Aporcelaimellus waenga ( Yeates, 1967 ) Peña-Santiago & Ciobanu, 2008

Álvarez-Ortega, Sergio, Abolafia, Joaquín & Peña-Santiago, Reyes, 2013, Studies on the genus Aporcelaimellus Heyns, 1965 (Nematoda, Dorylaimida, Aporcelaimidae). Four typical species with simple uterus from Southern Iberian Peninsula, Zootaxa 3613 (1), pp. 36-60 : 50-59

Aporcelaimellus waenga ( Yeates, 1967) Peña-Santiago & Ciobanu, 2008

( Figs 7–11 )

Material examined. Sixty-four females from ten locations, in general in good state of preservation. Measurements. See Table 4.

Description (Mainly based on population from Sierra de las Nieves).

Female: Moderately slender to slender nematodes of medium size, 1.57–2.24 mm long. Body cylindrical, tapering towards both extremities, but more so towards the posterior end. Habitus curved ventrad after fixation, especially in posterior body region, C-shaped. Cuticle three-layered, 1.5–2.5 µm at anterior region, 2–6 µm in midbody and 5–8 µm on tail, bearing fine transverse striation only visible under SEM; outer and intermediate layers thinner than the inner one, with dissimilar refraction, more perceptible at caudal region. Cervical lacunae absent or hardly perceptible. Lateral chords 5–9 µm wide or 7–14% of mid-body diameter. Two ventral and two dorsal body pores are usually present at level of odontophore; ventral body pores often conspicuous throughout the body, reaching the level of the intestine-prerectum junction. Lip region offset by deep constriction, 2.7–3.2 times as wide as high and one-fourth to one-third (26–34%) of body diameter at neck base; lips (SEM observations) mostly amalgamated, each lateral lip slightly more offset from its corresponding subdorsal and subventral ones than the subdorsal and the subventral ones between them; labial and cephalic papillae prominent, button-like and surrounded by one (outer labial and cephalic papillae) or two (inner labial papillae) ring-like striations; oral aperture a dorsoventral, hexagonal, open slit -morphology of lips and oral aperture confer a biradial symmetry to lip region-; oral field with radial striations running from oral aperture to the margins. Amphid fovea funnel-shaped, its aperture 8–10 µm or two-fifths to five-ninths (42–54%) of lip region diameter. Cheilostom nearly cylindrical, lacking any differentiation. Odontostyle typical of the genus, 4.1–4.9 times as long as wide, 0.8–1.0 times as long as lip region diameter, and 0.75–0.99% of body length; aperture 10–12 µm long or occupying three-fifths to two-thirds (59–68%) its length. Guiding ring plicate. Odontophore linear, rod-like, 1.7–2.0 times the odontostyle. Anterior region of pharynx enlarging gradually; basal expansion 5.9–8.2 times as long as wide, 3.7–5.1 times as long as body diameter, and occupying 48–57% of total neck length; pharyngeal gland nuclei located as follows: DN = 54–59, S 1 N 1 = 65–70, S 1 N 2 = 71–77, S 2 N = 80–86. Nerve ring located at 150–179 µm from anterior end or 30–34% of total neck length. Cardia conical rounded, 15–20 x 15–20 µm; a ring-like structure is present surrounding its junction to pharyngeal base, which appears more developed in its dorsal side, forming a small lobe. A dorsal cell mass is present at cardia level. Genital system didelphic-amphidelphic, with both branches equally and moderately developed, the anterior 155–255 µm or 7–12% of body length [240, 262 µm or 12% (n=2) of body length with an uterine egg inside], and the posterior 152–253 µm or 8–13% of body length [271 µm or 14% (n=1) of body length with an uterine egg inside]: ovaries variably sized, the anterior 86–232 µm and the posterior 80–217 µm long, with oocytes arranged first in two or more rows, then in a single row; oviduct 79–142 µm long or 1.2–2.1 times the corresponding body diameter and consisting of slender part with prismatic cells and a more or less developed pars dilatata; oviduct and uterus separated by a marked narrowing surrounded by a strong sphincter; uterus a simple tube 50–104 µm long or 0.8–1.5 times the corresponding body diameter (122 µm long or 1.7 times the corresponding body diameter with an uterine egg inside); uterine egg ovoid, 97–110 x 43–47 µm (n=4), 2.1–2.6 (n=4) times as long as wide; vagina extending inwards 23–32 µm or one-fourth to four-ninths (33–56%) of body diameter, pars proximalis 13–24 x 13–16 µm and with somewhat sigmoid walls surrounded by weak musculature, pars refringens with two triangular to rounded pieces measuring 5–7 x 4–5 µm and with a combined width of 8–12 µm, and pars distalis 1–3 µm; and vulva an equatorial, small, oval, transverse slit. Prerectum 1.6–4.2, rectum 1.1–1.6 times the anal body diameter. Tail convex-conoid with broadly rounded terminus; showing a distinct intracuticular hyaline portion. Caudal pores two pairs, one lateral and another subdorsal, both at the anterior half of tail.

