Inbreeding question

[wilkyb]

If I adopt guppy fry from all the same mother, will the coming generations of offspring develop fading colours? Weaker immune systems etc?

 

I think I already know the answer, but if you have anything more to add then please do!

[Keeg]

Yes, overtime the offspring will be more likely to be deformed and have weaker immune systems. If you want to keep the color of a fish to be passed down, I would recommend getting a common female guppy. They are very dull in color, but when they breed, the baby boy's will almost have 100% of the colorings of their father. Make sure to get/ raise a virgin female for this as female guppies can hold sperm for a very long time. Plus if you have two males and want both of their genes, you might want to put them in separate containers to breed with females because the dominant trait almost always wins. Though breeders inbreed their guppies for particular traits, it will over time take a toll. You might be safe for awhile, just not forever.

Here's an article for a more scientific view

https://www.sciencedirect.com/science/article/pii/S0014489416300807

[Brandy]

No. 

Not necesarily. 

Guppies are fast breeders and sort of don't "bottleneck" easily. You WILL  have to select the best of each generation to carry on the line. This is true no matter where your stock comes from. I am basing this on years of experience breeding sibling crosses in a number of scientific settings. The genes that are "bad" have to be in the starting population and then have to be selected for either on purpose or accidentally. Colors fade because of depredation for instance, or if a negative gene (like embryonic lethality) is coexpressed with a desirable trait. A hobby breeder can and should be able to maintain a line starting from a trio, but they will need to be diligent and willing to cull.

Edited February 11, 2021 by Brandy

[Brandy]

In @Keeg's article, the scientists were NOT selecting for fitness. They were deliberatly only crossing sibling to sibling which does intensify recessive traits, not all of which are bad. In a colony breeding scenario you would have a "control" group of random matings, some cross generational some sibling to sibling. In a selective breeding program you can include in your selection criteria measures of fitness--size, health, growth rate, number of fry produced, color, etc. This will rapidly shift your population genetics in whatever direction you choose, provided you are able to be consistent. Not choosing the sickly but pretty male for instance. 

[lefty o]

with a large enough number of offspring, it shouldnt really be a big issue, but ideally at least every couple of generations you want to outcross them to help minimize the negatives of inbreeding the same family line.

[wilkyb]

48 minutes ago, Keeg said:

Yes

 

42 minutes ago, Brandy said:

No. 

HOW CAN THIS BE?|?!?!

[Keeg]

I would go with brandy, they have more experience. Ive just bred guppies from chain stores so their genes aren't the greatest to begin with. 

[wilkyb]

thanks for the quick response y'all,

I'll be more considerate of cross-breeding and breaking the lineage throughout the life of my aquariums

I'll be sure to make a family reunion themed aquarium, where all the cousins and brothers & sisters can have a ball.

[Brandy]

15 minutes ago, wilkyb said:

 

HOW CAN THIS BE?|?!?!

Lol. It very much depends on how you manage the line.

I do actually maintain inbred stock for years and years as part of my job. If you go past about the 5-10 year mark and you weren't paying attention, genetic drift can creep in and mess things up. But if you just want pretty and healthy guppies, you will be fine--remove any that are not pretty or healthy and within approximately 3 generations you will have one heck of a bulletproof line of pretty fish, assuming you started with pretty fish and they were reasonably healthy to begin with. The key is how many fry guppies have over their lives--if you deliberately CHOOSE  to keep crossing only the best, however you define that, then they will give you that because the top 10% of every generation is still a large number of individuals.

I have rescued inbred lines when they were near to failure by just using sibling crosses, breeding a ton, and culling hard. Most hobbyists don't want to do that, and it is certianly easier to start with healthy stock, but if it can be done with sick stock, it can surely be done with healthy. In our case we are working with geneitcally engineered strains and they are by definition sick to begin with, because the are disease research model animals. They are also worth hundreds and hundreds of dollars per individual.

Edited February 11, 2021 by Brandy

[wilkyb]

22 minutes ago, Brandy said:

Lol. It very much depends on how you manage the line.

I do actually maintain inbred stock for years and years as part of my job. If you go past about the 5-10 year mark and you weren't paying attention, genetic drift can creep in and mess things up. But if you just want pretty and healthy guppies, you will be fine--remove any that are not pretty or healthy and within approximately 3 generations you will have one heck of a bulletproof line of pretty fish, assuming you started with pretty fish and they were reasonably healthy to begin with. The key is how many fry guppies have over their lives--if you deliberately CHOOSE  to keep crossing only the best, however you define that, then they will give you that because the top 10% of every generation is still a large number of individuals.

I have rescued inbred lines when they were near to failure by just using sibling crosses, breeding a ton, and culling hard. Most hobbyists don't want to do that, and it is certianly easier to start with healthy stock, but if it can be done with sick stock, it can surely be done with healthy. In our case we are working with geneitcally engineered strains and they are by definition sick to begin with, because the are disease research model animals. They are also worth hundreds and hundreds of dollars per individual.

so this genetic disparity is inevitable due to the nature of sexing?

 

Meaning somebody who breeds guppies for the best genetics would have an interest in having a tank of inbreds that are deemed at some point worth culling?

 

I suppose within a closed group of guppies who breed, the culling of degenerates is a requirement if we want to reduce the chances of the lower 10% mixing with the top 10% (where the top 10% have less to gain from the lower 10% in terms of new genetic code)

how bout’ them apples? am I on the right track here?

 

Edited February 11, 2021 by wilkyb

[Brandy]

26 minutes ago, wilkyb said:

 

how bout’ them apples? am I on the right track here?

 

I think so. It is also because guppies breed so fast and make so many combinations that you have more chances, getting some of everything, and SOME of those will be what you want. If 50% of those are absolutely NOT what you want, no big deal, you still have plenty to pick from. As long as the ones you don't want are removed, and you keep breeding, you WILL eventually get what you do want, provided it was there in some way in the first place--they won't grow feathers no matter how hard I try. I think that project might take longer...

Humans on the ohter hand only produce a handful of offspring in their lives. If half your children are culls this is a tragedy, which led to the taboo against inbreeding in humans, and is also why this is to be avoided in larger animals in general.

[Socqua]

Culling of children also was frowned upon in certain small circles 🤐

 

[Brandy]

Well, yes. There is that. 🙂

I am so glad this is not the sort of place one will get flamed for this type of conversation.

I love genetics and explaining how they work. I may love selectively breeding animals and I have a degree in molecular biology which just means I planned to become a genetic engineer, but I am NOT a fan of human eugenics for a million ethical reasons. I love the mechanics of how population genetics work but I have no interest in attempting to direct human population genetics. 

 

Edited February 12, 2021 by Brandy

[wilkyb]

56 minutes ago, Brandy said:

Well, yes. There is that. 🙂

I am so glad this is not the sort of place one will get flamed for this type of conversation.

I love genetics and explaining how they work. I may love selectively breeding animals and I have a degree in molecular biology which just means I planned to become a genetic engineer, but I am NOT a fan of human eugenics for a million ethical reasons. I love the mechanics of how population genetics work but I have no interest in attempting to direct human population genetics. 

 

Observing genetic phenomena is fascinating, but replicating it in a lab does have this odd sort of interest about it, doesn’t it? Our labs being our aquarium

Edited February 12, 2021 by wilkyb