Photorefractoriness in birds—photoperiodic and non-photoperiodic control

Dawson, Alistair; Sharp, Peter, J.. 2007 Photorefractoriness in birds—photoperiodic and non-photoperiodic control. General and Comparative Endocrinology, 153. 378-384.

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Avian breeding seasons vary in length and in the degree of asymmetry with respect to the annual cycle in photoperiod to suit species-specific food resources. Asymmetry is the result of photorefractoriness. The degree of photorefractoriness, absolute or relative, is related to the length and asymmetry of the breeding season. Absolute photorefractoriness is associated with a marked decrease in hypothalamic cGnRH-I. However, during the initiation of absolute photorefractoriness there is a transient period during which the gonads regress in advance of the decrease in cGnRH-I, and this stage may be analogous to relative photorefractoriness. Photoinduced prolactin secretion has an inhibitory modulatory role during the initiation of absolute photorefractoriness, but is unlikely to be the only factor involved, while a possible role for avian gonadotrophin inhibitory hormone is not established. The first stage in the termination of photorefractoriness is the resumption of cGnRH-I synthesis. The major environmental cue driving gonadal maturation, and the transitions between the photosensitive state and photorefractoriness is the annual cycle in photoperiod. A range of non-photoperiodic cues may also play a role: social cues, climatic factors (temperature, rainfall, etc.), food availability and nutritional state. There is considerable evidence that these cues can influence gonadal maturation and the timing of egg-laying. There is some evidence that non-photoperiodic cues (certainly temperature and possibly social cues and food availability) can affect the timing of the onset of photorefractoriness, but no evidence that they can influence the time of the end of photorefractoriness.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Programmes pre-2009 publications > Biodiversity
UKCEH and CEH Sections/Science Areas: Watt
ISSN: 0016-6480
Additional Keywords: photoperiodism, photorefractoriness, Non-photoperiodic cues, GnRH; prolactin, GnIH, bird
NORA Subject Terms: Zoology
Ecology and Environment
Date made live: 19 Oct 2007 15:21 +0 (UTC)

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