1. Ocean College Zhejiang University, Dinghai Zhoushan 316021 P. R. China
2. College of Life Sciences and Medicine Zhejiang Sci-Tech University Hangzhou 310018 P. R. China
3. Omura Satoshi Memorial Institute Kitasato University 1-15-1 Kitasato Sagamihara Kanagawa 252-0373 Japan