1. Department of Physical Chemistry, Budapest University of Technology and Economics, H-1521 Budapest, Hungary, Department of Colloid Chemistry, Loránd Eötvös University, Pázmány Péter sétány 2, H-1117 Budapest, Hungary, Department of Surface Chemistry and Corrosion Research, CRC HAS, P.O. Box 17, H-1525 Budapest, Hungary, Department of General Zoology, Loránd Eötvös University, H-1088 Budapest, Hungary, and Biozentrum, University of Basel, CH-4056 Basel, Switzerland