Integrative Physiological Approaches to Thermoregulatory and Thermosensory Biology

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As a complex biological trait, animal thermal physiology involves the co-evolution of thermal sensation along with biochemical mechanisms of thermal tolerance. Therefore, animals with different body temperatures should show functional differences in the properties of their molecular thermal sensors that coincide with their optimal temperatures. Understanding the thermal physiology of animals is important from a basic and an applied perspective, particularly as climate change models predict steep changes in environmental temperatures. The volitional thermal choices made by animals will play an important role in mitigating the effects of climate warming, especially if temperatures rise at rates faster than physiological tolerances evolve. Therefore, understanding how organisms regulate their body temperature is important since it illustrates their potential to respond to change in the environment. Indeed, recent studies suggest that species with narrow behavioural niches will be more adversely affected by rising temperatures; conversely, species with narrow thermal optimalities will be forced to compensate behaviourally in the future in order to achieve body temperatures within this narrow range.Traditionally, much thermal biology research focuses on the effects that temperature pose on animals rather than the influence animals have on their own temperature. My laboratory focuses on both the conserved as well as the unique mechanisms available to animals that bestow their abilities to modify and regulate their internal body temperature; these include behavioural, physiological, molecular and biochemical. In order to control body temperature, animals require: an ability to sense temperature, a central organizer to process and direct thermoeffector responses, and an array of effectors to bring out changes in temperature. This diffusively organized control system is phylogenetically ancient and exhibits remarkable variability. Yet certain elements seem relatively preserved, namely the sensation of temperature, which appears to derive from molecular thermosensors sharing similar biochemical properties and theintegration of these signals in the brain, which seem to share dual set-point like behaviour. Below the brain is where the thermoregulatory systems diverge, with various anatomical, biochemical, physiological and behavioural adaptations responsible for effecting thermally relevant changes. The sensory system is the first filtering mechanism available to animals in responding to their thermal environment. Recent advances have used genetic, molecular and in vitro approaches to understand an ever burgeoning array of putative temperature sensors, yet definitive information that these sensors are necessary and sufficient to produce real-life thermosensory behaviours in vivo are lacking. Knock-out models show some promise in this regard, yet suffer from the usual problems in that pleiotropic effects of genes are masked or the ability of the organism to compensate with other pathways is assumed to be absent. Over the next five years we will: 1) study the regulatory pathways (behavioural and physiological) that control Tb in animals by examining the physiological relevance of altered thermoregulatory states (e.g. hypoxia, hydrogen sulfide); 2) examine the mechanisms of warm and cold thermosensation and establish their roles in thermoregulatory behaviours through a comparative analysis of animals with different thermoregulatory preferences; 3) study the development and plasticity of thermoregulatory "appendages" and the interactions between water conservation and temperature regulation.