This squirrel, whose photo was sent in by reader Craig, looks as it if fell into some bleach. It is probably a mosaic for leucism, though it could also be a true albino in its nether parts (I’m guessing the former).
There are two possibilities here. One, perhaps less likely, is that the zygote of this animal was homozygous for leucism or albinism. (Leucism and albinism involve different recessive genes altering pigmentation. I’ve seen albino squirrels, and I know there are also white squirrels with leucism.)One of the “white” alleles could have mutated to its wild-type form in the embryonic head region during development, giving it a normal color in that part of the body.
Alternatively, the animal could have been heterozygous for either the melanism or leucism allele (one copy of a white-color allele, the other copy for normal color), but then one of its “wild-type” alleles mutated to the white form during development, making it white behind the neck.
There are probably other genetic possibilities at all, but I’m too tired to think of them.
Perhaps a reader can tell us which gene has mutated here, though I suspect you’d have to genotype the animal. If the head were white and the eyes were pink, it would certainly be an albino.
Wouldn’t a tetragametic chimera be a third possibility?
I thought it could be a chimera too!
There’s a boatload of white squirrels about 4 hours south of you:
http://www.ci.olney.il.us/visitors/white_squirrels/index.php
According to the city’s website these are true albinos.
Also, “Squirrels are protected in the City of Olney, causing them harm in any way is unlawful . Squirrels are granted right-of-way on all streets as well as sidewalks. Fines for violation of the squirrel protection laws can be as much as $750 per offense.”
Ceiling cat approved, I should think.
Treeload! 😉
It’s a piebald squirrel.
what you said is possible… it also could be a piebald. This sort of pattern already exists and is well established in rats, goats, sheep. Mostly white body with colored head/neck.
If it happens to be genetic and dominant, it would show up in the offspring.
If not somatic, as IIRC it may have been in Snowflake the gorilla’s case, then it’s not heritable.
That is what I thought – but looked it up & a piebald is leucistic, isn’t it?
Doesn’t a piebald animal exhibit less aggression, in other words when humans breed animals the pied ones are a by product of the process – ?
I assume it’s not simple X-based mosaicism? What chromosome are the coat color genes on?
And isn’t an early fusion of two embryos possible? Curt–Is that what you meant by “tetragametic chimera”?
Bill,
Yes. Rare cases have been documented in humans:
http://www.nejm.org/doi/full/10.1056/NEJMoa013452
Thanks, Curt. I’ll look at that paper.
http://www.lastkisscomics.com/2013/11/24/nuts-to-you-2/
Another possibility — it was a heterozygote that underwent a mitotic recombination event (one of the possible outcomes of DNA damage repair) that producing a clone of homozygous albino cells.
The piebald gene in dogs creates a merle coat, and there is a squirrel like that in my neighborhood. It’s a merle squirrel 😀