1. Division of General Physiology, University of Oslo, P.O. Box 1051, Blindern, 0316 Oslo 3, Norway
2. Fisheries and Oceans, Arctic Biological Station, Ste‐Anne de Bellevue, Province de Québec, Canada H9X 3R4
3. Norwegian Polar Institute, Box 158, 1330 Oslo Lufthavn, Norway; and Division of General Physiology, University of Oslo, P.O. Box 1051, Blindern, 0316 Oslo 3, Norway