Aporcelaimellus hyalinus, Álvarez-Ortega, Sergio, Abolafia, Joaquín & Peña-Santiago, Reyes, 2013

Álvarez-Ortega, Sergio, Abolafia, Joaquín & Peña-Santiago, Reyes, 2013, Studies on the genus Aporcelaimellus Heyns, 1965 (Nematoda, Dorylaimida, Aporcelaimidae). Four atypical species with simple uterus from Southern Iberian Peninsula, Zootaxa 3630 (3), pp. 401-423 : 406-414

Aporcelaimellus hyalinus sp. n.

( Figs 3 , 4 & 5 A–D)

Material examined. One hundred and one females and one male from 26 localities of southeastern Iberian Peninsula. Forty-seven females and one male, in good state of preservation, were measured.

Measurements. See Table 2.

Description. Adult: Slender nematodes of medium size, 1.49–2.23 mm long. Body cylindrical, tapering towards both extremities, but more so towards the posterior end. Habitus curved ventrad after fixation, C-shaped, often more so in posterior body region, occasionally somewhat sigmoid. Cuticle three-layered, 1.5–2.5 μm thick at anterior region, 2.5–4.5 μm in mid-body and 4–7 μm on tail; outer and intermediate layers thinner than the inner one, bearing fine but distinct transverse striation throughout the entire body, but more perceptible at anterior and caudal regions. Cervical lacunae usually present, but not well developed, extending to odontophore base. Lateral chord 4.5–11.0 μm wide or 9–19% of mid-body diameter, lacking any differentiation. Two ventral and two dorsal body pores are usually present at level of odontophore. Lip region offset by deep constriction, 2.6–3.1 times as wide as high and one-fourth to one-third (24–36%) of body diameter at neck base; lips (under SEM) mostly amalgamated excepting the lateral ones which are separated from the others by a deep incisure; oral aperture a dorsoventral, hexagonal orifice. Amphid fovea funnel-shaped, its aperture 6.5–8.5 μm or four-ninths to three-fifths (44–60%) of lip region diameter. Cheilostom nearly cylindrical, with no specialization. Odontostyle typical of the genus, 4.7–5.3 times as long as wide, 0.9–1.1 times as long as lip region diameter, and 0.68–0.97% of body length; aperture 9–11 μm long or occupying two-thirds to three-fourths (64–74%) its length. Guiding ring plicate. Odontophore linear, rod-like, 1.8–2.1 times the odontostyle. Anterior region of pharynx enlarging very gradually; basal expansion 6.5–10.6 times as long as wide, 3.3–5.3 times as long as body diameter, and occupying 45–53% of total neck length; pharyngeal gland nuclei located as follows: DN = 57–62; S1N1 = 70–72; S1N2 = 78–80; S2N = 88–91. Nerve ring located at 129–160 μm from anterior end or 30–37% of total neck length. Cardia conical, 9– 17 x 9–16 μm; a more or less developed (often distinct) ring-like structure present surrounding its junction to pharyngeal base. A distinct dorsal cell mass is visible in some specimens at level of the anterior end of intestine. Tail conical with rounded terminus, ventrally straight, dorsally slightly convex, sometimes with a very weak dorsal concavity; inner cuticle layer, especially distinct in specimens from Sierra Nevada, not reaching the tail terminus, hence showing a marked discontinuity; inner core somewhat irregular, often leaving a large hyaline portion occupying up to one-half of tail length. Caudal pores two pairs, one dorsal, another subdorsal.

