1. National Science Foundation Center for Biological Timing and Department of Biology, University of Virginia, P.O. Box 400328, Charlottesville, VA 22904–4328, USA.
2. Department of Arctic Biology and Institute of Medical Biology, University of Tromsø, N-9037 Tromsø, Norway.
3. Human Genome Center, Institute of Medical Science, University of Tokyo, Tokyo 108–8639, Japan.