Psittacofulvin
{{short description|Pigment in parrots}}
Psittacofulvin{{pronunciation needed}} pigments, sometimes called psittacins,{{cite web |last1=Feinstein |first1=Julie |title=Where feather colors come from: Why cardinals are red and grackles are shiny |url=https://www.birdwatchingdaily.com/news/birdwatching/where-feather-colors-come-from-why-cardinals-are-red-and-grackles-are-shiny/ |website=Birdwatching Daily |access-date=24 December 2020}} are responsible for the bright-red, orange, and yellow colors specific to parrots.{{cite journal |last1=Masello |first1=Juan F. |last2=Lubjuhn |first2=Thomas |last3=Quillfeldt |first3=Petra |title=Is the structural and psittacofulvin-based coloration of wild burrowing parrots Cyanoliseus patagonus condition dependent? |journal=Journal of Avian Biology |date=November 2008 |volume=39 |issue=6 |pages=653–662 |doi=10.1111/j.1600-048X.2008.04417.x }} In parrots, psittacofulvins are synthesized by a polyketide synthase enzyme that is expressed in growing feathers.{{cite journal |last1=Mundy |first1=Nicholas I |title=Colouration Genetics: Pretty Polymorphic Parrots |journal=Current Biology |date=February 5, 2018 |volume=28 |issue=3 |pages=R113–R114 |doi=10.1016/j.cub.2017.12.045 |pmid=29408256|doi-access=free |bibcode=2018CBio...28.R113M }} They consist of linear polyenes terminated by an aldehyde group.{{Cite journal|last1=Stradi|first1=R.|last2=Pini|first2=E.|last3=Celentano|first3=G.|title=The chemical structure of the pigments in Ara macao plumage|journal=Comparative Biochemistry and Physiology Part B: Biochemistry and Molecular Biology|volume=130|issue=1|pages=57–63|doi=10.1016/s1096-4959(01)00402-x|pmid=11470444|year=2001}} There are five known psittacofulvin pigments - tetradecahexenal, hexadecaheptenal, octadecaoctenal and eicosanonenal, in addition to a fifth, currently-unidentified pigment found in the feathers of scarlet macaws.{{cite journal |last1=McGraw |first1=Kevin J. |last2=Nogare |first2=Mary C. |title=Distribution of unique red feather pigments in parrots |journal=Biology Letters |date=15 February 2005 |volume=1 |issue=1 |pages=38–43 |doi=10.1098/rsbl.2004.0269 |pmid=17148123 |pmc=1629064 }} Colorful feathers with high levels of psittacofulvin resist feather-degrading Bacillus licheniformis better than white ones.{{cite journal |last1=Burtt |first1=Edward H. |last2=Schroeder |first2=Max R. |last3=Smith |first3=Lauren A. |last4=Sroka |first4=Jenna E. |last5=McGraw |first5=Kevin J. |title=Colourful parrot feathers resist bacterial degradation |journal=Biology Letters |date=23 April 2011 |volume=7 |issue=2 |pages=214–216 |doi=10.1098/rsbl.2010.0716 |pmid=20926430 |pmc=3061162 }}
File:Ara chloropterus -Apenheul Primate Park -Netherlands-8a.jpg]]
{{multiple image
|footer=Polyene-al molecular structures
|direction = vertical
|image1=Tetradecahexaenal.png|caption1=Tetradecahexaenal
|image2=Hexadecaheptaenal.png|caption2=Hexadecaheptaenal
|image3=Octadecaoctaenal.png |caption3=Octadecaoctaenal
|image4=Icosanonaenal.png |caption4=Icosanonaenal
}}
Both carotenoids and psittacofulvins have narrow-band absorbance spectra, reflecting pale yellow or red pigmentary colors, 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, the pigment's counterpart in most other birds.
Birds have tetrachromatic 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, and astaxanthin) that refine spectral sensitivities of the l, m, and s cone-types.{{cite journal |last1=Tinbergen |first1=Jan |last2=Wilts |first2=Bodo D. |last3=Stavenga |first3=Doekele G. |title=Spectral tuning of Amazon parrot feather coloration by psittacofulvin pigments and spongy structures |journal=Journal of Experimental Biology |date=2013 |volume=216 |issue=Pt 23 |pages=4358–4364 |doi=10.1242/jeb.091561 |pmid=24031051 |doi-access=free }}{{cite journal |last1=Stoddard |first1=Mary Caswell |last2=Prum |first2=Richard O. |title=How colorful are birds? Evolution of the avian plumage color gamut |journal=Behavioral Ecology |date=September 2011 |volume=22 |issue=5 |pages=1042–1052 |doi=10.1093/beheco/arr088 |doi-access=free |hdl=10.1093/beheco/arr088 |hdl-access=free }} 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.