......continued on the next page ……continued on the next page Female: Genital system didelphic-amphidelphic, both branches equally and well developed, the anterior 122–221 μm or 7–12% of body length, and the posterior 122–295 μm or 6–15% of body length. Ovaries variable in size, the anterior 55–259 μm and the posterior 59–209 μm long; oocytes arranged first in two or more rows, then in a single row. Oviduct 59–123 μm long or 1.0–2.3 times the corresponding body diameter, consisting of slender part with prismatic cells and a moderately developed pars dilatata, often with visible lumen. Oviduct and uterus are separated by a marked sphincter. Uterus a simple tube 44–96 μm long or 0.7–1.5 times the corresponding body diameter (106 μm long or 1.8 times the corresponding body diameter with a uterine egg inside). Uterine egg ovoid, 95, 110 x 44, 48 μm (n = 2), 2.2–2.3 times as long as wide. Vagina extending inwards 19–29 μm or one-third to one-half (31–55%) of body diameter: pars proximalis 12– 21 x 11–21 μm, with somewhat sigmoid walls and surrounded by weak musculature; pars refringens with two adjacent, triangular to trapezoidal pieces measuring 4– 7 x 2.5–5.0 μm and with a combined width of 5–10 µm; pars distalis short, 1–4 μm. Vulva a nearly equatorial, transverse slit about 6 µm (n=1) long. Prerectum 1.8–5.0, rectum 1.1–1.6 times the anal body diameter.

Male: Very rare. Genital system diorchic, with opposite testes. In addition to the ad-cloacal pair, situated at 11 μm from cloacal aperture, there is a series of seven irregularly spaced (8–17 µm apart) ventromedian supplements, the posteriormost of which is located, out the range of spicules, at 65 μm from the ad-cloacal pair. Spicules curved ventrad and robust, 5.1 times as long as wide, and 1.9 times as long as cloacal body diameter. Lateral guiding pieces 16 μm long, 6.3 times as long as wide. Prerectum 3.3, cloaca 1.5 anal body widths long.

Diagnosis. This species is characterized by its body length of 1.49–2.23 mm, lip region offset by deep constriction and 13–16 μm broad, odontostyle 14–16 μm long with aperture occupying 64–74% its length, neck 389–474 μm long, pharyngeal expansion 183–242 μm long or 45–53% of total neck length, uterus 44–106 μm long or 0.7–1.8 times the corresponding body diameter, pars refringens vaginae present, V = 48–55, tail conical with rounded terminus (27–41 μm, c = 38–68, c’ = 1.0–1.4) and short inner core, spicules 56 μm long, and seven irregularly spaced ventromedian supplements.

Relationships. In having medium size, narrow lip region, and short odontostyle the new species is morphologically close to a number of species, including A. amylovorus , A. brevicaudatus , A. clamus , A. punctatus Altherr in Altherr & Delamare-Deboutteville, 1972, A. salicinus , A. samarcandicus , and A. waenga . It can be distinguished from all of them except A. salicinus in the morphology of caudal region, with a terminal discontinuity of its inner cuticle layer (vs inner layer continuous at the end) and, consequently, a developed hyaline space. Besides, it differs from A. amylovorus in its shorter odontostyle (vs 17–19 μm long) with larger aperture (vs 58–63% of total length), arrangement of pharyngeal gland nuclei (DN = 57–62 vs 64–65; S1N1 = 70–72 vs 74–75; S1N2 = 78–80 vs 80–81), female tail conical (vs bluntly convex-conoid), and male present (vs absent). From A. brevicaudatus in its comparatively shorter odontophore (1.8–2.1 vs 2.1–2.3 times the odontostyle length), shorter neck (vs 512 μm long, b = 3.6), female conical tail (vs rounded to hemispherical) and comparatively longer (vs c’ = 0.6–0.7), and male present (vs absent). From A. clamus in its narrower lip region (vs 17.0–17.5 μm wide), shorter odontostyle (vs 19.0–19.5 μm long), shorter neck (vs 530–573 μm long), arrangement of pharyngeal gland nuclei (S1N1 = 70–72 vs 74–76; S1N2 = 78–80 vs 85–86; S2N = 88–91 vs 93–94), female tail conical (vs convex-conoid) and shorter (vs c’ = 0.9), and less (vs 10) ventromedian supplements. From A. punctatus in its narrower lip region (vs about 21 μm), shorter odontostyle (vs about 18 μm long), shorter female genital branches (vs occupying 24–26% of body length), and male present (vs absent). From A. salicinus , a species having similar caudal region (see also remarks), in its narrower (vs 16–18 µm) lip region, smaller odontostyle (vs 18–20 µm long) with larger aperture (vs 50–53% its length), and male present (vs absent). From A. samarcandicus in its more slender body (a = 29–44 vs a = 25–29), narrower lip region (vs 17–19 μm), shorter odontostyle (vs 18–19 μm), female tail conical (vs convex-conoid) and comparatively longer (vs c’ = 0.6–0.7), and male present (vs absent). And from A. waenga in its arrangement of pharyngeal gland nuclei (S1N1 = 70–72 vs 65–70; S1N2 = 78–80 vs 71–77; S2N = 88–91 vs 80–86), female tail conical (vs convex-conoid) and comparatively shorter (vs c’ = 0.5–1.0), and male present (vs absent).

