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Certain species of birds, such as the finch or sparrow, may also see ultraviolet light aside from their perception of visible light. Therefore, they are able to transmit information between each other in a way that is invisible to other species. Recent studies reveal how these birds "turn on" the vision of additional wavelength. It has been proven that there are two adaptations responsible for this: chemical changes occurring in light-filtering pigments (carotenoids) and the proper adjustment of opsins, namely light-sensitive receptors present in the retina.
There exist two types of light-sensitive cells (photoreceptors) in the eye: cones and rods. Cods are accountable for the perception of colours. The human eye has three types of cones responsible for the vision of such colours as blue, green and red, while there is the fourth type distinguished in birds that facilitates the vision of violet or ultraviolet light, depending on the species. The most recent research has provided an explanation of how birds enhance the number of colours perceived. It occurs through a change affecting the chemical structure of carotenoid pigments and the appropriate adjustment of sensitivity of blue-, violet- or ultraviolet-sensitive cons (depending on the species).
The authors of the study suggest that the ability of this kind has been evolutionarily developed, as the perception of an increased number of colours and the precise adjustment of sight may, for example, enable female birds to distinguish between subtle colour differences of the feathering of male birds for the purpose of choosing the strongest mates. Such an ability may also be advantageous in food foraging. Another step for the development of such research will relate to the investigation of molecular mechanisms responsible for coordinating the modification of carotenoids and opsins.
Source: www.sciencedaily.comOriginal paper: M.B. Toomey i in., eLIFE, 2016; 5:e15675DOI: http://dx.doi.org/10.7554/eLife.15675Image credits: wam1023Image source: www.pixabay.com