| With water eutrophication and global warming,cyanobacteria blooms have occurred frequently,and the interaction between M.aeruginosa and Daphnia has been widely paid attention by researchers.Although there are many studies about the effects of M.aeruginosa on the life-table of active populations in Daphnia species,the researches about the influence of M.aeruginosa on the life-history traits and physiological activity of resting-eggs populations in Daphnia species under different habitats are limited.Resting-eggs populations of two D.similoides sinensis strains from different sedimental layers(representing different ages)in Lake Chaohu(Located at the joint of the middle and lower reaches of the Yangtze River,having numerous lakes and rivers,with frequent outbreaks of cyanobacterial blooms)and Lake Junshan(In the upper reaches of the Yangtze River tributaries,with good water quality)were chosen as the experimental animals.Three food treatments(M0: 100% S.obliquus;M20: 80% S.obliquus+20% M.aeruginosa;M40: 60% S.obliquus+40% M.aeruginosa)were employed.The effects of M.aeruginosa on the life-history traits and SOD(Superoxide dismutase)activities of the mother and their offspring of D.similoides sinensis were studied,in order to further reveal the effects of M.aeruginosa on individual fitness and the tempo-spatial differences of D.similoides sinensis under different habitats.Main conclusions are as follows:1.We examined the effects of M.aeruginosa on the life-history traits and SOD activity of D.similoides sinensis from two lakes(Lake Chaohu and Lake Junshan).With the increase of M.aeruginosa concentration,the life-history traits of D.similoides sinensis were all inhibited,time to maturation prolonged.SOD activities of D.similoides sinensis from two lakes all increased,which the maximum(1401.73±380.03U·g FW-1)appeared in the modern population of Lake Junshan in the M40 food treatment whereas the minimum value(113.66 ± 25.92 U·g FW-1)appeared in the ancient population of Lake Chaohu in the M0 food treatment.Multivariate analysis of variance showed that the sedimentary layer(age),clone,food treatment and their interaction had all significant effects on the life-history parameters and SOD activities of D.similoides sinensis(P<0.05).M.aeruginosa had significant negative effects onthe body length,time to maturation,eggs numbers at first brood and offspring numbers at first reproduction of ancient populations in D.similoides sinensis from two lakes.When M.aeruginosa concentration increased in food,the negative effects were more obvious.D.similoides sinensis might enhance its resistance to M.aeruginosa by up-regulating SOD activity.2.Compared with D.similoides sinensis hatched from the resting eggs in different lakes or during different historical periods,it was found that the effects of M.aeruginosa on the life-history parameters and SOD activities of resting-eggs populations in D.similoides sinensis existed tempo-spatial and clonal differences.The life-history traits of the modern populations were significantly higher than those of the ancient populations in Lake Junshan.No significant differences about the body length at maturity(BL1),body length at the end of the experiment(BL2)and eggs numbers at first brood between the modern and ancient populations in Lake Chaohu were observed.Offspring numbers at first reproduction of modern populations were smaller than those of ancient populations in Lake Chaohu in the M20 and M40 food treatments,and their time to maturation were prolonged.Moreover,the SOD activities of modern populations were significantly higher than those of ancient populations in two lakes.Compared with D.similoides sinensis populations in Lake Chaohu,the tolerance of modern populations to M.aeruginosa was better than that of ancient populations in Lake Junshan.The results suggested that D.similoides sinensis populations would have undergone adaptive evolution with the changes of its living environments,and the tolerance of D.similoides sinensis to M.aeruginosa might be related to their habitat environments and genotypes.3.This study further investigated the effects of M.aeruginosa on the life-history traits and SOD activities of the progeny of ancient populations in D.similoides sinensis from different historical periods of Lake Chaohu.Compared with the M0-F1,the body lengths of M20-F1 and M40-F1(except for BL1)in clone 1(from modern population)increased in the M20 and M40,and the body lengths of M20-F1(except for BL2 in the M20 food treatment and BL1 in the M40 food treatment)and M40-F1(except for BL2 in the M40 food treatment)in clone 3(from ancient population)increased in all three food treatments.The results suggested that early exposure of the mother to toxic M.aeruginosa could increase the tolerance of their offspring to M.aeruginosa,and the increase of D.similoides sinensis tolerance to M.aeruginosa had obvious differences among both clones and their different offspring.Therefore,maternal effects of D.similoides sinensis had clonal specificity,and this difference might be related to Daphnia genotypes or result from clonal variations during long-term historical succession in the presence of Microcystis. |
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