Stress Effects Of Atrazine On The Inducible Defense Characteristics Of Flea-like Fleas In Response To Fish Predation And Their Related Gene Expression

Atrazine,one of the most used herbicides in the world,has excellent effects in controlling weeds in the field.Because atrazine has the characteristics of water solubility,fluidity,long half-life,poor adsorption capacity in soil organic matter and high leaching potential,it can not only exist stably in terrestrial ecosystems for a long time,but also flowing with surface runoff,underground runoff,rainfall and evaporation enter the water ecosystem.However,atrazine in the water environment may affect the survival,growth and reproduction of a variety of non-target organisms,which threatens the stability of the population and the sustainability of the ecology.Organisms can recognize the risk of predation by detecting the chemical signals(kairomone)released by predators,thereby exhibiting inducible defenses.This is the adaptive response of prey to predation risk,which can increase the fitness of the prey,thereby promoting the stability of the population and the multi-trophic community.Cladocera is not only an important part of the freshwater ecosystem,but also an ideal model organism for studying the predator-prey relationship,it plays an extremely important ecological function.The changes in the external environment often lead to changes in the cladocerans'anti-predator strategys.Therefore,how will cladocerans respond to predator cues under the influence of atrazine?How will the population dynamics change?What will happen to the expression level of genes?These scientific questions need to be answered accurately.In this paper,the effects of atrazine on the inducible anti-predator defenses of Daphnia pulex induced by atrazine were firstly studied,and the changes of population dynamics caused by individual traits were analyzed synthetically.Finally,the mechanism of the changes in the anti-predator defenses of D.pulex under atrazine exposure was preliminarily studied.The specific research results are as follows:1.The effects of atrazine on inducible anti-predator defenses traits of D.pulexIn this study,the anti-predation defense strategys of D.pulex were studied under different atrazine concentrations(0,0.05,0.1,0.5,1 and 2 mg L^-1)to deal with predation risk of fish,and we measured the responses of inducible anti-predator defenses of D.pulex under different atrazine concentrations.The results showed that atrazine had adverse effects on the growth rate,body size and reproduction of D.pulex,and the degree of influence depended on the concentration of atrazine and the duration of action.In addition,this experiment found that atrazine can affect the strength of the cladocerans'morphological defense response and anti-predation defense strategy,so that the cladocerans cannot accurately respond to the predation risk.In addition,predation risk cues will weaken the negative effects of high concentrations of atrazine on the life history traits of D.pulex.Our results indicated that the influence of atrazine on the morphology and life history traits of cladocerans and its indirect effects on the anti-predator of cladocerans may affect the interaction between predators and prey of higher nutritional levels,and thus further affect the stability of the community structure.2.The effect of atrazine on the population dynamics of D.pulexThis experiment studied the response and the population dynamics of D.pulex to predation cues under the influence of atrazine of different concentrations(0,0.05,0.1and 1 mg L^-1).The results showed that the predator kairomone caused a slowdown in maximum population density and a decrease in the total biomass,but it increased the population density during the stable period and promoted the production of dormant eggs.The presence of atrazine affected the time to the maximum population density and the fitness of the population,and had a negative impact on the population dynamics in the presence of predation risk cues,including the decline of population density and the reduction of dormant eggs production.At the same time,fish kairomone weaken the negative impact of atrazine on the population.Our results indicated that changes in the morphology and life history traits of cladocerans under atrazine may cause changes in population dynamics,which may ultimately affect the stability of both predator and prey populations.3.The effect of atrazine exposure on the anti-predator defense and gene expression related to anti-predator defense in D.pulexIn this study,we investigated the effects of atrazine exposure at different concentrations(0,0.1 and 1 mg L^-1)on the body type and the expression of genes related to anti-predator defense-related genes in D.pulex.Cladocerans were exposed to different combinations of predator cues and atrazine of different concentrations for 24,48 and 72 h,and body size and gene expression were measured.The results showed that atrazine had a negative effect on the growth of Cladocerans and made them smaller in body size.Atrazine affected morphological defense of D.pulex to a certain extent.In addition,fish kairomone significantly affected the expression level of most of the tested genes of D.pulex with temporal differences.For example,under the regulation of fish kairomone,the expression of trypsin gene and carbohydrate binding module gene is first down-regulated,then gradually induced and up-regulated after 48 h;G protein-coupled receptors gene was induced to significantly up-regulate and the degree of up-regulation over time continuously strengthening;the expression of heat shock protein gene was first down-regulated,and then recovered after 72 h.These adjustments would improve the ability of organisms to adapt to predators in complex food webs.But atrazine can have a negative effect on this adaptive ability of cladocerans.In summary,atrazine has adverse effects on the growth and reproduction of freshwater cladocerans D.pulex,and the degree of influence depends on the concentration of atrazine and the duration of action.Atrazine also has a negative effect on the anti-predator defense traits of cladocerans,which weakens the ability of cladocerans to accurately respond to predation risk cues.The influence of atrazine on the individual defense traits of cladocerans would further change the population dynamics,reducing the maximum population density under the fish kairomone treatment,and inhibiting the promotion effect of fish kairomone on the production of dormant eggs and the reduction effect on the total biomass.At the same time,atrazine exposure affected the expression of key genes that D.pulex had to deal with predation risk,and brought about individual-level effects.At the same time,this study found that fish kairomone would weaken the negative impact of atrazine on the life history traits and population dynamics of D.pulex.This study not only expands the understanding of zooplankton under the stress of atrazine in the environment,but also enriches the research data on the effects of atrazine on interspecific relationships in freshwater ecosystems.This will help us to accurately assess the risk of exposure to artificial compounds in freshwater ecosystems,and it is of great significance for us to deeply understand the impact of environmental changes in the water ecosystem on the inducible anti-predator defense of prey.