Aporcelaimellus tenuis, Álvarez-Ortega, Sergio, Abolafia, Joaquín, Liébanas, Gracia & Peña-Santiago, Reyes, 2012

Álvarez-Ortega, Sergio, Abolafia, Joaquín, Liébanas, Gracia & Peña-Santiago, Reyes, 2012, Studies on the genus Aporcelaimellus Heyns, 1965 (Nematoda, Dorylaimida, Aporcelaimidae). Four new species with complex uterus from Southeastern Iberian Peninsula, Zootaxa 3551, pp. 1-24 : 18-22

Aporcelaimellus tenuis sp. n.

( Figs 8 & 9 )

Material examined. Five females and three males; in general in good condition. Measurements. See Table 3 .

Population Hoya de Baza, Granada

Holotype Paratypes

Description. Adult: Slender to very slender nematodes of medium size, 1.89–2.70 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, 3.0–4.5 μm in midbody and 4.0–6.5 μm on tail; outer layer thin a with perceptible transverse striation, especially at anterior region, intermediate layer nearly as thick as inner one except at caudal region, and inner layer thicker and more refractive than the others. Cervical lacunae not observed in the specimens examined. Lateral chord 6–10 μm wide or 11–18% of mid-body diameter. Two ventral and two dorsal body pores often present at level of odontophore. Lip region offset by deep constriction, 2.8–3.3 times as wide as high and one-fourth to one-third (26–34%) of body diameter at neck base; lips rounded and rather separated, with low papillae. Amphid fovea funnel-shaped, its aperture 7.5–9.0 μm or about one-half (49–53%) of lip region diameter. Cheilostom nearly cylindrical, lacking any differentiation. Odontostyle typical of the genus, 4.5–5.5 times as long as wide, 0.9–1.1 times as long as lip region diameter, and 0.57–0.84% of body length; aperture 9.5–13 μm long or occupying three-fifths to two-thirds (60–70%) its length. Guiding ring plicate. Odontophore linear, rod-like, 1.6–2.0 times the odontostyle. Anterior region of pharynx enlarging very gradually; basal expansion 8.4–9.9 times as long as wide, 5.0–6.1 times as long as body diameter, and occupying 51–57% of total neck length; pharyngeal gland nuclei located as follows: DN = 54–56 (n=3), S1N1 = 69 (n=1), S1N2 = 73–76 (n=2), S2N = 82–87 (n=2). Nerve ring located at 148–187 μm from anterior end or 29–32% of total neck length. Cardia conical, 14– 21 x 14–17 μm; a ring-like structure is present surrounding its junction to pharyngeal base. A dorsal cellular mass about 100 μm long is present at level of the anterior end of intestine. Tail short, convex conoid; inner cuticle layer not reaching the tip, hence a short hyaline portion is visible in all the specimens examined since the intermediate layer becomes thickened. Caudal pores two pairs, one lateral and other subdorsal, at the middle of the tail.

Female: Genital system didelphic-amphidelphic, with both branches equally and moderately developed, the anterior 271–351 μm or 10–14% of body length, and the posterior 234–345 μm or 11–13% of body length. Ovaries often not reaching the sphincter level, the anterior 71–108 μm and the posterior 60–125 μm long; oocytes arranged first in two or more rows, then in a single row. Oviduct 80–144 μm long or 1.5–2.8 times the corresponding body diameter, consisting of slender part with prismatic cells and a well developed pars dilatata with visible lumen. Oviduct and uterus are separated by a strong sphincter. Uterus 135–213 μm long or 2.5–3.8 times the corresponding body diameter and bipartite, consisting of a narrower and shorter distal region with narrow lumen, and a wider proximal part having thicker walls and distinct lumen; one female bearing sperm cells inside the uterus. Vagina extending inwards 25–34 μm or up to one-half (45–50%) of body diameter; pars proximalis 16– 23 x 12–20 μm, with somewhat sigmoid walls and surrounded by weak musculature; pars refringens with two triangular to trapezoidal pieces measuring 5.5–9.0 x 4–7 μm and with a combined width of 10–16 µm; pars distalis short, 2–3 μm. Vulva a slightly post-equatorial, transverse slit. Prerectum 2.5–6.3, rectum 1.1–1.7 times the anal body diameter.

