Testosterone levels and the free running rhythm of feeding activity in Japanese quail in darkness.
Castrated male Japanese quail were reared in total darkness for 7 months. In order to mimic changes in concentration of plasma testosterone during sexual development, the birds were implanted on three occasions with increasing numbers of testosterone-filled capsules. The feeding activity of each bird was recorded and concentrations of plasma testosterone were measured before and after capsules were implanted. The concentration of testosterone was around 0.05 ng/ml and the period of the free running feeding rhythm was 22.5 hr before testosterone-filled capsules were implanted. The free running period lengthened after testosterone-filled capsules were implanted in 79% of the cases (N = 66), with a direct relationship between the concentration of plasma testosterone and the length of the free running period of the feeding rhythm. A direct relationship between the variation of the amount of feeding activity and the variation of the period of the free running rhythm was also established. During a seasonal breeding cycle, this change in circadian organization would lead to a slower advance of feeding activity, allowing the dawn chorus to precede the daily onset of feeding activity as well as result in a better adjustment of daily foraging time.
Laboratoire d'Ethologie, U.A. C.N.R.S. 373, Rennes, France.
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Guyomarc'h
D000818:Animals; D002940:Circadian Rhythm; D003370:Coturnix / Q000502:physiology*; D003624:Darkness; D005247:Feeding Behavior; D008297:Male; D012741:Sexual Maturation; D013739:Testosterone / Q000097:blood*; D013997:Time Factors
D013739:Testosterone