Finally, the new species also resembles A. deserticola sp. n. and A. obtusicaudatus . It can be distinguished from both by its shorter odontostyle (vs 18–29 µm long). In addition, it differs from A. deserticola sp. n. in its relatively larger odontostyle aperture (vs 55–61%), longer odontophore (1.8–2.1 vs 1.4–1.6), more anterior position of S1N1 (70–72 vs 73–76), female tail with inner cuticle layer showing a marked discontinuity (vs continuous), and male present (vs absent). And from A. obtusicaudatus in its narrower lip region (vs 16–23 µm), shorter odontostyle (vs 19–29 µm), female tail conical (vs rounded to conical with broadly rounded terminus) with inner cuticle layer showing a marked discontinuity (vs continuous), and shorter spicules (vs 74–86).

Type locality and habitat. Spain, eastern Andalucía, Almería province, “Sierra Nevada-Alpujarras” shire, near the road from Canjáyar to Ugíjar, in association with Mediterranean plants such as thyme and Cistus sp.

Other localities and habitats. Province of Almería: (i) Sierra de los Filabres, Escúllar, esparto (needle grass) field; (ii) Sierra de los Filabres, road to Caniles, pine forest ( Pinus sp.); (iii) Sierra de Gádor, road from Ugíjar to Berja, thyme, Cistus sp., Asphodelus sp., almond trees ( Prunus dulcis ) and Retama sphaerocarpa ; (iv) Sierra de Gádor, road from Alhama to Canjáyar, thyme, Cistus sp. and esparto (needle grass) field; (v) Sierra Nevada- Alpujarras, road from Canjáyar to Ugíjar, thyme, R. sphaerocarpa and esparto (needle grass) field; (vi) Cabo de Gata-Níjar Natural Park, Isleta del Moro, grass; and (vii) Cabo de Gata-Níjar Natural Park, Cabo de Gata harbour, Chamaerops humilis . Province of Cádiz: (viii) Sierra del Pinar, El Torreón, Abies pinsapo . Province of Granada: (ix) Sierra Arana, Iznalloz, holm oak ( Quercus rotundifolia ); (x) Sierra Arana, Darro, wheat field; (xi) Sierras de la Sagra, Jurena y Guillimona Natural Park, Sierra de la Sagra, road from Huéscar to La Losa, almond trees, esparto (needle grass) field, holm oak trees, thyme and pine trees; (xii) Sierra Nevada-Alpujarras, road to Lajarón, R. sphaerocarpa , esparto (needle grass) field and Erinacea anthyllis ; (xiii) Sierras de la Sagra, Jurena y Guillimona Natural Park, road from Huéscar to Castril, juniper ( Juniperus oxycedrus ), Ulex sp. and thyme; (xiv) Sierra de Castril Natural Park, road from Castril to Pozo Alcón, pine forest; (xv) Sierra de Huétor Natural Park, road to Fuente de la Teja, oak trees ( Quercus faginea ); (xvi) Sierra de Huétor Natural Park, road from La Zubia to Dílar, thyme; (xvii) Sierra Nevada-Alpujarras, road from Torviscón to Órgiva, pine forest, R. sphaerocarpa and thyme; (xviii) Sierra de Almijara, Sierras Alhama, Tejeda y Almijara Natural Park Road, La Axarquía shire, road from Jayena to Almuñécar, esparto (needle grass) field; (xix) Sierra de Almijara, Sierras Alhama, Tejeda y Almijara Natural Park, La Axarquía shire, La Cabra road, pine trees, Juniperus sp, R. sphaerocarpa and thyme; and (xx) Sierra Nevada Natural Park, road to Sierra Nevada, R. sphaerocarpa and thyme; Province of Jaén: (xxi) Sierra de la Pandera, Mediterranean brushwood, whose dominant species were Echinospartum boissieri, Salvia lavandulifolia, Lavandula latifolia and E. anthyllis ; Province of Málaga: (xxii) Sierra de Almijara, Sierras Alhama, Tejeda y Almijara Natural Park, De la Miel river, C. humilis ; (xxiii) Sierra de Almijara, Sierras Alhama, Tejeda y Almijara Natural Park, road to Canillas de Aceituno, holm oak forest; (xxiv) road from Archidona to Villanueva del Trabuco, holm oak forest; (xxv) Sierra de Alhama, Sierra de Alhama, Tejeda y Almijara Natural Park, road from Periana to Viñuelas, olive trees ( Olea europaea ) and Carob tree ( Ceratonia siliqua ); and (xxvi) Montes de Málaga, road from El Trapiche to Triana, cane ( Arundo donax ).

