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Guppy genetics question


Scapexghost
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Some of you my remember the guppy i had in This tank a while back, and while the little lady has since passed she is survived by a dozens of sons and daughters and hundreds of grandsons and granddaughters. The strange thing is, all the daughters and granddaughters have blue tails like their matriarch while the males all have red tails. Is this common? I understand variation in color in offspring but i dont understand why it would be tied to sex.

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Very common in guppies and other fish to show coloration differences between sexes. Most female guppies are more of a drab color, while the males get to show off. Very common in nature as well. Called sexual dimorphism. It’s why male cardinals are bright red and females are brown. Also why big box pet stores mostly sell only male guppies. They have the best appearance 

It’s males competing with other males for mating rights 

 

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On 2/2/2024 at 10:03 PM, Tony s said:

Very common in guppies and other fish to show coloration differences between sexes. Most female guppies are more of a drab color, while the males get to show off. Very common in nature as well. Called sexual dimorphism. It’s why male cardinals are bright red and females are brown. Also why big box pet stores mostly sell only male guppies. They have the best appearance 

It’s males competing with other males for mating rights 

 

I understand that, but thats not what i am saying. The males are much more colorful that the females, but its the color itself i find odd. In most guppy strains, the amount of coloration varies, but not the color

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It may just be a side effect of the breeding. The color of a lot of animals is on the x gene. When you have males they’re missing the tail of the x. So it shows differently. It’s why you can’t have male calico cats. Males only express one gene while females express both. So male cats have either red or gray, not both. Females can show both red and gray, so they have calicos 

guessing it’s the same mechanism In guppies. There’s one species of cichlid that the male is purple but the female is yellow. (Or vice versa). Was trying to find the species, but the name escapes me for the moment 

 

Edited by Tony s
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I’m not super familiar with guppy genetics(or really genetics at all if I’m realistic lol) but it sounds like the colors could be sex linked traits where the gene determining color is in the sex chromosomes like Tony was talking about. It’s be really interesting to continue breeding them and see if that was indeed the case or if you could get blue tailed males or red tailed females.
 

After a quick search I found that guppies do indeed have sex chromosomes as most fish do. I know at least some reptiles and I believe some fish actually don’t have sex chromosomes and their sex is determined by temperature during embryonic development. I couldn’t name any fish off the top of my head but I recall reading somewhere that there are fish like this. I’d guess in those cases maybe sex linked traits aren’t a thing but again my genetics knowledge is lacking. Kind of went on a tangent there but a cool concept nonetheless. 
 

Pretty neat to have a split like that show up in your tank!

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My “purple dragon” guppies that were supposedly pure for many generations, fairly frequently have red pop out in the male’s tails but none in females tails.

There are many, many instances of sex linked color differences across many families - fish, birds, reptiles, spiders, other insects, to name a few, and including mammals - like the example cited for how rare calico manifests in male cats (something like 1 in 10,000 is what I read / hear most often but I’ve never seen a legit source quoted to back that number) and nearly all male calicos are reported to be sterile.

I don’t know enough about guppy genetics to give you the specific reason why the red only manifests in your males @Scapexghost, but I’m certain there’s differences in either gene presence or expression / suppression / activity that’s behind it.

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On 2/4/2024 at 2:05 PM, Odd Duck said:

My “purple dragon” guppies that were supposedly pure for many generations, fairly frequently have red pop out in the male’s tails but none in females tails.

There are many, many instances of sex linked color differences across many families - fish, birds, reptiles, spiders, other insects, to name a few, and including mammals - like the example cited for how rare calico manifests in male cats (something like 1 in 10,000 is what I read / hear most often but I’ve never seen a legit source quoted to back that number) and nearly all male calicos are reported to be sterile.

I don’t know enough about guppy genetics to give you the specific reason why the red only manifests in your males @Scapexghost, but I’m certain there’s differences in either gene presence or expression / suppression / activity that’s behind it.

purple is supposedly about the hardest color to keep pure in guppy's. purple dragons, i saw a tank full of them once, marked all sold, and they were very cool looking. i would have bought a trio or three of them, they are a great looking fish.

