Cladocerans are an essential component of freshwater ecosystems,bridging the aquatic food chain.As primary consumers,cladocerans often feed on planktonic algae.Meanwhile,they can also serve as food for predators such as fish.With global warming and eutrophication,blue-green algae dominate the com-position of phytoplankton communities in natural water bodies,and the interaction between cladocerans and blue-green algae has become a research focus in ecology.In the mixed food of natural water bodies,the popu-lation dynamics of Daphnia may be closely related to their filtration rates towards different algae(e.g.,blue-green and green algae).This research investigated the filtration rates of three Daphnia species(Daphnia pulex,D.galeata,and D.sinensis)at different growth stages(i.e.,6-h old neonate,adults at the first and fifth adult instar)on Microcystis aeruginosa and Tetradesmus obliquus to intensify the understanding of the species and growth stages of Daphnia cladocera to the feeding preferences of blue-green algae and green algae.The results showed that the differences in the filtration rates of the neonates of the three Daphnia species on each type of algae were all relatively minor.In the T.obliquus group,the filtration rate of D.pulex at the first adult instar was significantly higher than that of both D.galeata and D.sinensis.In contrast,the filtration rate of D.pulex at the fifth adult instar was significantly lower than that of D.galeata.In both M.aeruginosa and mixed food group,there were no signif-icant differences in the filtration rates of D.pulex at different growth stages on M.aeruginosa.In the mixed food group,compared with the filtering to M.aeruginosa cells,D.sinensis at the first and fifth adult instar showed a strong preference for T.obliquus,whereas D.galeata at the fifth adult instar had a higher filtration rate for both algae.In addition,in the mixed food group,the filtration rate of D.pulex at the first adult instar on M.aeruginosa was significantly higher than that of D.galeata,whereas the filtration rate of D.galeata at the fifth a-dult instar was significantly higher than that of D.sinensis.The results suggest interspecific differences in the feed-ing of blue-green algae and green algae among different Daphnia species.In addition,there are differences in the filtration rates of blue-green and green algae among different Daphnia species at different growth stages.These results will provide important references for understanding the interaction relationship between cyanobacteria and Daphnia species,and they also provide basis for the managements of cyanobacterial blooms in eutrophic lakes.
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