Study of the presence of pheomelanin in parakeet feathers

Study of the presence of pheomelanin in parakeet feathers

By Dirk Van den Abeele
Ornitho-Genetics VZW
MUTAVI, Research & Advice Group

Published online 30/3/2021

The colours in a bird’s feathers are formed in two different ways: pigments and light refraction caused by the structure of the feather. Each bird species can be recognized by its own typical plumage, and is actually a result of millions of years of evolution. Every scientist is therefore formal: feathers are one of the most complex structures that exist.

The most common pigments in feathers are melanins (eumelanin – normally coloured black and pheomelanin – reddish brown) and carotenoids (yellow – red). We find these pigments in most feathers. Except in parrot-like [Psittaciformes], we do not find carotenoids in feathers to begin with [1]. C.F.W. Krukenberg already proved in 1883 that the red, orange and yellow color in parrot feathers is caused by psittacofulvins (also known as parrodienes or psittacine) [2] – [4]. In aviculture in Europe they prefer the more popular name psittacine because this term has been used for years in almost every article about budgerigars [Melopsittacus undulatus]; and as we know this is largely the basis of the hobby for parakeet lovers. However, scientific publications recommend the use of psittacofulvins. Of course, the choice is yours.

In MUTAVI, however, we have investigated several mutations / feathers of parakeet-like in the past and never (visually) pheomelanin was found (investigation by means of cross-sections of feathers under light and electron microscope). MUTAVI, Research & Advice Group started as early as the early 1980s in the Netherlands with research into pigment abnormalities in various colour mutants in birds (www.mutavi.info). It was John van Eerd who founded MUTAVI. Later Inte Onsman joined the troops and after the sudden death of John van Eerd, I was also allowed to make his modest contribution.

We could not detect pheomelanin during the MUTAVI studies, but of course we had to take into account that it is always possible that there are very small pigments that cannot be detected under the microscope (30 years ago this was about the only way to examine feathers). This was thus communicated. Nevertheless, we were fairly certain, especially since there were never actually reports that pheomelanin could be seen in certain mutations in parakeets. For the sake of a good order I should mention that some people long ago thought that the cinnamon mutant did form pheomelanin, but it soon turned out that it was only brown eumelanin [6]. Auber already proved this in 1941 and then also mentioned that there was no pheomelanin in the feathers of budgerigars.

Also, to our knowledge, there has been no scientific study to confirm the presence or absence of pheomelanin in parakeet feathers. There is only one paper in which the author indicates that pheomelanin, along with carotenoids and eumelanin, is responsible for colouring in parakeets [7]. He cited some studies that were supposed to confirm this statement, but we couldn’t find any study that actually showed the presence of pheomelanin in parakeet feathers. In addition, we also know with fairly high certainty that parakeets do not have carotenoids in their feathers, but psittacine instead [8]. So parakeets seemed to be different from most other bird species. But the question of whether parrots can synthesize pheomelanin in feathers and whether pheomelanin is present in parrots’ feathers was still not been answered with 100% certainty and has not been sufficiently and purposefully researched with modern technology.

There are mutants or feather fields in parakeets that show a brown-red colour and that gave rise to a lot of discussions among enthusiasts. Is that pheomelanin or not?

Of course, these yes-no games are not giving us any answer and the only way to confirm or disprove is to do targeted research. Now a days, there are a number of new contemporary technologies that can help us with this and we went for research with Raman spectroscopy. Raman spectroscopy is a type of laser that is used to identify pigments / molecules present in certain substances. Just think of the scanners at airports, for example, where they can detect the smallest presence of drugs on clothes, luggage, etc. with comparable technology. In other words, the Raman spectroscopy is the perfect method to identify pigments in feathers. Obviously, these devices are not frequently present or available and that is why we went to a researcher in Spain.

Because it is financially and practically impossible to investigate the feathers of all parakeet species, it was necessary to make a good selection of the feathers / species where pheomelanin may be present. We are talking about the brownish / orange red feathers. That is why we were looking for a number of specialists / enthusiasts to make an accurate selection for us. It’s a matter of being able to conduct our research very objectively.

• Mr. Daniel Nuijten (Nature Conservation – Belgium)
• Mr. Bert Van Gils (chairman BVP Belgian association of parakeets and parrot lovers – Master of Bioscience Engineering – Belgium)
• Mr. Nico Rosseel (Aviculturist – Belgium)
• Mr. Jef Kenis (Judge – Aviculturist – Belgium)
• Mr. Eric Gennissen (Aviculturist – The Netherlands)
• OFM Heinz Schnitker (Taxonomist – Germany)
• Mr. Glenn Ooms (Aviculturist – editor-in-chief BVA-International – Belgium)
selected 30 species / subspecies and some color mutations that were POSSIBLE candidates to produce pheomelanin in the feathers.

