Evolution of Temperature Receptors and Their Roles in Sensory Diversification and Adaptation

Among various environmental factors, temperature is one of the critical factors for organisms since it can affect most, if not all, biological processes. Therefore, animals precisely sense ambient and body temperatures and physiologically and behaviorally respond to temperature changes. Taking such nature into consideration, alteration of thermal perception should have played a pivotal role in adaptation to diverse thermal niches. Temperature as well as other physical and chemical stimuli are perceived by the primary afferent neurons where transient receptor potential (TRP) channels are expressed, and these channels serve as multimodal receptors in the somatosensory system. To understand the roles of TRP channels in the evolution of sensory perception, comparative analyses have been performed using various animal species, and their functional diversity has been well documented over the past 2 decades. Furthermore, in recent years, species differences in the thermal responses of TRP channels have been found among closely related species inhabiting different thermal niches, which have uncovered the contributions of TRP channels to environmental adaptation in various vertebrate species. The purpose of this review is to summarize the studies that addressed the functional evolution of TRP channels associated with sensory diversification and environmental adaptation.