Environmental Temperature and Life Span in Poikilotherms

Abstract

The controversy about the cause of the inverse relationship between the life span of poikilothermic animals and environmental temperature has not been settled. Pearl1, as a result of his own observations and those of earlier workers on the life-shortening effect of raised environmental temperatures in Drosophila and other poikilotherms, suggested that the rate of living, like the rate of a chemical reaction, is increased at raised temperatures. Clarke and Maynard Smith2–4 and I5 cast doubt on this seemingly well established theory when we demonstrated by means of split temperature experiments in Drosophila subobscura that (a) exposures to high temperatures before transfer to a low temperature resulted in adult flies dying at the same age as flies kept continuously at the low temperature; (b) exposure of flies to a low temperature followed by their transfer to high temperatures at different ages reduced their initial expectation of life at the high temperatures by one day for every day spent at the low temperature.