Temperature and the respiratory properties of whole blood in two reptiles, Pogona barbata and Emydura signata

We investigated the capacity of two reptiles, an agamid lizard Pogona barbata and a chelid turtle Emydura signata, to compensate for the effects of temperature by making changes in their whole blood respiratory properties. This was accomplished by measuring the P50 (at 10, 20 and 30 °C), hematocrit (Hct), haemoglobin concentration ([Hb]) and mean cell haemoglobin concentration (MCHC) in field acclimatised and laboratory acclimated individuals. The acute effect of temperature on P50 in P. barbata, expressed as heat of oxygenation (ΔH), ranged from − 16.8 ± 1.84 to − 28.5 ± 2.73 kJ/mole. P50 of field acclimatised P. barbata increased significantly from early spring to summer at the test temperatures of 20°C (43.1 ± 1.2 to 48.8 ± 2.1 mmHg) and 30 °C (54.7 ± 1.2 to 65.2 ± 2.3 mmHg), but showed no acclimation under laboratory conditions. For E. signata, ΔH ranged from − 31.1 ± 6.32 to − 48.2 ± 3.59 kJ/mole. Field acclimatisation and laboratory acclimation of P50 did not occur. However, in E. signata, there was a significant increase in [Hb] and MCHC from early spring to summer in turtles collected from the wild (1.0 ± 0.1 to 1.7 ± 0.2 mmol/L and 4.0 ± 0.3 to 6.7 ± 0.7 mmol/L, respectively).