Type material. Female holotype and ten female paratypes, deposited in the nematode collection of the University of Jaén, Spain. Two female paratypes deposited with USDA Nematode Collection, Beltsville, Maryland, USA.

Etymology. The specific epithet refers to the hyaline portion at caudal region that characterizes this species.

Remarks. The abundant material examined of this species shows some variability mainly affecting morphometrics as well as some morphological features such as the development of cervical lacunae, shape of pars refringens vaginae, inner core of caudal region, etc. Nevertheless, it forms a rather homogeneous group since relevant overlap is found in the morphometric ranges, and morphological differences do not alter important diagnostic features.

The new species is especially close to A. salicinus from California, but the differences in lip region width and particularly in odontostyle (longer, more slender and with larger aperture) are significant enough to provisionally support their separate status.

Figures

FIGURE 3. Aporcelaimellus hyalinus sp. n. A: Anterior region in median view. B: Same in lateral, surface view. C: Pharyngeal expansion. D: Anterior genital branch. E: Female, posterior body region. F: Male, posterior body region. G: Female, entire body. H: Spicule and lateral guiding piece. I: Vagina. J: Male, entire body.

FIGURE 4. Aporcelaimellus hyalinus sp. n. (LM, female). A: Female, entire. B, C: Anterior region in median, lateral view. D: Cardia. E: Neck region. F: Lip region in lateral, surface view. G, J, K: Vagina. H: Anterior genital branch. I: Posterior body region. L – O: Caudal region. (Scale bars: A = 500 µm; B, D = 20 µm; C, L – O = 10 µm; E = 100 µm; E, F, J, K = 5 µm; H, I = 50 µm).

FIGURE 5. Aporcelaimellus hyalinus sp. n. (SEM, female). A: Lip region, in face view. B: Lip region, lateral view. C: Vulva region. D: Vulva. A. salicinus Álvarez-Ortega, Subbotin & Peña-Santiago, 2013 (SEM, female). E, F: Lip region, lateral view. (Scale bars: A, E, F = 2 µm; B = 5 µm; C = 10 µm; D = 2.5 µm).