This is my third segment of Silver Fox Genetics 101 that will cover how and why there are also red-eye white (REW) Silver Foxes. (Some call them Ruby-Eyed Whites.) There are advantages and disadvantages to having a REW Silver Fox, but it is not a showable color and not likely to be because of the lack of contrast for the silvering. However, in dying the white pelt, the white guard hairs do not dye the same as the rest of the fur, which is interesting to anyone into the fur dying aspect.
The REW is caused by homozygous “cc” alleles on the C-locus. You probably have already determined, because of what you have learned from the previous segments, that because the “c” is a lower case letter it is recessive and it would take a double recessive like “cc” to be expressed. That is correct, but the C-locus is a bit more complicated than the B and D loci that have been covered previously because the C-locus has more than just two possible alleles, in fact, there are five, but it still can only hold two!
With Silver Foxes, we really do not give the C-locus much thought because ours is a full color “C” breed with a few “cc” REWs showing up here and there. However, a breeder should be aware of the other possible alleles because it is partly from this locus that we have seen some funky colors in Silver Foxes, like blue-gray, bright blue, or marbled eyes from the chinchilla allele. Also, just to add to the confusion, the C-locus color names are from the genotype, but there are also rabbit breeds with some of the same names!
In the order of dominance:
- C – full color (as a Silver Fox should be)
- cchd – chinchilla (both a rabbit breed and a color)
- cchl – sable (think of a Siamese cat or the American Sable rabbit breed)
- ch – Himalayan (both a rabbit breed and a color) or pointed white
- c – red-eyed white
The order of dominance is important to know because all of the alleles except for “C” is in lower case and recessive to “C,” but “cchl” sable is dominant to “ch” himi (short for Himalayan) but recessive to “cchd” chin (short for chinchilla).
Silver Foxes must have at least one “C” to have the proper coloring of fur and eyes, but it can hide or carry any one of the other four alleles that are recessive to it, which is not a problem until there are two rabbits with hidden recessives bred together. The easiest method to test breed what is hidden on the C-locus of one rabbit is to use a REW with the most recessive “cc” and the second-best method for test breeding is using a REW carrier with one “c.”
While you should be aware of the variations that may come from the C-locus, in the Silver Fox breed, we usually have two that present themselves: dominant “C” and recessive “c” and for the purposes of this discussion, these are the two that will be addressed from this point on.
Similar to the on-off switch of dense and dilute on D-locus, “C” is the on-switch for full color and “c” is the off-switch for color, restricting any and all color.
With these two alleles, there are only three combinations:
- CC = full color
- Cc = full color carrying white
- cc = REW
As always, when the second allele is unknown:
- C_ = full color with unknown second allele
A black Silver Fox will have at least one "B" and "D" whether or not the second alleles are known on the B- and D-loci, but this is also because the C-locus has “C.” With the three loci we have covered so far, every black SF has B_ C_ D_.
However, a rabbit can have the dominant black “B” allele and the dominant dense “D” allele with “cc”, as in B_ cc D_ and the “cc” turns off all the color so its phenotype is completely and entirely white with red eyes.
If you think of “cc” as a thick blanket of snow that covers the rabbit so you cannot tell if it is genetically black, blue, chocolate, or lilac rabbit, but it still will have one of those colors in its genotype hidden beneath the white, you can understand how a REW may be considered the wildcard color and its genotype is most often written as __ __ cc __ __. (Yes, there are two more loci to cover after this one, the A- and E-loci.)
Let's take a look at the B-, C-, and D-loci when breeding a REW with a double heterozygous black.
- __ cc __ x Bb C_ Dd = ?
It cannot really be known in advance what will be found in the nesting box, but black is likely because there is a dominant "B" and "D." The other possibilities are chocolate, blue, lilac, and white. If there are REWs from this breeding then you know that the second allele on the C-locus of the black is “c.” Otherwise, the possibilities are the same as were covered in the second segment.
If you see a lilac or both chocolate and blue you at least know that the REW has recessive “b” and “d,” which you should write a bit differently with the underscores before the recessive alleles: _b cc _d. In this case, the white hides the dominants and recessives, whichever is there, so we leave the spaces before the recessives that the breeding revealed. Even if there are blacks, those dominant alleles could have come from the black so we cannot know the underlying color of the white. It also should be noted that all the offspring of a REW will be REW carriers.
This is where a lilac comes in very handy because it would reveal any and all dominants and recessives of the REW rabbit and REW would reveal if the lilac is carrying REW.
However, in some cases, we may have more information about the genotype of the REW. For instance, if the white had two chocolate parents, we would know that the “bb” must be in the REW but we cannot know for certain what is on the D-locus: bb cc __. (We also know both parents carried REW.) If one parent was blue and the other lilac, the genotype of the REW would be: _b cc dd, because we cannot know whether the dominant “B” or another recessive “b” was passed to the REW from the blue parent.