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Synthetic insecticides are recognized as a major factor contributing to the global decline in insect abundance and diversity. Within this context, anthranilic diamides have gained increasing market share in Europe since 2018. We investigated the second-generation diamide cyantraniliprole, which induces aberrant cytoplasmic calcium release in honeybee skeletal muscle cells. In vivo assays demonstrated that acute contact toxicity varied with exposure site, being more severe when applied to the abdomen, antennae, or ventral thorax compared with the dorsal thorax. Following thoracic exposure to sublethal doses, continuous 21-h monitoring revealed a dose-dependent alteration of behavior, with a reduction in locomotor activity, including maximal velocity and total distance traveled. Notably, at the lowest concentration, antennal exposure elicited stronger behavioral impairments, indicating potential disruption of sensory processing and environmental cue perception. Importantly, cyantraniliprole and its parent compound, chlorantraniliprole, also triggered anarchic calcium mobilization in mammalian skeletal muscle fibers, highlighting potential cross-taxa effects. These results strengthen previous evidence of diamides toxicity in bee cardiomyocytes and neurons and emphasize significant gaps in current risk assessment frameworks. Collectively, our findings indicate that anthranilic diamides represent not only an ecological threat to pollinators but also raise concerns for mammalian health, warranting more stringent evaluation of this insecticide class.

The global decline of honeybee colonies represents a major ecological concern, primarily attributed to simultaneous exposure to multiple stressors. These include biotic pressures, such as parasitic infections, and abiotic pressures, such as exposure to ionizing radiation, which remains poorly understood. Assessing their combined effects provides novel insights into how biological and radiological stressors interact within the organism. Here, we investigated the individual and combined effects of Vairimorpha ceranae (formerly Nosema ceranae ) infection and chronic gamma irradiation (14 µGy/h or 14 × 10³ µGy/h) on honeybee health. Measurements included survival, syrup consumption, spore load, and biomarkers related to energy metabolism, antioxidant defenses, immunity, detoxification, and neural enzyme activity. Two successive experiments, conducted at different collection periods, allowed us to account for biological variability between bee cohorts. Infection by V. ceranae caused high mortality and major impairments in metabolic, antioxidant, and immune functions. Ionizing radiation induced more moderate effects, characterized by redox imbalance and reduced detoxification capacity, which varied with dose rate. Under combined exposure, the two stressors produced mainly antagonistic interactions affecting antioxidant, immune, and detoxification systems. However, a synergistic effect was observed on ATP production, suggesting an energetic compensation mechanism. These findings highlight complex physiological disturbances, revealing the multifactorial vulnerability of honeybees and emphasizing the need to integrate interactions between multiple stressors and natural biological variability into ecotoxicological assessments.

During all their life stages, bees are exposed to residual concentrations of pesticides, such as insecticides, herbicides, and fungicides, stored in beehive matrices. Fungicides are authorized for use during crop blooms because of their low acute toxicity to honey bees. Thus, a bee that might have been previously exposed to pesticides through contaminated food may be subjected to fungicide spraying when it initiates its first flight outside the hive. In this study, we assessed the effects of acute exposure to the fungicide in bees with different toxicological statuses. Three days after emergence, bees were subjected to chronic exposure to the insecticide imidacloprid and the herbicide glyphosate, either individually or in a binary mixture, at environmental concentrations of 0.01 and 0.1 μg/L in food (0.0083 and 0.083 μg/kg) for 30 days. Seven days after the beginning of chronic exposure to the pesticides (10 days after emergence), the bees were subjected to spraying with the fungicide difenoconazole at the registered field dosage. The results showed a delayed significant decrease in survival when honey bees were treated with the fungicide. Fungicide toxicity increased when honey bees were chronically exposed to glyphosate at the lowest concentration, decreased when they were exposed to imidacloprid, and did not significantly change when they were exposed to the binary mixture regardless of the concentration. Bees exposed to all of these pesticide combinations showed physiological disruptions, revealed by the modulation of several life history traits related mainly to metabolism, even when no effect of the other pesticides on fungicide toxicity was observed. These results show that the toxicity of active substances may be misestimated in the pesticide registration procedure, especially for fungicides.

