Departamento de Ecología, Genética y Evolución, Instituto IEGEBA (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina; Institut de Recherche sur la Biologie de l'Insecte, UMR 7261 CNRS, Université de Tours, France.
Departamento de Ecología, Genética y Evolución, Instituto IEGEBA (CONICET-UBA), Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina.
J Insect Physiol. 2018 Jul;108:10-16. doi: 10.1016/j.jinsphys.2018.04.012. Epub 2018 Apr 21.
The increase in body temperature over that of the environment has been frequently reported in insects, in particular in relation with flight activity. Scarab beetles of the genus Cyclocephala living in tropical areas are known to exploit the heat produced by thermogenic plants, also producing heat by endothermy. Here, we report the first case of endothermy in a species of this genus living in a temperate region, Cyclocephala signaticollis. We characterised the phenomenon in this beetle using infrared thermography and exposing them to different thermal conditions. We evaluated the frequency of endothermic bouts, the nature of their periodic occurrence and their association with the activity cycles of the beetles. We found that endothermy occurs in both males and females in a cyclic fashion, at the beginning of the night, around 21:00 local time. The mean temperature increase was of 9 °C, and the mean duration of the bouts was 7 min. During endothermic bouts, the temperature of the thorax was on average 3.6 °C higher than that of the head and 4.8 °C above that of the abdomen. We found no differences between females and males in the maximum temperature attained and in the duration of the endothermy bouts. The activity period of the beetles extends throughout the whole night, with maximum activity between 22:00 and 23:00. By subjecting the beetles to different light regimes we were able to determine that the rhythm of endothermy is not controlled by the circadian system. Finally, we experimentally tested if by performing endothermy the scarabs try to reach a particular body temperature or if they invest a given amount of energy in heating up, instead. Our results indicate that at lower ambient temperature beetles show higher increase in body temperature, and that endothermy bouts last longer than at relatively higher ambient temperatures. We discuss our findings in relation to the ecology and behaviour of this beetle pest.
昆虫经常会出现体温高于环境温度的情况，特别是与飞行活动有关时。生活在热带地区的 Cyclocephala 属金龟子已知会利用生热植物产生的热量，同时也通过体温调节产热。在这里，我们报告了首例生活在温带地区的该属物种 Cyclocephala signaticollis 体温调节的情况。我们使用红外热成像技术对这种甲虫进行了特征描述，并将其暴露在不同的热条件下。我们评估了体温调节的频率、其周期性发生的性质及其与甲虫活动周期的关联。我们发现，雄性和雌性甲虫都会以周期性的方式在当地时间 21 点左右开始夜间活动时进行体温调节。体温平均升高 9°C，体温调节的持续时间平均为 7 分钟。在体温调节过程中，胸部温度平均比头部高 3.6°C，比腹部高 4.8°C。我们发现，雌性和雄性在达到的最高温度和体温调节的持续时间方面没有差异。甲虫的活动期贯穿整个夜晚，最大活动时间在 22 点到 23 点之间。通过对甲虫进行不同的光照处理，我们能够确定体温调节的节律不受昼夜节律系统的控制。最后，我们通过实验测试了甲虫是否通过进行体温调节来尝试达到特定的体温，或者它们是否投入了一定的能量来加热。我们的结果表明，在较低的环境温度下，甲虫的体温升高幅度更高，体温调节的持续时间也比在相对较高的环境温度下更长。我们将我们的发现与这种甲虫害虫的生态和行为联系起来进行了讨论。
