Effect of melatonin supplementation on the sexual development in European quail (Coturnix coturnix)

At the end of their wintering phase, male European quails were exposed to a stimulation photoperiod of light/dark 12:12 h for 10 days to induce sexual development. A daily oral melatonin supplementation was then given to one group Of treated males (N=11) and the alcohol solvent was given to a contro l group of males (N= 10). These solutions were provided during the final 3 h of the photophase for 28 days, then during the final 4 h for 18 days. The re were no significant differences between the two groups with respect to f at levels. However, 3 weeks after the beginning of melatonin supplementatio n, the sexual development of the treated birds slowed down. The importance of this decline varied to a greater or lesser degree between individual bir ds. When melatonin supplementation stopped, sexual development resumed. Act ivity recordings revealed a decrease in feeding activity when melatonin sup plementation was provided. However, this response showed important interind ividual variability. The birds that produced the most marked responses to m elatonin during the first 3 weeks of supplementation were those that also s howed the most obvious decline in sexual development. It seems that, in Eur opean quail, a wild migratory species that always shows a natural biologica l annual rhythm, a melatonin signal could play a role in regulating reprodu ction. (C) 2001 Elsevier Science B.V. All rights reserved.