Growth and maturation in Microtus montanus: effects of photoperiods before and after weaning

Growth and reproductive development of voles are known to be significantly affected by photoperiod. The data presented herein demonstrate that the response of a juvenile vole to a given photoperiod is dependent on the photoperiod present prior to weaning. Voles were raised in one of two different photoperiods prior to weaning. At weaning, voles from each preweaning photoperiod were transferred to photoperiods consisting of either 8 h (8 h light: 16 h dark, 8L:16D), 14 h (14L:10D), or 16 h (16L:8D) of light per day. Voles from the short preweaning photoperiod were inhibited by the 8L:16D postweaning photoperiod, but stimulated by both the 14L:10D and 16L:8D postweaning photoperiods. Voles from the long preweaning photoperiod were inhibited by both the 8L: 16D and 14L:10D photoperiods, but stimulated by the 16L:8D photoperiod. The 8L:16D postweaning photoperiod elicited different amounts of inhibition in voles from the two preweaning photoperiods. Voles from the short preweaning photoperiod were larger and had heavier reproductive tracts in 8L: 16D than did voles from the long preweaning photoperiod.