Since climate change is expected to bring more severe and frequent extreme weather events such as heat waves, assessing the physiological and behavioural sensitivity of organisms to temperature becomes a priority. We therefore investigated the responses of honeybees, an important insect pollinator, to simulated heat waves (SHW). Honeybees are known to maintain strict brood thermoregulation, but the consequences at the colony and individual levels remain poorly understood.For the first time, we quantified and modelled colony real-time activity and found a 70% increase in foraging activity with SHW, which was likely due to the recruitment of previously inactive bees. Pollen and nectar foraging was not impacted, but an increase in water foragers was observed at the expense of empty bees. Contrary to individual energetic resources, vitellogenin levels increased with SHW, probably to protect bees against oxidative stress. Finally, though immune functions were not altered, we observed a significant decrease in deformed wing virus loads with SHW. In conclusion, we demonstrated that honeybees could remarkably adapt to heat waves without a cost at the individual level and on resource flow. However, the recruitment of backup foraging forces might be costly bylowering the colony buffering capacity against additional environmental pressures.

In honeybees ( 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.

Plant protection spray treatments may expose non-target organisms to pesticides. In the pesticide registration procedure, the honey bee represents one of the non-target model species for which the risk posed by pesticides must be assessed on the basis of the hazard quotient (HQ). The HQ is defined as the ratio between environmental exposure and toxicity. For the honey bee, the HQ calculation is not consistent because it corresponds to the ratio between the pesticide field rate (in mass of pesticide/ha) and LD50 (in mass of pesticide/bee). Thus, in contrast to all other species, the HQ can only be interpreted empirically because it corresponds to a number of bees/ha. This type of HQ calculation is due to the difficulty in transforming pesticide field rates into doses to which bees are exposed. In this study, we used a pragmatic approach to determine the apparent exposure surface area of honey bees submitted to pesticide treatments by spraying with a Potter-type tower. The doses received by the bees were quantified by very efficient chemical analyses, which enabled us to determine an apparent surface area of 1.05 cm(2)/bee. The apparent surface area was used to calculate the exposure levels of bees submitted to pesticide sprays and then to revisit the HQ ratios with a calculation mode similar to that used for all other living species. X-tomography was used to assess the physical surface area of a bee, which was 3.27 cm(2)/bee, and showed that the apparent exposure surface was not overestimated. The control experiments showed that the toxicity induced by doses calculated with the exposure surface area was similar to that induced by treatments according to the European testing procedure. This new approach to measure risk is more accurate and could become a tool to aid the decision-making process in the risk assessment of pesticides.

The global decline of honeybee colonies represents a major ecological concern, primarily attributed to simultaneous exposure to multiple stressors. These include biotic pressures, such as parasitic infections, and abiotic pressures, such as exposure to ionizing radiation, which remains poorly understood. Assessing their combined effects provides novel insights into how biological and radiological stressors interact within the organism. Here, we investigated the individual and combined effects of Vairimorpha ceranae (formerly Nosema ceranae) infection and chronic gamma irradiation (14 [micro]Gy/h or 14 x 10³ [micro]Gy/h) on honeybee health. Measurements included survival, syrup consumption, spore load, and biomarkers related to energy metabolism, antioxidant defenses, immunity, detoxification, and neural enzyme activity. Two successive experiments, conducted at different collection periods, allowed us to account for biological variability between bee cohorts. Infection by V. ceranae caused high mortality and major impairments in metabolic, antioxidant, and immune functions. Ionizing radiation induced more moderate effects, characterized by redox imbalance and reduced detoxification capacity, which varied with dose rate. Under combined exposure, the two stressors produced mainly antagonistic interactions affecting antioxidant, immune, and detoxification systems. However, a synergistic effect was observed on ATP production, suggesting an energetic compensation mechanism. These findings highlight complex physiological disturbances, revealing the multifactorial vulnerability of honeybees and emphasizing the need to integrate interactions between multiple stressors and natural biological variability into ecotoxicological assessments.

