Call me Koryos. I study biology and psychology and I write novels. Right now my goals are to a) go to grad school and b) get published.
My blog is like 50% animal science and 50% ace attorney with a smattering of kvetchy text posts so I hope you're ok with that. And I also like... write fiction... occasionally.
I KNOW I WROTE THAT CAT POST BUT I CAN'T DIAGNOSE YOUR CAT'S BEHAVIORAL PROBLEMS PLEASE TALK TO A VET I AM NOT A VET
MOONY IS AN AXOLOTL AND IT ALSO SAYS WHAT HE IS AT THE TOP OF THAT POST QUIT ASKIN ME WHAT HE IS
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CAN I PRESENT TO YOU THE GREATEST 5 AND A HALF MINUTES OF YOUR LIFE????
alstroemeric replied to your post:Hello, I enjoy your blog quite a bit and recently…
Question! If a cat is all black (down to paws, nose, and even whiskers) but has two little white spots, is he still melanistic?
That’s a good question, and the answer is that I do not know! The only definition I could find for melanism is that it’s an abundance of melanistic pigment in the skin and tissues of an animal. So I’m not sure if there’s a more scientific description specifying what separates melanistic animals from animals with species-typical pigment. It might be better to say that the cat with white feet has melanistic fur in most areas.
(The ancestral fur color of the domestic cat is the tabby pattern, but I’m not sure if you’d call it species-typical considering the diversity of coat patterns now present in domestic cat… though then again the domestic cat is actually just a subspecies of the African wildcat, not its own species so I guess tabby would be species typical.)
Melanism (for those who don’t know) is a phenotype where unusually high amounts of melanin are produced in the skin and sometimes body tissues. This can lead to solid black or very dark brown-looking animals.
Solid black cats are affected by melanism.The genetics of this are a bit complicated, so bear with me a second. There are three genes we’re going to be examining- the black gene, the agouti gene, and the tabby gene.
The black gene in cats (Bb) controls the concentration of eumelanin granules within the fur. However, in order for a cat to be solid black, the gene that codes for agouti (banded hair) must be suppressed. The recessive phenotype aa at this locus allows for individual hairs to be solid instead of banded.
(A- refers to the fact that the expression will be the same whether the genotype is AA or Aa.)
This gene is also epistatic to the tabby gene (Tt), meaning if the agouti gene is suppressed, the tabby gene will also not be visibly expressed. Tabby coloration is what produces stripes of differing darkness on cats- you can see that this cat has solid black stripes in some areas and agouti stripes in others. Its genotype should be something along the lines of A- B- T-.
Basically, if expression of agouti hair is blocked (genotype aa), it should also block expression of the striping regardless of what type of tabby gene your cat has because, obviously, the agouti stripes don’t exist! This leaves a solid-colored cat, which would naturally be black or brown, depending on which dominant or recessive alleles it had in its black gene (Bb). Black cats have a genotype of aa B- with any tabby gene.
Interestingly the gene for orange hair actually overrides the non-agouti (aa) expression, so orange patches of fur on cats will ALWAYS have a tabby pattern.
…Okay. That’s all a bit complicated and probably far more than you wanted to know. But as to your cat, her occasionally-visible striping is probably due to slight expression of the agouti gene. And the fact that her hair looks to be lighter brown in the sunlight? She could possibly be carrying the Siamese gene (cs) which actually causes fur to turn lighter-colored due to heat.
Her white blotches are controlled by yet another set of genes, the spotted gene (Ss) which has incomplete dominance and causes patches of fur to develop without pigment, hence the white color.
The really interesting thing, going back to wild cats, is that while melanism is common in a number of wild cat species, only three express melanism because of the same combination of genes that domestic cats do. Others are black due to mutations in completely different areas! This trait was clearly important enough to evolve at least four separate times within the cat lineage.
It’s thought that melanism in cats may actually confer resistance to some diseases, which is why some populations of wild cats may have high concentrations of melanistic individuals after an epidemic.
All in all, it’s fascinating stuff.
Here’s the study that discusses the separate evolution of melanism in the cat family- I unfortunately don’t have access to a full text version.