In the end, we were able to collect feathers from 28 parakeet species, from the three existing families: Psittaculidae (parrots of the old world) – Psittacidae (parrots of Africa and the new world) and Cacatuidae (the cockatoo family) (see table). Feathers from a few mutants were also sent, so that we could also investigate this track.
All feathers were analysed in the autumn of 2019, except those of the budgerigar. These feathers did not come under the scanner because other studies had already shown that they do not contain pheomelanin [6]. So it was no use to spend an extra budget on that, because this boy has to pay for everything himself.

With the help of Dr. Ana Carolina de Oliveira Neves (Institute of Chemistry, Federal University of Rio Grande do Norte, Natal, Brazil) and Dr. Ismael Galván from the Department of Evolutionary Ecology, Doñana Biological Station, CSIC, Seville, Spain, all feathers were examined.
The result was what we already knew and could expect in aviculture with a fairly high degree of certainty: no evidence has been found that pheomelanin would be present in Psittaciformes feathers. The results of the study was published in July 2020 in the scientific journal Experimental Biology [9]. In other words: Inte Onsman and John van Eerd were indeed right back then.

The reddish brown colour we see in some feathers is probably created by the combination of eumelanin and psittacine (psittacofulvin) and not by pheomelanin. In addition, we must also take into account the fact that the keratin from which the feather is built also reflects various colours that we cannot always perceive with the human eye or that reflect colours that we see, but certainly would not expect [10] – [12]. That too can put us on the wrong track visually.

Whereas in most birds a combination of eumelanin and pheomelanin is present and the red and yellow colours are often caused by carotenoids, in parakeets there have been clearly some changes during the course of evolution. In parakeets, for example, we find psittacine instead of carotenoids [8] and now we can also add that the ability to produce pheomelanin in parakeets, probably a long time ago, will have been lost in one of the common ancestors of our parakeets.
The wonders of nature. She never ceases to amaze us.

Dirk Van den Abeele

Download here the results in pdf
Literature:
[1] C. F. Krukenberg, ‘Der federfarbstoffe der Psittaciden’, Vgl.-Physiol. Stud., vol. 3, pp. 29–36, 1883.
[2] R. Morelli, R. Loscalzo, R. Stradi, A. Bertelli, en M. Falchi, ‘Evaluation of the antioxidant activity of new carotenoid-like compounds by electron paramagnetic resonance.’, Drugs Exp. Clin. Res., vol. 29, nr. 3, pp. 95–100, 2003.
[3] D. Van den Abeele, Lovebirds Compendium, 1ste dr. Warffum- The Netherlands: About Pets, 2016.
[4] G. E. Hill en K. J. McGraw, Bird Coloration. Volume 1. Mechanisms and measurements. Harvard University Press, 2006.
[5] S. Ito en K. Wakamatsu, ‘Chemistry of Mixed Melanogenesis—Pivotal Roles of Dopaquinone†’, Photochem. Photobiol., vol. 84, nr. 3, pp. 582–592, 2008, doi: 10.1111/j.1751-1097.2007.00238.x.
[6] L. Auber, ‘Colors of feathers and their structural causes in varieties of the budgerigar, Melopsittacus undulatus (Shaw)’, 1941.
[7] K. Delhey en A. Peters, ‘The effect of color?producing mechanisms on plumage sexual dichromatism in passerines and parrots’, 2017, Geraadpleegd: jun. 07, 2019. [Online].
[8] K. J. McGraw en M. C. Nogare, ‘Distribution of unique red feather pigments in parrots’, Biol. Lett., vol. 1, nr. 1, pp. 38–43, mrt. 2005, doi: 10.1098/rsbl.2004.0269.
[9] A. C. de O. Neves, I. Galván, en D. V. den Abeele, ‘Impairment of mixed melanin-based pigmentation in parrots’, J. Exp. Biol., jan. 2020, doi: 10.1242/jeb.225912.
[10] L. D’Alba, L. Kieffer, en M. D. Shawkey, ‘Relative contributions of pigments and biophotonic nanostructures to natural color production: a case study in budgerigar (Melopsittacus undulatus) feathers’, J. Exp. Biol., vol. 215, nr. 8, pp. 1272–1277, apr. 2012, doi: 10.1242/jeb.064907.
[11] J. Tinbergen, B. D. Wilts, en D. G. Stavenga, ‘Spectral tuning of Amazon parrot feather coloration by psittacofulvin pigments and spongy structures’, J. Exp. Biol., vol. 216, nr. 23, pp. 4358–4364, 2013.
[12] J. E. Barnsley, E. J. Tay, K. C. Gordon, en D. B. Thomas, ‘Frequency dispersion reveals chromophore diversity and color-tuning mechanism in parrot feathers’, R. Soc. Open Sci., vol. 5, nr. 7, p. 172010, jul. 2018, doi: 10.1098/rsos.172010.