized that the new species displays other features (nearly truncate and continuous lip region with corrugated anterior margin, broad cheilostom, weakly sclerotized but perceptible cephalic framework, presence of a coelomocyte shortly behind the nerve ring, dorsal gland pharyngeal nucleus in rather posterior position, etc.) that conform a peculiar pattern that might deserve separate generic status if other species are found that share it.

Figures

FIGURE 1. Eudorylaimus kahaqensis sp. n. (Female, LM). A: Entire. B: Lip region in surface lateral VieW.C: Lip region in median lateral VieW.D: Anterior genital branch. E: Posteriorbody region.

FIGURE 2. Eudorylaimus kahaqensis sp. n. (Male). A: Neck, posterior region. B: Entire. C,D: Posterior body region. E, F: Lateral guiding piece.G: Spicule.

FIGURE 3. Eudorylaimus kahaqensis sp. n. (Female, LM). A, B: Entire. C, D: Anterior genital branch. E: Posterior body region. F: Caudal region. G: OViduct-uterus junction. H, I: Vagina. (Scale bars: A, B = 200 µm; C, D = 50 µm; E–G = 20 µm; H, I = 10 µm.)

FIGURE 4. Eudorylaimus kahaqensis sp. n. (Anterior and neck regions, LM). A, B: Anterior region in lateral, median VieW. C: Pharyngeal expansion. D: Neck region. E: Lip region and amphid in lateral, surface VieW. F: Coelomocyte a short distance behind thenerVe ring.G:Posteriorhalf of pharyngeal expansion andpharyngo-intestinal junction shoWing S1N2, S2N and dorsal cell mass. H: Posterior part of pharyngeal expansion and pharyngo-intestinal junction shoWing S2N and dorsal cell mass.I, J: Dorsal cell mass atleVel of pharyngo-intestinal junction.(Scale bars: A, B,F, I, J = 10 µm; C = 50 µm; D = 100 µm; E= 5µm; G, H = 20 µm.)

FIGURE5. Eudorylaimus kahaqensissp. n. (Male, LM).A: Entire.B–D:Spicules.E, H:Caudal region.F, G:Posteriorbody region.(Scale bars:A = 200 µm; B–D, E, H = 10 µm; F, G = 50 µm.)

FIGURE 6. Lip region of Eudorylaimus kahaqensis sp. n. (SEM). A: SubVentral VieW. B: Sublateral VieW.C: En face VieW. (Scale bar = 2 µm.)