The light of the cities violated the secretion of melatonin in perch

Scientists have found that light cities, which is reflected from clouds, may reduce the secretion of melatonin in the river perch. Even a very weak light at night has significantly changed the rhythm of melatonin in fish in the experiment. Article published in the journal Environmental Pollution.

The change of the light and the night time is the main objective with which living organisms sinhroniziruete your circadian rhythms. Man creates artificial light, and night is not as dark as has been the case for the evolution of species around us. A primary regulator of biological rhythms — melatonin is destroyed by light, and light pollution disrupts its production in the dark in some animals.

The main light pollution create a city, often located near fresh water. City light reflected from clouds, spread and can disrupt circadian rhythms of the inhabitants of the waters, including fish. It is known that direct exposure to artificial light reduces melatonin levels in fish, however, the influence of ambient lighting that is reflected from the clouds, – for freshwater fish is little studied.

Scientists from Germany under the leadership of Francisco Cuprate (Franziska Kupprat) from the Institute of freshwater ecology and inland fisheries Leibniz Association measured the concentration of melatonin (the hormone through the gills into the water) in the aquarium with the river perch (Perca fluviatilis). Only used 720 fish.

The researchers simulated daylight, dusk and dawn, and “night” covered aquarium lights light intensity of 0.01, 0.1 or 1 Suite. Urban diffuse illumination varies between 0.03 and 0.55 in suites, and at a depth of 50 cm in clear water the light intensity decreases two times.

The impact of artificial light all three brightness night significantly reduced concentrations of melatonin in the aquarium compared to the control (p < 0,0005). The intensity in one Suite has changed the amount of melatonin more than the less bright light (p < 0.05). The concentration of the hormone was lower not only at night but in the following light period (p < 0.005).

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