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 photoperiodic information to their male fetuses, and this information can influence their postnatal gonadal development In this study, we investigated the effects of gestation in long (16L:8D) and shea (10L:14D) day lengths on the rates of juvenile testicular growth in several different 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 data indicated that 15L and 14L are the minimal day lengths required to prevent complete inhibition of testis growth in long (16L) and short day (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'' postnatal day lengths (14L to 15L), but that gestation photoperiod does not alter the pattern of testis development in hamsters exposed to other (i.e., longer or shorter) postnatal photoperiods. Thus, both the absolute length and the direction of change of photoperiods experienced in early life can influence prepubertal testis growth.