| Biological clocks and regulation of seasonal reproduction and migration in birds. | |
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MedLine Citation:
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PMID: 20604684 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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Timekeeping is important at two levels: to time changes in physiology and behavior within each day and within each year. For the former, birds have a system of at least three independent circadian clocks present in the retina of the eyes, the pineal gland, and the hypothalamus. This differs from the situation in mammals in which the input, pacemaker, and output are localized in different structures. Each bird clock interacts with at least one other clock, and together, they appear to form a centralized clock system that keeps daily time. These clocks have a powerful endogenous component, and the daily light-dark cycle entrains them to 24 h. The timing and duration of life history stages that make up annual cycle of an individual must also be controlled by some form of timekeeping. However, evidence for the existence of an equivalent endogenous circannual clock is less clear. Environmental cues, particularly photoperiod, appear to have a more direct role than simply entraining the clock to calendar time. For example, the timing of migration is probably greatly influenced by photoperiod, but its manifestation each day, as Zugunruhe, appears to be under circadian control. Migration involves marked changes in physiology to cope with the energetic demands. There is still much that we do not know about how organisms' timekeeping systems respond to their natural environment, particularly how salient signals from the environment are perceived and then transduced into appropriately timed biological functions. However, given that changes in environmental input affects the clock, increasing human disturbance of the environment is likely to adversely affect these systems. |
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Authors:
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Vinod Kumar; John C Wingfield; Alistair Dawson; Marilyn Ramenofsky; Sangeeta Rani; Paul Bartell |
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Publication Detail:
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Type: Journal Article; Research Support, U.S. Gov't, Non-P.H.S. |
Journal Detail:
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Title: Physiological and biochemical zoology : PBZ Volume: 83 ISSN: 1537-5293 ISO Abbreviation: Physiol. Biochem. Zool. Publication Date: 2010 Sep-Oct |
Date Detail:
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Created Date: 2010-08-20 Completed Date: 2010-12-20 Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 100883369 Medline TA: Physiol Biochem Zool Country: United States |
Other Details:
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Languages: eng Pagination: 827-35 Citation Subset: IM |
Affiliation:
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Department of Science and Technology, University of Delhi, Delhi 110 007, India. drvkumar11@yahoo.com |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Animal Migration
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physiology* Animals Biological Clocks / physiology* Birds / physiology* Circadian Rhythm / physiology* Climate Change* Hypothalamus / physiology Photoperiod* Pineal Gland / physiology Retina / physiology |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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