Age-related changes in the rate of water loss and survival time in dry air of active Drosophila melanogaster

By continuously monitoring the weight loss in dry air at 24.5°C of active individual male Drosophila melanogaster, it was shown that: (i) during the active period, weight loss is a linear function of time, but once the body water content is reduced to below a critical level, activity ceases and the rate of weight loss increases rapidly; the time at which the rate of weight loss increases probably coincides with the time of death; (ii) the sudden change in the rate of weight loss can be prevented by blocking the spiracles; (iii) the rate of weight loss in the active period is positively correlated with age; (iv) young flies can tolerate a greater reduction in total body water than old flies. It is suggested that the age-related decrease in survival time in dry air is a consequence of changes in the initial water content of the flies, in their rate of water loss, in their activity, and in their tolerance of low water content.