Abstract Background Variation in circadian rhythms and nocturnality may. hypothetically. be related to or independent of genetic variation in photoperiodic mediation of seasonal changes in physiology and behavior. We hypothesized that strain variation in photoperiodism between photoperiodic F344 rats and nonphotoperiodic Harlan Sprague Dawley (HSD) rats might be caused by underlying v... https://stilleners.shop/product-category/mud-flap-kit/