Heat adaptations in reptiles and the mechanism of their formation

This article deals with the main concepts and other aspects of thermobiology of reptiles that must be taken into account considering the problems of reptiles’ thermal adaptation. The difference between the "thermobiological features” and "thermal adaptation" often used as synonyms is defined. It is shown, that in adapting reptiles to external conditions the complex of thermophysiological indicators and reactions responsible for the conditions of full activity is of great importance. The connection between the thermophysiological features defining the condition of full activity and the parameters of environment is not always unequivocal. There is an important intermediary between them - the behavioral and physiological thermoregulation, which significantly disturbs the unambiguity of this connection. Due to these thermoregulation reactions (basically behavioral) the mesophilic species can successfully inhabit hot regions, but some reptiles, which need regular heating up to 30-34˚C, can inhabit cold regions. The significance of behavioral regulatory reactions, physiological temperature-dependent and thermoregulatory, temperature-controlling reactions in the complex of reptiles’ thermal adaptation is analyzed. It is determined, that the complex of thermophysiological, stabile (geographically and seasonally invariable) thermoregulating indicators of homeostasis is of key value in reptiles’ adaptation to natural climatic conditions. The mechanisms forming space-time structure of daily and seasonal activity and regulation of endogenous annual feeding and breeding cycles are described. It is shown that the individual reptiles adapt to the thermal environment mainly not owing to modification of thermophysiological features, but due to the fine adjustment of space-time structures of daily and seasonal activity. It occurs with the help of behavioral regulatory reactions, which allow the homeostatic characters, included in the physiological ecological matrix to remain unchanged. At that, the main aim of individual thermal adaptations is to save unchangeable homeostatic indicators, included in the physiological ecological matrix, in different environmental conditions. In the studies of reptiles’ thermobiology, it is proposed to change the focus from the investigations of plasticity of thermobiological features to those of thermal stability of the thermobiological homeostasis complex (physiological ecological matrix), i.e. thermal needs of the organism, and methods of preservation of this invariability in different environmental conditions.