连续温度梯度下昆虫趋温性的研究现状与展望

Current status and future perspectives for behavioural response of insects to temperature gradient

昆虫作为一种能够自由活动的生物,可以通过运动主动选择对其有利的环境温度。大多数研究中昆虫被迫接受人为设定的恒温或变温,并未体现出昆虫本身对适宜温度的主动选择性。连续温度梯度是在某一介质的两端产生由高到低连续变化的温度范围。在一定温度梯度中昆虫趋温行为的研究揭示了其主动选择的适宜温度,这对了解昆虫的空间动态、提高测报准确性和开发防治新方法有重要意义。总结了产生连续温度梯度的各种装置,致冷、加热和温度测量方法以及昆虫趋温行为的观察装置和方法,包括在植物体上(内)及空气、下垫面、粮食和土壤等介质中产生温度梯度的方法及装置。各装置以水浴或电器设备制冷或加热,肉眼观察手工记录或以摄像机、声音信号采集系统等方法记录昆虫的行为。综述了多种昆虫生长发育、栖息、产卵或取食的偏好温度,总结了性别、发育阶段和生态型等生理因素及光照、湿度和预适应温度等环境因子对昆虫偏好温度变化的影响。昆虫的趋温性因种而异,同种昆虫不同发育阶段或不同生命活动所趋温度不同。多数种类昆虫雄性成虫的偏好温度比雌性略高。某些昆虫的多型现象可能导致其种内不同生态型的偏好温度存在差异。光照和湿度的变化会影响某些昆虫对温度的反应。有些昆虫经预适应温度训练后,其偏好温度发生改变。某些昆虫对温度的偏好呈现出一定的日变化和季节变化规律。饥饿条件下昆虫的偏好温度降低。温度梯度的有无及其方向、温度的高低、温差的大小等因素都会影响昆虫的活动性。最后分析了本类研究中存在的问题和不足,并展望了未来的研究方向,指出开展对重要农林作物害虫和天敌趋温行为及其生理学机制,外界环境因素影响昆虫趋温性等方面的探索将是未来该领域研究的重点内容。

Insects , as free-moving living organisms, can avoid detrimental temperatures and search for favourite temperatures by active crawling or flying under natural conditions. However, the tested insects were forced to live under uniform temperature conditions in most experiments for studying effects of constant or alternative temperatures on insects. Results from those experiments cannot demonstrate what are the favourite temperatures for those insects in nature. Temperature gradient is a temperature field in which temperature continuously decreases or increases from one side to the other. Investigations on thermotactic behaviours of insects in temperature gradients can show preference of insects to the optimal temperature, and it is useful for understanding spatial dynamics, improving prediction techniques and innovating new control methods of those insects. We reviewed the research progress on behaviors of insects in temperature gradients and the devices used in those experiments. We described the methods to produce a temperature gradient across a plant organ, a circular plate,a rectangular board, a cylinder of grain or soil. Those devices cooled or heated the experimental arena with water bath or electronic thermostat, measured temperatures with a group of thermometers, thermocouples or temperature sensors and recorded the behaviors of insects with naked eyes, video cameras or a group of microphones. We listed preferred temperatures of 16 species of insects for development, inhabitation, deposition or feeding. The changes of preferred temperature of insects were attributed to both internal physiological and external environmental conditions. The preferred temperatures of insects were different not only between various species but also between different development stages or life activities of the same species. Males preferred higher temperature than females for most species of insects. Different type of a polymorph insect species might prefer different temperatures. Light and relative humidity were important factors that affect the response of insect to temperature gradient. Preferred temperatures of insects might alter after a period of temperature acclimation. Some species of insects performed particular diurnal or seasonal responses rhythms to temperature gradient. Usually, unfed insects had lower preferred temperatures than the fed ones. The existence, directions and extent of the temperature gradient influenced activities of insects. We analysed the weak aspects of previous studies and pointed out the works needed to do in the future. Entomologists have not yet explored thermotactic behaviours of most species of the important insect pests and their natural enemies in China. We should investigate the behaviours and the physiological mechanisms of those insects in temperature gradient. Moreover, we should clarify the effects of environmental conditions on thermotactism of the important insect species in the future.