Biogenic Amines and Division of Labor in the Honey Bee Society

Abstract

Brain levels of biogenic amines, dopamine, serotonin, and octopamine, were measured in relation to both age-related division of labor and differences in task specialization, independent of age, in honey bee colonies. There were distinct differences associated with age-related division of labor. Older bees, notably foragers, had significantly higher levels of all three amines than did all younger bees working in the hive. Some amine level differences were significant in similar aged bees performing different tasks. Soldiers had significantly lower octopamine levels than foragers. Middle-aged food storers and undertakers had significantly lower dopamine levels than comb builders and guards, and lower serotonin than comb builders. Using social manipulations to unlink behavioral status and chronological age, octopamine was found to exhibit a robust association, independent of age, between behavior and amine level. Octopamine levels were significantly lower in normal-age nurses than precocious foragers, and in overaged nurses than normal-age foragers. In reversion experiments, octopamine did not differ between reverted nurses and similarly-aged forager sisters. Dopamine levels were significantly lower in normal-age nurses than precocious foragers, but higher in reverted nurses than same aged foragers. Reverted queen attendants had significantly higher brain levels of serotonin and significantly lower levels of octopamine than reversion colony nurses and foragers. The significance of these patterns is addressed. In a second study, bees were treated with methoprene, a juvenile hormone (JH) analog. I restricted a subset from flying/foraging. I collected both restricted and unrestricted bees at 7 and 14-days to measure brain levels of dopamine, serotonin, and octopamine and assess the effects of methoprene treatment. Octopamine levels, but not dopamine and serotonin, in methoprene-treated big back bees were significantly higher than controls. Most methoprene-treated bees flew earlier than controls, suggesting JH is exerting an effect on octopamine levels. Together these results suggest octopamine is involved in the regulation of age-related division of labor, and very likely foraging behavior, in honey bees.