Oxygen Consumption in the Lizard Uta Stansburiana

Abstract

Oxygen consumption of animals held in dark chambers was found to be minimal and stable over the night measuring the period (10 PM to 5 AM). Oxygen consumption stabilized by day 2 in the laboratory. There was no difference in mean weight specific metabolism at night of fasting animals in March measured on days 2 through 14. For three—day fasted animals (1 to 5 gms) measured at 30°C in March and April the exponent of weight (the value of b in the equation Qo2 = aWb) was 1.03. A lower value for b was obtained at other times of the year. Fasting lizards decreased their overall oxygen consumption in proportion to the weight lost. Two parallel lines formed boundaries enclosing all values obtained for minimum oxygen consumption. Values obtained during activity fell above the upper boundary. The increase in minimum oxygen consumption due to feeding averaged 160 mm3/hr or 32% of the previous minimum value. Multiple regression analysis of oxygen consumption measurements made at 3 temperatures (25, 30, 35°C) and 4 seasons (May, July, September, January) indicates that there is a clear seasonal difference, winter animals exhibiting higher rates of oxygen consumption. Juveniles showed high and variable rates of oxygen consumption when measured in July and August. By January juveniles are probably indistinguishable from adults. Lizards measured in the field in January had a lower mean body temperature and increased range of body temperatures as compared to September animals. There was little overlap in 2 ranges. Seasonal change in oxygen consumption may represent thermal acclimation accompanying the seasonal change in body temperatures. It is probably in part, however, due to the changing age composition of the population.