Aporcelaimellus rotundus, 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 : 46-48

Aporcelaimellus rotundus sp. n.

( Figs 5 & 6 )

Material examined. Seven females from two locations, in acceptable state of preservation. Measurements. See Table 3.

Description (mainly based on specimens from Sierra Nevada, Granada).

Female: Moderately slender to slender nematodes of medium size, 2.01–2.58 mm long. Body cylindrical, tapering towards both extremities, but more so towards the anterior end. Habitus curved ventrad after fixation, especially in posterior body region, C-shaped. Cuticle three-layered, 2–3 µm at anterior region, 2.5–4.5 µm in midbody and 5.5–8.0 µm on tail; outer layer thin and with fine but distinct transverse striation in some specimens, intermediate layer also thin, and inner layer thicker and showing radial striation. Cervical lacunae distinguishable in some specimens, but poorly developed, reaching up the odontostyle base. Lateral chord 7–13 µm wide or 11–18% of mid-body diameter. Lip region offset by constriction, 2.9–3.3 times as wide as high and one-fourth to three-eighths (27–37%) of body diameter at neck base. Amphid fovea funnel-like, its aperture 9–10 µm or about one-half (47–52%) of lip region diameter. Cheilostom nearly cylindrical, lacking any differentiation. Odontostyle 5.6–6.2 times as long as wide, 1.1–1.2 times as long as lip region diameter, and 0.85–1.07% of body length; aperture 11–13 µm long or occupying one-half to three-fifths (50–58%) its length. Guiding ring plicate. Odontophore linear, rod-like, 1.3–2.0 times the odontostyle length. Anterior region of pharynx enlarging very gradually; basal expansion 6.4–8.6 times as long as wide, 3.8–5.3 times as long as body diameter, and occupying 50–55% of total neck length; pharyngeal gland nuclei located as follows: DN = 60–63, S 1 N 1 = 75 (n=2), S 1 N 2 = 80, S 2 N = 90–91. Nerve ring located at 158–182 µm from anterior end or 30–35% of total neck length. Cardia conical, 16–20 x 15–17 µm; a ring-like structure is present surrounding its junction to pharyngeal base. A dorsal cellular mass about 30 µm long is present at level of cardia or the anterior end of intestine. Genital system didelphicamphidelphic, both branches equally and moderately large, the anterior 144–296 µm or 7–11% of body length [360 µm (n=1) or 14% (n=1) of body length, with two uterine eggs inside], and the posterior 153–220 µm or 7–10% of body length [217, 308 µm (n=2) or 11–12% (n=2) of body length, with a uterine egg inside]: ovaries variably sized, the anterior 126–299 µm and the posterior 106–233 µm long, with oocytes arranged first in two or more rows, then in a single row; oviduct 77–106 µm long or 1.0–1.6 times the corresponding body diameter, consisting of slender part with prismatic cells and a poorly developed pars dilatata with small lumen; oviduct and uterus separated by a marked narrowing; uterus a simple tube 28–74 µm long or 0.5–0.9 times the corresponding body diameter; uterine egg ovoid, 117–133 x 46–65 µm (n=3), 1.9–2.6 (n=3) times as long as wide; vagina extending inwards 27–32 µm or one-third to one-half (36–50%) of body diameter, pars proximalis 21–24 x 17–23 µm with more or less sigmoid walls surrounded by weak musculature, pars refringens with two, trapezoidal to drop-shaped, close pieces measuring 7–9 x 4–5 µm and with a combined width of 13–16 µm, and pars distalis 2–3 µm; and vulva a transverse slit. Prerectum 0.9–2.0, rectum 1.1–1.6 times the anal body diameter long. Tail short and conoid to rounded; inner cuticle layer often with dissimilar refraction to other layers, occasionally showing similar refraction; hyaline, terminal, intracuticular space nearly absent; caudal pores two pairs, one dorsal and another subdorsal.

Male: Not found.

