Comparison And Analysis Of Behavioral And Physiological Thermoregulation In Two Species Of Toad-head Lizard

Thermoregulation of animals includes behavioral thermoregulation and physiological thermoregulation.Behavioral thermoregulation studies focus on steady-state of body temperature?T_b?.Researches on physiological thermoregulation are about transient-state in thermoregulation processes,it is to estimate the ability of gain and maintain body temperature.Temperature is of utmost importance nature factor of biological metabolism and life activity,while preferred body temperature(T_sel)of ectotherm,which is an essential parameter of thermoregulation,plays an important role in ecological adaptation and evolution.Measurement of T_sel often encounters problems of low repeatability and poor accuracy because there are many factors could affect it.In this study,according to characteristics of very different habitants of two Phrynocephalus lizards,higher-altitude Phrynocephalus erythrurus and lower-altitude Phrynocephalus przewalskii,factors such as environment thermal quality,oxygen concentration of air and ultraviolet radiation were abstracted for influence analysis of thermoregulation.Two-level orthogonal array design of these factors were used for thermoregulation analysis in this article,varying thermal gradients were set under laboratory condition.By analysis of range and variance of orthogonal experiment,we tried to determine which factor is the most important to behavioral thermoregulation.For the purpose of more accurate comparison and evaluation of behavioral thermoregulation of two Phrynocephalus lizards,T_sel of two species were measured in proper thermal gradients with conditions most matched their natural habitats.Physiological thermoregulation of two species were estimated and compared with the cooling and warming rate,thermal time constant???,relationship between body weight and?,relationship of heart rate and core body temperature,and heart rate hysteresis.Results of orthogonal experiment analysis showed that:?1?Environmental thermal constraint is the most crucial factor of T_sel and basking frequency.?2?Compared with normoxia,hypoxia induced T_sel decrease but not significantly and basking frequency significantly increased in both species.?3?UVB caused T_sel and the time frequency decreased,but neither of two parameters was significant different.?4?In high thermal quality treatments,there was no significant difference in T_sel between two species and basking frequency of P.erythrurus was lower than that of P.przewalskii.In lower thermal quality treatments,T_sel and basking frequency of P.erythrurus were higher than that of P.przewalskii.Evaluating and comparing on behavioral thermoregulation of P.erythrurus and P.przewalskii showed that P.erythrurus have a subtler and effective cold-adaptive thermoregulation than P.przewalskii.The results of physiological thermoregulation studies showed that:?1?both rate and thermal time constants of cooling and warming of P.erythrurus showed a better heat flux than that of P.przewalskii;?2?Body mass have a significant positive influence on cooling time constant,but no significant on warming time constant;?3?there were significant differences between species in the cooling time constants,but no significant difference in the warming time constant;?4?the rate of warming/cooling time constant of two species was very close,implying P.przewalskii and P.erythrurus have very similar relative ability of physiological thermoregulation;?5?the above results are the same with warming-cooling order process conclusions,meaning that there are nothing to do with the order process.Analysis of the results of relationship between T_b and heart rate of fixed lizard during and between cooling-warming process show that:?1?the rapid increase or decrease of heart rate caused by the rapid rise or decrease of T_b in both lizards;?2?heart rate in cooling process always exceed that in warming at the same T_b in cooling-warming process experiment,in other words,heart rate hysteresis was also existed in cooling-warming process,so we could say the phenomenon of heart rate hysteresis is a delay from the former state to the latter state.