Abstract
Animals that have a long pre-reproductive adult stage often employ mechanisms that minimize aging over this period in order to preserve reproductive lifespan. In a remarkable exception, one tephritid fruit fly exhibits substantial pre-reproductive aging but then mitigates this aging during a diet-dependent transition to the reproductive stage, after which life expectancy matches that of newly emerged flies. Here, we ascertain the role of nutrients, sexual maturation and mating in mitigation of previous aging in female Queensland fruit flies. Flies were provided one of three diets: ‘sugar’, ‘essential’, or ‘yeast-sugar’. Essential diet contained sugar and micronutrients found in yeast but lacked maturation-enabling protein. At days 20 and 30, a subset of flies on the sugar diet were switched to essential or yeast-sugar diet, and some yeast-sugar fed flies were mated 10 days later. Complete mitigation of actuarial aging was only observed in flies that were switched to a yeast-sugar diet and mated, indicating that mating is key. Identifying the physiological processes associated with mating promise novel insights into repair mechanisms for aging.
Highlights
Selection pressures on aging are usually strongest prior to reproduction, because at this time the full extent of reproductive potential remains at stake
Micronutrients in the ESS diet substantially increased longevity of female Q-flies with ESS-0 flies living over twice as long as SUG-0 flies (Table 1; 42.6 vs. 17.0 days, t1323 = 28.46, p < 0.001). This is reflected in the shape of their mortality schedules (Fig 1A; χ2 = 124.41, p < 0.001); ESS-0 showed a gradual increase in mortality rate with age whereas SUG-0 flies showed a rapidly increasing mortality rate for the first 20 days and remained fairly steady for the 30 days (Fig 1A)
A comparison of mortality trajectories from day 20 between ESS-20 and ESS-0 revealed no significant difference in mortality rates (χ2 = 1.12, p = 0.40)
Summary
Selection pressures on aging are usually strongest prior to reproduction, because at this time the full extent of reproductive potential remains at stake. Once the adult stage is reached, the soma is mainly post-mitotic, resulting in the accumulation of somatic damage and aging [1, 3]. Insects that reproduce soon after reaching the adult stage are exposed to minimal fitness costs of cumulative somatic damage as their reproductive potential may be largely fulfilled before being constrained by aging. Some insects require substantial time during the adult stage to complete sexual development (e.g. mosquito [4]; blowfly [5]; lubber grasshopper [6]), resulting in a sometimes lengthy period of susceptibility to pre-reproductive aging. Insects have evolved several mechanisms that enable them to traverse pre-reproductive adult stages and enter their reproductive stage with minimal accrual of somatic damage and aging
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