The Different Mechanisms Of Hypoxic Acclimatization And Adaption In Lizard Phrynocephalus Vlangalii,thermo Regulatory And Metabolic Responses To Hypoxia In Lizard, Phrynocephalus Przewalskii

Phrynocephalus vlangalii is a species of lizard endemic in China, which lives on Qinghai-Tibet Plateau ranging from2000to4600m above sea level. In this study, P. vlangalii were collected from low altitude (2750m)and high altitude (4564m).The lizards from low altitude were acclimatized in simulated hypoxic chamber (equivalent to4600m) for7,15and30days. The hematological parameters, heart weight, myocardial capillary density and myocardial enzyme activities were examined. The results showed that acclimatization to hypoxia significantly increased hemoglobin concentration([Hb]), hematocrit (Hct), heart weight (HW), heart weight to body mass (HW/BM), lactate dehydrogenase (LDH) activity, but markedly decreased mean corpuscular hemoglobin concentration (MCHC) and succinate dehydrogenase (SDH) activity. Red blood cell (RBC) count, body mass (BM), myocardial capillary density did not change markedly during hypoxic acclimatization. On the other hand,[Hb], Hct, MCHC, HW/BM, myocardium capillary density, and SDH activity of P. vlangalii from high altitude were remarkably higher than those from low-altitude; however, LDH activity of high-altitude P. vlangalii was lower than that of low-altitude lizards. There was no significant difference in HW or BM between populations of high-altitude and low-altitude. Based on the present data, we suggest that P. vlangalii has special anatomical, physiological and biochemical accommodate mechanisms to live in hypoxic environment, and the regulative mechanisms are different between hypoxic acclimatization and adaptation.In the second section we studied the effects of hypoxia on behavioral thermoregulation, rate of heating and cooling, hysteresis of heart rate, and standard metabolic rate (SMR) were investigated in Phrynocephalus przewalskii, a small size toad headed lizard. Preferred temperature (Tb) descended when lizards were exposed to severe hypoxia (8%O2and6%O2) for22hours,and lizards were able to maintain preferred Tb after one week at12%and8%O2respectively. The whole time of heating increased after being treated with hypoxia (12%and8%O2) for one week. Hysteresis of heart rate appeared at any given body temperature and oxygen level except at39℃and40℃at8%O2.SMR significantly increased after one-week acclimatization to12%and8%O2when ambient temperature (Ta) was2℃, however, it did not change at35℃. Thus, we suggest that P. przewalskii has special thermoregulatory and metabolic mechanisms to acclimatize to the hypoxic environment.