THE UTILIZATION OF GLYCOGEN BY FLIES DURING FLIGHT AND SOME ASPECTS OF THE PHYSIOLOGICAL AGEING OF DROSOPHILA

Abstract

The role of glycogen in the flight physiology was studied for two species of flies, Drosophila funebris and Lucilia sericata. Glycogen was determined by microchemical methods. The flight ability was measured stroboscopically in terms of the total number of wing-beats, under standardized conditions, in continuous flights to exhaustion.Glycogen was found to be of primary importance in the physiology of flight. During continuous flight the concentration of this substance gradually decreases in both the entire animal and the thorax.The decrease in glycogen during the first stages of such flights has no marked effects on the intensity of flight, in terms of the frequency of wing-beat.Near the end of continuous flight the concentration of glycogen becomes limiting and wing-beat frequency rapidly decreases until flight ceases before the frequency becomes as low as 100 double-beats per second.Both the flight ability of Drosophila and the concentration of glycogen vary as functions of age. During the first week of adult life the average length of flight increases from 26 minutes on the first day to 110 on the seventh and the total number of wing-beats from 225,000 to more than a million. Simultaneously the glycogen concentration rises from about 2.5 to 6 per cent of the live weight. In animals older than two weeks the flight ability and glycogen concentration decrease rapidly and then more slowly until, by the thirty-third day, the average length of flight is reduced to 19 minutes (170,000 double wing-beats) and the glycogen concentration to about 3.5 per cent of the live weight. This correlation, although not exact, suggests that the physiological ageing of the flight ability results to a large degree from the simultaneous changes in the concentration of glycogen.