1. Department of Biological Engineering and Division of Comparative Medicine; Massachusetts Institute of Technology; Cambridge MA 02139 USA
2. Department of Fisheries, Wildlife and Conservation Biology; University of Minnesota; St. Paul MN 55108 USA
3. U.S. Geological Survey; Alaska Science Center; Anchorage AK 99508 USA
4. Institute of Arctic Biology; University of Alaska Fairbanks; Fairbanks AK 99775 USA
5. Department of Pathology, Microbiology and Immunology; School of Veterinary Medicine; University of California; Davis CA 95616 USA