Dietary dopamine causes ovary activation in queenless Apis mellifera workers

Abstract

Groups of young honey bee workers were fed a diet containing dopamine while confined in small cages at 34°C and 80% RH in absence of a queen for 8 to 13 days. The bees in eight pairs of cages, each pair containing an equal number of workers, received a pollen-rich diet supplemented with dopamine (10 μg/g of diet) (DOP groups), or not supplemented (controls). The rate of consumption of the diet was monitored continuously during the confinement period, after which the workers were dissected to assess follicle development in the ovaries. The results showed a significantly higher proportion (P = 0.004) of workers with activated ovaries in the DOP groups than in control groups. The number of bees surviving confinement was significantly higher in the control groups than in the DOP groups (P ≤ 0.01), possibly reflecting a deleterious effect of dopamine. The surviving bees from both groups consumed equivalent amounts of diet (P = 0.687), showing that ovary activation was not due to differential diet consumption. The results suggest a role of dopamine in the chain of events mediating changes in the reproductive status of orphan honey bee workers.