Meeting Abstract

51.5  Tuesday, Jan. 5  Reproductive aging in Siberian hamsters: greater litter success in older females when short photoperiod is initiated after rather than before puberty PLACE, N.J.**; CRUICKSHANK, J.; Cornell University, Ithaca njp27@cornell.edu

Fertility and fecundity decline with age in female mammals, and in Siberian hamsters, Phodopus sungorus, litter success rate was markedly lower in 12-mo-old than in 4-mo-old females. However, when hamsters were exposed to short photoperiod (SP) for a duration of 6 months, their litter success at 12 months of age was significantly greater than in females maintained in long photoperiod (LP). The timing of the SP exposure relative to sexual maturation had a significant effect on litter success in older females. Because SP exposure retards postweaning growth and delays sexual maturation in juvenile hamsters, we expected hamsters exposed to SP before puberty (from conception to 6 months of age) to have greater reproductive success than females exposed to SP after puberty (from 3 to 9 months of age). To our surprise, SP after puberty was associated with significantly greater litter success (77%) than was SP before puberty (35%). Regardless of which SP regime was used, litter success of SP females at 12 months of age was substantially greater than females held continuously in LP (6%). These results definitively demonstrate that pubertal delay is not an essential mechanism for the deceleration of female reproductive aging by SP. Possible explanations for the greater benefits of SP after puberty will be discussed.