Male: Prerectum 5.0, cloaca 1.6, 1.7 times the anal body diameter long. Genital system diorchic, with opposite testes. In addition to the ad-cloacal pair, situated at 9–10 μm from cloacal aperture, there is a series of 11, 12 (n=2) irregularly spaced (6–14 µm apart) ventromedian supplements, the posteriormost of which is situated at 53, 62 μm (n=2) from ad-cloacal pair and out the range of spicules. Spicules curved ventrad and robust, 5.8–6.0 times as long as wide, and 1.6–2.0 times as long as anal body diameter. Lateral guiding pieces 19–20 μm long, 7.8–8.9 times as long as wide.

Diagnosis. This species is characterized by its body 1.89–2.70 mm long and comparatively slender (a = 35–49), lip region offset by constriction and 15–18 μm broad, odontostyle 15–21 μm long with aperture occupying 60–70% of its length, neck 488–645 μm long, pharyngeal expansion 251–366 μm long or 51–57% of total neck length, a dorsal cellular mass at anterior end of intestine, uterus bipartite and 135–213 μm long or 2.5–3.8 times the corresponding body diameter, pars refringens vaginae with two well developed sclerotized pieces, vulva transverse (V = 55–58), tail convex conoid with rounded terminus (25–40 μm, c = 64–92, c’ = 0.8–1.1) and bearing a perceptible hyaline portion, spicules 52–66 μm long, and 11–12 irregularly spaced ventromedian supplements with hiatus.

Relationships. The combination of two characters, namely the comparatively slender body (a = 35–49) and its long and bipartite uterus, are very useful to compare the new species to its congeners.

In having medium size (L = 1.89–2.70 mm) and odontostyle comparatively short (15–21 µm long), the new species is very similar to A. amylovorus , A. clamus Thorne, 1974 , A. samarcandicus , and A. vanderlaani , from which it is easily distinguishable in its more slender body (vs a = 24–37). Moreover, it differs from A. amylovorus in its longer body (vs L = 1.63–1.79 mm) and neck (vs 382–405 μm long), longer uterus (vs about 45 μm long), vulva more posterior (vs V = 50–53), tail comparatively shorter (c’ = 1.1–1.3), and male present (vs absent); from A. clamus (mainly based on data provided by Álvarez-Ortega & Peña-Santiago, 2010b) in its longer and bipartite uterus (vs 0.9–1.0 times of corresponding body diameter and simple), and more posterior vulva (vs V = 50–52); from A. samarcandicus in its longer body (vs L = 1.47–1.70 mm) and neck (vs 434–466 μm long), longer odontostyle aperture (vs occupying about one-half of total length or a little more), and male present (vs absent); and from A. vanderlaani in its more posterior vulva (vs V = 50–51) and longer female tail (vs 18 μm long, c’ = 0.7).

In having uterus long and bipartite, the new species is close to A. communis sp. n. and A. pycnus , but it differs from both species in its smaller general size (vs L very exceptionally under 2.50 mm), narrower lip region (vs 19 μm wide or more), and lower number of ventromedian supplements (vs 16–25). Besides, it can be distinguished from A. communis sp. n. in often bearing cuticular irregularities at vulva area, caudal region bearing a well (vs hardly) perceptible hyaline portion, and shorter spicules (vs 89–118 μm long); and from A. pycnus in its more slender body (vs a = 21–27), more posterior location of S1N2 (closer to S2N than to DN vs closer to DN than to S2N), uterus with two sections of dissimilar (vs similar size), and spicules regularly curved ventrad (vs L-shaped).

