Effects Of Cadmium On The Survival,Physiology And Gut Microbiota In Honeybee (Apis Mellifera Ligustica)

The honeybee（Apis mellifera ligustica）plays an important role in plant pollination and are vulnerable to environmental pollutants during their activities.As the most common heavy metal pollutant in China,cadmium may pose a threat to the health of bees.This study aims to investigate the sublethal effects of a series concentrations of cadmium chloride（10mg/L,1 mg/L and 0.1 mg/L）on the survival,food consumption,the expression of immune,detoxification and antioxidant genes,three functional enzymes activities and gut mircrobiota in honeybees during 10 d oral exposure.The results are as follows:（1）The 10 mg/L of cadmium chloride（Cd Cl₂）significantly reduced the survival rate of honeybees（P<0.05）,and the other two concentrations did not affect the survival rate of honeybees（P>0.05）.The 10 mg/L of Cd Cl₂ significantly reduced the sucrose solution consumption of honeybees（P<0.05）,and the three concentrations did not affect the pollen consumption of honeybees（P>0.05）.（2）The expression changes of immune,detoxification and antioxidant genes of honeybees treated with Cd Cl₂ were detected by q PCR.The 10 mg/L and 1 mg/L of Cd Cl₂ significantly up-regulated the expression of Abaecin in the head of honeybees,and significantly inhibited the expression of Apidaecin（P<0.05）,the 10 mg/L of Cd Cl₂ significantly up-regulated the expression of Abaecin in the midgut of honeybees（P<0.05）,the 1 mg/L and 0.1 mg/L of Cd Cl₂ significantly inhibited the expression of Abaecin in the midgut of honeybees（P<0.05）;the 10 mg/L of Cd Cl₂ significantly up-regulated the expression of CYP9Q1 and CYP6AS5 in the head and midgut of honeybees,and the 1 mg/L of Cd Cl₂ significantly inhibited the expression of CYP9Q1,CYP9Q3,CYP6AS5 and CYP6AS14 in the head of honeybees（P<0.05）,Cd Cl₂ significantly inhibited the expression of CYP9Q3 in the midgut of honeybees（P<0.05）;the 10 mg/L of Cd Cl₂ significantly up-regulated the expression of SOD1 in the head and midgut of honeybees,and the 1 mg/L and 0.1 mg/L of Cd Cl₂significantly inhibited the expression of SOD2 in the head and midgut of honeybees（P<0.05）.（3）Cd Cl₂ treatment did not affected the activity of Acetylcholinesterase（Ach E）and Superoxide Dismutase（SOD）（P>0.05）,10 mg/L Cd Cl₂ significantly increased the activity of Polyphenol oxidase（PPO）（P<0.05）.（4）16S rDNA sequencing technology was used to analyze the gut microbiota in honeybees.Proteobacteria,Firmicutes and Actinobacteriota were the dominant bacteria groups in the gut of honeybees,accounting for more than 99.36%of all bacteria groups,Under the exposure of Cd Cl₂,the abundance of Snodgrassella,Frischella and Faecalibacterium decreased significantly.The abundance of Lachnochlorostridium,Klebsiella,increased significantly（P<0.05）.Cd Cl₂ treatment did not affect the alpha and beta diversities of gut microflora.In conclusion,cadmium exposure affected the sucrose solution consumption of honeybees,significantly reduced the survival rate of honeybees,damaged the immune system,detoxification system and antioxidant system in honeybees,and affected the abundance of gut microbiota in honeybees.