Dietary dopamine causes ovary activation in queenless Apis mellifera workers

Groups of young honey bee workers were fed a diet containing dopamine while confined in small cages at 34 degreesC 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 mug/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.