Ichiro Terashima1, Yanhong Tang2, Hiroyuki Muraoka3. 1. Department of Biological Sciences, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan. itera@bs.s.u-tokyo.ac.jp. 2. Center for Environmental Biology and Ecosystem Studies, National Institute for Environmental Studies, Onogawa 16-2, Tsukuba, 305-0053, Japan. 3. River Basin Research Center, Gifu University, 1-1 Yanagido, Gifu, 501-1193, Japan.