Physiological correlates of natural activity and locomotor capacity in two species of lacertid lizards

1. Physiological factors relating to activity metabolism were measured in two species of African lacertid lizards that differ greatly in natural foraging patterns:Eremias lineoocellata, a sit-and-wait predator, and E. lugubris, a widely foraging animal. 2. Maximal oxygen consumption at 37°C is greater in E. lugubris [3.22 ml O₂/(gxh)] than in E. lineoocellata [2.49 ml O₂/(gxh)]. 3. Anaerobic scope and capacity at 37°C are greater in E. lineoocellata [2.56 mg lactate/(gx min) and 1.81 mg lactate/g] than in E. lugubris [2.12 mg lactate/(gxmin) and 1.40 mg lactate/g]. 4. Relative heart mass and hematocrit are greater in E. lugubris than in E. lineoocellata (0.28% and 0.24% body mass; 30.1 and 24.4 respectively). 5. No significant interspecific differences occur in hind limb muscle mass as a percentage of body mass or in myoglobin concentration, citrate synthase or myofibrillar ATPase activity of hind limb skeletal muscle. 6. No significant interspecific differences occur in isometric contractile properties (twitch and tetanic tension, twitch rise time and half-relaxation time, and fatigue response to tetanic stimulation) of the iliofibularis muscle. 7. Organismal metabolic patterns of aerobic and anaerobic capacity reflect differences in locomotor capacity and natural foraging patterns of these species.