Anticipation of oxidative damage decelerates aging in virgin female medflies: hypothesis tested by statistical modeling

Empirical analysis of survival data obtained from large samples of Mediterr anean fruit flies shows that the trajectory of the mortality rate for virgi n females departs from that for females maintained in mixed sex cages. It i ncreases, decelerates, reaches its maximum, declines and then increases aga in within the reproductive interval. Non-virgin females, however, display a n early-age plateau instead of this dip. We assume that these deviations ar e produced by the interplay between changes in oxygen consumption associate d with reproductive behavior and the antioxidant defense that acts against anticipated oxidative damage caused by reproduction. Since there are no dat a on antioxidant mechanisms in medflies available that explain the observed patterns of mortality, we develop a model of physiological aging based on oxidative stress theory, which describes age-related changes in oxygen cons umption and in antioxidative capacity during the reproductive period. Using this model, we simulate virtual populations of 25,000 virgin and non-virgi n flies, calculate the respective mortality rates and show that they practi cally coincide with those of experimental populations. We show that the hyp othesis about the biological support of reproduction used in our model does not contradict experimental data. The model explains how the early-age dip and plateau might arise in the mortality rates of female medflies and why the male mortality pattern does not exhibit such deviations. (C) 2000 Elsev ier Science Inc. All rights reserved.