In an article appearing in this week's Science (vol. 281, 14 August 1998), James R. Carey of the University of California/Davis, James W. Vaupel of the Max Planck Institute for Demographic Research in Rostock, Germany, and their co-authors present the results of new research on the life spans of Mediterranean fruit flies.
Balancing the need to survive with the need to reproduce, Mediterranean fruit flies appear to age in two distinct modes, depending on the availability of food, reports a team of researchers led by entomologist James R. Carey of the University of California/Davis and demographer James W. Vaupel of the Max Planck Institute for Demographic Research in Rostock.
When food, particularly protein, is in limited supply, female medflies slip into a survival mode, delaying reproduction even until an advanced age. But as soon as a complete diet is available, they shift into high gear, producing eggs and aging rapidly.
The researchers compared the fertility and life span of 2,500 medflies receiving a diet of only sugar to those receiving a complete diet including protein, which is crucial for reproduction and often difficult for medflies to find in the wild. They observed how the reproductive status and longevity of the sugar-only flies changed when protein was introduced to their diets. "One of the most notable findings was that in the sugar-only group, even 4- to 5-month-old medflies - the equivalent of 90-year-old humans - could produce a moderate number of eggs once protein was added to their diet," said Carey, who is currently lecturing at a workshop on longevity at the Max Planck Institute for Demographic Research in Rostock.
The researchers suggest that further studies of the physiological shifts that occur between the waiting and reproductive modes in medflies may yield a better understanding of the fundamental processes that determine longevity. Specifically, it seems that reproduction could in fact be a pacemaker for the aging process.
Co-authors are: Pablo Liedo, Hans-Georg Müller, Jane-Ling Wang.
Contact: James W. Vaupel
Max Planck Institute for Demographic Research,