Biochemical Mechanisms That Buffer the Effects of High Temperatures in the Sand-Dwelling Lizard Holbrookia propinqua

Reptiles, as ectothermic organisms, rely on environmental temperatures for optimal physiological performance. The thermal requirements for optimal locomotion in reptiles can severely affect their reproduction. However, some species are successful in environments with temperatures exceeding 40 °C. Holbrookuia propinqua is a species that reproduces at high temperatures, a difference from most species in the family Phrynosomatidae, to which it belongs. Adult male H. propinqua specimens were collected at their reproductive stage, kept in separate terrariums, and divided into four groups that were exposed to different temperatures. After seven days of exposure, both the testes and epididymides were removed. The organs were processed for immunohistochemistry and to determine SOD, CAT, and GPX activity. A sperm sample was obtained from the vas deferens. The GSI decreased with temperature, and the EI presented its maximum value at 24 °C. Sperm viability was lower at the highest temperature, and motility at 28 and 32 °C exceeded 90%. The specific SOD activity in the testis at 41 °C decreased by ~75%. In the epididymis, SOD activity decreased at 28 and 32 °C. Transient Receptor Potential Vanilloid 1 (TRPV1) increased after 28 °C at the interstitial level and increased almost twofold in the seminiferous tubules.