Thursday, July 19, 2012

Hairless Breeds and Skin Color

I was recently asked by a confused reader about what sort of link there is between skin color and hair color in hairless breeds. In breeds like the Chinese crested, it's not uncommon for a dog with dark skin to have pale hair. In other cases, the skin matches the hair. So, what causes this? To answer this, I'm going to look at a number of dogs and discuss the genes that are likely causing their hair and skin colors. First, though, some notes.

As a general rule, the darkest skin color should match the black pigmentation that would be seen in the coat. Patches of pink skin, whether spotted or not, represent what would be white markings on a dog with a full coat. By taking into account these characteristics, plus what's seen in whatever hair the dog happens to have, you can get a pretty good approximation of what genes are causing the dog's appearance.These rules don't always work, but I'll try to explain these exceptions.

This dog is really straightforward and a good place to start. It has minimal white and its skin matches its hair almost perfectly. In this case, the dog is black. Probably dominant black (K-). The white that is seen includes markings on all four paws, the chest, neck, and a bit on the face. This fits with minimal Irish markings (sisi) and would cause a dog with fur to look kind of like this.

This dog is also black, but clearly there is more going on here. Instead of having very little white, this dog has a lot of it. This explains all of the pink skin and white hair. In fact, it appears that this dog is extreme white (swsw), which results in a dog who is almost completely white. If this dog had a full coat it would look rather like this. Since this dog has so few spots, it probably doesn't have a copy of the ticking gene.

This dog is almost identical to the dog above with one notable difference: spots! White the dog above has almost no spots on its skin, this dog has a lot of them. It's quite possible that this dog has a copy of the ticking gene, but this isn't necessarily the case. Most dogs with white markings will have at least some skin spots, but more spots are seen in dogs with ticking. This dog is rather a lot like my dad's greyhound, Siggy, whose skin spots overwhelm his red ticking spots because his fur is so thin.

This dog is expressing something a bit different. Thought its skin is pink, this is due to something other than a white gene. This dog is sable (Ay-), which explains the dark tips on its hair. The skin color on sable dogs can vary from completely matching the color of its nose to something like this. In dogs like this, the nose, eye rims, and paw pads would be dark, but the predominant skin color is actually pink. If there are any white markings on the dog, it would be difficult or maybe even impossible to tell. If this dog had fur, it would look kind of like this.

You can also find a number of dogs that look like this. Clearly, the dog's skin and hair are completely different colors. This dog is most likely a recessive red (ee) that's been diluted down to white. Recessive red is a gene that doesn't allow any black in the coat, so it can hide a lot of different colors. This appears to be a common color in the breed, probably due to the flashy appearance of pale hair on a dark body. In cases like this, the dog is probably black behind the recessive red, which would explain the dark skin. As before, the spotted areas are white markings, which are basically indistinguishable from the pale color of the rest of the hair. If this dog had fur, it would look somewhat like this.

For simplicity's sake, I will end with this dog. This dog again has two skin colors, but both of them are pale. Unlike the dogs before who have black pigment, this dog's pigment has been diluted down. Since its skin is so pale, I suspect that it's expressing both the blue (dd) and liver (bb) genes, making it fawn or Isabella. I have actually heard of cresteds that are this sort of color being called palomino which is an...interesting way of looking at it. The genes behind horse color are completely different from those behind dog color, so those sorts of naming schemes don't make sense to me. Anyway, the fawn coloration doesn't just change a dog's coat color, but it also dilutes down the skin color. In combination with this, the dog is also expressing the recessive red gene. This explains why it has white hair. If this were not true, the hair would be similar in color to the skin,and the dog would look more like this.


Images are from Wikimedia Commons and Flickr.com under Creative Commons licenses: one, two, three, four, five, six.

4 comments:

  1. as a Crested fancier I despise the "palomino" term. Just a pet peeve, and certainly in the minority.
    I've never seen a true 'dd' blue/isabella in person or photos. Greying, or silver, is very common in the breed with extreme variation in the degree of fading.
    You don't address the specifics of dogs who would have the same hair color if coated but have very different skin colors. I have in mind particularly two dogs I know who both have black furnishings, one has distinctly black skin and the other deep brown with clear red-brown tones.

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  2. Here is black and tan (the leaping pup) and merle is expressed in Xolos:

    Black and Tan

    Merle

    Merle appears to be invisible on a hairless dog unless the eyes (or enough body hair) give the dog away, since any white spotting on the skin looks identical to the white speckling common in both Xolos and Cresteds.

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  3. Pai, is that blue-eyed dog tested merle? any pictures of merle in a coated Xolo?

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  4. found a bunch of lovely merle Xolos pictured here:

    https://www.facebook.com/xolonation.mexico/photos

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