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I have 15 1/2 inch fry. They are just starting to shorten up and really look like angels. They all are dark with what look like stripes on their sides. The father is a gorgeous veiltail gold koi, mom is a regular marble. So do they change colors as they age? Or is this the color they will be staying?

"Constant vigilance!"
Mad-Eye Moody

Google is your friend ...

Detailed primer on Angelfish genetics

Angelfish genetics part 2 - Koi angels

More Angelfish genetics, including links to the definitive research work by Dr Joanne Norton

That should keep you in bedtime reading for about a month.


Panda Catfish fan and keeper/breeder since Christmas 2002

Thanks for the links, unfortunately I don't think I understand much of what I'm reading. I suppose I'll just wait and see!

"Constant vigilance!"
Mad-Eye Moody

OK, here's a crash course.

The simplest case is what's known as single factor inheritance. This takes place when a single gene determines a fish's attribute (say, for example, the Melanin gene that codes for black pigment). If the gene resides on one of the non-sex chromosomes (these are known as autosomes) then the gene is an autosomal gene, and most genes are in fact autosomal. Genes that are found on the sex chromosomes are sex-linked genes, and the classic example of one of these is the gene for blood clotting factor VIII in humans - a mutant form of this gene causes haemophilia in males that inherit it.

Now in the case of autosomal genes, you have to remember that the autosomes (the non-sex chromosomes) exist in identical pairs. And thus, there are two copies of the gene present, one on each half of the chromosome pair.

I chose the Melanin gene because it's an autosomal gene, and there exists, in quite a few organisms, a mutant form of the gene. So, If the standard gene is labelled M, and the defective version is labelled m, four possibilities arise. An organism can have the following combinations of genes:

MM - a normal gene on both halves of the chromosome pair
Mm and mM - one copy of each gene on the different halves of the chromosome pair
mm - a copy of the defective gene on both halves of the chromosome pair

Now, what happens is determined by which gene takes precedence. The one that takes precedence is the dominant gene, and the other one (the one that is overridden) is the recessive gene. Dominant genes are usually labelled with capital letters, recessive genes with small ones. Which, should tell you that the normal Melanin gene is dominant, if you look at the above!

So, if a fish inherits a normal M from the mother, and a normal M from the father, the fish will be MM, and produce mormal Melanin (black pigment). If the fish inherits an M from one parent, and an m from the other, it will be Mm or mM. in this case, it will still produce normal black pigment because the normal version of the gene, being dominant, overrides the defective version.

Now, if a fish inherits a defective m from both parents, it will end up as an mm fish, and will not produce black pigment. It will be an albino. Albino Corys follow this pattern.

That's the basic mechanics of single factor inheritance in a nutshell. Any visual feature of a fish that is controlled by a single gene will operate in this manner. If the visual feature is controlled by more than one gene, then it starts to get a bit more complicated, but even so, the basic rules of heredity still apply if the gene in question is an autosomal dominant/recessive type gene. If the gene is a sex-linked one, then you're in for some fun and games, because with sex-liked genes, usually only males (or females, depending upon the chromosome determination for the organism in question) express the characteristic. This is what happens in human haemophilia - the factor VIII gene resides on the X chromosoms, and there are two versions, H (normal clotting factor gene) and h (defective). In this setup, a woman can possess the combination Hh on her X chromsosome pair. If she has a daughter, the daughter can inherit either H or h from the mother, but the father usually passes on an H gene, so the daughter becomes a carrier of the trait like her mother if she inherits h from her mother. If the woman has a son, however, and passes on the h gene in the X chromsosome, the father's Y chromosome doesn't have a matching copy, and hey presto, the son is a haemophiliac. In the past, haemophiliac males tended to die before they could reproduce, but the daughters continues carrying the gene.

Most selectively bred colour varieties of Angelfish are the result of performing selective matings between fishes that developed mutant genes. Knowing whether the mutant gene is dominant or recessive helps determine what kind of mating will be needed to preserve the new colour variety, and how 'true' the new variety will breed. Typically, a mutation for a new colour variety will be recesive, and back-crossings further up the parental line will be needed to 'fix' the new colour variety and create a breeding population to work with. However, some mutations are dominant, and when they appear, they breed 'true' appearance wise even when crossed with a normal fish. Knowing which is which will go a long way toward determining the outcome of your intended mating experiment.


Panda Catfish fan and keeper/breeder since Christmas 2002