Multiphotoreceptor and multioscillator system in avian circadian organization

Photoperiodism and circadian rhythms have been studied intensively in birds because Aves are typical seasonal breeders and diurnal animals. Light is t he most important environmental factor involved in entrainment of circadian rhythms and photoperiodism. The eyes and the extraocular photoreceptors, s uch as the pineal organ and hypothalamus, are reported to have an important function not only for photoreception but also for circadian organization i n nonmammalian vertebrates, including birds. In this report, we review the roles of the eyes, pineal organ, and deep brain as the components of the mu ltiphotoreceptor and multioscillator system in avian circadian organization . Microsc. Res. Tech. 53:43-47, 2001. (C) 2001 Wiley-Liss, Inc.