Amrita Ibold of Sweet Water Farm shared this photo of her green-eyed perlino Akhal-Teke, Kegas. This photo shows the darker golden ring around his eye, which gives his eye a green, rather than a blue, appearance.

Since starting this blog, I have gotten a number of emails from owners of homozygous cream dilute horses saying that their horses did not have truly blue eyes. Perhaps the most striking of these has been the Morgan stallion Amberfields Desperado. Many people have questioned whether or not a horse like that could even be a cremello, but he is an 18 year-old breeding stallion with a large number of foals on the ground. His eyes may be well beyond the norm for the color, but he has by all reports bred like one. This past weekend I met someone with a double-dilute from him, also with the same greenish eyes. When I get pictures, I will share those, too.

At the same event I ran into an unrelated cremello. This guy was a rescue, so nothing was known about his background. He did have blue eyes, but they had brown striations around the outer edge of the iris, as well as small flecks of brown inside.

Seeing these horses has made me wonder if the rule that homozygous creams are blue-eyed is absolute, or if there is a little more variety. And if that is the case, what causes the eye color to be different?

We already know that human eye color – the iconic subject for teaching about dominance – is not actually as simple as once thought. There are a number of genes in human beings that modify eye color. There is even evidence that some changes in eye color after maturity (once thought not to happen) probably have a genetic basis. I had often wondered if that was the case because my mother’s eyes lightened over time, and in more recent years I have had friends notice the same thing happening to me.

The photo to the left was taken at age 23, when my eyes were brown. The image to the top right is my twin brother approximately ten years older, with eyes that are light brown. (I could not find pictures of me at that age, but we had the exact same eye color.)  The image at the bottom right is me twenty years later, age 43, with noticeably lighter green-brown eyes. My mother’s eyes are several shades lighter than this. From what I have read, this kind of lightening is more common, but darkening was observed in some people, too.

If there are numerous genes influencing eye color in human beings – even changing them over time – what is to say that the same might not be true of other animals?

Advertisements