Longidorus nevesi Macara, 1985

Archidona-Yuste, Antonio, Cantalapiedra-Navarrete, Carolina, Castillo, Pablo & Palomares-Rius, Juan E., 2019, Molecular phylogenetic analysis and comparative morphology reveals the diversity and distribution of needle nematodes of the genus Longidorus (Dorylaimida: Longidoridae) from Spain, Contributions to Zoology 88, pp. 1-41 : 33-37

Longidorus nevesi Macara, 1985 ( fig. 12 , table 5)

Remarks. The Spanish population of this species is characterised by a long body, ventrally curved in an open C when killed by heat, lip region conoid and continuous with body contour. Amphidial fovea bilobed, slightly asymmetrical, odontostyle long and robust, approximately 2 times longer than odontophore. Female tail short, bluntly conoid with rounded terminus and c’ <1.0. Males frequent with robust spicules, ventrally arcuate approximately 100 μm long. The morphology and morphometrics of this population closely agree with the original description (Macara, 1985). Apart from the original description, this species has been reported also from forests in Portugal (Macara, 1994; Bravo & Lemos, 1997), and to our knowledge, this is the first report from Spain. This new report confirms the hypothesis that this species is an Iberian endemic (Gutiérrez-Gutiérrez et al., 2016). According to the polytomous key by Chen et al. (1997), the supplement by Loof & Chen, (1999), and additional codes (Peneva et al., 2013; Archidona et al., 2016), this species has the following code: A56-B34-C34-D1-E3-F35-G12-H1-I2 -J1–K3.

Longidorus cf. olegi Kankina & Metlitskaya, 1983

( figs. 13 and 14 , table 6)

Remarks. This species was described by Kankina & Metlitskaya (1983) from the rhizosphere of raspberry at the experimental farm of the Rossoshanski fruit-berry experimental station in the Rossoshanski region of Voronezh Province ( Russia), based only on two females and three males; there is no other report on it. The Spanish population of Longidorus collected from the rhizosphere ofPortugueseoak (Quercusfaginea Lam.), atArroyo Frío, Jaén province, Spain showed morphological and morphometric characteristics resembling this species, which prompted us to study this population, characterising morphologically females and males, as well as providing descriptions for the first time of first-, second-, third- and fourth-stage juveniles, including a new molecular characterisation by D2–D3,ITS1, and partial 18S sequences (supplementary fig. S1 and table 6). Given the low number of specimens used in the original description of this species, a detailed characterisation of both morphology and morphometrics was provided in the present study. However, the taxonomic assignment is here given as L. cf. olegi because of the few specimens used in the original species description. For this reason, we consider this species as L. cf.olegi until topotypes of this species can clarify the similarity, or not, with the Spanish population.

The morphology and morphometrics of the Spanish population from Portuguese oak at Arroyo Frío, Jaén Province, agree closely with those of the original description by Kankina & Metlitskaya (1983) ( table 6), except for a slightly shorter odontostyle (av. 104.5 (96.0–115.0) μm vs. 112.0–116.0 μm); slightly longer distance from anterior end to guiding ring (34.4 (32.0–37.0) vs. 32.0 μm); slightly higher V ratio (54.0 (51.5–57.5) vs. 52.6 (51.3–54.0); and spicules (81.0 (80.0–82.0) μm vs. 66.0 (62.4– 73.2) μm). These differences further expand the intraspecific variation in this species that can be a consequence of the few specimens measured in the original description by Kankina & Metlitskaya (1983). The population examined by us represents the first report of the species in a country outside of Russia. According to the polytomous key by Chen et al. (1997), the supplement by Loof & Chen (1999), and additional codes (Peneva et al., 2013; Archidona et al., 2016), this species has the following code (codes in parentheses are exceptions): A4(3)-B2(3)-C4-D1-E2-F4-G2-H1-I2-J1–K6.

