Pungentus engadinensis (Altherr, 1950)

Peña-Santiago, Reyes, Ciobanu, Marcel & Abolafia, Joaquin, 2013, Characterization of Iberian species of the genus Pungentus Thorne & Swanger, 1936 (Nematoda, Dorylaimida, Nordiidae), European Journal of Taxonomy 52, pp. 1-17 : 6-9

Pungentus engadinensis (Altherr, 1950)

Figs 1 D-H, 3-4

Diagnosis

This species is distinguished by its body length of 0.77-1.21 mm, a three-layered cuticle (especially distinct at caudal region), a lip region offset by a constriction and being 8-10 μm wide, an odontostyle 14-20 μm long and 1.7-1.9 times the lip region width or 1.5-2.2% of the total body length, a neck 194- 280 μm long, a pharyngeal expansion 71-115 μm long or 35-42% of total neck length, a monodelphicopisthodelphic female genital system, with anterior genital branch absent, uterus a simple tube 39-44 μm long or 1.4-1.8 times the body diameter, V = 41-54, a rounded tail (14-28 μm, c = 40-63, c’ = 0.8-1.1), spicules 25-28 μm long and three to five widely spaced, ventromedian supplements that lack hiatus.

Material examined

More than one hundred females and one male from more than 20 locations, in various states of conservation.

Morphometrics

See Table 1 .

Description

General features of adults

Slender nematodes of small to medium size, 0.77-1.21 mm long. Habitus after fixation curved ventrad, C-shaped in females, G-shaped in male. Body cylindrical, tapering towards the anterior end. Cuticle three-layered, especially distinguishable at caudal region, 1.5-2.5 μm thick in anterior region and at mid-body and 2.5-4.0 μm on dorsal side of tail; outer layer with very fine transverse striation. Lateral chord 5.5-6.5 µm wide or occupying 19-24 % of mid-body diameter, very granular but lacking any differentiation. Ventral body pores perceptible along the entire body. Lip region offset by constriction, 2.4-3.2 times as wide as high and ca. one-third (31-38%) of body diameter at neck base. Under SEM, lips mostly amalgamated and somewhat angular, lacking any distinguishable striation; labial and cephalic papillae very distinct and visibly protruding, the inner labial papillae situated at the top of low but perceptible lobes; perioral area with (apparently) four small elevations (liplets) surrounding the short dorsoventral, slit-like oral opening. Amphid fovea cup-shaped, opening at level of cephalic constriction, occupying 5.0-5.5 μm or about three-fifths of lip region diameter. Cheilostome almost cylindrical, but a little wider at its posterior half and with its walls distinctly thicker at the anterior half; circum-oral refractive dots very conspicuous. Odontostyle 11-14 times as long as wide, 1.8-1.9 times longer than lip region diameter or 1.5-2.2% of total body length; aperture 2.5-3.0 μm long or less than one-sixth its length. Odontophore rod-like, but with small thickenings at its base, nearly as long (0.9-1.1 times) as odontostyle. Guiding ring double, located at 10-11 μm or 1.1-1.3 times the lip region diameter from anterior end. Pharynx enlarging very gradually; basal expansion 5.5-7.4 times as long as wide and 3.1- 3.9 times the corresponding body diameter, occupying about two-fifths (36-41%) of total neck length. Pharyngeal gland nuclei obscure in the specimens examined. Nerve ring at 80-91 μm from anterior end or 32-38% of total neck length. Cardia rounded conoid, 5.0-6.5 x 7-10 μm.

