Contributions to Zoology, 70 (2) (2001)Leonor Cristina de Villalobos; Ignacio Ribera; David T. Bilton: First data of Iberian Nematomorpha, withredescription of Gordius aquaticus Linnaeus, G. plicatulus Heinze, Gordionus wolterstorffii (Camerano) and Paragordius tricuspidatus (Dufour)
Systematics

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Gordionus wolterstorffii (Camerano, 1888)

(Fig. 4)

Camerano (1888: 6)

Gordius pleskei Camerano (1896)

Parachordodes wolterstorffii Camerano (1897)

Parachordodes pleskei Camerano (1904)

Gordionus wolterstorffii Heinze (1937)

Diagnosis. – Dimensions as in table 1. Body pale brown. Anterior end pointed (Fig. 4A). Posterior end bilobed, with lobes (in the studied specimen) 413 µm long and 146 µm wide (Fig. 4B). Precloacal area (Fig. 4C) with bristle fields formed by long setae (some of them bifurcated). The bristle fields do not join above the cloacal opening. Cloacal opening oval, surrounded by short and sparse circumcloacal bristles; distance between cloacal opening and the base of the lobes 60 µm. Area posterior to the cloacal opening and internal side of the lobes up to the middle of their length with numerous bristles with acuminate apices, 13 µm long (Figs 4D, E).

FIG2

Fig. 4. Gordionus wolterstorffii, male. A, anterior apex; B, posterior apex; C, precloacal bristles or bristle fields (note the bifurcated apex of some of them); D, internal side of the terminal lobes with postcloacal spines. co, cloacal opening; if, interareolar furrow; mg, adhesive warts (or “lateral blumps”); mc, areoles; l, lobes; p, pores; pb, precloacal bristles; ps, postcloacal spines; s, spines. Scale bars of A= 500 µm; B, C, D, F and G= 100 µm; E= 10 µm; H= 20 µm.

Areoles of the cuticle with some variations depending on the region of the body (as seen with light microscope), some large and others shallower, very flat in appearance, with or without defined edges. In the dorsal region (Fig. 4H) the flat areoles fuse to form long strings, with almost indistinguishable limits between them, and separated by very irregular interareolar furrows. In the ventral region (Figs 4F, G) the cuticular areoles are better defined, with granules and rounded apex setae in the interareolar furrows, with an irregular rectangular shape (length from 20.5 to 23.3 µm, width from 7 to 14 µm) (although in the posterior end of the body they also form longitudinally arranged strings in which the anterior and posterior limit of each individual areole are difficult to distinguish). In the posterior extreme of the ventro-lateral area (Figs 4F, G) there are oval structures (“lateral blumps” according to Cham et al., 1983; “adhesive warts” in the more recent terminology of Schmidt-Rhaesa, in press), at a distance about 0,6 mm anterior to the cloacal openning. These structures become larger, oval, longitudinally aligned, and with depressions in the interareolar spaces (as observed with SEM), with length from 17.6 to 26.5 µm and width from 4.0 to 6.2 µm. They are surrounded by a deep sulcus, and usually occur in pairs, alternate or aligned (but not contiguous), with spiniform structures between them.

FIG2

Fig. 4. Gordionus wolterstorffii, male. E, detail of the postcloacal spines; F and G, cuticle of the lateroventral area; H, cuticle of the dorsal area of the body. co, cloacal opening; if, interareolar furrow; mg, adhesive warts (or “lateral blumps”); mc, areoles; l, lobes; p, pores; pb, precloacal bristles; ps, postcloacal spines; s, spines. Scale bars of A= 500 µm; B, C, D, F and G= 100 µm; E= 10 µm; H= 20 µm.

Remarks. – Although the the species of Gordionus have only one type of areoles, Gordionus wolterstorffii has some transitional changes in the type of areoles across different regions of the body (without defining clear types).

It is interesting to note the different interpretation of the granulated structures of the areoles. Camerano (1888) and Cham et al. (1983) note a large quantity of these granulated structures in the interareolar depressions on most of the cuticle. According to our observations with the light microscope, the cuticle in the dorsal region seemed to have long elevated ridges separated by criss-crossing rows with granules. When observed with SEM, they appeared as areoles with poorly defined edges, with lateral projections instead of granules (it cannot be discarded the possibility that the observed areoles were a transition form to ventral areoles). Similarly, what appear to be pores in the spaces between flat areoles proved to be a continuous sulcus surrounding them. In the ventral side the interareolar spaces have both lateral projections and very small seta, more like granules. We thus agree with Cham et al. (1983) in the observation of differences in the structure of the areoles in different parts of the body.

The posterior apex of Gordionus wolterstorffii has the same general structure as that of G. violaceus, G. linourgos de Villalobos, Ribera & Downie, 1999 and G. diligens de Villalobos, Ribera & Downie, 1999 (de Villalobos et al., 1999), with bristle fields at the sides and anterior to the cloacal opening, and postcloacal spiniform structures along the inner side of the terminal lobes. The cuticle of all these species is, however, clearly different: G. violaceus has well defined round and polygonal areoles, with a large number of short hairs in the interareolar sulcus; G linourgos has oval areoles and the cuticle is covered with transversal striae; and G. diligens has round areoles connected between them by cuticular projections crossing the interareolar sulci.

The species was previously recorded from Britain, Belgium, north Italy and central Europe (Schmidt-Rhaesa, 1997).

Ecological notes. – The single studied specimen was found in a marginal pond associated with a mountain river (Table 2). Known from a number of Coleoptera hosts, mainly Carabidae (Schmidt-Rhaesa, 1997).

Genus Paragordius Camerano

Type species Filaria tricuspidata Dufour, 1828

Camerano (1897: 400)

Diagnosis. – Anterior end distinctly tapered. Posterior apex of males bilobed, with long and narrow lobes. Cloacal opening oval, without circumcloacal spines or bristles, but with short acute postcloacal bristles covering also the inner side of the terminal lobes. Some species (e.g. the European P. tricuspidatus (Dufour, 1828), and the American P. varius (Leidy, 1851) and P. esavianus (Carvalho, 1942)) have precloacal bristles extending anteriorly along the longitudinal ventral sulcus. Posterior end of females trilobed, with terminal cloacal opening among the lobes. Cuticle similar in both sexes, with poorly defined, shallow areoles.