School of Life Sciences, Arizona State University, Tempe, AZ 85281.
Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071.
Proc Natl Acad Sci U S A. 2024 Jan 23;121(4):e2311025121. doi: 10.1073/pnas.2311025121. Epub 2024 Jan 16.
Heat waves are becoming increasingly common due to climate change, making it crucial to identify and understand the capacities for insect pollinators, such as honey bees, to avoid overheating. We examined the effects of hot, dry air temperatures on the physiological and behavioral mechanisms that honey bees use to fly when carrying nectar loads, to assess how foraging is limited by overheating or desiccation. We found that flight muscle temperatures increased linearly with load mass at air temperatures of 20 or 30 °C, but, remarkably, there was no change with increasing nectar loads at an air temperature of 40 °C. Flying, nectar-loaded bees were able to avoid overheating at 40 °C by reducing their flight metabolic rates and increasing evaporative cooling. At high body temperatures, bees apparently increase flight efficiency by lowering their wingbeat frequency and increasing stroke amplitude to compensate, reducing the need for evaporative cooling. However, even with reductions in metabolic heat production, desiccation likely limits foraging at temperatures well below bees' critical thermal maxima in hot, dry conditions.
由于气候变化，热浪越来越常见，因此识别和了解昆虫传粉媒介（如蜜蜂）避免过热的能力至关重要。我们研究了炎热干燥的空气温度对蜜蜂携带花蜜负荷飞行时使用的生理和行为机制的影响，以评估过热或干燥如何限制觅食。我们发现，在空气温度为 20 或 30°C 时，飞行肌肉温度随负荷质量呈线性增加，但在空气温度为 40°C 时，随着花蜜负荷的增加，肌肉温度没有变化。飞行时携带花蜜的蜜蜂能够通过降低飞行代谢率和增加蒸发冷却来避免在 40°C 时过热。在高温下，蜜蜂显然通过降低翅膀拍打频率和增加冲程幅度来提高飞行效率来进行补偿，从而减少蒸发冷却的需求。然而，即使减少了代谢热的产生，在炎热干燥的条件下，蜜蜂的临界热极值以下，干燥很可能限制觅食。
