Many of the genes in rabbits and cavies are the same, but they are just enough different to confuse people who are familiar with rabbits and trying to learn about cavy genetics. This article is an attempt to clear up the confusion by going through each series in cavies and compare genes from one species to another. This article assumes you are knowledgeable in rabbit coat color genetics.
Agouti Series
A – Agouti
Agouti is the same as the A gene in rabbits, it creates defined rings on each hair resulting in an overall ticked appearance over the body. While the eye circles, belly band, etc. are all present in cavies as they are in rabbits like there are in cavies, it is desired for these to be minimal.
ar – Solid
Ar is unique to cavy genetics, though solid and the steel gene have similar effects. Unlike steel, however, Solid is on a different locus (A instead of E) and ar is completely dominant over lower alleles. It causes the ticking to extend, eliminating the eye circles, belly band, etc.
at – Tan
The at gene is the same in rabbit and cavy genetics. It removes the ticking, leaving only the black while leaving the red portion of the belly band, eye circles, etc. unaffected.
a – Self
Like the tan gene, the self gene is the same in rabbit and cavy genetics. It removes all ticking as well as the eye circles, belly band, etc. leaving a guinea pig of all one color.
Black Series
B – Black
This is the same as the B gene in rabbits, it leaves both the red and black pigment unaffected.
b – Chocolate
The b gene in rabbits and cavy genetics is the same, it dilutes the black pigment to a chocolate, while leaving the red unaffected, but gives a ruby cast to the eye.
Color Dilution Series
(incompletely dominant)
C – Intense Color
Like the C gene in rabbits, it leaves the red and black pigment unaffected and is completely dominant over the other alleles in the series.
cd – Dark Dilution
This gene is completely different from any gene in rabbits, it dilutes the red pigment depending on what other alleles it is combined with. It also changes the dark eye to one with a slight ruby cast. When homozygous it is gold, when combined with the cr, it is cream, and when combined with ch it is sable.
cr – Ruby-Eyed Dilution
This is also different from any gene currently in rabbits (though the effect in the homozygous state is somewhat similar to that of the cchd gene in rabbits, removing all red), this gene further dilutes the red pigment depending on what allele it is combined with and changes the eye to dark with a definite ruby cast. When homozygous, it dilutes the red pigment to white, when combined with ch it creates a sable.
ch – Himalayan
Himalayan (sometimes written as ca, since it is incorrectly considered an Albino gene), this is the same as the ch gene in rabbits, removing all red pigment, but allows for black pigment to be produced based on temperature, creating what we know as the Himalayan. Dilutes eyes to pink.
Dilute Series
It is worth mentioning this gene, however, it should be noted that it has only been recently discovered in cavy genetics and isn’t prevalent in the states yet. What is referred to in the standard as a “blue” at this time is actually a slate (see the P series).
D – Non-Dilute
Like the D gene in rabbits, it leaves both the red and black pigment unaffected.
d – Dilute
The d gene in cavies and rabbits is the same, it dilutes the black pigment to a dark blue color while leaving the eye color unaffected (or possibly giving it a slight ruby cast).
Extension Series
E – Full Extension
In rabbits and cavies, the E gene is the same, it leaves both the red and black pigment unaffected.
ep – Partial Extension
The ep gene in guinea pigs is both similar and different than the ep gene in rabbits. Like the ep gene in rabbits, this creates a patched or brindle effect (modifiers will determine which of these, or if it will be in between). Unlike in rabbits, in cavy genetics, this can be combined with A, creating an agouti and red animal, when in combination with ar it creates a solid and red patched animal, with at it would create an animal that is tan and red, while combined with a it creates a red and black animal.
e – Non-Extension
The e gene in rabbit and cavy genetics has a similar effect, it removes black pigment, leaving only red pigment. Because there has not yet been a true albino gene found in cavies, the ee gene combined with chch is the most common way to have a pink-eyed white animal. Unlike in rabbits, however, ee has the same effect on an agouti, solid, tan, or self animal, so there is no tort or fox in cavies, only red.
Pink-Eyed Series
The P series has only just been discovered in rabbits but has been around in cavy genetics for a long time. The partial pink-eye is a newer discovery but has been around longer than the dilute above.
P – Normal Eye
P leaves both the red and black pigment unaffected.
pg – Partial Pink-Eye (or Grey)
Only found in cavies (at this time), this dilutes the black pigment to Slate (dark grey) and dilutes the eyes to a dark ruby (not ruby cast, but a true ruby, darker than a pink eye, but lighter than a dark eye with a ruby cast), the red pigment is left unaffected. When combined with chocolate, it creates Caramel.
p – Pink Eye-Dilution
Recently discovered in rabbits, primarily in Europe, where they are now breeding a “Lutino” (red-eyed orange), this dilutes the black pigment to Lilac (varies from light grey to almost white) and dilutes the eyes to pink, red pigment is left unaffected. When combined with chocolate, it creates Beige.
Spotted Series
S – Non-Spotted
This causes a guinea pig is solid, with no white. Some small white markings on the toes, forehead, or crest may appear, such as the white on the White Crested though do not appear to be caused by this gene.
s – Spotted
The effect of this gene could be compared to the English spotting gene or possibly even the Dutch gene as it does create the Dutch guinea pig, however, it is actually a different gene. A ss pig will typically have at least white on the nose and feet, but may have any amount of white patching anywhere on the body. Unlike the English spotting gene, the spotting doesn’t follow any sort of pattern.
Roan Series
(incompletely dominant)
Rn – Roan
Roan doesn’t exist in rabbits and there is no similar gene yet known either. Roaning causes white hairs to be interspersed throughout the body of the cavy – but often leaves the feet and head with little to no roaning. The gene is incompletely dominant, in the homozygous dominant form (RnRn) it results in what is referred to as a “lethal” white. This is a bit of a misnomer as the gene combination is not necessarily lethal, but it does create a red-eyed white pig with deformities of the teeth and/or eyes who may also experience issues with vision and/or hearing. The heterozygous form creates what is known and shown as roan in cavies.
rn – Non-Roan
The homozygous recessive form leaves all other coloring unaffected.