Postponed aging and desiccation resistance in Drosophila melanogaster

Studies with the fruit fly, Drosaphila melanogaster, have repeatedly shown that selection for postponed reproduction leads to increases in mean life s pan and increased stress resistance; including increased resistance to desi ccation, starvation and ethanol vapors. We show that desiccation resistance declines with age in both short- and long-lived flies suggesting that desi ccation resistance may serve as a useful biomarker for aging-related declin es in physiological performance. We examined the physical basis of desiccat ion resistance in five replicate populations selected for postponed reprodu ction and five replicate control populations. The variables examined were w ater content, rates of water loss during desiccation, and water content at time of death due to desiccation. In the absence of desiccation stress, bot h the flies exhibiting postponed senescence and their controls maintained c onstant water content throughout their lifetimes. In the presence of desicc ation stress, the short-lived flies showed significantly higher rates of wa ter loss at all ages than did the long-lived flies. Flies from the two trea tments did not differ in water content at death. Our results indicate that water loss rates are the major determinant of desiccation resistance. Water loss rates are under genetic control and covary with age in populations wi th,genetically-determined postponed senescence. (C) 2000 Published by Elsev ier Science Inc.