Influence of near-ultraviolet radiation on reproductive and immunological development in juvenile male Siberian hamsters

The aim of this study was to characterize the lenticular ultraviolet transm ission of the Siberian hamster (Phodopus sungorus) and to probe the range o f near-ultraviolet (UV-A, 315-400 nm) and visible wavelengths (400-760 nm) for modulating the photoperiodic regulation of its reproductive and immune systems. Ocular lenses from adult hamsters were found to transmit UV-A wave lengths at similar levels to visible wavelengths, with a short-wavelength c ut-off of 300 nn. Five separate studies compared the responses of juvenile male hamsters to long photoperiods (16 h:8 h L:D), short photoperiods (10 h :14 h L:D) and short photoperiods interrupted by an equal photon pulse of m onochromatic light of 320, 340, 360, 500 or 725 nm during the night. The re sults show that UV-A wavelengths at 320, 340 and 360 nm can regulate both r eproductive and immune short-photoperiod responses as effectively as visibl e monochromatic light at 500 nm. In contrast, long-wavelength visible light at 725 nm did not block the short-photoperiod responses. These results sug gest that both wavelengths in the visible spectrum, together with UV-A wave lengths, contribute to hamster photoperiodism in natural habitats.