1. Department of Aquatic Bioscience (T.H., K.N., K.H., Y.K., K.O.), Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo, Tokyo 113–8657, Japan;
2. Division of Reproductive Biology (Y.N.), National Institute for Basic Biology, Okazaki, Aichi 444–8585, Japan;
3. Institution for Collaborative Relations (Y.N.), Ehime University, Matsuyama, Ehime 790–8577, Japan