Theory Regarding Axolotl Color Genetics

Hi. So I have two grown axolotls, from different sources: a melanoid gfp female, and a wild type male. They both have siblings and apparently the female has had offspring (not on my watch, but before I got her) that were leucistic. Both have much lighter undersides. Judging from many of the photos I've seen on this forum, it seems most non-leucistic axolotls are fairly evenly colored.

I am thinking that maybe axolotls heterozygous (not completely positive for, but carrying, with one positive allele) for leucistic actually express the gene, but only halfway, so that they don't have even coloring like one completely negative for the gene, but also don't have pigment only isolated to their head or dorsal crest. I have read that none of the pigment modifier genes have any effect unless the individual is completely positive for the gene, but I'm wondering if leucistic might be an exception to that rule.

Do any of you have axolotls that you know are carriers of the leucistic gene and have lighter bellies? Do any of you have axolotls that you know are not at all carriers of the leucistic gene, but have lighter bellies? I''d like to know how common this is, and if there is in fact a pattern.

I doubt that's the case. For one, heterozygous just means they have two different alleles; it has nothing to do with expression. Leucisism has nothing to do with color. It's just a gene that dictates whether or not the color cells migrate off the neural crest. It's either expressed, and the animal is leucistic (which can also be albino) and the color cells do not migrate off the neural crest; or it's not expressed, and the color cells DO migrate off the neural crest (melanoid, wildtype, or albino).

Two: I have a melanoid male (who is purplish with a grey belly), and an EXTREMELY dark (not melanoid) female who regularly give me 25% leucistic offspring. They're both recessive for the gene, and pass it on to their offspring, but do not express it themselves.

There's a huge variation in color expression in axolotls. They can range from very pale grey/brown/tan to black, and all shades in between.

hi kaysie. thanks for the reply. i understand what you're saying.

however, i think having two different alleles has everything to do with expression. for dominant genes, even one allele for a trait makes the trait express. for truly recessive traits, two positive alleles are needed to express the gene. but a lot of other genes in various species are partially or inconsistently expressed if they have only one positive allele for the gene. hence my theory.

i know that leucistic means the pigment does not migrate off the neural crest, and that that migration is suppressed to varying degrees (some leucistics have only pigmented eyes, some have a few dark spots on their heads, and some have pigment over their entire dorsal fin). It doesn't seem so implausible to me that an axolotl with one allele for leucistic could exhibit a partial migration of pigment.

so basically, out of your two axolotls that are heterozygous for leucistic, one has a different colored belly than the rest of its body? that's valuable info.

Do all leucistic' axies get dark spots? I have one that is solid white and wondering if it'll have any change, Its roughly a year old and around 6" inches long if that makes any difference.

I'm pretty sure I've seen a mature "spot free" leucistic, so no they do not always develop spots.

I do not believe Leucistic is partially expressed in the heterozygote "carrier" state. My understanding is a single copy of the normal allele results in a totally normal extracellular matrix and normal pigment migration. Nonetheless it is plausible there could be a subtle effect in the heterozygote, but if this change was marked I suspect someone would have spotted it already.

Many axies are a bit paler underneath, and there is quite a lot of variation.

I wish you luck if you can sort out leucistic carriers from non carriers in the brood resulting from crossing two known carriers, where 75%of the offspring are wildtypes, and two out of three of them will be heterozygotes. I'm pretty sure the only way to sort out reliably if an animal is heterozygotic is to know its parentage and/or progeny in appropriate crosses.

Update:
It turns out both Mudkip and Minty are confirmed carriers of leucistic, as about 25% of their first group of children are leucistic.

And of those progeny that were not leucistic, about 66% have markedly lighter undersides. This seems consistent with the statistics, as two carrier parents should have 25% expressers, 50% carriers, and 25% non-expresser, non-carriers.

So my personal experience this far has coincided with my theory. Not that it's proven by this, but it's still not disproven that I can see. I would like a wider sample of info. to draw on though. Anyone with axolotls of known genetic makeup, please chime in!

It´s perfectly normal for a wild type to have a brighter belly, it´s actually what it should be like.
Since laucism is not codominant, heterozigotic animals simply don´t express the gene and therefore there is normal cell migration from the neural crest.