Mechanism And Risk Assessment Of Acetamiprid Toxicity On Apis Mellifera Larvae

Acetamiprid is one of the neonicotinoid insecticides.In recent years,it has been widely used as a plant protection reagent due to its lower toxicity than imidacloprid and thiamethoxam.Although larval health is an important basis for colony survival and bee larvae may be exposed to acetamiprid by consuming pollen and nectar,the risk of acetamiprid to bee larvae has not attracted more attention.In this thesis,the acute and chronic toxicity to western honeybee larvae and field residues of acetamiprid were determined.In addition,the risk to bee larvae was preliminarily evaluated,and the mechanism of action of acetamiprid on bee larvae was analyzed through transcriptome and metabolomics studies.Under laboratory conditions,the acute oral toxicity to 4-day-old western honeybee larvae was firstly tested.The results showed that the LC₅₀ of acetamiprid to western honeybee larvae was 188.49mg/L.Based on acute toxicity,the chronic toxicity test was performed on 3,4,5,6-day-old western honeybee larvae.The results showed that the larvae survival of acetamiprid at 10,20,40,80 mg/L was significantly lower than the negative and solvent controls,while 2.5 mg/L or 5 mg/L acetamiprid had no significant effect on the survival rate of larvae.Therefore,the no observed adverse concentration?NOAEC?of acetamiprid treatment was 5 mg/L.There was no significant change in larval body weight between the treatment group and the solvent control group at the 7^th day.Larvae feeding with 20 or 80mg/L acetamiprid solution showed significantly lower body weight than the negative control.Further,we analyzed the residues of acetamiprid in pollen and nectar samples collecting from the three habitats of farmland,semi-forest and forest.The results showed that all pollen residues were detected in the farmland,with a range of 5.73-54.08?g/kg.One of the four pollen samples in semi-forest habitat was detected with a residual value of 4.22?g/kg.None of the four pollen samples in the forest habitat was detected.The nectar samples showed no acetamiprid residues in any of the three habitats.Taking into account acute toxicity,chronic toxicity and residual levels,LD₅₀,NOAEC and theoretical and actual residual values were used to assess the risk of acetamiprid to western honeybee larvae.The results showed that the risk value?RQ?of acute toxicity and the chronic toxicity were lower than the level of concern?LOC?,indicating that the risk of acetamiprid to bee larvae was acceptable.The larvae treated with NOAEC acetamiprid were further analyzed by transcriptome sequencing and found that there were 22 differential genes compared with the solvent control.The two genes with the highest GO classification among the up-regulated differential genes were the gene encoding vitamin K-dependent gamma-carboxylase?GB40614?and the gene encoding ubiquitin carboxyl-terminal hydrolase ZUFSP?GB41610?.The two genes may play a role in the process of detoxification of cells.Down-regulated differential genes are mainly involved in lipid metabolism,amino acid metabolism and energy metabolism.At the same time,the larvae were analyzed by metabonomics.The results showed that glutamate metabolism,ABC transporter metabolism and glycerophospholipid metabolism were up-regulated,and valine,leucine,and isoleucine metabolism were down-regulated.These metabolic pathways are all related to detoxification.This study provides technical support for scientific assessment of the risk of pesticides on bee larvae,which has certain theoretical and practical significance for protecting bees and reducing pesticide hazards.