Ref ID : 2838
Anna Hillbricht-Ilkowska; Response of Planktonic Rotifers to the Eutrophication Process and to the Autumnal Shift of Blooms in Lake Biwa, Japan. II. Changes in Fecundity and Turnover Time of the Dominant Species. Jap.J.Limnol. 44(2):107-115, 1983
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The egg-female ratio, i.e. the ratio of the numbers of amictic eggs to the number of females was analysed for the dominant species, Keratella cochlearis, K. quadrata and Polyarthra vulgaris together with P. dolichoptera from September to December 1980 at six stations in the southern part of Lake Biwa. Irrespective of the decrease in water temperature from about 26 degrees C in September to about 6 degrees C in December, there was a considerable increase in the fecundity of these species in November. It was probably the effect of the temporal improvement of the food conditions, i.e., the increased detritus particles and nanoplanktonic algae. The birth rates were calculated as well as the tentative number of parthenogentic generations for each sampling interval and for the whole sampling period; it ranged from 15 to 29 generations for K. cochlearis, 12-30 for P. dolichoptera and P. vulgaris, and 2-12 for K. quadrata, varying for each stations.