Male: Not found.

Molecular characterization. Two identical sequences (763 bp) were obtained ( Fig. 10 ) from two females from Sierra de las Nieves population .

Diagnosis (based in the whole material examined). This species is characterized by its body 1.57–2.24 mm long, lip region offset by deep constriction and 16–19 µm broad, odontostyle 16–19 µm long or 0.75–1.06% of body length with aperture occupying 57–68% its length, neck 453–553 µm long, pharyngeal expansion 223–314 µm long or 48–57% of total neck length, a dorsal cell mass at cardia level, uterus simple and 29–122 µm long or 0.4–1.7 times the corresponding body diameter, pars refringens vaginae present, vulva transverse (V = 49–58), tail convex-conoid (19–36 µm, c = 56–93, c’ = 0.5–1.0), and male absent. Besides, a distinctive feature of this species is the comparatively anterior location of pharyngeal gland nuclei.

Distribution. Province of Granada: (i) Campotéjar, Puerto del Zegrí, Sierra del Zegrí, Ulex parviflorus and thyme ( Thymus sp. ); (ii) Darro, Sierra Arana, esparto field; Road from Huéscar to La Losa, Sierra de la Sagra, Sierras de la Sagra, Jurena y Guillimona, (iii) associated to Scirpus holoschoenus and (iv) associated to holm oak ( Q. rotundifolia ); (v) Road from Huéscar to La Puebla de Don Fadrique, Sierra Jurena, Sierras de la Sagra, Jurena y Guillimona, pastureland; (vi) Road from La Puebla de Don Fadrique to Santiago de la Espada, Sierra de Guillimona, Sierras de la Sagra, Jurena y Guillimona, R. sphaerocarpa ; La Zubia road, Sierra Nevada-Cerro Huenes, (vii) associated to meadow and (viii) associated to holm oak forest ( Q. rotundifolia ). Province of Jaén: (ix) Acebeas forest road, Sierra de Segura, Sierras de Cazorla, Segura y Las Villas, Natural Park, hazel tree ( Corylus avellana ). Province of Málaga: (x) Ronda, Cañada de las Ánimas, Sierra de las Nieves, Abies pinsapo .

Remarks. The abundant material studied of this species forms a rather homogeneous group, with scarce morphological variations. On the contrary, its morphometrics, as usual in widely spread taxa, show appreciable variability in their ranges, for instance those referring to lengths of uterus (29–122 µm or 0.4–1.7 times the body diameter) and caudal region (19–36 µm, c = 56–93, c’ = 0.5–1.0), and some differences are occasionally observed when compared specimens from separated locations.

