Effects of body temperature on action potential responses of target-selective descending neurons in Aeshna dragonflies
Dragonflies are able to thermoregulate, considerably changing their body temperature through both behavioral and physiological adaptations. The genus Aeshna of the insect family Aeshnidae are known as fliers, meaning that they primarily spend their time in flight. This behavior significantly heats body temperature. When active in flight, fliers are able to capture their prey of small flying insects. Tuned specifically for visualizing and assisting in the capture of these prey are a group of descending visual neurons known as the target-selective descending neurons (TSDNs). These neurons are a relay station between the visual information collected in the eyes and the motor systems of the wings. Collectively, the TSDNs are composed of two separate connectives of 8 different neurons, each of which has its own receptive field, preferred target size, and directional preference. In other neural models, temperature changes are known to affect responses, leading to a reduction in action potential amplitude and duration upon temperature increase. Shifts in temperature have also been shown to cause changes in membrane resting potentials. Due to dragonflies’ ability to change body temperature so drastically, we sought to analyze the effects that temperature increase plays on the neural functioning in TSDNs. Using extracellular hook-electrodes on various species of Aeshna dragonflies, we recorded TSDN activity. Our results indicate that in certain instances, an increase in temperature will lead to a faster rate of action potential firings. In all tested scenarios, increasing temperatures reduced response latency to the presented stimuli.