Metaporcelaimus romanicus ( Popovici, 1978 ) Andrássy, 2001

Krainer, Liubomyr, Susulovsky, Andrij & Peña-Santiago, Reyes, 2018, The genus Metaporcelaimus Lordello, 1965 (Nematoda, Dorylaimida, Aporcelaimidae) in Ukraine: Description of one known and two new species without hiatus, Zootaxa 4497 (1), pp. 127-140 : 128-131

Metaporcelaimus romanicus ( Popovici, 1978) Andrássy, 2001

( Fig. 1 )

Material examined: Fifteen females and eight males from a single location, in good state of preservation.

Morphometrics. See Table 1.

Description. Adult: Slender (a = 38–46) nematodes of medium to large size, 2.82–3.83 mm long. Body cylindrical, tapering towards both extremities, but more so towards posterior end as tail is conical. Habitus curved ventrad after fixation, especially in posterior body region, J- or C-shaped. Cuticle two-layered, 2–2.5 µm thick at anterior region, 4–4.5 µm at mid-body, and 9–10.5 µm on tail; outer layer thin, with constant thickness throughout body and fine but distinct transverse striation; inner layer thicker than outer one. Cervical lacunae absent. Lateral chord 18–24 µm wide, occupying 23–31% of mid-body diameter. Lip region offset by deep constriction, 2.6–3.1 times as broad as high and less than one-third (21–28%) of body diameter at neck base; lips separate, angular, with weakly protruding labial and cephalic papillae. Amphid fovea funnel-shaped, its aperture 8–10 µm or ca one-half (47–58%) of lip region diameter. Cheilostom nearly cylindrical, lacking any differentiation. Odontostyle typical of the genus, 4.3–5.1 times as long as wide, nearly equal (1.0–1.1 times) to lip region diameter, and 0.5–0.7% of body length; aperture 10–13.5 µm long or occupying up to three-fourths (56–74%) its length. Guiding ring plicate. Odontophore linear, rod-like, 1.5–1.9 times the odontostyle length. Anterior region of pharynx enlarging very gradually, basal expansion 401–535 µm, occupying up to two-thirds (53–64%) of total neck length; gland nuclei located as follows (n = 1): DO = 46%, DN = 51%, S1N1 = 61%, S1N2 = 72%, S2N = 79%. Nerve ring at 186–219 µm or 24–28% of total neck length from the anterior end. Cardia conical, 25–34 × 14–27 µm. Pharyngo-intestinal junction surrounded by a delicate ring-like structure, which appears visibly asymmetrical as its dorsal side is more developed and forms a lobe. A dorsal cell mass is perceptible in several specimens at level of anterior end of intestine. Tail conical with rounded tip, ventrally nearly straight, dorsally convex with a very weak but perceptible terminal concavity in some specimens; inner core nearly reaching the tail tip and visibly notched at its dorsal side; terminal hyaline portion 7–12.5 µm long; inner cuticle layer bearing a gap (discontinuity) at tail end; caudal pores two pairs, one subdorsal and one sublateral, both in posterior half of tail.

Female: Genital system didelphic-amphidelphic, with both branches equally developed, anterior 399–641 µm or 13–18% of body length, and posterior 404–674 µm or 13–19% of body length. Ovaries large, anterior 137–336 µm, posterior 74–370 µm long, with oocytes arranged first in two or more rows, then in a single row. Oviduct consisting of slender part consisting of prismatic cells and moderately developed pars dilatata with distinct lumen. A distinct narrowing with muscular sphincter separates oviduct and uterus. Uterus 281–397 µm long or 3.8–4.8 times of corresponding body diameter, and tripartite, that is consisting of a nearly spheroidal distal portion, a slender intermediate section with narrower lumen, and a thicker proximal portion with wide lumen. Abundant sperm cells observed in both distal and proximal uterine sections. Uterine egg ovoid, 85–114 × 37–50 µm (n = 16), ca 2.3 times longer than wide. Vagina extending inwards 36–45 µm, to ca one-half (45–58%) of body diameter: pars proximalis 27–34 × 14–21 µm, with somewhat sigmoid walls and surrounded by weak musculature, pars refringens with two adjacent trapezoidal pieces measuring 7–10 × 7–8 µm and a combined width of 15–19 µm, pars distalis 2.5–4.5 µm long. Vulva a nearly equatorial, transverse slit. Prerectum 3.1–5.3, rectum 1.2–1.6 anal body diameters long.

Male: Genital system diorchic, with opposed testes. Sperm cells 7–8.5 × 3–3.5 µm, oval in shape. In addition to the ad-cloacal pair, there is a series of 9–12, more or less regularly spaced, 14–21 µm apart, ventromedian supplements, one or two of them lying within the range of spicules, with the most posterior of them situated at 45–57 µm from the cloacal aperture. Spicules dorylaimid, their total length along the arc 1.2–1.3 times that at the chord, 4.6–5.8 times longer than wide and 1.9–2.3 times longer than body diameter at cloacal aperture: dorsal side regularly convex and ventral contour bearing prominent hump and hollow, the former located at 33–40% of spicule total length from its anterior end; curvature 116–120°; head well developed, 12–16 µm long, occupying 13–18% of total spicule length, its dorsal side conspicuously curved at its anterior end and 1.4–1.7 times longer than the ventral one, which is almost straight; median pieces 12–16 times as long as wide, occupying 25–33% of spicule maximum width, reaching the tip of the spicule; posterior end of spicules 6.5–8 µm wide. Lateral guiding pieces with slightly sigmoid edges, 24–26 µm long, distally slightly bifurcate.

Locality and habitat. Ukraine, Uzhhorod (N 48°38'39.52", E 22°18'11.73"), in soil around roots of Quercus robur L.

Remarks. The Ukrainian population of M. romanicus is nearly identical to previously reported populations from Romania and Switzerland ( Popovici 1978, Andrássy 2001, Álvarez-Ortega & Peña-Santiago 2010), with no remarkable differences, either morphological or morphometric. This report suggests that the species might be widely spread in soils of Central and Eastern Europe.

Figures

FIGURE 1. Metaporcelaimus romanicus (Popovici, 1978) Andrássy, 2001. A: Anterior region in lateral, median view. B, C: Female, caudal region. D: Vagina. E: Pars dilatata oviductus-uterus junction. F: Uterine egg. G: Pharyngo-intestinal junction. H, I: Male, caudal region. (Scale bars = 10 µm.)