Format

Send to

Choose Destination
Philos Trans R Soc Lond B Biol Sci. 2001 Nov 29;356(1415):1801-10.

Complex bird clocks.

Author information

1
Department of Biological Rhythms and Behaviour, Max-Planck Research Centre for Ornithology, Von-der-Tann-Strasse 7, D-82346 Andechs, Germany. gwinner@erl.ornithol.mpg.de

Abstract

The circadian pacemaking system of birds comprises three major components: (i) the pineal gland, which rhythmically synthesizes and secretes melatonin; (ii) a hypothalamic region, possibly equivalent to the mammalian suprachiasmatic nuclei; and (iii) the retinae of the eyes. These components jointly interact, stabilize and amplify each other to produce a highly self-sustained circadian output. Their relative contribution to overt rhythmicity appears to differ between species and the system may change its properties even within an individual depending, for example, on its state in the annual cycle or its photic environment. Changes in pacemaker properties are partly mediated by changes in certain features of the pineal melatonin rhythm. It is proposed that this variability is functionally important, for instance, for enabling high-Arctic birds to retain synchronized circadian rhythms during the low-amplitude zeitgeber conditions in midsummer or for allowing birds to adjust quickly their circadian system to changing environmental conditions during migratory seasons. The pineal melatonin rhythm, apart from being involved in generating the avian pacemaking oscillation, is also capable of retaining day length information after isolation from the animal. Hence, it appears to participate in photoperiodic after-effects. Our results suggest that complex circadian clocks have evolved to help birds cope with complex environments.

PMID:
11710987
PMCID:
PMC1088556
DOI:
10.1098/rstb.2001.0959
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for HighWire Icon for PubMed Central
Loading ...
Support Center