Monday, April 14, 2014
Ornaments and Opportunity
The Age of Acne
I’m sure we all remember those awkward middle school days of acne and bed head. You walked around school avoiding bullies, eyeing the crush of your dreams and trying for the life of you to figure out some way to talk to him or her without making yourself look more inept than you may have already felt . (If you’ve never experienced this, consider yourself a step above the normal human race.) However, I’m even more certain that we’re all grateful those middle school days are long behind us, with only a hidden yearbook picture as a dreaded reminder.
Imagine if you will though, that those acne spots and uncontrolled hair were all that mattered in your future for finding that special someone. And even now, whatever blemishes you may or may not have, will signify to a future mate the compatibility and long life you may (or may not) be able to have. Such a terrifying concept is, fortunately for us, just a dream world for the human race as few people hold an unsightly stage of adolescents, or an unfortunate week of pimples, against someone they could see as a potential mate.
The animal world, on the other hand, is not so forgiving. Often features that animals consider attractive, such as a jungle foul’s cock comb or the yellow of a gold finch’s feathers, make all the difference in the world in being forever alone or happily mated in the animal kingdom. While many people struggling with acne are trying all sorts of treatments from ProActiv to home remedies, animals must deal with treatments of their own in order to maintain attractiveness whether they are conscious of this fact or not.
Take Care of those Carotenoids
Male partridges are prized by their female counterparts for their red beaks and red accents around their eyes1. Such attractive feature can be attributed to carotenoids. These pigments can act to either brighten an animal’s coloration or increase its immune response5. Although carotenoids are highly valuable for their attracting tendencies, they can only be found in food and cannot be self made. Therefore, the allocation of carotenoids is very important in being able to attract a mate with one’s bright and bold ornamentation.
The Hamilton-Zuk hypothesis explains that these vibrant ornaments are an indication of an individual’s health 4. Females look for those males with big bold secondary sex characteristics because they can indicate his parasite load and overall genetic vigor. As an individual’s parasite load increases, his health decreases and, subsequently, so does the attractiveness of his secondary sex characteristics4.
Although testosterone is, by itself an immunosuppressant, it does act to increase an individual’s dietary carotenoid uptake1,2 . As testosterone increases so does the uptake of dietary carotenoids which can either be used to fight free radicals in the blood stream in an anti-oxidant capacity, which increases the cell-mediated immune response, or as pigmentation to make ornaments flashier and brighter. The more carotenoids used in an immune response to build T-cells, the less there will be for pigmentation of ornaments3.
A relatively recent study was performed on Alectoris rufa, also known as the red-legged partridge, in which scientists infected the birds with an intestinal parasite, coccidian and then tested the birds for their immune response and the effect that response had on secondary sex characteristics2. The study found that males with a redder beak and eye rings also had less parasites and higher carotenoid levels. This indicates that while testosterone provides information to potential mates about long-term health and potentially resistant genes passed to offspring, carotenoid levels indicate the individual’s current health and virility.
In summary, testosterone is a hormone that starts functioning at the onset of puberty to increase size and structure of prominent secondary sex characteristics. If an individual is infected by parasites from the beginning, and has nonresistant genes to such parasitic attacks, then that individual's ornamentation will be lacking in form and structure. However if an individual can afford high testosterone levels and attractive ornamentation he must have good genes. Furthermore, if an individual has attractive ornamentation that is also bright in coloration, then he must have an ample supply of carotenoids to spare.
It's hard to cheat in the animal world. No amount of plumage serum or beak brightener can help turn an awkward pubescent partridge into a strapping specimen to mate with. It either has it or it hasn't. I'm grateful that I can safely say no braces and acne stage can be held against anyone in the big scheme of things. At least…I hope not.
1) Blas, J., L. Perez-Rodriguez, G. R. Bortolotti, J. Vinuela, and T. A. Marchant. "Testosterone Increases Bioavailability of Carotenoids: Insights into the Honesty of Sexual Signaling." Proceedings of the National Academy of Sciences 103.49 (2006): 18633-8637.
2) Mougeot, Francois, Lorenzo Perez-Rodriguez, Nuria Sumozas, and Julien Terraube. "Parasites, Condition, Immune Responsiveness and Carotenoid-based Ornamentation in Male Red-legged Partridge Alectoris Rufa." Journal of Avian Biology 40 (2009): 67-74.
3) Peters, Anne. "Testosterone and Carotenoids: An Integrated View of Trade-offs between Immunity and Sexual Signalling." BioEssays 29.5 (2007): 427-30.
4) Shykoff, Jacqui A., and Alex Widmer. "Parasites and Carotenoid-based Signal Intensity: How General Should the Relationship Be?" Naturwissenschaften 83.3 (1996): 113-21.
5) Zuk, M. Riddled with Life: Friendly Worms, Ladybug Sex, and the Parasites That Make Us Who We Are. Orlando: Harcourt, 2007. pp 180-206.
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