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Psittacofulvin pigments, sometimes called psittacins are responsible for the bright-red, orange, and yellow colours specific to parrots. In parrots, psittacofulvins are synthesized by a polyketide synthase enzyme that is expressed in growing feathers. They consist of linear polyenes terminated by an aldehyde group. Colourful feathers with high levels of psittacofulvin resist feather-degrading '' Bacillus licheniformis'' better than white ones.Edward H. Burtt, Max R. Schroeder, Lauren A. Smith, Jenna E. Sroka, Kevin J. McGraw (2010): Colourful parrot feathers resist bacterial degradation, Biology Letters, The Royal Society, .
Both carotenoids and psittacofulvins have narrow-band absorbance spectra, reflecting pale yellow or red pigmentary colours, making them difficult to distinguish between using spectral measurements. However, there are differences between them when researched spectroscopically. The carotenoid and psittacofulvin yellows are very similar, but the red parrot pigment offers an advantage: it creates a more deep-red color when compared to
Psittacofulvin pigments, sometimes called psittacins are responsible for the bright-red, orange, and yellow colours specific to parrots. In parrots, psittacofulvins are synthesized by a polyketide synthase enzyme that is expressed in growing feathers. They consist of linear polyenes terminated by an aldehyde group. Colourful feathers with high levels of psittacofulvin resist feather-degrading '' Bacillus licheniformis'' better than white ones.Edward H. Burtt, Max R. Schroeder, Lauren A. Smith, Jenna E. Sroka, Kevin J. McGraw (2010): Colourful parrot feathers resist bacterial degradation, Biology Letters, The Royal Society, .
Both carotenoids and psittacofulvins have narrow-band absorbance spectra, reflecting pale yellow or red pigmentary colours, making them difficult to distinguish between using spectral measurements. However, there are differences between them when researched spectroscopically. The carotenoid and psittacofulvin yellows are very similar, but the red parrot pigment offers an advantage: it creates a more deep-red color when compared to astaxanthin
Astaxanthin is a keto- carotenoid within a group of chemical compounds known as terpenes. Astaxanthin is a metabolite of zeaxanthin and canthaxanthin, containing both hydroxyl and ketone functional groups. It is a lipid-soluble pigment with r ...
, the pigment's counterpart in most other birds.
Birds have tetrachromatic
Tetrachromacy (from Greek ''tetra'', meaning "four" and ''chromo'', meaning "color") is the condition of possessing four independent channels for conveying color information, or possessing four types of cone cell in the eye. Organisms with tetr ...
vision, which means that they have four types of cone cells with peak sensitivities to longwave (''l''), mediumwave (''m)'', shortwave (''s''), and ultraviolet (''uv'') or violet (''v'') light as well as transparent oil droplets made of carotenoid filters (with mainly the pigments galloxanthin, zeaxanthin
Zeaxanthin is one of the most common carotenoids in nature, and is used in the xanthophyll cycle. Synthesized in plants and some micro-organisms, it is the pigment that gives paprika (made from bell peppers), corn, saffron, goji ( wolfberries), ...
, and astaxanthin
Astaxanthin is a keto- carotenoid within a group of chemical compounds known as terpenes. Astaxanthin is a metabolite of zeaxanthin and canthaxanthin, containing both hydroxyl and ketone functional groups. It is a lipid-soluble pigment with r ...
) that refine spectral sensitivities of the ''l'', ''m'', and ''s'' cone-types. These filters in front of the photoreceptors tune their spectral sensitivity to longer wavelengths. Birds have yet another spectral filter allowing them to absorb wavelengths in the far UV wavelength range.
Psittacofulvins in parrots and carotenoids in passerine
A passerine () is any bird of the order Passeriformes (; from Latin 'sparrow' and '-shaped'), which includes more than half of all bird species. Sometimes known as perching birds, passerines are distinguished from other orders of birds by t ...
s have nearly the same range of colors, but neither pigment is found in the immediate common ancestor of these two groups. Parrots even have a concentration of carotenoids in their blood. This implies that both groups convergently evolved
Convergent evolution is the independent evolution of similar features in species of different periods or epochs in time. Convergent evolution creates analogous structures that have similar form or function but were not present in the last com ...
red, orange, and yellow pigmentation and that parrots did not evolve psittacofulvin to avoid the use of carotenoids.
References
Biological pigments Parrots Polyenes {{parrot-stub