Effects of Ionizing Radiation on Apis mellifera L. Queens

In honeybees (<i>Apis mellifera</i> L.), the queen ensures the reproduction of the colony. Environmental contamination that could alter this function could compromise the survival of the colony. Ionizing radiation could be such a factor, but its effects have never been studied in queens. The effects of gamma irradiation on queen bees were evaluated under laboratory conditions. The queens were irradiated for 14 days at dose rates of 0.1, 13, and 3500 µGy/h, and mortality, reproductive potential, and several physiological biomarkers were investigated. Irradiation did not affect the survival of the queens or the number of sperm stored in the spermatheca. However, sperm viability and reproductive potential decreased significantly at 13 and 3500 µGy/h. Among the biomarkers analyzed (antioxidant defenses, detoxification, metabolism, immunity, neural activity), no significant differences were observed between the modalities, with the exception of an increase in thoracic LDH activity at 13 µGy/h, confirmed by multivariate analyses indicating metabolic changes. These results show that ionizing radiation does not induce lethality at the tested dose rates, but significantly impaired fertility and metabolism of queen bees, with potential consequences for colony stability, whose ecological significance remains to be confirmed under field conditions.