As I mentioned in a previous post, I was fortunate enough to get some wonderful comparison shots while I was in Kentucky. It seems a good time to share this one since I touched on the topic of merle in dogs in the last few posts. This is Lily, a sable merle Collie. Here she is with her ordinary sable companion.
As I had mentioned in a previous post about merle in dogs, the merle gene effects black pigment. This is why the sabled areas on head are muted on Lily compared to her friend. With only a small amount of black pigment present, the effect is pretty subtle. From a distance Lily looks a little washed out and pale. Her blue eye is quite a giveaway for the merle gene, since those happen even with merles that are completely red pigmented. Her ears, which are often the blackest area on a sable Collie, are the other giveaway.
Her other ear and the colored area along her back skull are all visibly merled.
I should also clarify that she is what Collie breeders call a color-headed white with a single merle gene. She is extensively white because she is homozygous for the color-headed gene, and not because she has two copies of the merle gene.
Here is a typical (non-merle) color-headed Collie. (Photo from Wikimedia.)
Unlike double merles – and the white Boxers in the previous post – the gene responsible for this pattern usually leaves the head, nose and ears dark.
Here is my friend Andrea Caudill’s merle Cocker Spaniel, Domino. (Thank you, Andrea, for letting me use pictures of your sweet boy!)
Domino is probably a double merle. Although many double merles are very white, especially on the face, some carry enough color that they could be mistaken for a dog that had a single merle gene and one of the more extensive piebald patterns.
Since posting about the fact that merle acts on black pigment, several people contacted me about red dogs that were merle. In some breeds, red is used to describe liver, which is a form of black pigment. The people writing were not talking about liver red. In these cases, what was meant was truly red (or yellow) pigment. Some of the dogs did in fact look red, or had what looked like merling in their red-pigmented areas as well as their black. It was often less extensive, but still it was enough to make me wonder how absolute the connection was to black pigment.
If you look closely at Lily (the images link to larger pictures), the area at the corner of her blue eye, running towards the blaze, is roaned. Here is a sable Dachshund with an even more merling in the red areas of his face. (For comparison, here is a sable Dachshund puppy with the merling mostly confined to his sable areas.)
It is also true that merle, when paired with the harlequin (Harl), will effect red pigment. In Danes these dogs are called fawnequins. (Image from Wikimedia.)
The harlequin gene has much the same effect on brindles that inherit the merle gene, which are known as brindlequins. Compare that to a more typical brindle merle here, where the red/yellow pigment is not especially altered.
So it appears that the link between merle and black is not absolute. I know I’ll be looking at merles with red pigment more closely in the future. I am curious to see how common this is, and why it happens in some red dogs but not most.
(I promise to return to horse colors with the next post, which will have the Dominant White stallion Sato!)