1. Graduate School of Science and Engineering Iwate University 4‐3‐5, Ueda Morioka Iwate 020‐8551 Japan
2. Institute of Cetacean Research 4–5 Toyomi‐cho, Chuoku Tokyo 104‐0055 Japan
3. School of Advanced Science and Engineering Waseda University 3‐4‐1, Okubo, Shinjuku‐ku Tokyo 169‐8555 Japan
4. Laboratory of Animal Reproduction Department of Agriculture Kindai University Nara 3327‐204 Japan
5. Exploratory Oncology Research and Clinical Trial Center National Cancer Center 6‐5‐1, Kashiwanoha, Kashiwa Chiba 277‐8577 Japan
6. Wildlife Research Center Kyoto University 2–24, Tanakasekiden‐cho, Sakyo‐ku Kyoto 606‐8203 Japan