EVALUATING METABOLIC RATE, SURVIVAL, FEEDING BEHAVIOR AND ENERGETIC DEMAND IN TWO GENOTYPES OF APIS MELLIFERA

Abstract

In animals, metabolic processes play a pivotal role in shaping behavior and physiology, particularly in organisms whose energetic demands are closely linked to their performance in nature. In social insects like honeybees, variation in metabolic rate and energy intake can influence individual performance, leading to colony-level outcomes. However, metabolic processes can be influenced by both genotype and resource availability, but the relative contributions of these factors to individual performance and colony-level outcomes remain unclear.This study takes advantage of two known genotypes of honeybee (slow, or SS and fast or FF) that can differ in metabolism. Using these metabolic genotypes, I examined how genotype and carbohydrate availability interact to shape physiological performance, short-term survival and feeding behaviors. Physiological performance was evaluated using standard metabolic rate, maximum metabolic rate, and aerobic scope. Workers of the two genotypes were provided either low (20%) or high (40%) sucrose diet treatments in a controlled laboratory environment, and then their metabolic rates were measured. Survival over 24 hours of the two genotypes was tracked under conditions of starvation, and with access to sucrose solutions of a range of concentrations. Feeding behavior of the two genotypes was compared by evaluating gustatory responsiveness to different concentrations of sucrose, as well as by evaluating hunger-driven feeding. Contrary to expectations based on prior work with these genotypes, metabolic traits did not differ significantly between SS and FF genotypes or between low or high sucrose diet treatment, and no genotype × diet interactions were detected. Short-term survival was strongly influenced by sucrose availability, with bees fed sucrose solutions showing substantially lower mortality risk than unfed bees. In both SS and FF bees, gustatory responsiveness increased with increased sucrose concentration, with FF bees showing slightly, but not significantly, higher responsiveness than SS. The hunger assay showed initially high intake, with similar temporal intake trajectories for both SS and FF bees. Together, these results suggest that immediate energetic state and dietary treatments influence short-term survival, and hunger driven feeding behavior more than genotype under a controlled laboratory environment. Only gustatory responsiveness differed consistently between the two genotypes, indicating that sensitivity to food rewards can remain genotype dependent even if metabolic traits do not differ significantly. These findings suggest that metabolic genotype effects in honeybees are context dependent. These effects may be expressed more strongly under conditions of sustained energetic demand. This highlights how energetics mold honeybee behavior and performance, and influence overall metabolic demand and survival in them.