Development of sable merle

Sable change colour of time. Because merle (in heterozygous form) affects eumelanin but not phaeomelanin, this means that a merling may be more visible in a puppy, which has heavier shading, and less so in the full grown dog. These photos show a sable merle shetland sheepdog growing up, and how her merling is visible to different degrees. The photos belong to Nightstorm.

This photo doesn't show the body, but we can see this dog is a merle thanks to the merling on the ears, and the one blue eye. As sable puppies have more shading, they can be easier to identify as merles than their adult counterparts.

At a passing glance, a sable merle can be hard to tell apart from a regular sable. If the dog has a blue eye, it is however a good sign (though blue eyes can also be inherited as a separate gene in some breeds, like the siberian husky).

Here our sheltie is all grown up. Because she is a fairly heavily shaded sable, some merling is still visible on her body. In a clear sable, it would have been much harder to see. The merling is more visible on the shorthaired areas, like the legs, than on the longhaired back and sides where it mingles more with the other colours.