Description. Female. Body cylindrical, tapering towards anterior end, usually assuming an open C-shape when heat relaxed. Cuticle 3.0–4.5 µ m at mid-body, and 11.5–15.5 µ m at tail tip, and marked by very fine superficial transverse striae mainly in tail region. Lip region rounded, continuous with body contour. Amphidial fovea pocket-shaped; deeply bilobed and slightly asymmetrical. Odontostyle moderately long and narrow, 1.9 ± 0.4 (1.5–2.6) times as long as odontophore, straight or slightly arcuate; odontophore weakly developed, with rather weak basal swellings. Pharynx consisting of an anterior slender narrow part, extending to a terminal pharyngeal bulb, well demarcated anteriorly and cylindrical, 134.9 ± 8.7 (120.0–148.0) μm long, occupying approximately 25% of total pharyngeal length, and 31.1 ± 4.6 (24.5–31.0) μm wide. Glandularium 117.4 ± 7.3 (106.0–128.0) μm long. Normal arrangement of pharyngeal glands (Chen et al., 1997; Loof and Chen, 1999): DN and SVN pharyngeal gland located at 34.5 ± 4.1 (26.9–39.6), 57.6 ± 2.9 (53.4–62.2) % of distance from anterior end of pharyngeal bulb, respectively. Dorsal gland nucleus slightly larger than nuclei of two SVN (3.5–5.0 vs 3.0–4.5 μm in diam.). Cardia well-developed, hemispherical to conoid, 16.3 ± 6.7 (12.0–24.0) μm long. Reproductive system with both genital branches equally developed, 8.3 ± 1.1 (7.0–10.2), 8.2 ± 1.3 (5.8–9.8) % of body length, respectively. Vulva in form of a transverse slit, located slightly posterior to mid-body, vagina perpendicular to body axis, 28.1 ± 2.7 (24.0–32.0) μm long, or 30–45% of corresponding body width, surrounded by well-developed muscles. Uterus and oviduct of about equal length, usually with sperm cells in the female specimens examined. Prerectum very long, 1,235.2 ± 175.7 (1,055 –1,545) μm, and rectum 0.8 ± 0.1 (0.7–1.0) times as long as anal body diameter, anus a small rounded slit. Tail relatively short, convex-conoid to bluntly conoid, with rounded terminus, bearing two or three pairs of caudal pores.

Male. Very rare, only two male specimens were found (1:7 ratio). Morphologically similar to female except for genital system and posterior region slightly curved ventrally. Tail convex conoid, ventrally slightly concave with broad blunt terminus and thickened outer cuticular layer. Male genital tract diorchic with testis opposed, containing multiple rows of spermatogonia in the germinal zone. Spicules arcuate, robust, 1.6–1.8 times longer than tail length, lateral guiding pieces more or less straight. One pair of adanal supplements preceded by a row of 13–14 ventromedian supplements.

Juveniles. All four juvenile stages (J1–J4) distinctly separated by differences in body length, odontostyle and replacement odontostyle length (Robbins et al., 1996) were detected ( figs. 13 and 14 ). Morphologically, juveniles resemble adults except for the smaller size and undeveloped reproductive system. J1s were characterised by a subdigitate tail with a rounded tip and a c’ ratio 2.4–2.6 ( table 6). J2–J4 tails dorsally convex conoid and terminus bluntly rounded comparable to that of female in shape ( fig. 13 and table 6).

Figures

FIGURE 1 Phylogenetic relationships within the genus Longidorus. Bayesian 50% majority rule consensus tree as inferred from D2 and D3 expansion domains of 28S rRNA sequence alignment under an SYM model with invariable sites and a gamma-shaped distribution (SYM + I + G). Posterior probabilities greater than 0.70 are given for appropriate clades.Newly obtained sequences in this study are shown in bold. Scale bar = expected changes per site. ** = Branches collapsed, indicating clustered Longidorus species.For a more specific detail of collapsed clades, see supplementary fig.S1.

FIGURE 12 Light micrographs of Longidorus nevesi Macara 1985.(A) female anterior region.(B) female lip region. (C) vulval region. (D) female tail. (E)–(F) male tail with detail of spicules.Abbreviations:a = anus; gr = guiding ring; spl = ventromedian supplements; V = vulva.Scale bars = 20 μm

FIGURE 13 Light micrographs of Longidorus cf.olegi Kankina & Metlitskaya, 1983.(A)–(B) female anterior region. (C)–(F) female lip regions. (G) detail of basal bulb. (H) vulval region.(I)–(L) female tails. (M) and (N), male tail with detail of spicules.(O)–(R) First-, second-, third-, and fourth-stage juvenile (J1–J4) tails, respectively. Abbreviations: a = anus; af = amphidial fovea; gr = guiding ring. Scale bars = 20 μm

FIGURE 14 Relationship of body length to length of functional and replacement odontostyle (Ost and rOst, respectively) length in all developmental stages from first-stage juveniles (J1) to mature females of Longidorus cf.olegi Kankina & Metlitskaya, 1983