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) litres of D. melanogaster that hav e been selected for late-life reproduction and extended longevity On day 4 post-eclosion, O females had more ovarioles than control (B)females, but th is difference diminished at older ages. From days 4 to 24, O females showed a marked increase in average,vitellogenic oocyte stage, whereas this param eter did not increase in B females as they aged The previtellogenic gradien t of oocyte maturation declined in both B and O females. Specifically, term inal previtellogenic stages were lost with advancing age, and this loss occ urred relatively gradually in O females regardless of food regime. Among th e reproductive traits assessed, differential persistence of the previtellog enic gradient of maturation is most strongly associated with selected versu s control line differences in longevity.