Departamento de Biociências, Universidade Federal Rural do Semi-Árido, Avenida Francisco Mota, 575, Presidente Costa e Silva, Mossoró, RN 59625-900, Brazil.
Departamento de Biociências, Universidade Federal Rural do Semi-Árido, Avenida Francisco Mota, 575, Presidente Costa e Silva, Mossoró, RN 59625-900, Brazil; Departamento de Biologia, Universidade Federal do Ceará, Avenida Mister Hull, s/n, Campus do Pici, Fortaleza, CE 60440-900, Brazil.
J Insect Physiol. 2020 May-Jun;123:104056. doi: 10.1016/j.jinsphys.2020.104056. Epub 2020 May 6.
The thoracic temperature (T) of foraging bees usually exceeds ambient air temperatures (T) by several degrees. In hot tropical climate zones, therefore, individuals may reach body temperatures close to their critical thermal maxima, which might constrain their activity. In the present study, we tested the hypothesis that thermal stress increases with flight distance in nectar foragers of M. subnitida, a stingless bee species native to the hottest regions of the Brazilian tropical dry forest. Using infrared thermography, we recorded the body surface temperature of individuals foraging at distances of 15, 50, and 100 m. Closest to the nests, foragers stabilized T at 40 °C when collecting sugar solution at T > 30 °C. The simultaneous decrease of the temperature excess ratio of head and abdomen suggests evaporative cooling at these body parts. With increasing foraging distance, foragers increased heat dissipation to the head and abdomen. Thus, despite more intensive heating of the thorax due to faster and longer flights, the bees maintained similar T as foragers at close feeding sites. However, at T > 30 °C, bees could no longer compensate the elevated heat gain at the head (50 m) and abdomen (50, 100 m), which caused an increasing temperature excess in these body parts. Thus, foragers of M. subnitida suffer overheating of the head and abdomen instead of the thorax when foraging in high temperatures at far feeding sites. Consequently, to avoid heat stress in the Brazilian tropical dry forest, the bees should forage close to the nest.
觅食蜜蜂的胸部温度（T）通常比环境空气温度（T）高出几度。因此，在炎热的热带气候带，个体可能会达到接近其临界热极值的体温，这可能会限制它们的活动。在本研究中，我们检验了一个假设，即在原产于巴西热带干旱森林最热地区的无刺蜜蜂物种 M. subnitida 的花蜜觅食者中，热应激随飞行距离的增加而增加。使用红外热成像技术，我们记录了在距离蜂巢 15、50 和 100 米处觅食的个体的体表温度。在采集 T>30°C 的糖水时，距离蜂巢最近的觅食者将 T 稳定在 40°C。头部和腹部的温差比同时下降表明这些身体部位有蒸发冷却。随着觅食距离的增加，觅食者增加了对头部和腹部的散热。因此，尽管由于飞行速度更快、时间更长，胸部受到更强烈的加热，但蜜蜂在近距离觅食时仍保持与近距离觅食者相似的 T。然而，在 T>30°C 时，蜜蜂无法再补偿头部（50 米）和腹部（50、100 米）升高的热量摄入，这导致这些身体部位的温差增加。因此，当在远离巢穴的高温环境中觅食时，M. subnitida 的觅食者头部和腹部会过热，而不是胸部。因此，为了避免在巴西热带干旱森林中出现热应激，蜜蜂应该在靠近巢穴的地方觅食。
