INFLUENCE OF PRENATAL AND POSTNATAL PHOTOPERIODS ON POSTNATAL TESTIS DEVELOPMENT IN THE SIBERIAN HAMSTER (PHODOPUS-SUNGORUS)

In Siberian hamsters, juvenile testicular development is regulated to a large extent by photoperiod. Mother hamsters are able to pass photop eriodic information to their male fetuses, and this information can in fluence their postnatal gonadal development In this study, we investig ated the effects of gestation in long (16L:8D) and shea (10L:14D) day lengths on the rates of juvenile testicular growth in several differen t postnatal photoperiods. On the day of parturition, parents and young from each gestation photoperiod were raised in 14L:10D through Day 13 of Life and then were exposed to one of six photoperiods-16L:8D, 15L: 9D, 14L:10D, 13L:11D, 12L:12D, or 10L:14D-until Day 32 of age. The dat a indicated that 15L and 14L are the minimal day lengths required to p revent complete inhibition of testis growth in long (16L) and short da y (10L)-gestated hamsters, respectively. These results support earlier findings suggesting that gestation photoperiod can influence the rate of reproductive development in a certain range of ''intermediate'' po stnatal day lengths (14L to 15L), but that gestation photoperiod does not alter the pattern of testis development in hamsters exposed to oth er (i.e., longer or shorter) postnatal photoperiods. Thus, both the ab solute length and the direction of change of photoperiods experienced in early life can influence prepubertal testis growth.