Here ya go...here is a more easily understood explanation of the eye glow in Yorkies....
Yorkie Eye Shine.....if you want to get the nitty gritty, full blown explanation of exactly HOW this is genetically dictated, read Dr.Little's "Inheritance of Coat Color in Dogs"......Thank you for this more easily understood contribution/explanation, Darinda Tanner. Also, I want to just throw a bone out there...the very first sentence in this explanation, clearly explanes the absolute requirement for proper nutrition for a Yorkie to grow and maintain a gorgeous coat....you can not just throw any cheap ole slop at a Yorkie, call it food, and expect the results for proper health and coat to be met.
""First Yorkies are almost "unique" in the dog world. They carry a silk gene, and if they are breed correctly carry 2 blue (bb) or 2 black genes (BB) and 2 progressive graying genes. In addition, they also have a dilute gene.....this is what determines how light or dark the blue pigment color of the saddle is. When all these genes are present in the correct combination in one dog you have one beautiful animal. There's a lot more to this part of the blue coat.....but you need to read Dr. Little's "Inheritance of Coat Color in Dogs". He did much study on many breeds and although written long ago is still considered the bible of coat color in dogs.
The eye in all animals except pigs and man have a reflective layer along the back of the retina called the tapetum. This layer serves to reflect light to allow maximal usage of the available light. In some animals the tapetum is colored in others it is not.
The reddish color that you see in human eyes is the reflection of the blood vessels in the back of the eye because the tapetum is NOT colored. This is the same in the "red eye" of the Yorkie.
The blue and green you see in the Yorkie's are from a pigmentation in the tapetum -- how this relates to coats I am not sure.....but could be that pigmentation of the eye and coat texture are related genetically. Tapetums are very beautiful -- metallic, brilliant colors in most animals.
You can watch Yorkies, clipped down or in full coat, outside in the sunshine ... and you can easily separate them into two groups - those with a "blue cast" to the coat, and those with a "gold cast" to the coat.
Those with gold or bronze cast to the coat have eyes that reflect a flash bulb or flashlight with the "red eye" or "shiny" red reflection to the pupil.......no pigment.
Those blue cast dogs always seem to reflect blue or green from the pupil.....pigment.
The "red eye" dog has a thicker, softer, more opaque (not shiny silky) coat ... silky coated pups look kind of straggly.
What is going on is that those with the gold/bronze cast has LESS eumelanin (black) and more phaomelanin (yellow). Typically phaomelanin (yellow) does NOT get put in the tapetum. So NO tapetal pigment results in red color from the blood vessels. Whereas the blue cast dogs have more eumelanin resulting in a pigmented tapetum and the reflection that you see is bluish or green. It's very similar in chocolate and black Labs-- chocolate labs tend to have pale gold or red tapetums while the black labs have brilliant green and blue tapetums.Again it has to do with overall production of melanin (pigment) and where it is put. It also has to do with whether the dog carries the genes for true blue, clerical blue or black AND whether they also carry the gene for progressive graying (dilute). That is my explanation I have learned from study of the breed and genes and pigment. ""
Is it any wonder that Yorkies are difficult to breed to the standard......<g> |