Institution: | (1) Present address: Institute of Limnology, B. P. 11 F, F-74203, Thonon-les-Bains CEDEX, France;(2) Present address: Department of Biology and Ecology, University of Savoie, B. P. 1104, F-73001 Chambery CEDEX, France;(3) Lincoln College, P. O. Box 56, New Zealand |