DJRansome wrote:I think I got about 1/3 of that. So many of the fish marketed as albinos are hybrids. When breeders create these fish, do they have to start with a fish that has a mutation that causes a lack of pigment? As opposed to starting with a true albino? Because any cross between a true albino and a normal fish will not show any albino characteristics because the albino genes are recessive?
I seem to have done more to confuse the situation than to clarify it, which was not my intent. There are several issues here; so let's try to parse them out.
First, let's clear up the confusion regarding true albino fishes and amelanotic fishes. Both of these seem to be called 'albinos' in the aquarium hobby.
A true albino cannot make any pigment. There are several genes that can result in this phenotype, and they are all inherited as autosomal recessives. Albino fishes tend to look like this; that is, they have no pigment-
Fishes with ocular albinism
are amelanotic, that is, they cannot make black (melanin) pigment. Thus, they have pink eyes, and lack melanin pigment elsewhere in the body as well. Such a fish may look like this-
Clearly this fish has lots of (yellow) pigment; it is just lacking black pigment. The genes causing ocular albinism
are X-linked, and are inherited differently from those encoding true albinism. Or to put it another way, albinism
and ocular albinism
are two completely different phenotypes that are completely independent of each other. That said, for the sake of this discussion, let's just use the term 'albino' to refer to either phenotype, as this is how the term is used in the hobby.
So to your questions, a bit out-of-order.
(1) 'When breeders create these fish, do they have to start with a fish that has a mutation that causes a lack of pigment? As opposed to starting with a true albino?'
No. As I tried to explain above, true albinism and lack of melanin pigment are two different phenotypes. What the breeder will do is look for fishes that are different among the many thousands that they raise every year. Some of these may be true albinos, some may be amelanotic; either are easy to spot amongst a group of wild-type fishes. Those 'sports' are then set aside, crossed to normal fishes, and their progeny are backcrossed using standard genetic strategies to get pure albino or amelanotic strains.
(2) 'So many of the fish marketed as albinos are hybrids.'
That may be true for Malawians, because they hybridize so readily. Thus, if you have an albino of Species A (something that occurs only rarely), you might try to get the albino
gene into a new genetic background by making an interspecific hybrid between Species A and Species B. This seems to be a common practice among peacocks, which hybridize readily and look very similar anyway. As noted by noki
, some albino Mbuna may also be interspecific hybrids. But that has nothing to due with whether pure abinos are healthy or not; it's just a shortcut to move albino
alleles between species.
(3) 'Because any cross between a true albino and a normal fish will not show any albino characteristics because the albino genes are recessive?
' Yes, just that. It is only in the second generation that albino fishes start to appear; in the previous generation all the fishes appear wild-type,although some of them are 'carriers' of the albino gene.
I hope that helps!