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

Abstract

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 P 50 (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 P 50 in P. barbata, expressed as heat of oxygenation (Δ H), ranged from − 16.8 ± 1.84 to − 28.5 ± 2.73 kJ/mole. P 50 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, Δ H ranged from − 31.1 ± 6.32 to − 48.2 ± 3.59 kJ/mole. Field acclimatisation and laboratory acclimation of P 50 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).