Effects of Low-Temperature Acclimation on Nutrients of Bumble Bee Bombus terrestris Queens during Prediapause and Diapause

SIMPLE SUMMARY: Bumble bees live through two phases during their life cycle: single queens and colonies. Queens enter diapause after mating as a survival strategy to avoid harsh environmental conditions. The energy requirements of queens during diapause depend mainly on the nutrient reserves at the prediapause stage. Temperature acclimation can improve the queen’s survival during diapause. Therefore, it is important to understand the effects of temperature acclimation on the prediapause nutritional reserves and energy consumption of bumble bee queens. In this study, we evaluated the effects of three acclimation temperatures and three acclimation times on the free water, protein, lipid, and total sugar reserves of bumble bee queens during prediapause and the energy consumption of queens during the 3-month diapause period. Overall, lower temperature acclimation increased queens’ lipid reserves during prediapause and reduced the consumption of protein, lipids, and total sugars during diapause. Therefore, low-temperature acclimation could be more beneficial for bumble bee queens to improve cold resistance and increase reserves of major nutrient lipids during diapause. ABSTRACT: A queen’s diapause is a key period of the bumble bee life cycle that enables them to survive under unfavorable conditions. During diapause, queens fast, and nutritional reserves depend on the accumulation of nutrients during the prediapause period. Temperature is one of the most important factors affecting queens’ nutrient accumulation during prediapause and nutrient consumption during diapause. Here, we used a 6-day-old mated queen of the bumble bee Bombus terrestris to evaluate the effect of temperature (10, 15, and 25 °C) and time (3, 6, and 9 days) on free water, protein, lipids, and total sugars during prediapause and at the end of 3 months of diapause. Stepwise regression analysis revealed that total sugars, free water, and lipids were much more affected by temperature than protein (p < 0.05). Lower temperature acclimation significantly increased (p < 0.05) free water and lipid accumulation by queens during prediapause. In contrast, higher temperature acclimation significantly increased (p < 0.05) protein and total sugar accumulation by queens during prediapause. The effect of temperature acclimation on the queen survival rate was not significantly different (p > 0.05) after 3 months of diapause. Moreover, lower temperature acclimation reduced protein, lipid, and total sugar consumption by queens during diapause. In conclusion, low-temperature acclimation increases queens’ lipid accumulation during prediapause and reduces the nutritional consumption of queens during diapause. Low-temperature acclimation during prediapause could benefit queens by improving cold resistance and increasing reserves of major nutrient lipids during diapause.