Analysis of reproduction in extended longevity lines of Drosophila melanogaster

Lines of Drosophila melanogaster selected for late life fecundity have demonstrated a correlated increase in longevity and a reduction in early fecundity. In the studies presented in this dissertation, reproductive traits have been investigated in selected (O) and control (B) line female D. melanogaster at early ages, as well as throughout the lifespan of the females raised on a diet with and without supplemental yeast. The overall goal of this study was to characterize oocyte stage, ovariole number and yolk protein (yp) gene mRNA as factors which may underly fecundity lifespan differences between B and O lines. On days one and four post-eclosion, O line females demonstrate slower vitellogenic oocyte maturation relative to B line females. Similarly, the percentage of vitellogenic ovarioles is lower for O females than for B females on day four post-eclosion. However, there is little evidence that differential yp gene mRNA abundance at early ages is responsible for line type differences in oocyte maturation. In general, early age vitellogenic oocyte production is relatively slower in the O lines and this may be responsible for reduced fecundity observed as a correlated response to selection for late-life fecundity. At early ages, there is evidence that O females have a greater number of ovarioles than B females. However, it appears that this difference between lines decreases with age. Added yeast does not appear to have an effect on ovariole number in either line. Lifetime profiles demonstrate that the incidence of vitellogenic oocytes per ovariole depends to a greater degree on added yeast rather than line type. Moreover, both lines are stimulated to a similar degree by the addition of yeast. The previtellogenic gradient of maturation loses terminal stages at a younger age in B lines than in O lines. This effect is largely independent of the additional yeast, suggesting that a shortage of nutrients available for the developing egg is not responsible for this phenotype associated with later age.