Light increases the rate of embryonic development: implications for latitudinal trends in incubation period
Article first published online: 14 MAR 2011
© 2011 The Authors. Functional Ecology © 2011 British Ecological Society
Volume 25, Issue 4, pages 769–776, August 2011
How to Cite
Cooper, C. B., Voss, M. A., Ardia, D. R., Austin, S. H. and Robinson, W. D. (2011), Light increases the rate of embryonic development: implications for latitudinal trends in incubation period. Functional Ecology, 25: 769–776. doi: 10.1111/j.1365-2435.2011.01847.x
- Issue published online: 1 JUL 2011
- Article first published online: 14 MAR 2011
- Received 13 July 2010; accepted 7 February 2011 Handling Editor: Alistair Dawson
- avian incubation period;
- embryonic metabolic rate;
- house sparrow;
- life-history evolution;
- Passer domesticus;
1. In wild birds, incubation period shortens and the general pace of life quickens with distance from the equator. Temperature and various biotic factors, including adult behaviours, cannot fully account for longer incubation periods of equatorial birds and only explain some of the variation between tropical and temperate life histories. Here we consider the role of differences in light in driving variation in incubation period. In poultry, incubation periods can be experimentally shortened by exposing eggs to light. The positive influence of light on embryonic growth, called photoacceleration, can begin within hours after an egg is laid.
2. We artificially incubated house sparrow (Passer domesticus) eggs under photoperiods similar to those found at temperate (18Light : 6Dark) and tropical (12L : 12D) latitudes. We also measured embryonic metabolic rate during light and dark phases.
3. Eggs of house sparrows collected from the wild developed more rapidly under ‘temperate’ than ‘tropical’ photoperiods and had higher metabolic rates during phases of light exposure than during phases of darkness. Metabolic rates during light phases were high enough to account for a 1 day difference in incubation periods between temperate and tropical birds.
4. Based on a synthesis of photoacceleration studies on domesticated galliformes and our experimental results on a wild passerine, we provide the first support for the testable hypothesis that differences in photoperiod may influence variation in the rate of embryonic development across latitudes in birds.