Aporcelaimellus baeticus, Álvarez-Ortega & Abolafia & Peña-Santiago, 2013

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 : 37-43

Aporcelaimellus baeticus sp. n.

( Figs 1 & 2 )

Material examined. Thirty-six females and four males, in good state of preservation in general.

Measurements. See Table 1.

Description (based only on the type population, also see remarks).

Adult: Moderately slender nematodes of medium size, 2.24–2.95 mm long. Body cylindrical, tapering towards both extremities, but more so towards the posterior end. Habitus curved ventrad after fixation to a more or less open C shape. Cuticle three-layered, 2.0–2.5 µm thick at anterior region, 4.0–5.5 µm in mid-body and 4.5–8.0 µm on tail; outer layer thin and nearly smooth under LM, intermediate layer also thin, and inner layer thicker than the others but not especially refractive in the specimens examined. Lateral chord 10–17 µm wide or 10–16% of midbody diameter. Two ventral and two dorsal body pores are usually present at level of odontophore, while other body pores are often more inconspicuous, although perceptible in some specimens along the ventral side of body. Lip region offset by deep constriction, 2.9–3.3 times as wide as high and 22–30% of body diameter at neck base; lips moderately separated and somewhat angular, papillae slightly protruding. Amphid fovea funnel-shaped, its aperture 9–12 µm or two- to three-fifths (45–61%) of lip region diameter. Cheilostom nearly cylindrical, lacking any differentiation. Odontostyle typical of the genus, 4.4–4.9 times as long as wide, 0.9–1.1 times as long as lip region diameter, and 0.63–0.95% of body length; aperture 13–14 µm long or occupying two-thirds to three-fourths (64–75%) its length. Guiding ring plicate. Odontophore linear, rod-like, 1.8–2.1 times the odontostyle length. Anterior region of pharynx enlarging very gradually; basal expansion 6.8–7.8 times as long as wide, 3.2–4.2 times as long as body diameter, and occupying 48–54% of total neck length; pharyngeal gland nuclei located as follows: DN = 56–63, S 1 N 1 = 71–74, S 1 N 2 = 78–81, S 2 N = 87–90. Nerve ring located at 180–198 µm from anterior end or 31–35% of total neck length. Cardia conoid, 16–26 x 14–17 µm, partially surrounded by intestinal tissue; a ringlike structure is present surrounding its junction to pharyngeal base, which appears more developed in its dorsal side, forming a small lobe. A dorsal cellular mass about 100 µm long is visible in many specimens at level of anterior end of intestine.

Female: Genital system didelphic-amphidelphic, with both branches equally developed and comparatively short: the anterior 214–284 µm or 8–10% of body length, and the posterior 220–296 µm or 8–10% of body length. Ovaries moderately developed, often reaching and even surpassing the sphincter level: the anterior 141–245 µm and the posterior 127–247 µm long; oocytes arranged first in two or more rows, then in a single row. Oviduct 85–122 µm long or 1.0–1.2 times the corresponding body diameter, consisting of slender part with prismatic cells and conspicuous pars dilatata which lacks a distinct lumen. Oviduct and uterus are separated by an abrupt narrowing, apparently encircled by a weak sphincter. Uterus a simple tube, 95–139 µm long or 0.9–1.4 times the corresponding body diameter. Vagina extending inwards 29–33 µm or one-third to three-eighths (30–38%) of body diameter; pars proximalis 20–24 x 14–19 µm, with somewhat sigmoid walls and surrounded by weak musculature; pars refringens with two drop-shaped to trapezoidal pieces measuring 9–10 x 5.0–7.5 µm and with a combined width of 12–16 µm; pars distalis 1.5–2.5 µm. Vulva a nearly equatorial, transverse slit. Prerectum 2.8–3.3, rectum 1.0–1.3 times the anal body diameter long. Tail convex conoid with broadly rounded terminus; inner cuticle layer not reaching the tail tip, hence a more or less (usually readily) perceptible, intracuticular terminal hyaline space is present; caudal pores two pairs, one dorsal, another subdorsal.

Male: Genital system diorchic, with opposite testes. In addition to the ad-cloacal pair, situated at 11–12 µm from cloacal aperture, there is a series of 18–21 irregularly spaced (8–31 µm apart) ventromedian supplements, one to three of which lie within the range of spicules, the posteriormost of which is situated at 27–34 µm from adcloacal pair. Spicules curved ventrad, relatively slender, 6.2–7.0 times as long as wide and 2.1–2.2 times as long as anal body diameter. Lateral guiding pieces 20–22 µm long, 6.0–6.6 times as long as wide. Prerectum 2.1–4.6, cloaca 1.4–1.6 anal body widths long. Tail somewhat more conoid than female, dorsally convex and ventrally straight or slightly curved ventrad; other features similar to those of female.

