The effect of developmental temperature on olfaction in a moth revealed by its interaction with body mass

There is a growing interest in the effects of climate warming on olfaction, as temperature may affect this essential sense. In insects, the response of the olfactory system to developmental temperature might be mediated by body size or mass because body size and mass are negatively affected by developmental temperature in most ectotherms. We tested this hypothesis of a mass-mediated effect of developmental temperature on olfaction in the moth Spodoptera littoralis. We measured the olfactory sensitivity of male to female sex pheromone and five plant odors using electroantennography. We compared males reared at an optimal temperature (25°C with a daily fluctuation of ± 5°C) and at a high temperature (33 ± 5°C) close to the upper limit of S. littoralis. On average, the olfactory sensitivity of males did not differ between the two developmental temperatures. However, our analyses revealed an interaction between the effects of developmental temperature and body mass on the detection of the six chemicals tested. This interaction is explained by a positive relationship between antennal sensitivity and body mass observed only with the high developmental temperature. Our results show that the effect of developmental temperature may not be detected when organism size is ignored.

学界对气候变暖对嗅觉（olfaction）的影响日益关注，因为温度可调控这一至关重要的感官功能。在昆虫中，嗅觉系统对发育温度的响应或可通过体型或体重介导——因绝大多数变温动物（ectotherm）的体型与体重均会受到发育温度的负面影响。本研究以海灰翅夜蛾（Spodoptera littoralis）为实验对象，验证了“发育温度通过体重介导影响嗅觉”这一假说。研究采用触角电位法（electroantennography）测定了雄虫对雌性性信息素及5种植物气味的嗅觉敏感性，并比较了两种发育温度下饲养的雄虫：一组为适宜温度组（25℃，日波动幅度±5℃），另一组为高温组（33±5℃，该温度接近海灰翅夜蛾的生存温度上限）。整体而言，两种发育温度下雄虫的嗅觉敏感性并无显著差异。但分析结果显示，发育温度与体重对受试6种化学物质的检测效果存在交互效应。该交互效应可通过仅在高温发育组中观察到的触角敏感性与体重间的正相关关系得到解释。本研究结果表明，若忽略生物体型因素，则无法检测到发育温度对嗅觉的影响。