Compounds that give birds sexually attractive colours also boost their ability to reproduce

Washington, February 14 (ANI): Carotenoids, the compounds responsible for amping up red, orange, and yellow colours of birds, seem to play a significant role in colour perception and a bird's ability to reproduce, according to a study.

Kevin McGraw, an Arizona State University assistant professor in the School of Life Sciences, said so while making a presentation at the American Association for the Advancement of Science annual meeting in Chicago.

"Carotenoids play fascinating and multifaceted roles in the lives of animals. For years, we have known that, as antioxidants, they boost human health and, as colorants, make birds colourful and sexually attractive. Now, we are blending as well as expanding these paradigms and studying how consumption of carotenoids can improve or 'tune' their colour vision, promote the health of offspring as they develop in the egg, and possibly improve male sperm quality," McGraw said.

The researcher pointed out that scientrists have long thought that carotenoids - responsible for the orange color of carrots and the red of lobster - play an important role in the evolutionary lives of birds by providing them with health benefits and vibrant colours.

Given that such pigments are limited in the diet and for physiological purposes, according to him, their use in coloration provides "honest, accurate information" about the bird's overall quality as a mate.

McGraw says that his latest study expands the scope of research on carotenoids to include many other behavioral and physiological benefits they may provide, including superior colour perception and gamete formation.

"Like in humans, carotenoids are also deposited in the retina, where they may protect the eye from photodamage by the Sun. There also is evidence that they can shape how well colors can be discriminated visually," he said.

"Ultimately, we envision a model where the more carotenoids you eat, the better you can see colour, the better mates you choose, and the redder the foods you choose, thus giving you even more carotenoids for health, attractiveness and vision. In a sense it is a carotenoid circle of life," he added.

His team are focussing their studies on a native Arizona desert songbird species called the house finch, and two widespread ducks called mallard and northern pintail, to better understand how carotenoids are allocated and prioritised among all of these diverse fitness functions.

"For decades, poultry scientists and human egg-consumers have been interested in the carotenoids that chicken hens put into their yellow egg yolks. We now know that these nutrients aid in the health, growth, and perhaps eventual coloration and mate quality of their offspring," McGraw said.

The researcher also says that carotenoids may affect the male sperm.

"Testes and seminal fluid can be enriched with carotenoids, preventing sperm cells from oxidative damage and resulting in greater fertilization ability of males. If this is the case, carotenoids really could enhance nearly every life-stage and aspect of survival and reproduction in birds," McGraw said.

"We are proposing a positive fitness feedback loop for these 'self-loving molecules,' given how high carotenoid accumulation can improve one's state and one's interest in selecting carotenoid richness in mates and food. This provides a window into how major sexual selection models, such as sensory biases and assortative mating, may be explained by a common, nutritional and narcissistic currency," McGraw added. (ANI)