Aporcelaimellus brevicaudatus, 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 : 43-46

Aporcelaimellus brevicaudatus sp. n.

( Figs 3 & 4 )

Material examined. Four females, in variable state of preservation. Measurements. See Table 2.

Description. Female: Moderately slender to slender nematodes of medium size, 1.54–2.14 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- or G-shaped. Cuticle three-layered, 1.5–2.0 µm at anterior region, 2.5–3.5 µm in mid-body and 6.5–7.5 µm on tail; outer and intermediate layers thin, inner layer thicker than the others. Cervical lacunae absent. Lateral chord 6–11 µm wide or 10–16% of mid-body diameter. One ventral and two dorsal body pores are usually present at level of odontophore. Lip region offset by a more or less distinct constriction, 3.1–3.4 times as wide as high and one-fourth to one-third (24–31%) of body diameter at neck base. Amphid fovea funnel-shaped, its aperture 8–9 µm or about five-ninths (53–60%) of lip region diameter. Cheilostom nearly cylindrical, lacking any differentiation. Odontostyle typical of the genus, 4.6–5.2 times as long as wide, hardly shorter (0.9 times) than lip region diameter and 0.65–0.84% of body length; aperture 9–10 µm long or occupying five-sevenths to three-fourths (70–75%) its length. Guiding ring plicate. Odontophore linear, rod-like, 2.1–2.3 times the odontostyle length, Anterior region of pharynx enlarging very gradually; basal expansion 8.5 (n=1) times as long as wide, 4.4 (n=1) times as long as body diameter, and occupying 50% (n=1) of total neck length; pharyngeal gland nuclei obscure in the specimens examined. Nerve ring located at 150 µm (n=1) from anterior end or 29% (n=1) of total neck length. Cardia conical to rounded, 12–15 x 13 µm; its junction to pharyngeal base surrounded by a weak ring-like structure. Genital system didelphic-amphidelphic, both branches equally and moderately developed, the anterior 121–209 µm or 8–12% of body length (316 µm or 15% of body length in one female bearing an uterine egg), and the posterior 155, 166 µm (n=2) or 9–10% (n=1) of body length (195, 272 µm or 11, 13% of body length in two females bearing uterine eggs): ovaries relatively large, the anterior 79–237 µm and the posterior 83–213 µm long, with oocytes arranged first in two or more rows, then in a single row; oviduct 63–98 µm long or 1.3–1.7 times the corresponding body diameter, consisting of slender part with prismatic cells and a poorly developed pars dilatata; oviduct and uterus are separated by a sphincter; uterus a simple tube 39–57 µm long or 0.9–1.0 times the corresponding body diameter; vagina extending inwards 25–30 µm or less than half (44–47%) of body diameter, its pars proximalis 18–22 x 18–19 µm, with somewhat sigmoid walls surrounded by weak musculature, pars refringens with two triangular to trapezoidal, close pieces measuring 6–7 x 3–5 µm and with a combined width of 12–14 µm, and pars distalis 2.5–4.0 µm. Vulva a transverse slit. Prerectum 2.3 (n=1), rectum 0.9–1.0 times the anal body diameter. Tail short and rounded to nearly hemispherical; inner core distinctly shortened and loose from inner cuticle layer, forming a caudal lacuna; caudal pores two pairs, one lateral and another subdorsal, both are in the middle of the tail.

Male: Not found.

Diagnosis. This species is characterized by a body length of 1.54–2.14 mm, lip region offset by a more or less distinct constriction and 14–16 µm broad, odontostyle 13–15 µm long with aperture occupying 70–75% its length, neck 512 µm long, pharyngeal expansion 255 µm long or 50% of total neck length, uterus simple and 39–57 µm long or 0.9–1.0 times the corresponding body diameter, pars refringens vaginae present, V = 50–55, tail short and rounded to hemispherical (24–27 µm, c = 66–82, c’ = 0.6–0.7) with inner core hardly reaching the middle of tail length, and male unknown.

Relationship. In having medium size (L = 1.54–2.14 mm), narrow lip region (14–16 µm wide) and short odontostyle (13–15 µm long) the new species is close to a few species, namely A. amylovorus , A. punctatus , A. samarcandicus , and A. waenga , from which it is easily distinguished by the morphology of caudal region, shorter and more rounded, nearly hemispherical. Besides, it differs from A. amylovorus in its shorter odontostyle (vs 17–19 µm long) with larger aperture (vs occupying 58–63% of total length), longer neck (vs 382–406 µm long), and shorter tail (vs 32–36 µm long, c’ = 1.1–1.3). From A. punctatus in its more slender body (a = 29–31 vs 26), narrower lip region (vs about 21 µm broad), shorter odontostyle (vs about 18 µm long), shorter female genital branches (vs occupying 24–26% of body length), and comparatively shorter tail (vs c’ = 0.9). From A. samarcandicus in its narrower lip region (vs 17–19 µm wide), shorter odontostyle (vs 18–19 µm long) with larger aperture (vs occupying about one-half of total length or a little more), prerectum lacking any blind sac (vs often bearing), and tail lacking any dorsal concavity (vs with a very slight dorsal concavity). And, from A. waenga (see description bellow) in its shorter odontostyle (vs 16–19 µm long) with larger aperture (vs occupying 53–69% of total length), and comparatively longer odontophore (2.1–2.3 vs 1.7–2.0 times the odontostyle length).

The new species also resembles A. clamus , A. obtusicaudatus and A. salicinus . It can be distinguished from A. clamus in its shorter general size (vs L = 2.14–2.29 mm; neck 530–573 µm long), narrower lip region (vs 17–17.5 µm broad), shorter (vs 19–19.5 µm long) and more slender (4.6–5.2 vs 4.5–4.6 times as long as wide) odontostyle, rounded to hemispherical (vs convex-conoid) and shorter (vs 31–33 µm long, c’ = 0.9) female tail, and male absent (vs present). From A. obtusicaudatus in its narrower lip region (vs 16–23 µm broad), shorter odontostyle (vs 19–29 µm long) with larger aperture (vs occupying 49–72% of total length), and male absent (vs present). And, from A. salicinus in its narrower lip region (vs 16–18 µm broad), shorter (vs 18–20 µm long; 0.9 vs 1.1–1.2 as long as lip region diameter) and more robust odontostyle (4.6–5.2 vs 5.8–6.3 times as long as wide) with larger aperture (vs occupying 50–53% of total length), rounded to hemispherical (vs conical to convex-conoid) and shorter (vs 31–38 µm long, c’ = 1.0–1.4) tail.

Type locality and habitat. Spain, eastern Andalucía, Málaga province , La Axarquía shire, in tropical crops .

Type material. Female holotype and three female paratypes, deposited in the nematode collection of the University of Jaén , Spain .

Etymology. The specific epithet refers to the short caudal region that characterizes this species.

Figures

FIGURE 3. Aporcelaimellus brevicaudatus sp. n. (female). A: Anterior region in median view. B: Same in lateral, surface view. C: Pharyngeal expansion. D: Anterior genital branch. E, F: Posterior body region. G: Vagina. H: Entire body.

FIGURE 4. Aporcelaimellus brevicaudatus sp. n. (LM, female). A: Lip region in surface lateral view. B: Anterior region in median, lateral view. C: Vagina. D: Posterior body region. E, F, H: Caudal region. G: Entire. (Scale bars: A = 5 µm, B, C, E, F, H = 10 µm; D = 50 µm; G = 500 µm).