Aporcelaimellus castaneanus, 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 : 7-10

Aporcelaimellus castaneanus sp. n.

( Figs. 3 & 4 )

Material examined. Three females and three males; in good state of preservation.

Measurements. See Table 1.

Description. Adult: Moderately slender nematodes of medium size, 2.18–2.83 mm long. Body cylindrical, tapering towards both extremities, but more so towards the posterior. Habitus curved ventrad after fixation, especially in posterior body region, C– or G-shaped. Cuticle three-layered, 2–3 μm at anterior region, 4–5.5 μm in mid-body and 5–7 μm on tail; inner layer thicker than outer one. Cervical lacuna present, reaching the level of middle odontophore. Lateral chord 11–16 μm wide or 10–15% of mid-body diameter. Two ventral and two dorsal body pores are usually present at level of odontophore. Lip region somewhat angular, offset by constriction, 2.8–3.2 times as wide as high and one-fifth to one-fourth (19–27%) of body diameter at neck base; lips mostly separated, with hardly protruding papillae. Amphid fovea funnel-shaped, its aperture 11–13 μm or about foursevenths (53–58%) of lip region diameter. Cheilostom nearly cylindrical, lacking any differentiation. Odontostyle typical of the genus, 4.8–5.2 times as long as wide, 1.0–1.1 times as long as lip region diameter, and 0.77–0.99% of body length; aperture 14–15 μm long or occupying about two-thirds (62–67%) its length. Guiding ring well distinct, plicate. Odontophore linear, rod-like, 1.8–2.0 times the odontostyle. Anterior region of pharynx enlarging very gradually; basal expansion 5.4–7.6 times as long as wide, 2.7–4.2 times as long as body diameter, and occupying 50–54% of total neck length; pharyngeal gland nuclei located as follows: DN = 59, S1N1 = 71 (n=1), S1N2 = obscure; S2N = 88–89. Nerve ring located at 185–210 μm from anterior end or 31–33% of total neck length. Cardia conical, 20– 23 x 18–20 μm; a ring-like structure is present surrounding its junction to pharyngeal base, and a dorsal cell mass is perceptible in several specimens at level of anterior end of intestine. Tail conoid with broadly rounded terminus, ventrally more straight, dorsally convex. Caudal pores two pairs, one dorsal and other subdorsal, both at the middle of tail and very close.

Female: Genital system didelphic-amphidelphic, with both branches equally and well developed, the anterior 284 μm (n=1) or 13% (n=1) of body length [529 μm (n=1) or 19% (n=1) of body length with an uterine egg inside], and the posterior 310, 471 μm (n=2) or 14, 17% (n=2) of body length [608 μm (n=1) or 22% (n=1) of body length with an uterine egg inside]. Ovaries large, often reaching and surpassing the sphincter level, the anterior 150–351 μm and the posterior 142–371 μm long; oocytes arranged first in two or more rows, then in a single row. Oviduct 111–229 μm long or 1.2–1.8 times the corresponding body diameter, consisting of slender part with prismatic cells and a moderately developed pars dilatata. Oviduct and uterus are separated by a well perceptible sphincter. Uterus 164–253 μm (n=2) long or 1.8–2.1 (n=2) times the corresponding body diameter (306, 348 μm (n=1) long or 2.4, 2.7 (n=1) times the corresponding body diameter with uterine eggs inside), tripartite, i.e. consisting of a dilated distal portion close to sphincter, a narrower, short, intermediate section with visible lumen, and a longer and wider proximal portion; two females contain sperm cells within the proximal portion. Uterine egg ovoid, 97 x 70 μm (n=1), 1.4 (n=1) times as long as wide. Vagina extending inwards 44–49 μm or one-third to one half (34–53%) of body diameter; pars proximalis 33– 37 x 19–25 μm, with somewhat sigmoid walls and surrounded by weak musculature; pars refringens with two triangular to trapezoidal, close pieces measuring 11– 12 x 8–9 μm and with a combined width of 13–16 µm; pars distalis very short, 2–3 μm. Vulva a post-equatorial, transverse slit. Prerectum 2.0–2.4, rectum 1.2–1.3 times the anal body diameter long.

Male: Genital system diorchic, with opposite testes. In addition to the ad-cloacal pair, situated at 11–13 μm from cloacal aperture, there is a series of 14–15 irregularly spaced (11–31 µm apart) ventromedian supplements, one to three of them lying within the range of spicules, and posteriormost of which is situated at 33–34 μm from adcloacal pair. Spicules curved ventrad and robust, 5.7–6.7 times as long as wide, and 1.8–2.1 times as long as anal body diameter. Lateral guiding pieces 22–24 μm long, 6.8–7.6 times as long as wide. Prerectum 2.0–3.3, cloaca 1.4–1.5 times the anal body diameter long.

