1. Dipartimento di Biologia, Universitàdegli Studi di Milano, Via Celoria 26, I-20133 Milano, Italy
2. Department of Environmental Sciences, College of Nyíregyháza, PO Box 166, H-4401 Nyíregyháza, Hungary
3. Laboratoire de Parasitologie Evolutive, CNRS UMR 7103, Université Pierre et Marie Curie, 7 quai Saint Bernard, Case 237, F-75252 Paris Cedex 05, France