Western Fence Lizards, Sceloporus occidentalis, are frequently parasitized by the malaria-causing protozoan Plasmodium mexicanum, reducing hemoglobin concentrations, increasing reliance on anaerobic metabolism, and elevating the cost of recovery. We examined the influence of malarial infections in Fence Lizards on aerobic capacity, blood metabolites, and cardiopulmonary activity following activity (<2 min of maximal activity) on a treadmill at 35.0 ± 1.0°C. Aerobic capacity was determined from resting and maximal oxygen uptake. Blood glucose and lactate were measured before activity and at 15 min intervals during 60 min of recovery. Heart rate and ventilation rate were determined from electrocardiograph tracings. Maximal aerobic capacity was over 35% higher in uninfected lizards compared to both malaria-infected lizards and anemic-uninfected animals. Malarial infection decreased lizard resting blood glucose levels, yet induced hyperglycemia during recovery; blood glucose levels were elevated by about 27% from resting in malaria-infected lizards after 60 min of recovery. Malarial infection significantly increased anaerobic metabolism during activity; blood lactate levels in infected lizards were elevated above those in uninfected animals for 45 min of recovery. Heart rate was limited severely in malaria-infected lizards following activity; mean heart rate was over 20 beats per minute lower (170 ± 6.7 vs. 193 ± 5.0) in infected lizards compared to uninfected animals. The major disruptions to recovery metabolism in malaria-infected lizards, glucose, lactate, and cardiac dysfunction, are similar to those reported for severe Plasmodium infections in mammals.
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Vol. 46 • No. 4