Diagnosis. The new species is characterized by its body 2.18–2.83 mm long, lip region offset by constriction and 20–23 μm broad, odontostyle 22–24 μm long with aperture occupying 62–67% its length, neck 581–662 μm long, pharyngeal expansion 300–355 μm long or 50–54% of total neck length, a dorsal cell mass present behind the level of cardia, uterus tripartite and 164–348 μm long or 1.8–2.7 times the corresponding body diameter, pars refringens vaginae present, V = 52–58, tail conical with rounded terminus (44–52 μm, c = 48–60, c’ = 0.8–1.1), spicules 94–103 μm long, and 14–15 irregularly spaced ventromedian supplements which lack hiatus.

Relationships. The new species shows an atypical combination of two characters within Aporcelaimellus : female with uterus long and tripartite and male without pre-cloacal space (hiatus). Such a combination allows comparison and separation from its congeners.

In having medium size (L = 2.18–2.83 mm), comparatively wide lip region (20–23 μm) and long odontostyle (22–24 µm) the new species is morphologically close to several species, namely A. crassus Andrássy, 2009c , A. futaii Khan & Araki, 2002 , A. micropunctatus Botha & Heyns, 1990 and A. porcus Thorne, 1974 . It differs from A. crassus in its comparatively shorter odontostyle (vs about 1.2 times as long as lip region diameter), more posterior vulva (vs V = 47–51), tail comparatively shorter (vs c’ = 1.1–1.3) lacking any dorsal concavity (vs with a slight concavity), and male present (vs absent); from A. futaii in its tail conoid with rounded terminus and lacking any dorsal concavity (vs tail convex conoid with a dorsal concavity at its terminal portion), higher number (vs 7–10) of ventromedian supplements without (vs with) hiatus, and longer spicules (vs 82–90 µm long); from A. micropunctatus in having inconspicuous (vs conspicuous) body pores along the entire body, complex uterus (tripartite vs simple), higher number (vs 7–9) and irregularly (vs nearly regularly) spaced ventromedian supplements without (vs with) hiatus, and longer spicules (vs 79–87 µm); and from A. porcus in its more posterior vulva (V = 46), and male with higher number (vs 8) of ventromedian supplements.

Finally, in having uterus tripartite, A. castaneanus sp. n. is close to A. alpujarrensis sp. n., A. kikereensis , A. porosus , and A. propinquus . It can be distinguished from A. alpujarrensis sp. n. is its larger general size (vs L = 1.72–1.91 mm), wider lip region (vs 14–15 µm), longer odontostyle (vs 14–16 µm), higher number of ventromedian supplements (vs 7–9) without (vs with) hiatus, and longer spicules (vs 56–60 µm long). From A. kikeerensis in its more slender (vs a = 18–21) and longer (vs L = 1.10–1.45) body, shorter odontostyle (vs 26–28 µm or 1.3–1.4 lip region widths long), more anterior vulva (vs V = 60–61), female tail conoid with rounded terminus (vs conical digitate and dorsad bent) and longer (vs 30–36 µm, c = 37–50), and male present (vs absent). From A. porosus in having inconspicuous (vs especially conspicuous) body pores along the entire body, shorter odontostyle (vs 26–30 µm), tail conoid and longer (vs rounded and 25–33 µm long, c’ = 0.5–0.7), shorter spicules (vs 81–87 µm), and higher number of ventromedian supplements (vs 8). And, from A. propinquus in its larger general size (vs L = 1.06–1.18 mm, neck 286–329 µm long), wider lip region (vs 13–14 µm), longer odontostyle and aperture (vs 32–38 µm long, aperture 42–47% of total length), longer tail (vs 17–19 µm), lower number (vs 31–34) and irregularly spaced (vs almost continuous) ventromedian supplements, and longer spicules (vs 32–38 µm).

Type locality and habitat. Spain, province of Granada, Sierra Nevada National Park, where it was collected in forest soil whose dominant tree species were chestnut ( Castanea sativa ) and oak ( Quercus sp.).

Other locality and habitat. The new species was also collected in association with willow in a dry river from eastern Andalucía, Granada, in the natural areas “Sierra Nevada-Cerro Huenes”.

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 chestnut (genus Castanea ), one of the dominant tree species in the type habitat of the new taxon.

Figures

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

FIGURE 4. Aporcelaimellus castaneanus sp. n. (LM). A: Female, entire. B: Male, entire, C, D: Anterior region in median, lateral view. E: Neck region. F: Lip region in lateral, surface view. G: Female, anterior genital branch. H: Male, posterior body region. I: Cardia. J: Vagina. K: Male, spicules and caudal region. L: Male, caudal region. M: Female, caudal region. (Scale bars: A, B = 500 µm; C, I, L, M = 20 µm; D, F, J = 10 µm; E, G, H = 100 µm; K = 50 µm).