Female

Genital system monodelphic-opisthodelphic: anterior branch absent and posterior one moderately developed, 76-125 μm long. Ovary 53-110 μm long, often reaching and surpassing the sphincter level; oocytes first in two or more rows, then in one row. Oviduct 39-63 μm long, or 1.5-2.4 times the body diameter, consisting of a slender portion with prismatic cells and a moderately developed pars dilatata. Sphincter distinct between oviduct and uterus. Uterus a simple tube-like structure, 39-44 µm long or 1.4- 1.8 times the body diameter. Uterine egg 82-92 x 21-26 μm, 2.5-3.5 times as long as the corresponding body diameter. Vagina extending inwards 12-17 μm or one-half to three-fifths (50-60%) of body diameter; pars proximalis 7-9 x 6-12 μm, with parallel or distally convergent walls and enveloped by weak circular musculature; pars refringens with two small, rectangular or triangular pieces measuring 1 x 3 μm and with a combined width of 5-6 μm; and pars distalis 3-4 μm long. Vulva a nearly equatorial, about 5 μm long, transverse slit. Prerectum 2.3-4.1, rectum 0.8-1.2 anal body diameters long. Tail short and rounded, visibly more convex dorsally; the cuticle at its level consisting of a thick inner layer, a distinct intermediate layer and thinner outer layer, occasionally bearing blister-like structures (saccate bodies). Two pairs of causal pores, one subdorsal, another sublateral, at the middle of the tail.

Male

Very rare, only one specimen found among several dozens of females. Genital system diorchic, with opposite testes. In addition to the ad-cloacal pair, situated at 6.5 µm from cloacal aperture, there is a series of five widely spaced, 10-20 µm apart, ventromedian supplements, the most posterior of which is located 9.5 µm from the ad-cloacal pair, within the range of spicules. Spicules dorylaimoid, about 5.0 times as long as wide and 1.2 times the body diameter. Lateral guiding pieces obscure. Caudal region similar to that of the female.

Distribution

Pungentus engadinensis is the most widely spread species of its genus in the southern Iberian Peninsula, having been collected from more than 20 locations with many kinds of natural and cultivated systems, whose dominant plant species are holm-oak ( Quercus spp.), Mediterranean brushwood ( Cistus spp.), pine ( Pinus spp.), poplar ( Populus nigra Linnaeus, 1753 ), almond ( Prunus amygdalus Batsch, 1801 ), Mahaleb cherry ( Prunus mahaleb Linnaeus, 1753 ), hazel ( Corylus avellana Linnaeus, 1753 ), etc.

Remarks

The above description of Iberian populations perfectly fits the available information about this species, especially the contributions by Andrássy (1962) and Coomans & Geraert (1962), who provided detailed data and illustrations. Nevertheless, some relevant features such as the three-layered nature of the cuticle, the morphology of the lip region and the structure of the female genital system are here described for the first time. Besides, the range of some measurements (body length, tail length, etc.) and morphometrics (vulva position) are in general extended.

Pungentus engadinensis is certainly the most common species in this genus, having been reported from eleven countries on three continents, all of them in the Holarctic: Belgium ( Coomans & Geraert 1962), Canada ( Winiszewska-Slipinska 1987a; Andrássy 1991), Hungary ( Andrássy 1962, 1991, 2009), Iraq ( Vinciguerra 2006), Italy ( Zullini 1971, 1975), Poland ( Brzeski 1963; Winiszewska-Slipinska 1987a, b), Spain ( Castillo et al. 1985), Switzerland ( Altherr 1950b, 1952, 1953), the Netherlands ( Loof & Coomans 1970; Bongers 1988), United Kingdom (Wasilewska 1967) and USA ( Vinciguerra 2006).

Figures

Fig. 1. Iberian Pungentus species. – A-C. Pungentus clavatus Ahmad & Jairajpuri, 1979. – D-H. Pungentus engadinensis (Altherr, 1950). – I-K. Pungentus marietani Altherr, 1950. – L-N. Pungentus silvestris Coomans & Geraert, 1962. – A, D, I, L. ♀, anterior region in lateral median view. B, E, J, M. ♀, genital system. C, G, K, N. ♀, posterior body region. F. ♂, posterior body region. H. ♀, caudal region.