ABSTRACT
Exposure to continuous darkness and chronic treatment with melatonin, for six weeks, stimulated reproduction in the male Indian desert gerbil as evidenced by morphometric data. Exposure to continuous light, for same duration, on the other hand inhibited reproduction. The results are opposite to those reported from similar studies on temperate zone species. Surface areas of abdominal scent glands increased following both, exposures to continuous darkness and the treatment with melatonin. Exposure to continuous light decreased the scent gland surface area. Assessment of scent gland activity could be useful in evaluation of reproductive function as they are dependent on sex steroids. Melatonin that mediates photoperiodic influence on reproduction is not always inhibitory to gonads.