Dietary dopamine supplementation has no effect on ovary activity in queen-less or queen-right honeybee (Apis mellifera) workers

Abstract

Eusociality in honeybees (Apis mellifera) is characterised by a reproductive division of labour, where the queen monopolises reproduction while worker reproduction is constrained. This constraint is mediated by queen mandibular pheromone (QMP), which inhibits worker ovary development through Notch signalling and possibly oocyte apoptosis. Dopamine has been implicated in regulating reproduction in worker honeybees, with prior studies suggesting that dietary dopamine enhances ovary activity in queen-less workers. This study aimed to test whether dopamine supplementation could overcome QMP-mediated reproductive constraint in worker honeybees. Using caged honeybee experiments, we administered dopamine and its precursor L-dopa at a range of concentrations, both in the presence and absence of QMP. Results showed that neither dopamine nor L-dopa supplementation affected ovary development, survival rates, or food intake, which contrasts with a previous study. These findings suggest that dopamine may not be a major factor in QMP-mediated reproductive inhibition. Instead, we suggest that the multifaceted nature of QMP’s components together with the complexity of neuroendocrine signalling makes it likely that multiple redundant mechanisms regulate worker reproduction. Future research should investigate the interplay between nutrition, dopamine and QMP components to fully understand the regulation of ovary activation in honeybee workers.