Originally described as type species of Takamangai Yeates, 1967 , the re-examination of type material of this species by Peña-Santiago and Ciobanu (2007, see also 2008) revealed it belonged to Aporcelaimellus . More recently, Álvarez-Ortega and Peña-Santiago (2010b) studied four specimens of Thorne’s collection from Florida ( USA) and China, identified them as A. waenga , regarded A. laevis Tjepkema, Ferris & Ferris, 1971 as its junior synonym, and stated that this species probably occupies a very wide geographical range. The abundant Iberian material herein examined is morphometrically very similar to Thorne’s specimens, being especially remarkable the coincidence in the (anterior) location of pharyngeal gland nuclei; nevertheless, there are some differences, such as slightly larger general size although with visible overlapping (body length 1.57–2.24 vs 1.31–1.71 mm in Thorne’s specimens; neck length 453–553 vs 390–480 µm) and wider lip region (16–19 vs 13–16 µm), which are interpreted as geographical variations. When compared with the American type material of A. laevis , the Iberian specimens show also larger general size (vs body length 1.27–1.57 mm, neck 320–340 µm long) but totally coincident lip region width (17.6±0.5 µm).

Aporcelaimellus waenga is morphologically nearly identical with A. obtusicaudatus , and, because of their ubiquity, both species may be found in the same locations, raising some difficulties in their identification. However, the odontostyle length (16–19 vs 19–29 µm, respectively) and the position of pharyngeal gland nuclei (more anterior in A. waenga ) are good diagnostic characters for separating them.

This species is also morphologically close to A. amylovorus , A. baeticus sp. n., A. clamus , A. punctatus , and A. samarcandicus , but it can be distinguished from them in the (more anterior) location of pharyngeal gland nuclei. Besides, it differs from A. amylovorus in its longer neck (vs 382–406 µm; b = 3.4–4.3 vs 4.2–4.6) and comparatively shorter tail (vs c = 44–54, c’ = 1.1–1.3). From A. baeticus sp. n., a very similar species (see above), in its shorter odontophore (29–34, n=64 vs 35–41, n = 35) and male absent (vs present). From A. clamus in its more stout body (a = 23–34, n = 64 vs a = 33–37, n = 3), smaller odontostyle aperture (vs 70–73% its length), and male absent (vs present). From A. punctatus in its narrower lip region (vs about 21 µm wide), shorter genital branch (vs about 500 µm long or occupying 20–24% of body length) and convex-conoid tail (vs conical). And from A. samarcandicus in its larger odontostyle aperture (vs about one-half or little more its length), prerectum lacking (vs often bearing) any blind sac, and tail lacking (vs bearing) any dorsal concavity.

The phylogenetic tree ( Fig. 11 ) inferred from the analysis of the D2–D3 expansion segments of the LSU rDNA gene shows that the two sequences of Iberian A. waenga cluster together with other sequences of A. obtusicaudatus , a very similar species (see above). These results suggest that this branch of the tree represents the most typical species of the genus.

Figures

FIGURE 7. Aporcelaimellus waenga (Yeates, 1967) Peña-Santiago & Ciobanu, 2008 (female). A: Anterior region in median view. B: Same in lateral, surface view. C: Pharyngeal expansion. D: Anterior genital branch. E: Entire body. F: Posterior body region. G: Vagina.

FIGURE 8. Aporcelaimellus waenga (Yeates, 1967) Peña-Santiago & Ciobanu, 2008 (LM, female). A: Entire. B, C: Anterior region in median. D: Neck region. E: Lip region in surface, lateral view. F: Pharyngo-intestinal junction. G, I: Vagina. H: Posterior body region. J-N: Variation in caudal region. O: Detail of ventral body pore. (Scale bars: A = 500 µm; B, C, G, J-N = 10 µm; D = 100 µm; F, H, O = 20 µm).

FIGURE 9. Aporcelaimellus waenga (Yeates, 1967) Peña-Santiago & Ciobanu, 2008 (SEM, female). A, C: Lip region, in face view. B: Lip region, in ventral view. D: Vulva. E: Vulva region. F: Caudal region, in lateral view. (Scale bars: A-D = 2 µm; E, F = 4 µm).

FIGURE 10. 28S rDNA gene sequences of Aporcelaimellus waenga (Yeates, 1967) Peña-Santiago & Ciobanu, 2008.

FIGURE 11. Bayesian 50% majority rule consensus trees as inferred from D2-D3 expansion segments of 28S rDNA gene sequence alignments under the GTR+I+G model. Posterior probabilities are given for appropriate clades. Newly obtained sequences are indicated by bold letters.