1. Laboratory of Aquatic Ecology, Evolution and Conservation; KU Leuven; Deberiotstraat 32 B-3000 Leuven Belgium
2. Department of Invertebrate Zoology and Limnology; University of Szczecin; Waska 13 71-415 Szczecin Poland
3. Terrestrial Ecology Unit; Department of Biology; Ghent University; K.L. Ledeganckstraat 35 B-9000 Ghent Belgium