Effects Of Larval Exposure To The Insecticide Flumethrin On The Development And Post-Adult Life Of Honeybee(Apis Mellifera)Workers

Honeybee is a kind of insect that is very important to human beings.It has significant value in the economy,ecology and scientific research.However,a parasite in bee colonies----the bee mite,not only threatens honeybees’ health but also hinders beekeeping development.Flumethrin is a widely used acaricide,but improper use of it often leads to residue accumulation in bee colonies,thus threatening the health of larval stages especially.This study was conducted on honeybees(Apis mellifera).We simulated the situation of honeybee larvae feeding on flumethrin residues in the hive and investigated the effects of flumethrin residues on honeybee larvae development and adults by feeding honeybee larvae with sublethal concentrations of flumethrin sugar solution.Sugar solutions containing 0.01,0.1,and 1 mg/L flumethrin were prepared according to the residual concentration of flumethrin in honeycomb and bee products.Sugar solutions were fed to larvae from 2 days of age until capping,with 50% sucrose solution as the control.We examined the effects of larval survival and adult stage on learning memory ability,fixed distance homing ability,and learning memory-related gene expression.The results showed that the survival rate of worker bee larvae in the dose group above 0.1 mg/L was significantly lower than that of the 0.01 and 0 mg/L dose groups;the correct respond rate of worker bees in the 1 mg/L dose group was significantly lower than that in the other three groups at 7 days of age;the homing rate of worker bees in the 1 mg/L dose group was also significantly lower than that in the other three groups.The relative expression levels of Nmdar1 and Tyr1 genes in the 7 days old worker bees in the 1 mg/L dose group were significantly lower than those in the control group,but the relative expression levels of Glu RA,Nmdar1,Tyr1 in the 1,0.1,and 0.01 mg/L dose groups were significantly lower than those in the control group at 20 days old.This also indicated that flumethrin residues above 0.01 mg/L will impact the physiology of honeybees.And with increased concentration,the impact will become more apparent,even affecting the larval survival,learning and memory behavior.The RFID monitoring system was used to monitor the impact of ingestion of flumethrin residues in the larval stage of honeybees on their adult life cycle activities.The results showed that workers in the 1 mg/L dose group would leave the nest early for collection,and their average lifespan,average collection time,and average collection times were significantly reduced.In addition,the rest ratio of this group of worker bees has increased significantly,indicating that ingestion of 1 mg/L of flumethrin residues by honeybee larvae will have a sustained impact on adults,significantly reducing the collection ability of worker bees,and causing a slowdown in work.Through the high throughput RNA sequencing(RNA-Seq),we analyzed the effect of flumethrin feeding during the larval stage of honeybees on the gene expression in the head of worker bees after their emergence.The results showed that the number of differentially expressed genes in the treatment groups increased with increasing concentrations of flumethrin;some genes involved in substance metabolism and physiological and biochemical processes were significantly down-regulated in the heads of honeybees in all flumethrin treatment groups;some olfactory-related genes and antioxidant-related genes were significantly down-regulated in the head of honeybees in the dose group above 0.1mg/L,and some immune and detoxification-related genes were significantly downregulated in the 1 mg/L dose group.This indicates that the higher the concentration of flumethrin,the greater the effect and damage on honeybees,and that flumethrin also affects the expression of genes involved in material metabolism and physiological and biochemical processes in honeybees at very low concentrations.Through the Me DIP-sequencing,we analyzed the effect of flumethrin ingestion during the larval stage of honeybees on genome-wide methylation in the head of worker bees after their emergence from the colony.The results showed that methylation levels in the 0.1 and 1 mg/L dose groups showed a downward trend compared to the 0.01 and 0mg/L dose groups,and the differentially methylated genes in the three treatment groups were mainly enriched in some key signaling and metabolism-related pathways.Signaling pathways include m TOR signaling pathway,Hippo signaling pathway-fly,Mark signaling pathway and TGF-beta signaling pathway,metabolic pathways including carbon metabolism,drug metabolism-other enzymes,metabolic pathway,pyruvate metabolism,which could affect changes in key biochemical pathways in honeybees,thus affecting the longevity and various physiological functions of worker bees.