1. Department of Biosciences, The Faculty of Mathematics and Natural Sciences; University of Oslo; P. O. Box 1066 0316 Oslo Norway
2. Zoophysiology; Aarhus University, Department of Bioscience; C. F. Møllers Allé 3 8000 Aarhus C Denmark
3. UMR 9190 Centre for Marine Biodiversity Exploitation and Conservation; Université Montpellier 2; Place Eugène Bataillon 34095 Montpellier cedex 5 France
4. Department of Physiological Sciences; Federal University of São Carlos; SP Brazil