30 August 2008

About those chicken earlobes...

As I was getting ready to go to the Minnesota State Fair, I encountered a newspaper article reporting that the color of a chicken's egg can be predicted from the color of the chicken's earlobe.

This has to fit in the category of "you learn something every day," because I frankly didn't know chickens had earlobes. Ears, yes. But earlobes?

This anatomical drawing portrays the location of the earlobe, and as a bonus you can see the locations of the fluff, hock, hackle, and sickle. The embedded photo (credit to My Pet Chicken) shows a white patch just above the wattle at the location of the earlobe.

Regarding the color of eggs, the often interesting (and very professional) Colour Lovers blog has an article on the subject:
Pearly white, cream, yellow, brown, gray, blue, violet, green, olive. Chicken eggs are colorful even before they’re dyed and decorated for Easter celebrations. “The color of eggs comes exclusively from the pigment in the outer layer of the shell and may range from an almost pure white to a deep brown, with many shades in between. The only determinant of egg color is the breed of the chicken. . . ."

“All eggs are initially white, and shell color is the result of the pigments called porphyrins being deposited while the eggs are in the process of formation. In the case of the Rhode Island Red, the brown pigment protoporphyrin, derived from haemoglobin in the blood, is what gives the shell its light brown color. The Araucana produces a pigment called oocyanin, which is a product of bile formation, and results in blue or bluish-green eggs. Interestingly, the color goes right through the shell, making the eggs difficult to candle... during incubation.”

Interestingly, the light of the sun can fade the color of an egg’s shell, even before it has been laid. This is a phenomenon that especially affects free-range chickens in hotter climates.
Sunlight can fade an eggshell before it is laid? How? And underlying all of this is the interesting question of why chickens have earlobes - and more to the point, why people have them. What functional advantage did earlobes have during evolution to allow the structure to be preserved? I have four days worth of links to catch up on, so I'll have to defer investigation of this topic to someone else...

1 comment:

  1. According to wikipedia:

    Since the earlobe does not contain cartilage the earlobe has a large blood supply and may help to warm the ears and maintain balance but generally earlobes are not considered to have any major biological function.

    HOWEVER: The earlobe contains many nerve endings, and for some people is an erogenous zone.

    So there you have it. The obvious purpose of the earlobe is planetary population ;)


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