Photoperiod Effects on Leptin Levels in Goldfish

Photoperiod Effects on Leptin Levels in Goldfish

Alvin Sherman Library 2053

Previous studies have shown a relationship between photoperiod and hormone production in vertebrates. Goldfish (Carassius auratus auratus) are freshwater fish commonly found in tropical and temperate waters in Asia with exotic introduction world wide. During different seasons of the year these fishes are exposed to wide variations in light intensity and duration. These variations in photoperiod cause hormone levels to fluctuate triggering seasonal changes in the fish’s physiology. Leptin, an adipocyte-derived hormone, promotes weight loss through energy expenditure. In this experiment we will examine the effects of these variations in photoperiod on Leptin levels in goldfish. Sixteen goldfishes will be exposed to an extended (16 hour) photoperiod. Following a two week acclimation to this light cycle, blood samples will be collected from all fishes. Over the next two weeks the photoperiod will be gradually reduced to eight hours. The fish will be acclimated to this second, shortened photoperiod and additional blood samples will be collected. All blood samples will be permitted to clot and blood serum will be isolated. The blood serum will be tested for Leptin levels using a commercial Leptin ELISA kit (ALPCO Diagnostics). We anticipate significant differences between Leptin levels with long (high Leptin levels) and short (low Leptin levels) photoperiods and expect that this difference will correlate with the increased body fat necessary for seasonal reproduction.