Finally, A. tenuis sp. n. can be also compared with A. kazirangus and A. micropunctatus , from which it is distinguished in the uterus morphology (bipartite vs simple tube). Moreover, it differs from A. kazirangus in its narrower lip region (vs 19–21 μm wide) and longer odontostyle aperture (vs occupying about one-half of total length); and from A. micropunctatus in its ventral body pores along entire body absent only present at anterior region level (vs ventral body pores very abundant along entire body), higher number (vs 7–9 ventromedian supplements) and irregularly (vs nearly regularly) spaced ventromedian supplements, and shorter spicules (vs 79–87 μm long).

Type locality and habitat. The new species was collected in eastern Andalucía, Granada, in the natural area “Hoya de Baza”, in association with willow ( Salix sp.) and esparto field ( Stipa tenacissima ).

Type material. Female holotype and three female and one 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 is a Latin term that means ‘slender’, and refers to the very slender body.

Figures

FIGURE 8. Aporcelaimellus tenuis sp. n. A: Anterior region in median view. B: Same in lateral, surface view. C: Male, entire body. D: Female, anterior genital branch. E: Pharyngeal expansion. F: Female, entire body. G: Male, posterior body region. H: Female, posterior body region. I: Spicule and lateral guiding piece. J: Vagina.

FIGURE 9. Aporcelaimellus tenuis sp. n. (LM). A: Female, entire. B, C: Anterior region in median, lateral view. D: Lip region in surface, lateral view. E: Vagina. F: Female, bipartite uterus. G: Female, posterior body region. H: Dorsal cellular mass at anterior end of intestine. I: Pharyngo-intestinal junction. J: Male, lateral guiding pieces. K, L: Female, caudal region. M: Male, caudal region. N: Spicules. (Scale bars: A = 500 µm, B, I, N = 20 µm; C, E, K-M = 10 µm; D, J = 5 µm; F-H = 50 µm).

Tables

TABLE 3. Morphometric data of Aporcelaimellus tenuis sp. n. Measurements in μm (except L, in mm), and in the form: mean ± standard deviation (range).

Character	n Ƥ	4ƤƤ	333
L	2.60	2.34 ± 0.31 (2.02–2.70)	2.21 ± 0.29 (1.89–2.46)
a b c	49 4.7 74	42.5 ± 4.9 (37–48) 4.4 ± 0.5 (4.1–5.0) 80.7 ± 10.9 (67–92)	39.8 ± 4.4 (35–44) 5.0 (n=1) 72.6 ± 8.9 (64–82)
c' V	1.1 57	0.9 ± 0.1 (0.8–1.0) 56.2 ± 1.8 (55–58)	0.9 ± 0.0 (0.9–1.0) –
Lip region diam.	15	16.0 ± 1.4 (15–18)	15.5 ± 0.7 (15–17)
Odontostyle length	18	17.2 ± 2.6 (15–21)	16.7 ± 1.4 (15–18)
Odontophore length Guiding ring from ant. end	31 8	30.4 ± 4.8 (28–38) 8.9 ± 0.9 (8–10)	29.0 ± 1.4 (28–31) 7, 8 (n=2)
Neck length Pharyngeal expansion length	553 292	545 ± 87 (495–645) 298 ± 60 (251–366)	488 (n=1) 272 (n=1)
Diam. at neck base	49	52.6 ± 11.5 (45–70)	51, 58 (n=2)
at midbody	53	55.9 ± 12.4 (45–74)	55.9 ± 8.5 (47–65)
at anus/cloaca	32	33.4 ± 8.9 (27–46)	32.5 ± 2.5 (30–35)
Prerectum length	111	140.5 ± 40.3 (112–169)	175 (n=1)
Rectum length Tail length	45 35	46.8 ± 10.4 (37–62) 29.5 ± 7.0 (25–40)	51, 56 (n=2) 30.6 ± 3.5 (28–35)
Spicule length	–	–	59.2 ± 6.9 (52–66)
Ventromedian supplements	–	–	11, 12 (n=2)