Cardiac responses to stress and activity in the armoured legless lizard Ophisaurus apodus: Comparison with snake and tortoise

Abstract

1. 1. Heart rate (HR) was measured during and after stress and activity in the armoured legless lizard Ophisaurus apodus, the snake Natrix natrix and the tortoise Testudo hermanni, at different body temperatures T b. These are discussed in relation to field T b, defensive behaviour and published V́O 2. 2. 2. Ophisaurus apodus used passive defence, including hemipenis or cloacal sac eversion and prolonged immobility after release. This was correlated with a low degree of tachycardia, bradycardia at low T b, low metabolism and armour. 3. 3. Defence behaviour was T b-dependent in wild T. hermanni, with passive withdrawal into the shell at low T b, and active struggling at high T b. The degree of tachycardia was lower at low T b. 4. 4. Standard and active oxygen pulse OP were insensitive to T b in O. apodus and N. natrix, and their SOP was lower than tetrapod lizards. Factorial scope of HR was reduced at 35°C, just above the activity T b range of these species. 5. 5. Recovery of HR after activity in T. hermanni was much more rapid than in the squamates, and of similar duration to recovery after stress. It is suggested that tortoises do not utilize anaerobic metabolism during activity.