The animal article of the month for August is ‘The effect of different wavelengths of light during incubation on the development of rhythmic pineal melatonin biosynthesis in chick embryos’

Melatonin is a neurohormone, which is involved in the control of day/night rhythms in a number of biochemical, physiological and behavioural processes. Melatonin biosynthesis occurs in the pineal gland and is controlled by the master circadian clock in the brain. In both diurnal and nocturnal animals melatonin concentrations are high during the dark- and low during the light-time. The rhythmic melatonin biosynthesis develops postnatally in mammals and our previous studies demonstrated the development of rhythmic melatonin production during the last third of embryonic development in chicken. Physiological significance of the early melatonin rhythmicity is not clear and we proposed that it can drive rhythmic processes in avian embryos, which develop outside of the maternal body. Rhythmic melatonin production is controlled by the lighting regime in chick embryos and the efficiency of different parts of spectra had not been studied yet.

In the present study we explore the effects of different wavelengths of light during incubation on the development of rhythmic melatonin biosynthesis in broiler breeder embryos. We incubated eggs in polychromatic white and monochromatic red, green and blue light under the 12 h light and 12 h dark cycle. Incubators were illuminated by light-emitting diode strips and temperature was controlled. We proved that the chick embryo, and possibly also embryos of other avian species, can discriminate between different colours or wavelengths of light. This finding opens several important questions: Can the avian embryo differentially respond to different wavelengths? Is it better to have a high- or low-amplitude melatonin rhythm? Is it better to be rhythmic already during the embryonic life if birds hatch to rhythmic environmental conditions?

Consequences of modification in the amplitude of the melatonin rhythm on development of physiological and behavioural traits are not known. We currently explore several possibilities, such as growth, immunity, development of the skeletal system and protection against reactive oxygen species, which are formed massively during the hatching process. Moreover, recent studies consider an involvement of melatonin in the epigenetic control of several genes, what deserves more comprehensive attention.

The animal article of the month for Animal is ‘The effect of different wavelengths of light during incubation on the development of rhythmic pineal melatonin biosynthesis in chick embryos’

Authors: A. Drozdova, M. Okuliarova and M. Zeman

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