Extended longevity lines of Drosophila melanogaster: characterization of oocyte stages and ovariole numbers as a function of age and diet.

Vitellogenic and previtellogenic oocyte stages, as well as ovariole numbers, were characterized in the selected (O) lines of D. melanogaster that have been selected for late-life reproduction and extended longevity. On day 4 post-eclosion, O females had more ovarioles than control (B) females, but this difference diminished at older ages. From days 4 to 24, O females showed a marked increase in average vitellogenic oocyte stage, whereas this parameter did not increase in B females as they aged. The previtellogenic gradient of oocyte maturation declined in both B and O females. Specifically, terminal previtellogenic stages were lost with advancing age, and this loss occurred relatively gradually in O females regardless of food regime. Among the reproductive traits assessed, differential persistence of the previtellogenic gradient of maturation is most strongly associated with selected versus control line differences in longevity.