Ok, hear me out.
In 1892, Wilhelm Mucke started trying to breed a white rabbit without red eyes. Reportedly, he started with breeding Dutch rabbits, and once he crossed them with the white varieties of Flemish Giant and Holland Lop he managed to get a pure white rabbit with blue eyes. He presented this in 1907 as the Vienna White. Now we know that the V locus controls the Vienna gene, separate from both albinism and Dutch, which created Vienna-marked rabbits in heterozygotes (that are similar to Dutches in some cases) and BEWs in homozygotes (although this gets covered by homozygous albinos.)
Another known example of this occurring is when the Lionhead rabbit was bred. Reportedly, mini Swiss Fox rabbits were bred to the Netherland Dwarf/Hermelin breed of rabbit. The Swiss Fox was a long-haired rabbit so I presume it was an angora genotype, ll. The ND is a dwarf rabbit, Dwdw. When bred together a novel mane gene arose that we know call M. Heterozygotes are single-maned, homozygotes are double-maned. This is also a dominant mutation, and like Vienna, is separate from angora or dwarfism. We can breed llMM rabbits (which is just too much wool if you ask me) and maned rabbits are starting to appear in full size, for example in European NZ meat herds. There's also the Belgische Bartkaninchen breed.
But people also cross/mix rabbits all the time and don't spontaneously cause new mutants. What could the X factor be?
I'm interested in the possibility of green-eyed rabbits. Blue eyes come from a lack of eumelanin produced in the stroma, causing the light to refract in the eyeball off the epithelium (which still has eumelanin pigment) and appear blue, for the same reasons water and air appear blue (they aren't actually pigmented blue!) Albinism causes no eumelanin in the epithelium either, so the light is reflected off the blood, hence red eyes. Lutino, from what I can gather, retains some pigment in the epithelium but to a lesser degree, hence pink or in some cases lilac. Now in humans, then the stroma has mild eumelanin pigmentation instead of full, we get hazel eyes; the brown affects the blue refration to get an in between. In rabbits that seems to appear as blue-gray instead, potentially due to the different structure of the eye. But in humans, when the stroma is pigmented by pheomelanin instead of eumelanin, we get green eyes.
Rabbits, of course, have eumelanin and pheomelanin too. That's where the coat colours come from. I would hypothesize that if a mutation occurred which cause the stroma to be pigmented by pheomelanin instead of eumelanin, a novel green (or possibly yellow-green given the different structure?) eye phenotype would occur.
The E locus affects the MC1R gene in such a way that dominant mutations overproduce eumelanin and recessive extensions produce none, so the melanocytes default to pheomelanin, at least in the coat. This doesn't seem to extend to the eyes though as non-extension red/fawn/cream rabbits still have brown eyes. Could a further recessive E locus mutation cause eumelanin production to cease in the stroma?
The C locus turns off pheomelanin production, leading towards albinism as we trend towards more recessive mutations. But hypothesize a super-dominant mutation on the C locus: could it result in an overproduction of pheomelanin? Say, in the stroma? That, paired with something which limits eumelanin in the stroma, could leave a stroma only pigmented with pheomelanin.
The B locus weakens eumelanin. Some people report young chocolate rabbits to have green eyes. This is probably more akin to hazel than true green, but following the trend of the creation of Vienna, it does seem that selecting for nearly-correct phenotypes with selective breeding can spontaneously trigger the desired mutation. Not sure what selective pressure would help that (reduced eumelanin in the stroma can lead to increased eye sensitivity in full sun, so perhaps darkness could provide pressures for lighter coloured eyes? In human history, moving north seems to correlate with lighter coloured eyes) but chocolate rabbits might be part of the solution.
Of course people have already been breeding chocolates, non-extensions, non-extension chocolates, and more. These mutations haven't spontaneously occurred that we know of so far. Whether it ended up being a mutation limited to an existant colour locus and thus was limited to a certain phenotype, or mutated in a new locus (allowing us to backbreed green eyes to any colour rabbit), I feel like this could end up a valuable pursuit.
Curious to get feedback on my line of thought here and if anyone knows anything more about this stuff that might help. Thanks!
