Photoperiodic induction of ovarian growth and plasma estradiol secretion in a migratory finch, Emberiza melanocephala: involvement of circadian rhythm.
To demonstrate the involvement of circadian rhythm in photoperiodic time measurement, photosensitive female blackheaded buntings were kept under different photoperiodic schedules consisting of 6 h of main photophase coupled with scotophases of various durations. Ovarian mass and circulating plasma estradiol concentration were found to be elevated in cycles of 6L:6D, 6L:36D, 6L:54D and in control 15L:9D groups. But cycles of 6L:18D, 6L:42D and 6L:66D did not stimulate ovarian growth or elevate circulating plasma estradiol concentration. These results are consistent with the Bünning hypothesis according to which a photoperiodic response is elicited as a result of the coincidence of light with the photoinducible phase of an endogenous circadian rhythm. The results thus indicate the involvement of a circadian rhythm of photoinducibility in ovarian growth and estradiol secretion.
Mishra
M K
MK
Department of Zoology, Banaras Hindu University, Varanasi, India.
Tewary
P D
PD
D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D004958:Estradiol / Q000097:blood*; D005260:Female; D009068:Movement; D010053:Ovary / Q000254:growth & development*; D017440:Photoperiod; D020308:Songbirds / Q000502:physiology*
D004958:Estradiol