溞属种类和生长阶段对两种藻类滤食率的影响

Species and growth stages of the Daphnia genus affecting the filtration rate of two algae

为加深溞属枝角类的种类、生长阶段对蓝藻和绿藻摄食偏好的理解,本实验比较研究了蚤状溞(Daphnia pulex)、盔形溞(D.galeata)和中华拟同形溞(D.sinensis)在不同生长阶段(即出生6 h的幼体、第一成龄成体和第五成龄成体)对100%铜绿微囊藻(Microcystis aeruginosa)、100%斜生四链藻(Tetradesmus obliquus)、50%铜绿微囊藻+50%斜生四链藻的滤食率。结果显示,三种溞属枝角类的幼体对铜绿微囊藻和斜生四链藻的滤食率差异均较小。在铜绿微囊藻组和混合食物组下,不同生长阶段的蚤状溞对铜绿微囊藻的滤食率组间差异均不显著。在混合食物组中,中华拟同形溞第一成龄成体和第五成龄成体,对斜生四链藻的滤食均表现出强烈的偏好性;而盔形溞第五成龄成体对两种藻类都有较高的摄食率。此外,在混合食物组中,蚤状溞第一成龄成体对铜绿微囊藻的滤食率显著高于盔形溞第一成龄成体,而盔形溞第五成龄成体的滤食率显著高于中华拟同形溞第五成龄成体。结果表明,除种间差异外,溞属枝角类的不同生长阶段对蓝、绿藻的摄食也存在差异性。

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 composition 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 population 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 significant 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 adult instar was significantly higher than that of D.sinensis.The results suggest interspecific differences in the feeding 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.