WHAT ARE THE POTENTIAL PHYSIOLOGICAL COSTS OF REDUCED MELATONIN LEVELS BY ARTIFICIAL LIGHT-AT-NIGHT, OR LIGHT POLLUTION, OFTEN SEEN IN THE HORSE INDUSTRY TO INCREASE THE LENGTH OF THE BREEDING SEASON OR PROMOTE EARLY SHEDDING OF WINTER COATS IN SHOW HORSES.
Thursday, October 24, 2013
Editor in GnIH, animals, birds, breeding, circadian rhythms, horses, light pollution, light-at-night, locomotor activity, melatonin, shedding, timing of reproduction

Urban-like night illumination reduces melatonin release in European blackbirds (Turdus merula): implications of city life for biological time-keeping of songbirds

Davide M Dominoni 1 2 3, Wolfgang Goymann 4, Barbara Helm 3 and Jesko Partecke 1 2

1 Department of Migration and Immuno-ecology, Max Planck Institute for Ornithology, Radolfzell, Germany

2 Department of Biology, University of Konstanz, Konstanz, Germany

3 Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK

4 Department of Behavioural Neurobiology, Max Planck Institute for Ornithology, Seewiesen, Germany

Abstract

Introduction

Artificial light-at-night is known to affect a broad array of behaviours and physiological processes. In urbanized bird species, light-at-night advances important biological rhythms such as daily cycles of activity/rest and timing of reproduction, but our knowledge of the underlying physiological mechanisms is limited. Given its role as chronobiological signal, melatonin is a strong candidate for mediating the effects of light-at-night.

Results

We exposed urban and rural European blackbirds (Turdus merula) to two light treatments equal in photoperiod but with different light intensities at night. The control group was exposed to 0.0001 lux (almost darkness), while Show Horse ~ CREDIT: wallyirthe experimental group was exposed to 0.3 lux at night, simulating conditions recorded previously on free-living urban blackbirds. We obtained diel profiles of plasma melatonin for all birds in summer (July) and winter (January), while simultaneously recording locomotor activity. Daily patterns of melatonin concentrations were clearly affected by light-at-night in both seasons. In winter, melatonin concentrations of light-at-night birds were lower in the early and late night than in those of birds kept in darkness. In summer, melatonin concentrations of the light-at-night birds were lower through all night compared to birds kept in darkness. Locomotor activity in light-at-night birds was overall higher than in control individuals, both during the day and at night, and it increased sharply before dawn. In winter, the amount of activity before dawn in the light-at-night group correlated with changes in melatonin from midnight to late night: the greater the decrease in melatonin, the greater the amount of pre-dawn activity. Urban and rural birds responded similarly to light-at-night with respect to melatonin, but differed in their behaviour, with rural birds showing more locomotor activity than urban counterparts.

Conclusions

This study points to reduced melatonin release at night as a potential physiological mechanism underlying the advanced onset of morning activity of urbanized birds. Based on the pattern of melatonin secretion, we suggest that birds responded to light-at-night as if they were exposed to a longer day than birds kept under dark nights.

From the full article please note the following excerpts:

“We suggest that the decrease in melatonin as a consequence of light-at-nightArtificially lit barn gives appearance of longer daylight hours to horses ~ CREDIT: jade in winter may provide animals with the physiological signal that the night is shorter than the actual photoperiod, and therefore speeds up reproductive activation. We have recently shown that the blackbirds subjected to 0.3 lux of light-at-night developed the reproductive system almost a month earlier than birds kept under dark nights [13]”

13. Dominoni DM, Quetting M, Partecke J: Artificial light at night advances avian reproductive physiology. Proc Biol Sci 2013, 280:20123017.

Light pollution, in the form of artificial outdoor and indoor lighting, has become a public health issue as it is now evident that exposure to light-at-night can promote de-synchronization between the endogenous circadian clock and the natural light/dark cycle, with profound downstream negative effects [2].”

2. Navara KJ, Nelson RJ: The dark side of light at night: physiological, epidemiological, and ecological consequences. J Pineal Res 2007, 43:215-224.

“Given our results of shortened duration of elevated melatonin and increased activity levels, we hypothesize that light-at-night may disrupt sleep, with potentially serious health consequences [75,77]. Furthermore, night-time light exposure may disrupt physiology through other mechanisms such as alterations in corticosterone rhythmicity or clock genes, as recently shown in rodents [78]. Taking this all together, we call for an improved understanding of the potential physiological costs of the reduction in melatonin levels caused by light-at-night.”

75. Bass J, Turek FW: Sleepless in America: a pathway to obesity and the metabolic syndrome? Arch Intern Med 2005, 165:15-16.

77. Kantermann T, Juda M, Vetter C, Roenneberg T: Shift-work research: Where do we stand, where should we go? Sleep Biol Rhythms 2010, 8:95-105.

78. Bedrosian TA, Galan A, Vaughn CA, Weil ZM, Nelson RJ: Light at night alters daily patterns of cortisol and clock proteins in female siberian hamsters. J Endocrinol 2013, 25:590-596. 

CITATION: Frontiers in Zoology 2013, 10:60 doi:10.1186/1742-9994-10-60 

Published: 3 October 2013

© 2013 Dominoni et al.; licensee BioMed Central Ltd. 

http://www.frontiersinzoology.com/content/10/1/60/abstract#

EXTENDED ARTICLE AND REFERENCES: http://www.frontiersinzoology.com/content/10/1/60

SOURCE: This is an Open Access article courtesy of BioMed Central - Creative Commons Attribution 2.0 License

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