Effect of light intensity on circadian activity in developing Japanese quail

WOS:000183009800009International audienceThe effects of constant light on the expression of the circadian rhythm of feeding activity in Japanese quail, and in particular on the clarity of the rhythm were investigated. We used 46 4-week-old birds (35 females and 11 males) issued from two lines selected for a more (line R: 25 females and 10 males) or less (line A: 10 females and I male) clear circadian rhythm of feeding activity. The birds, were placed successively under three light schedules: constant darkness (DD), constant dim green light (LLdim) and constant bright light (LLbright). Schedules were changed every 2 weeks. Feeding activity was recorded continuously, analysed by autocorrelation and spectral analysis, and the ratio of the correlation coefficients and the area of the spectrum peak were used as indexes to quantify the clarity of the circadian rhythm. During the experiment, some birds showed gonadal development. Therefore, we analysed separately birds showing either a high or low degree of sexual development at the end of the experiment. In DD, 35 birds showed a circadian feeding rhythm with a mean period of 22.5+/-0.1 h, wherea