Diagnosis (based on whole material, see also remarks). This species is characterized by its body 1.96–2.95 mm long, lip region offset by constriction and 17–20 µm broad, odontostyle 17–22 µm long with aperture occupying 64–75% its length, neck 510–635 µm long, pharyngeal expansion 250–335 µm long or 45–55% of total neck length, a dorsal lobe between pharyngeal base and cardia, a dorsal cell mass at level of anterior end of intestine, uterus simple and 60–150 µm long or 0.9–1.7 times the corresponding body diameter, vulva transverse (V = 48–54), tail convex conoid with broadly rounded terminus (30–46 µm, c = 47–80, c’ = 0.7–1.1), spicules 99–103 µm long, and 18–21 irregularly spaced ventromedian supplements which lack hiatus.

Relationships. The new species is morphometrically very similar to the type species of the genus, A. obtusicaudatus ( Bastian, 1865) Altherr, 1968 (for a recent concept of this species see Álvarez-Ortega & Peña- Santiago, 2012). The ranges of measurements and ratios of both species widely overlap, but they differ in spicule length (99–103 vs 74–86 µm in Iberian specimens) as well as in the number (18–21 vs 7–13) and arrangement (without vs with hiatus) of ventromedian supplements. Besides, A. baeticus sp. n. has a relatively shorter odontostyle (17–22 vs 19–29 µm), although some overlap exists, potentially making the separation of individual females problematic or impossible. In any case, the differences observed in ventromedian supplements are significant and support a separated status for both taxa.

Aporcelaimellus baeticus sp. n. is also morphologically close to A. alius Andrássy, 2002 , A. amylovorus ( Thorne & Swanger, 1936) Heyns, 1965 , A. clamus Thorne, 1974 , A. punctatus Altherr in Altherr & Delamare- Deboutteville, 1972, A. salicinus Álvarez-Ortega, Subbotin & Peña-Santiago, 2013 , A. samarcandicus ( Tulaganov, 1949) Baqri & Khera, 1975 and A. waenga ( Yeates, 1967) Peña-Santiago & Ciobanu, 2008 (= A. laevis Tjepkema, Ferris & Ferris, 1971 ). It differs from A. alius in its more slender body (a = 25–35 vs 20–24), larger odontostyle aperture (vs occupying a little more that half odontostyle length), shorter neck (vs 454–510 µm long) and pharyngeal expansion (vs occupying 56–60% of total neck length), vulva somewhat posterior (vs V = 46–49), female tail lacking any dorsal concavity (vs bearing), and male present (vs absent). From A. amylovorus (see redescription by De Ley et al., 1993) in its larger general size (vs body 1.63–1.79 mm long, neck 382–406 µm long), wider lip region (vs 15–17 µm broad), larger odontostyle aperture (vs occupying 58–63% of total odontostyle length), arrangement of pharyngeal gland nuclei (DN = 56–63 vs 64–65, S 1 N 1 = 71–74 vs 74–75), comparatively shorter female tail (vs c’ = 1.1–1.3), and male present (vs absent). From A. clamus (see recent description by Álvarez-Ortega and Peña-Santiago, 2010a), a very similar species, in the more anterior location of pharyngeal gland nuclei (S 1 N 1 = 71–74 vs 74–76; S 1 N 2 = 78–81 vs 85–86; S 2 N = 87–90 vs 93–94), and in the number of ventromedian supplements (vs 10) certainly with different arrangement (vs widely spaced and probably bearing hiatus, according to Fig. 6E in Thorne, 1974). From A. punctatus in its narrower lip region (vs about 21 µm broad), comparatively longer neck (b = 3.9–4.8 vs 4.9), shorter female genital branch (vs occupying 24–26% of total body length), and male present (vs absent). From A. salicinus in its larger general size (vs body length 1.45–1.94 mm, neck length 392–521 µm), more robust (4.4–4.9 vs 5.4–6.8 times as long as wide) and comparatively shorter (0.9–1.1 vs 1.1–1.3 times as long as lip region diameter) odontostyle with larger aperture (vs occupying 51–58% of total odontostyle length), and male present (vs absent). From A. samarcandicus (mainly based on data provided by Andrássy, 2002) in its longer body (vs L = 1.47–1.70), larger odontostyle aperture (vs occupying one-half of total odontostyle length or a little more), comparatively shorter neck (b = 3.9–4.8 vs 3.3–3.7), longer female tail (vs 20–26, c’ = 0.6–0.7), and male present (vs absent). And from A. waenga (see below), a very similar species, in its longer odontophore (35–41 µm, n = 35 vs 29–34 µm, n = 64), more posterior location of pharyngeal gland nuclei (S 1 N 1 = 71–74, S 1 N 2 = 78–81, S 2 N = 87–90 vs S 1 N 1 = 65–70; S 1 N 2 = 71–77; S 2 N = 80–86), and male present (vs absent).

