Changes in clinicomorphometrical findings, lipid profiles, hepatorenal indices and oxidant/antioxidant status as thermoregulatory adaptive mechanisms in poikilothermic Dabb lizard (Uromastyx aegyptia)

Abstract

Wildlife has exposed to various environmental stressors. Reptiles (ectothermic) are highly susceptible to climatic changes due to their behaviour, physiology, and life history that were so heavily reliant on the ambient environmental temperature. The present work aims to monitor different biochemical and haematological indices of Dabb lizards (Uromastyx aegyptia) at various thermal gradients as well as their adaptation to oxidative stress. This has been reflected through assessment of their impact on some adaptive physiological traits i.e. thermoregulation, and muscle metabolic biomarkers, blood pictures and oxidant/antioxidant status. This experiment is carried out on non-hibernating adult male Dabb lizards (U. aegyptia; n = 24) of age of 18–24 months. These Dabb lizards are divided into four equal groups (n = 6 for each one) where they are exposed to different thermal treatments for one week as following; control group [Exposed to terrarium temperature 38–39 °C], low temperature exposed group [Exposed to 12–14 °C], Gp. C; moderate temperature exposed group [Exposed to 41–43 °C] and high temperature exposed group [Exposed to 43–45 °C]. Each independent group (n = 6) are kept at separated glass terraria. The investigated lizards are monitored for body temperature, morphometric measurements i.e. body weight (g) and total body length (cm; TBL), muscle biochemical analysis, haematological pictures indices and serum biochemical assays including mainly oxidant/antioxidants biomarkers throughout the current experiment. The results state that the thermoregulatory behaviour of Dabb varies with the increase of concentration of muscular metabolic enzymes. In low temperature exposed group, the increase in red blood corpuscles (RBCs), haemoglobin concentrations (Hb), white blood cell (WBC), serum antioxidant biomarkers and anaerobic Lactate dehydrogenase (LDH) enzyme are associated with a marked reduction in serum levels of total cholesterol (TC), triglycerides (TGs), total proteins (TPs), albumin, glucose and electrolytes. In moderate temperature exposed group, a significant elevation in serum values of TC, TGs, TPs, glucose, urea and uric acids levels are mentioned. In high temperature exposed Dabb group, a remarkable increase in blood values of RBCs, Hb, haematocrit value (HCT), WBC, T. chol., TGs, TPs, glucose, urea, uric acids, triiodothyronine (T3) and thyroxine (T4) levels are also observed. Moreover, significant increases in muscular anaerobic/aerobic metabolic enzymes as well as stimulation of antioxidant defence system have been reported. Different significant correlations have been stated between variably estimated laboratory indices in the investigated Dabb lizards under different thermal treatments. The study concludes that the Dabb lizards have a strong antioxidant defence system and undergo physiological thermoregulatory adaptive mechanisms, that involve biochemical and metabolic acclimatization as a response to environmental temperature changes that act as a protective mechanism against oxidative stress as well as maintained homeostatic responses and normal physiological functions.

Mitochondrial Protein-Coding Gene Expression in the Lizard Sphenomorphus incognitus (Squamata:Scincidae) Responding to Different Temperature Stresses

“…Warmer environments promote faster development and increased metabolic activities in poikilothermic animals, implying higher energy demands [ 33 ]. Consistent with this pattern, transcript levels of seven PCGs showed upregulation under 34 °C conditions.…”

“…In warmer environments, organisms exhibit higher energy metabolism. Increased mitochondrial activity also promotes faster development in ectotherms [ 33 ]. However, this does not necessarily imply lower levels of damage, since high temperatures can lead to the redistribution of electron flux and proton motive force (Δp), reducing ATP synthesis efficiency and increasing the relative cost of mitochondrial maintenance, resulting in excessive production of reactive oxygen species and raising the energy cost of antioxidant defense.…”