Tag Archives | The Tetrarch

White ticking on dogs

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 – sometimes called chubari spotting – in 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.

Continue Reading

Depigmentation on greys

Depigmented

One of the best places to study horse color is the wash rack, and BreyerFest was no exception. This is one of the guest horses at the event, Pecos. He is a 13 year-old PRE stallion. As the pictures in the link show, he appears to be a grey that has turned uniformly white. When wet, though, small spots of depigmented skin are visible.

Many greys lose pigment as they age, and this seems particularly true of horses of Spanish descent. What makes the depigmentation on Pecos a bit unusual is that it is not concentrated on his face or his undersides. Notice in the picture above that his sheath area is still quite dark. (I did not think to take a shot of the area under his tail, unfortunately, but I suspect it too is still mostly dark.)

This shot shows that his face is also mostly dark.

Depigmented2

I did not get any shots of the front of his nose since he was rather intent upon wuffling the rack, but this picture shows how the area around the borders of his marking as started to mottle. That is common in older greys and seems especially common in the breeds that are prone to depigmentation.

Two of the breeds covered in the upcoming book – the Boulonnais and the Kladruber – get an even more dramatic form of pigment loss that appears to effect the face. Studies done in the Czech Republic suggested that the two types of depigmentation in greys – one concentrated on the undersides and one on the face – are genetically distinct from one another.

Neither look much like what is going on with Pecos. His owner said that this was a recent development and that they thought it was a reaction to medication.

The spots are also unlike Tetrarch spots, named for the famous grey racehorse who had them.

Tetrarch spots usually appear in the earlier stages of greying, and disappear as the horse greys out. Photos suggest that these kinds of spots have dark skin under the white hair, rather than white skin like the spots on Pecos.

Pictures of one of the extensively depigmented Kladrubers appear in the upcoming book. Horses like that are interesting because their presence could mask others kinds of patterning in an all-grey (or mostly grey) breed.

Continue Reading