Many generations of guppy inbreeding

[jz23534]

One of my teachers at school gave me some guppies (maybe five or six) about 8 years ago that I have kept ever since. They have continued to breed for several generations and I am wondering how many generations it will take for them to start having genetic problems. During the most recent batch of 3 fry, I noticed they appeared much darker in color than normal (some of them were nearly black compared to the light tan color they normally are). I usually separate them into another tank so they don't get eaten, but after a few days one of them died while the other two survived and have since grown up with no apparent problems.

This was the first time I've ever had a fry die on me (without being eaten by the bigger guppies). I don't know how likely it is that it would have been caused by a genetic problem. I also don't know why the fry were so much darker than I've ever seen before.

How many more generations can they go before having serious problems or becoming infertile? We are probably on generation 5 or so at this point. Should I buy new guppies at the store and add them into the tank to increase the genetic diversity?

 

[Alice B]

I hadn't bought guppies since probably 2005? eventually no pretty colors so in 2020 I added a male back in from the original group that had been at a friend's since 2017, and I got a little color. bought 2 fancy males in early 2022 and i have a lot of color now. Except the deformed spine that I think occurs because a fresh baby doesn't get to the surface for air fast enough, which I think I have one affected fish right now, I don't see any genetic problems

 

[jz23534]

I hadn't bought guppies since probably 2005? eventually no pretty colors so in 2020 I added a male back in from the original group that had been at a friend's since 2017, and I got a little color. bought 2 fancy males in early 2022 and i have a lot of color now. Except the deformed spine that I think occurs because a fresh baby doesn't get to the surface for air fast enough, which I think I have one affected fish right now, I don't see any genetic problems

So it sounds like they will be OK for many generations more then. Thanks

 

[Alice B]

I think so.

 

[CaptainBarnicles]

@emeraldking is the man to ask

 

[davros]

I am curious if the overall coloration has changed over this time?

 

[emeraldking]

It depends on the bloodline how strong or how weak the genetics will be. This means, there's no accurate number of generations to tell when the first deformities will show up.
About coloring differently within the same bloodline, means that some recessive genes that haven't been shown for generations came back. For if you cross brother and sister or cousins with the same dominant and recessive genes, recessive genes can be enhanced and come out phenotypically. That's what has happened in your case.

 

[Colin_T]

No animal (including birds, fish, reptiles, mammals, insects) should be inbred with it's siblings.

Any time you inbreed them, you risk increasing genetic weaknesses and destroying the organism. If a fish has a genetic weakness and you inbreed it, then all the offspring carry that weakness.

Fish from pet shops are generally related to begin with and having them inbred for multiple generations is not doing them any good. There's a reason why people aren't allowed to marry family members and genetic defects are the main reason. Get yourself some new fish and mix up the bloodlines.

Make sure you quarantine any new fish so they don't introduce diseases into your tank.

 

[emeraldking]

No animal (including birds, fish, reptiles, mammals, insects) should be inbred with it's siblings.

I do agree with that. But you know that most breeding forms of animals are a result of inbreeding to start with, before new blood was added to the bloodline.

Fish from pet shops are generally related to begin with

Exactly! You could just buy fish from different stores, but if they came from the same wholesaler, there's a good chance that those fish are related. So, buying fish from different stores to avoid inbreeding, doesn't guarantee anything.

There's a reason why people aren't allowed to marry family members and genetic defects are the main reason.

True! But it still happens. In certain cultures, it's even normal to wed within the family. I personally would resent that. But that's my point of view, of course.

 

[Alice B]

I just try to introduce new fish now and then, best I can manage, and I am keeping an eye on my albino bristle nose because there may be a daughter in with daddy. I'll try to catch her