Diagnosis. This species is characterized by its body 2.01–2.58 mm long, lip region offset by constriction and 19–20 µm broad, odontostyle 22–23 µm long with aperture occupying 50–58% its length, neck 455–579 µm long, pharyngeal expansion 226–316 µm long or 50–55% of total neck length, a distinct dorsal cell mass present at cardia level, uterus 28–74 µm long or 0.5–0.9 times the corresponding body diameter, V = 47–52, female tail conoid to rounded (27–33 µm, c = 64–90, c’ = 0.7–0.9) that lacks a perceptible intracuticular hyaline space, and males unknown.

Relationship. The new species is similar to A. alius , A. baeticus sp. n., A. crassus , A. hylophilus , A. medius , A. obtusicaudatus and A. salicinus , from which it differs in having caudal region with (vs without) especially thick inner cuticle layer and lacking (vs bearing) a perceptible intracuticular hyaline space at its terminal portion. Besides, it can be distinguished from A. alius in its more slender body (a = 28–37 vs 20–24), wider lip region (vs 17–19 µm broad), shorter pharyngeal expansion (vs 56–60% of total neck length), more posterior location of DN (DN = 60–63 vs 55–57) and tail more rounded (vs more conoid) and without (vs with) a dorsal concavity. From A. baeticus sp. n. in its longer (vs 17–22 µm or 1.1–1.2 times the lip region width) and more slender (5.6–6.2 vs 4.4–4.9 times as long as wide) odontostyle with smaller aperture (vs occupying 64–75% of total odontostyle length) and male absent (vs present). From A. crassus in its more slender body (a = 28–37 vs 21–23), smaller odontostyle (vs 24–26 µm long), more posterior location of DN (DN = 60–63 vs 51–57), and shorter (vs 40–58 µm, c = 41–49, c’ = 1.1–1.3) and conoid to rounded (vs conical) tail without (vs with) dorsal concavity. From A. hylophilus in its larger body (vs 1.61–2.11mm long), shorter odontostyle (vs 23–25 µm long), vulva more anterior (vs V = 51–57) and shorter tail (vs 36–48 µm, c = 42–51, c’ = 1.2). From A. medius in its larger (vs 1.74–1.86 mm long) and more slender (a = 28–37 vs 20–26) body, wider lip region (vs 17–18 µm broad), vulva more anterior (vs V = 52–54), female tail longer (vs 15–23 µm, c’ = 0.4–0.5) and male absent (vs present). From A. obtusicaudatus , morphometrically a very similar species, in its more slender odontostyle (5.6–6.2 vs 4.3–5.5 times as long as wide), and male absent (vs present). And, from A. salicinus in its larger general size (vs body 1.45–1.94 mm long), wider lip region (vs 16–18 µm broad), longer odontostyle (vs 18–20 µm long), more anterior location of DN (DN = 60–63 vs 63–68), and shorter tail (vs c = 39–59, c’ = 1.0–1.4).

Type locality and habitat. The new species was collected in association with poplar ( Populus alba ) forest from road from Trevélez to Ugíjar, in the natural area “Sierra Nevada-Alpujarras”, Granada, eastern Andalucía, Spain .

Other locality and habitat. The new species was also collected in association with poplar ( P. alba ) forest from Guadalquivir valley in Sierra de Cazorla, Sierras de Cazorla, Segura y Las Villas Natural Park, Jaén, eastern Andalucía, Spain.

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

Etymology. The specific epithet refers to the morphology of the caudal region (conoid to rounded) that characterizes this species.

Remarks. The most relevant feature of this species is the caudal region with especially thick inner layer and lacking a distinct intracuticular hyaline space at its terminal part, a peculiar character found in only a few other Aporcelaimellus species , such us A. macropunctatus ( Heyns, 1967) Jiménez-Guirado, 1994 . The identity of these species should be matter of further studies.

Figures

FIGURE 5. Aporcelaimellus rotundus sp. n. (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 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).