Greying


ChubariGreyhound

 

Elvis Brown posted this very interesting Greyhound to the blog’s Facebook page, and was kind enough to give me permission to share him here. Mr. Brown says he owned the dog from age three, and that he had always had the white spots, though at that time he was black. He is thirteen in this picture, and the greying is due to age. Mr. Brown also mentioned that someone from the Greyhound society had previously seen an Irish-bred Greyhound with a similar pattern.

These are somewhat reminiscent of Tetrarch Spots Рsometimes called chubari spotting Рin horses. Those take their name from the famous Thoroughbred, The Tetrarch, who was well-known for the unusual white spots on his coat. His daughter Mumtaz Mahal and (to a lesser extent) granddaughter Mumtaz Begum were similarly marked.

the_tetrarch_813

 

This kind of spotting in horses is associated with progressive greying, but progressive greying in dogs is different. In dogs grey is strongly associated with black pigment (eumelanin). It is most often seen in longhaired breeds, like the Bearded Collie, or in breeds that do not shed, like the Poodle and the Bedlington Terrier. Greyed dogs tend to be lightest where their hair is the longest, like on the topknot of some of the terriers, and darkest where the hair is short, like on the ears. This suggest that the hair loses pigment as it grows longer, rather than with each shed like a horse. Another interesting aspect of greying in dogs is that while it lightens black pigment, if the gene for black masking is present, it does not alter the black there. That is why Kerry Blue Terriers are born black and turn blue-grey while their face remains dark. The black mask, which would not otherwise be visible on a black dog, is revealed by the greying.

KerryBlue

 

Whatever caused the white ticking on this Greyhound, it does not sound like it is related to greying. In size and placement, the white spots actually look a bit more like Birdcatcher Spots, which are more common on red horses than black ones. Quite a few horse owners report those as increasing in number with age, so they could be considered progressive, though the various kinds of white ticking in horses is another under-researched topic. I have some images to post for that, as well as an update on a related horse from a previous post, for tomorrow.

In the comments section of the last post, some posters noted the similarity of the white areas to fleabitten grey. That is not an uncommon thing with appaloosa patterns. Although it is easiest to think of the action of Leopard Complex (Lp) as a form of progressive roaning, where white hairs gradually replace the colored ones to form what American horsemen call varnish roan, in actual practice the process can go both directions. That is, it can add white hairs to lighten the coat, and it can add concentrated bits of color to speckle the coat. These darker hairs are sometimes called repigmented spots because they typically occur after the coat has already begun to roan out, or in an area that previously had white patterning.

The varnish roan mare at the top of this post is a very good example. I have run photos of Freckles before for the series of posts on appaloosa mottling. I have easy access to her, since she shares a pasture with my own appaloosa pony, Sprinkles. This particular image shows her coloring from four years ago, when the lightest parts of coat were an even mixture of white and color. At that time, had she not had such pronounced varnish markings on her body, and a sprinkling of dark spots on her hips, she might easily have been mistaken for a pale grey. (This particular photo was taken in early May, so she had not fully shed out for the summer and was just a shade or two darker than she would be in summer coat.)

Here is Freckles as she appears now.

Each year she has gotten more pronounced dark ticking in the roaned areas of her coat, even as she gets lighter in the areas that were colored. This lighter ticking is most noticeable if you compare the right hind leg in the two pictures. The repigmented specks first began to appear on her shoulder, but over time they have spread across most of her body.

This close-up of her topline shows just how closely this resembles fleabitten grey. In fact, if I use Photoshop to remove the hip spots and what remains of her varnish marks, the resemblance to a true fleabitten grey is quite striking.

I suspect some type of repigmenting is part of what was going on with the roaned areas on the horse in the previous post. With Freckles, the flecking ties visually with what is already going on with her coat, so it looks less jarring. With the horse from the previous post, the odd transitions between his colored areas and the patterned areas make him look a bit like you pasted together parts of a bay appaloosa and a fleabitten grey.