Effect of temperature and different sex ratios on physical activity and life span in the adult housefly, musca domestica

Abstract

The objective of this investigation was to further examine the relationship between physical activity and life span in the adult housefly. Levels of physical activity were experimentally varied by alterations in the ambient temperature and sex ratios of the populations. In agreement with previous studies, life span of the flies was significantly longer at 18°C than at 28%C. Female flies lived longer than males. Male flies in a population with a high male to female ratio lived a shorter period than their counterparts without any females. These variations in life span seem to be related to differences in the level of physical activity of the flies. The walking and flying activities of the various groups were measured separately by a radar-Doppler system. Walking activity increases about 15-fold, whereas flying activity increased more than 10 times between 15 and 24.5°C; thereafter there was a slight decline in both up to 28°C. Populations with female flies only exhibited lower levels of physical activity as compared to populations of males only. Populations with a high male to female ratio had the highest levels of walking and flying activities. The life spans of the flies were thus inversely related to the level of physical activity. Results of this study support the concept that the rate of metabolic expenditure has a strong influence on life span. The nature of the underlying mechanisms is, however, as yet obscure.