Today's Glaser Ad.....

[BallAquatics]

Dennis

[BillT]

These guys do really great pictures all the time.

[PaulineMi]

Beautiful photos.

One thing I've noticed in wild caught vs "show quality" discus......the extreme circular shape seen in show fish isn't apparent in wilds.  Liz and Barb....care to comment on that? 

My initial reaction is that it's comparable to what we do with other species destined for the show ring. In fish there are many very beautiful man made specimen. Ma nature does exceptional work also. 

[BallAquatics]

My initial reaction is that it's comparable to what we do with other species destined for the show ring. In fish there are many very beautiful man made specimen. Ma nature does exceptional work also. 

I have heard Charles Clapsaddle of Goliad farms speak of this when trying to maintain lines of wild-type livebearers.  Homo sapiens is a conceited & invasive species that believes everything is better with their meddling.  LOL   

Dennis

[Ron Sower]

I have heard Charles Clapsaddle of Goliad farms speak of this when trying to maintain lines of wild-type livebearers.  Homo sapiens is a conceited & invasive species that believes everything is better with their meddling.  LOL   ;)Dennis

We are individual gods, aren't we?  At least that's the way humankind usually approaches nature, in my opinion. And I guess I'd better not get started on that rant.

[PaulineMi]

I know the natural-vs-man-made issue is a controversial one.  While nature does it best, I have a lot of respect for what some of the serious breeders create and dedicate a portion (or most) of their lives to developing.  It's when freaks like those seen in goldfish and parrot cichlids start showing up that I get disgusted with what we do.

[BillT]

I agree Pauline.

There are several ways that fish can get changed genetically through the breeding process in captivity:

1) intentional (human) selection for visible traits

2) unintentional selection for traits due to their being adaptive to a new (captive) environment. This could be something like fish the come to the front of the tank when they are fed get food and therefore have an adaptive advantage and are unintentionally selected for. I would usually consider this a bonus because these fish are better adapted to living in a fish tank and would do better. Another example could be likelihood to breed in a tank. An obvious adaptive trait for a tank as an environment.

3) Random genetic drift: This has to do with small breeding populations and not a lot of genetic mixing and introducing new genetics to restore which might be randomly lost.

Zebrafish (as a stand-in for other less well researched fish) have about 30,000 genes (coding for proteins). Genetic diversity is limited by the number of animals in the breeding population of the previous generation. The number of different alleles of a particular gene is limited to 2 times the animals in the breeding population. The closer the members of the breeding population are related, the less genetic diversity they will have. When two animals breed each individual fertilized egg is the result of a random grab of chromosome sets (one of each chromosome pair) from each parent. Gradually this process will eliminate particular alleles from the breeding population until only one may be left. This process is repeated 30,000 times for each gene everytime a cross is made. It will also build up each generation. Spontaneous mutation rares are small and will only maintain a small background level of diversity against this process. Introducing new fish with different genetics however will have a powerful effect on genetic diversity.

As Dennis said, Charles Clapsaddle is good at explaining these things. There are a few podcasts I have heard of him talking about this stuff.