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

To refer to this article use this url: http://contributionstozoology.nl/vol70/nr02/a02

Gordius aquaticus Linnaeus

(Fig. 1)

Diagnosis. – Dimensions as in table 1, from 75 to 987 mm. Male: body colour uniform pale brown (the specimens studied had no pale spots or dark ring behind the calotte, but see comments in Schmidt-Rhaesa, 1997). Anterior end acuminate, with subterminal mouth opening. Cloacal opening oval. Postcloacal crescent with a total length from 62.2 to 723.3 µm, and a maximum width from 12.5 to 87.0 µm in the specimens studied. Posterior lobes short and broad, between 42.3 × 33 and 400 × 73.3 µm (Fig. 1A); apex round, with sparse spiniform processes 15 µm long in the inner area of the lobe, no bristles or other spiniform structures on the lateral sides of the lobes (Fig. 1B). Cuticle smooth, only marked with fine subcuticular lines (Fig. 1C), with scattered acuminate tubercles no higher than 5.3 µm.

FIG2

Fig. 1. Gordius aquaticus, male. A, terminal lobes and postcloacal crescent; B, apex of the terminal lobes; C, cuticle. b, bristles; co, cloacal opening; l, lobes; pc, postcloacal crescent; t, tubercle. Scale bar of A= 1.000 µm; B= 100 µm, C= 10 µm.

Female: anterior end acuminate. Posterior end not bilobed, with a central cloacal opening. Cuticle as in males. See tables 1 and 2 for the material studied.

Remarks. – The Iberian specimens of G. aquaticus differ in some characters with respect to the description given in Schmidt-Rhaesa (1997) (e.g. cloacal opening not round, with some tubercles and bristles on the tail lobes, only visible using SEM, Fig. 1B). We consider these differences attributable to incomplete descriptions or to intraspecific variation. The identity of our specimens as G. aquaticus was established based on the smooth cuticle and the type of post-cloacal crescent, characters which present a higher constancy.

There is a strong length variation among the specimens studied, even among specimens from the same locality (Table 2). It is unknown if this variation corresponds to differences in the host or to other environmental or genetic factors (although previous studies suggest that there is no correlation between the size of the host and the length of the parasite, Schmidt-Rhaesa, 1997; de Villalobos et al., 1999). There are no significant length differences between the measured males and females (as measured with a two-tailed t-Student, p > 0.5).

 

Table 2: Description of the localities in which specimens of Nematomorpha were found.

No.

Station

1

Province of Barcelona, Caldes de Montbui, 2.12.1984, I. Ribera & J. I. Checa leg. Small stream on a substratum of coarse sand and pebbles, no aquatic vegetation.

2

Province of Barcelona, Montseny, Turó del Home, Torrente Castellà, 23.8.1988, I. Ribera leg. Small pond in open area, ca. 30 cm diameter, 2 cm depth. Beech forest with abundant litter, substratum of litter, sand and stones.

3

Province of Lleida, Val d’Aran, Montgarri, river Noguera Pallaresa, 2.7.1989, I. Ribera leg. Lateral pond ca. 2 m diameter and 15 cm depth, connected to the main river. Substratum of silt and fine detritus. PH 8.0, conductivity 110 µS.

4

Province of Lleida, Val d’Aran, Pla de Beret, 24.9.1988, I. Ribera leg. Ponds in pasture, near the source of the rivers Garona and Noguera Pallaresa, 1800-1900 m. a.s.l., pH 7.7 – 12.4; conductivity 130 – 320 µS, substratum of silt with fine detritus, with or without vegetation, visited by cattle.

5

Province of Girona, Riera de Torrelles, 10.9.1994, I. Ribera & P. Aguilera leg. Residual pond in temporary river, ca. 5 × 3 m, 30 cm depth. Substratum of coarse sand, with macrophytes, with anoxic water and black silt.

6

Province of Huesca, Benasque, river Esera, 10.9.1988, I. Ribera leg. Lateral pond at ca. 10 m of the main channel, 10 × 2 m, 20 cm depth. Substratum of silt with some stones.

7

Province of Huesca, Sabiñanigo, river Guarga, La Calama, 14.5.1995, I. Ribera & P. Aguilera leg. Slightly running water, shallow pools over stones and gravel, 5 – 15 cm depth. With filamentous algae. pH 7.0. (remains of 1 ex.).

8

Province of Burgos, river Arlazón, south of Pineda de la Sierra, Sierra de la Demanda. 22.07.1998, I. Ribera leg. Mountain stream, ca. 5 m wide, subtratum of pebbles and sand.

9

Province of Burgos, tributary of river Arlazón, ca. 1000m below pass S of Pineda de la Sierra, Sierra de la Demanda. D. Bilton leg. Small mountain stream with gravel in the margins, partly shaded by Quercus trees.

The species is distributed in western and central Europe (excluding UK) (Schmidt-Rhaesa, 1997).

Ecological notes. – Most of the specimens were collected either in ponds in a mountain pasture (with small streams nearby) (locality 4) or in a mountain stream (locality 9), on different types of substratum and vegetation (Table 2). Known hosts include large species of Dytiscidae and Carabidae (Coleoptera) (Schmidt-Rhaesa, 1997).