1. Department of Biological Sciences, Graduate School of Science, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
2. Department of Integrated Biosciences, Graduate School of Frontier Sciences, University of Tokyo, Bunkyo-ku, Tokyo 113-0033, Japan
3. Laboratory of Developmental Gene Regulation, Brain Science Institutes, RIKEN, Wako-shi, Saitama 351-0198, Japan
4. Division of Biological Sciences, Graduate School of Science, Hokkaido University, Sapporo 060-0810, Japan
5. Department of Fisheries, Faculty of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-01, Japan
6. National Research Institute of Aquaculture, Tamaki, Mie 519-0423, Japan
7. Department of Experimental Radiology, Shiga University of Medical Science, Ohtsu-shi, Shiga 520-2192, Japan