In honeybees (Apis mellifera 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. Chez l'abeille domestique (Apis mellifera L.), la reine assure la reproduction de la colonie. Toute contamination environnementale susceptible d'altérer cette fonction pourrait compromettre la survie de la colonie. Les rayonnements ionisants pourraient constituer un tel facteur, mais leurs effets n'ont jamais été étudiés chez les reines. Les effets de l'irradiation gamma sur les reines ont été évalués en laboratoire. Les reines ont été irradiées pendant 14 jours à des débits de dose de 0,1, 13 et 3 500 µGy/h, et la mortalité, le potentiel reproducteur et plusieurs biomarqueurs physiologiques ont été analysés. L'irradiation n'a pas affecté la survie des reines ni le nombre de spermatozoïdes stockés dans la spermathèque. Cependant, la viabilité des spermatozoïdes et le potentiel reproducteur ont diminué significativement à 13 et 3 500 µGy/h. Parmi les biomarqueurs analysés (défenses antioxydantes, détoxification, métabolisme, immunité, activité neuronale), aucune différence significative n'a été observée entre les modalités, à l'exception d'une augmentation de l'activité de la LDH thoracique à 13 µGy/h, confirmée par des analyses multivariées indiquant des modifications métaboliques. Ces résultats montrent que les rayonnements ionisants n'induisent pas de létalité aux doses testées, mais altèrent significativement la fertilité et le métabolisme des reines, avec des conséquences potentielles pour la stabilité des colonies. La signification écologique de ces conséquences reste à confirmer en conditions réelles.

Plant protection spray treatments may expose non-target organisms to pesticides. In the pesticide registration procedure, the honey bee represents one of the non-target model species for which the risk posed by pesticides must be assessed on the basis of the hazard quotient (HQ). The HQ is defined as the ratio between environmental exposure and toxicity. For the honey bee, the HQ calculation is not consistent because it corresponds to the ratio between the pesticide field rate (in mass of pesticide/ha) and LD.sub.50 (in mass of pesticide/bee). Thus, in contrast to all other species, the HQ can only be interpreted empirically because it corresponds to a number of bees/ha. This type of HQ calculation is due to the difficulty in transforming pesticide field rates into doses to which bees are exposed. In this study, we used a pragmatic approach to determine the apparent exposure surface area of honey bees submitted to pesticide treatments by spraying with a Potter-type tower. The doses received by the bees were quantified by very efficient chemical analyses, which enabled us to determine an apparent surface area of 1.05 cm.sup.2 /bee. The apparent surface area was used to calculate the exposure levels of bees submitted to pesticide sprays and then to revisit the HQ ratios with a calculation mode similar to that used for all other living species. X-tomography was used to assess the physical surface area of a bee, which was 3.27 cm.sup.2 /bee, and showed that the apparent exposure surface was not overestimated. The control experiments showed that the toxicity induced by doses calculated with the exposure surface area was similar to that induced by treatments according to the European testing procedure. This new approach to measure risk is more accurate and could become a tool to aid the decision-making process in the risk assessment of pesticides.

During all their life stages, bees are exposed to residual concentrations of pesticides, such as insecticides, herbicides, and fungicides, stored in beehive matrices. Fungicides are authorized for use during crop blooms because of their low acute toxicity to honey bees. Thus, a bee that might have been previously exposed to pesticides through contaminated food may be subjected to fungicide spraying when it initiates its first flight outside the hive. In this study, we assessed the effects of acute exposure to the fungicide in bees with different toxicological statuses. Three days after emergence, bees were subjected to chronic exposure to the insecticide imidacloprid and the herbicide glyphosate, either individually or in a binary mixture, at environmental concentrations of 0.01 and 0.1 μg/L in food (0.0083 and 0.083 μg/kg) for 30 days. Seven days after the beginning of chronic exposure to the pesticides (10 days after emergence), the bees were subjected to spraying with the fungicide difenoconazole at the registered field dosage. The results showed a delayed significant decrease in survival when honey bees were treated with the fungicide. Fungicide toxicity increased when honey bees were chronically exposed to glyphosate at the lowest concentration, decreased when they were exposed to imidacloprid, and did not significantly change when they were exposed to the binary mixture regardless of the concentration. Bees exposed to all of these pesticide combinations showed physiological disruptions, revealed by the modulation of several life history traits related mainly to metabolism, even when no effect of the other pesticides on fungicide toxicity was observed. These results show that the toxicity of active substances may be misestimated in the pesticide registration procedure, especially for fungicides.