The new species also resembles A. crassus Andrássy, 2009 , A. hylophilus Tjepkema, Ferris and Ferris, 1971 and A. medius Andrássy, 2002 . It can be distinguished from these in its smaller odontostyle (vs 22–26 µm long). Besides, it differs from A. crassus in having a more slender body (a = 25–35 vs 21–23), female tail convex-conoid (vs conical) and comparatively shorter (vs c’ = 1.1–1.3) that lacks (vs bears) a dorsal concavity, and male present (vs absent). From A. hylophilus in its larger odontostyle aperture (vs occupying 50–54% of total odontostyle length), longer prerectum (vs 46–70 µm long), and male present (vs absent). And from A. medius in its longer (vs 1.74–1.86 mm) and more slender (a = 25–35 vs 20–26) body, comparatively shorter neck (b = 3.9–4.8 vs 3.5–3.9), longer tail (vs 15–25 µm long, c’ = 0.4–0.5), longer spicules (vs 72 µm long), and higher number of ventromedian supplements (vs 10), lacking (vs with) hiatus.

Type locality and habitat. The new species was collected in association with holm oak ( Quercus rotundifolia ) and Retama sphaerocarpa from Fuente del Pintal, road from de La Puebla de Don Fadrique to Santiago de la Espada, Sierra de Guillimona, Sierras de la Sagra, Jurena y Guillimona, Granada, eastern Andalucía, Spain.

Other localities and habitats. Province of Almería: (i) Escúllar, Sierra de los Filabres, esparto field; and (ii) Caniles Road, Sierra de los Filabres, Mediterranean brushwood, whose dominant species was Erinacea anthyllis . Province of Granada: (iii) Puerto del Zegrí, Campotéjar, Sierra del Zegrí, meadow; (iv) Road from Huéscar to La Puebla de Don Fadrique, Sierra Jurena, Sierras de la Sagra, Jurena y Guillimona, pastureland; Puerto del Prior, road from La Puebla de Don Fadrique to Santiago de la Espada, Sierra de Guillimona, Sierras de la Sagra, Jurena y Guillimona Nautral Park, (v) associated to holm oak ( Q. rotundifolia ) and Mediterranean brushwood, whose dominant species were Erinacea anthyllis , Thymus sp. , Asphodelus sp. and Crataegus sp. and (vi) associated with meadow plants.

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

Etymology. The specific epithet refers to Baetica , the name of the Roman province corresponding to Southern Iberian Peninsula (now Andalucía), where the species dwells.

Remarks. This species is widespread in Eastern Andalusian soils. The specimens examined from seven locations show no relevant morphological difference and some but minor morphometrical ones, mainly affecting lip region width and odontostyle length, but the respective ranges notably overlap. As mentioned, the most characteristic features to distinguish it from its most relatives –several species are very similar to this one– are found in males, very especially the number and arrangement of ventromedian supplements.

Figures

FIGURE 1. Aporcelaimellus baeticus sp. n. A: Anterior region in median view. B: Same in lateral, surface view. C: Pharyngeal expansion. D: Anterior genital branch. E: Female, entire body. F: Female, posterior body region. G: Male, posterior body region. H: Spicule and lateral guiding piece. I: Vagina. J: Male, entire body.

FIGURE 2. Aporcelaimellus baeticus sp. n. (LM). A: Female, entire. B: Male, entire, C, D: Anterior body region in median, lateral view. E: Lip region in surface, lateral view. F: Pharyngeal expansion. G: Pharyngo-intestinal junction showing the dorsal lobe at cardia and the cellular mass at the anterior end of intestine. H: Female, posterior genital branch. I: Male, posterior body region. J: Vagina. K-M: Female, caudal region. N: Male, caudal region. (Scale bars: A, B = 500 µm; C, H = 20 µm; D, E, J, K- N = 10 µm; F = 100 µm; G, I = 50 µm).

FIGURE 6. Aporcelaimellus rotundus sp. n. (LM, female). A: Entire. B, C: Anterior region in median, lateral view. D: Vagina. E: Lip region in surface lateral view. F, J, K: Caudal region. G, H: Posterior genital branch, G with uterine egg. I: Pharyngo-intestinal junction, arrow head pointing at dorsal cellular mass. (Scale bars: A = 500 µm, B = 20 µm; C, D-F, J, K = 10 µm; G, H = 50 µm).