Short photoperiod exposure alters the testosterone surge during pubertal development in male mongolian gerbils (meriones unguiculatus)

Prepubertal male Mongolian gerbils (meriones unguiculatus) were exposed to short photoperiods (10L:14D) for up to 15 weeks to determine the photoperiodic involvement in the onset of reproductive activity. Gerbils were killed at the beginning of the experiment and after 3, 4, 7, 8, 11 or 15 weeks of photoperiodic exposure. Short photoperiod-exposed gerbils were compared to age-matched long photo-period-exposed (14L:10D) animals. Serum testosterone levels were depressed after 3, 4 and 8 weeks of short photoperiod exposure but were not different from long photoperiod exposed gerbils after 7, 11 or 15 weeks of photoperiod exposure. Testes weights increased throughout the pubertal period with a slight depression observed after 4 weeks of short photoperiod exposure. These data indicate that short photoperiod exposure alters the testosterone surge which occurs during pubertal development in the gerbil without major modifications in testicular development. It appears that short photoperiod exposure depresses or modifies the rhythm of pubertal testosterone production in male gerbils.