Abstract: 【Aim】 The Italian honey bee, Apis mellifera ligustica, is one of the most economically important pollinators in the world, and plays important roles in maintaining the ecological balance, improving the output of agricultural products and ensuring food safety. However, the bee suffers from huge annual loss worldwide due to infestation of Varroa destructor. The purpose of this study is to investigate the effects of V. destructor on the respiratory metabolism of A. mellifera ligustica workers, so as to lay a foundation for further studying the interaction between the mite and the bee. 【Methods】 The oxygen consumption, CO₂ emission and respiration quotient of V. destructor-infected and healthy workers of A. mellifera ligustica at different developmental stages (4-day-old larva, 5-day-old pupa, newly emerged adult and 6-day-old adult) were measured using SSI multi-channel insect respiration instrument, and the characteristics of their changes were analyzed. Meanwhile, the expression levels of respiratory metabolism-related genes (Coq7, COXⅠ, CytB, CytC and IF-2mt) in V. destructor-infected and healthy adult worker bees were analyzed using real-time fluorescence quantitative PCR (RT-qPCR). 【Results】 The oxygen consumption and CO₂ emission of A. mellifera ligustica worker bees first increased and then decreased after infection by V. destructor. After infection by V. destructor, the oxygen consumption decreased from 0.0244 mL/min in the 5-day-old pupal stage of A. mellifera ligustica to 0.0093 mL/min in the 6-day-old adult stage, and the CO₂ emission decreased from 0.0174 mL/min in the 5-day-old pupal stage to 0.0040 mL/min in the 6-day-old adult stage, which was significantly lower than that of the healthy worker bees of the same developmental stage. The respiratory quotient of healthy worker bees of A. mellifera ligustica increased gradually with larval age, and reached the peak (0.9169) at the 6-day-old adult stage, while the respiratory quotient of the V. destructor-infected worker bees decreased, and was the lowest (0.4424) at the 6-day-old adult stage, which was significantly lower than that of the healthy worker bees of the same developmental stage. The RT-qPCR results showed that the relative expression levels of CytB and CytC genes in the V. destructor-infected adult worker bees of A. mellifera ligustica were 1.7676 and 1.9929-fold as high as those of the healthy adult worker bees, respectively. 【Conclusion】 V. destructor infection can directly affect the respiratory metabolism of A. mellifera ligustica workers, leading to the disorder of their normal metabolic pathway, and seriously damaging the normal growth and development of bee colonies.

Key words: Apis mellifera ligustica; Varroa destructor, oxygen consumption, CO₂ emission; respiratory quotient, gene expression