STRESS EXPERIMENTS AS A MEANS OF INVESTIGATING AGE-SPECIFIC MORTALITYIN DROSOPHILA-MELANOGASTER

Age-specific mortality rates level off at older ages in genetically ho mogeneous experimental populations of Drosophila. Here we describe an experiment that is informative about the causes of mortality rate chan ges. By applying a brief, nondebilitating stress that increases mortal ity early in life and then observing subsequent mortality trajectories , it is possible to determine whether populations are heterogeneous fo r factors influencing mortality. We show that 24-h exposure to a desic cating air flow causes a spike and then a decrease in mortality rates in experimental populations compared to controls. If there is no stres s-induced enhancement of vitality, then the results demonstrate the ex istence of heterogeneity for mortality rates in genetically homogeneou s populations.