In 1892, Wilhelm Mucke started trying to breed a white rabbit without red eyes. Reportedly, he started with breeding Dutch rabbits, and once he crossed them with the white varieties of Flemish Giant and Holland Lop he managed to get a pure white rabbit with blue eyes. He presented this in 1907 as the Vienna White. Now we know that the V locus controls the Vienna gene, separate from both albinism and Dutch, which created Vienna-marked rabbits in heterozygotes (that are similar to Dutches in some cases) and BEWs in homozygotes (although this gets covered by homozygous albinos.)
Another known example of this occurring is when the Lionhead rabbit was bred. Reportedly, mini Swiss Fox rabbits were bred to the Netherland Dwarf/Hermelin breed of rabbit. The Swiss Fox was a long-haired rabbit so I presume it was an angora genotype, ll. The ND is a dwarf rabbit, Dwdw. When bred together a novel mane gene arose that we know call M. Heterozygotes are single-maned, homozygotes are double-maned. This is also a dominant mutation, and like Vienna, is separate from angora or dwarfism. We can breed llMM rabbits (which is just too much wool if you ask me) and maned rabbits are starting to appear in full size, for example in European NZ meat herds. There's also the Belgische Bartkaninchen breed.
But people also cross/mix rabbits all the time and don't spontaneously cause new mutants. What could the X factor be?
I'm interested in the possibility of green-eyed rabbits. Blue eyes come from a lack of eumelanin produced in the stroma, causing the light to refract in the eyeball off the epithelium (which still has eumelanin pigment) and appear blue, for the same reasons water and air appear blue (they aren't actually pigmented blue!) Albinism causes no eumelanin in the epithelium either, so the light is reflected off the blood, hence red eyes. Lutino, from what I can gather, retains some pigment in the epithelium but to a lesser degree, hence pink or in some cases lilac. Now in humans, then the stroma has mild eumelanin pigmentation instead of full, we get hazel eyes; the brown affects the blue refration to get an in between. In rabbits that seems to appear as blue-gray instead, potentially due to the different structure of the eye. But in humans, when the stroma is pigmented by pheomelanin instead of eumelanin, we get green eyes.
Rabbits, of course, have eumelanin and pheomelanin too. That's where the coat colours come from. I would hypothesize that if a mutation occurred which cause the stroma to be pigmented by pheomelanin instead of eumelanin, a novel green (or possibly yellow-green given the different structure?) eye phenotype would occur.
The E locus affects the MC1R gene in such a way that dominant mutations overproduce eumelanin and recessive extensions produce none, so the melanocytes default to pheomelanin, at least in the coat. This doesn't seem to extend to the eyes though as non-extension red/fawn/cream rabbits still have brown eyes. Could a further recessive E locus mutation cause eumelanin production to cease in the stroma?
The C locus turns off pheomelanin production, leading towards albinism as we trend towards more recessive mutations. But hypothesize a super-dominant mutation on the C locus: could it result in an overproduction of pheomelanin? Say, in the stroma? That, paired with something which limits eumelanin in the stroma, could leave a stroma only pigmented with pheomelanin.
The B locus weakens eumelanin. Some people report young chocolate rabbits to have green eyes. This is probably more akin to hazel than true green, but following the trend of the creation of Vienna, it does seem that selecting for nearly-correct phenotypes with selective breeding can spontaneously trigger the desired mutation. Not sure what selective pressure would help that (reduced eumelanin in the stroma can lead to increased eye sensitivity in full sun, so perhaps darkness could provide pressures for lighter coloured eyes? In human history, moving north seems to correlate with lighter coloured eyes) but chocolate rabbits might be part of the solution.
Of course people have already been breeding chocolates, non-extensions, non-extension chocolates, and more. These mutations haven't spontaneously occurred that we know of so far. Whether it ended up being a mutation limited to an existant colour locus and thus was limited to a certain phenotype, or mutated in a new locus (allowing us to backbreed green eyes to any colour rabbit), I feel like this could end up a valuable pursuit.
Curious to get feedback on my line of thought here and if anyone knows anything more about this stuff that might help. Thanks!
