1. Research Program for Marine Biology and Ecology; Japan Agency for Marine-Earth Science and Technology (JAMSTEC); Yokosuka Kanagawa 237-0061 Japan
2. Department of Disease Control, Graduate School of Veterinary Medicine; Hokkaido University; Sapporo Hokkaido 060-0818 Japan
3. Laboratory of Influenza Viruses, Department of Virology 3; National Institute of Infectious Diseases; Musashimurayama Tokyo 208-0011 Japan
4. The University of Tokyo; Ocean Research Institute; Nakano-ku Tokyo 164-8639 Japan
5. All-Russian Research Institute for Nature; Moscow Russia