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Do you find any Albino Corydoras in the wild?.

http://www.flickr.com/photos/corydoras/
Member of the Malta Aquarist Society - 1970.
http://www.maltaaquarist.com

Very, very, rarely, if at all.

It is entirely possible since albinism is a naturally occuring mutation in many animals, but chances are the albino cory would be picked off very early in life by predators because they lack any sort of camouflage.

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I'm not your neighbor, you Bakersfield trash.

Indeed. albinism is more common than one would expect in the wild (not that it is common to any extent). However, again, physical limitations disallow the survival of the indivdual fish.

Thanks alot for your reply's.

http://www.flickr.com/photos/corydoras/
Member of the Malta Aquarist Society - 1970.
http://www.maltaaquarist.com

Of course, one hsd to be careful here, as I was reminded by one of the Cichlid keepers - there's a difference between single-factor recessive albinism (which is the kind of albinism being discussed here) and polygenetic albinism (which I am told occurs in Kribs among other fishes).

Single-factor recessive albinism, as the name suggests, is controlled by a single gene - the gene that codes for the production of melanin. If that gene becomes faulty, then chances are you won't notice the fact becuse the 'normal' melanin gene (usualy labelled 'M' in elemntary studies - dominant genes are labelled with capital letters) is usually dominant. As fishes, like most vertebrates, have two copies of the gene (one on each part of the relevant chromosome pair) the 'normal' gene, if present, masks the effect of the defective gene (usually labelled 'm' - recessive genes are labelled with small letters). Albinism in this case only manifests itself visibly if the fish inherits TWO copies of the defective gene, one from the mother and one from the father. In that case, melanin production is disrupted, and the classic pink body colour and red pupils shows up. That, incidentally, is how you know that the albinism you're dealing with is single-factor recessive albinism - the pupils are red, because there's no melanin to mask the blood in the retina showing through.

With polygenetic albinism, it's a different story. Here, there are multiple genes responsible for the overall pigmentation of the fish, and these are integrated into what is called a 'polygene complex' - similar to the complex that is responsible for the Rhesus factor in humans. Incidentally, one of the former members of my Entomology Society won accolades for his work on polygenes, which he originally studied in Papilio dardanus butterflies (in this species, the polygene complex governs the wing pattern of the mimetic females, which differs from population to population across Africa - males are all uniformly black and white). When doing this research in his spare time, Professor Sir Cyril Clarke, who was the leading light of my Entomology Society until his death in 2000 AD, realised that a similar mechanism governed the appearance of the Rhesus factor in humans, and thus allowed him to devise means of treating the so-called 'Rhesus baby syndrome' when he worked as a doctor at a Liverpool hospital in the 1950s. For his work, and the resultant saving of many childrens' lives, Cyril Clarke was knighted, and ultimately became the President of the Royal College of Physicians, and in 1980 won the Lasker Award jointy witn Professor Ronald Finn, a co-worker, for research into the causes and prevention of Rhesus Haemolytic Disease in babies. (He was also nominated for a Nobel prize, but in 1980 that prize went to Benasserat, Daucet & Snell for their work in the genetic of the immune system).

Polygenetic albinism usually (but not always) differs in that melanin production does not cease altogether, but is absent from the outer integument. Polygentic albinos may have 'normal' looking eye pupils, and can be sometimes difficult to distinguish from 'xanthic' morphs, where the black pigment is reduced and increased yellow pigment supplants it.

Albino Corys are, as far as I am aware, the products of single-factor recessive albinism. There is an easy way of determining this, and that is by mating an albino with a 'normal' fish. If the 'normal' fish has no defective gene present in its genotype, all of the offspring will be normal-looking, but have one copy of the M (normal melanin) gene, and one copy of the m (defective melanin) gene. Mating the offspring will produce a distribution of young as follows:

25% with MM genotype (true normals)
50% with Mm genotype (albino carriers, normal in apperance)
25% with mm genotype (albino individuals)

If the 'normal' fish in the first mating is a Mm individual instead of an MM indivdual, then the outcome of the first mating will be:

50% Mm (albino carriers, normal in appearance)
50% mm (albino individuals)

As albino Corys are usually albino individuals of the Bronze Cory, Corydoras aeneus, and this species produces a LOT of eggs and fry when mated, the ratios are usually replicated with only a small margin or error, as the population of offspring is large enough (a large female can lay 400 eggs).

With polygenetic albinos, the situation is FAR more complex, and you would need the assistance of a professional geneticist to work out the likely ratios of mating a polygenetic albino to a 'normal' fish, the resulting offspring almost certainly turning up a range of interesting patterns!


Panda Catfish fan and keeper/breeder since Christmas 2002