Interactions between injury, stress resistance, reproduction, and aging in Drosophila melanogaster.

An important aspect of the aging process in Drosophila melanogaster is the natural loss of antennae, legs, bristles, and parts of wings with age. These injuries lead to a loss of hemolymph, which contains water and nutrients. Stress-resistant lines of D. melanogaster are sometimes longer-lived than the populations from which they are derived. One hypothesis tested here is that increased stress-resistance fosters longevity because it allows fruit flies to cope with the loss of hemolymph due to injury to the aging fly. We tested the effects of surgically induced injury on the aging and reproduction of five replicate populations. We then tested the effects of injury on populations that had been selected for different levels of stress resistance and on control populations. Injury affected aging more in males than in females, in part because of a counter-balancing reduction in female reproduction brought about by injury. More specifically, injury reduced female fecundity and male virility. Injury significantly reduced the starvation resistance in some groups of flies, but not in others. These findings undermine any simple interpretation of the interactions between injury, reproduction, and aging based on stress resistance. But they do indicate the existence of significant interactions between these biological processes, interactions that should be resolved in greater mechanistic detail than has been managed here.