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@Scapexghost your question intrigued me enough to take a look at the scientific papers on this. I have never owned guppies, nor am I super knowledgable about genetics, so take it with a grain of salt. Just to look fancy I'll throw in a reference at the end, if someone wants to take a look. I won't bring too much new to the discussion, but hopefully this helps you forward. I'd also appreciate if someone with real experience in guppy genetics could chime in.

As others pointed out, the reason for males having red tails and the females blue, lies in the colour genes being on the sex chromosomes. In the case of guppies they're in the X- and Y-chromosomes. These are not quite like the human ones as far as I've understood, the Y-chromosome on guppies being larger and housing more genes than the human one. But they are otherwise similar enough for our purpouse. The colour coding genes are usually on the Y-chromosome, but they can jump (usually through crossing-over events) to the X-chromosome too. This is why guppy males are usually colourful, while female are drab, but also why the females too can get some colours.

In your case, my guess is that the father fish had a red tail gene on his Y-chromosome, while your mother fish had the blue tail gene on her X. Since females only get X-chromosomes they will also only inherit the blue tail. What makes me scratch my head however, is the fact that males get just red tails. See, both colours are dominant, so a male with X(blue) and Y(red) should theoretically express both and maybe have some blending of both. Or there should be some blue tailed mles, if the genes are shut off randomly. If that's not the case, then I would guess there are some male hormones that suppresses the expression on the X-chromosome (maybe the whole chromosome or maybe just some genes?). That's all I got for now, I'll await eagerly for the critics to tear me apart 😅

Here's a paper that kind of summarizes work on the colour genes involved:
Khoo, G., Lim, T. M., Chan, W.-K., Phang, V. P. E. 1999. Linkage Analysis and Mapping of Three Sex-Linked Color Pattern Genes in the Guppy, Poecilia reticulata. Zoological Science 16(6):893-903

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On 2/9/2024 at 1:44 PM, Dreams of Aquariums said:

What makes me scratch my head however, is the fact that males get just red tails. See, both colours are dominant, so a male with X(blue) and Y(red) should theoretically express both and maybe have some blending of both.

Some of the males have some green in their tales, especially the youngest generation. So, id say your theory holds water.

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On 2/4/2024 at 3:05 PM, Odd Duck said:

There are many, many instances of sex linked color differences across many families - fish, birds, reptiles, spiders, other insects, to name a few, and including mammals - like the example cited for how rare calico manifests in male cats (something like 1 in 10,000 is what I read / hear most often but I’ve never seen a legit source quoted to back that number) and nearly all male calicos are reported to be sterile.

The reason male calicos are sterile is that they have triploid genes. not xy any longer but xxy. and the extra x chromosome is what carries the second color. triploidy also causes then to be sterile as the chromosomes no longer match with the female cat. 

Edited by Tony s
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On 2/9/2024 at 2:06 PM, Tony s said:

The reason male calicos are sterile is that they have triploid genes. not xy any longer but xxy. and the extra x chromosome is what carries the second color. triploidy also causes then to be sterile as the chromosomes no longer match with the female cat. 

Triploidy calico males (the most common male calico (around 1:1000 or 1:3000 or 1:10,000 depending on the resource) are nearly always sterile, but male chimera calicos or even more rare, spontaneous mutation while developing males, can be fertile.  These very rare conditions are likely no more than 1:10,00 or 1:100,000 depending on which resource you quote.

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That is true. I'm guessing it's closer to the 1:100000. A male chimera (cats that have the split face, color dividing line down the middle) contains 2 complete set of DNA to start with, and one of those sets has to be the triploid. the 1:3000 to 1:10000. It's usually fertile from the other set of DNA and not the triploid set

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On 2/9/2024 at 6:29 PM, Tony s said:

That is true. I'm guessing it's closer to the 1:100000. A male chimera (cats that have the split face, color dividing line down the middle) contains 2 complete set of DNA to start with, and one of those sets has to be the triploid. the 1:3000 to 1:10000. It's usually fertile from the other set of DNA and not the triploid set

Chimera can be orange patches on white one side, black patches on white on the other, so each could be fertile but by the definition of calico, still a calico and perfectly fertile but would not throw calicos of course.

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On 2/9/2024 at 8:26 PM, Tony s said:

Yeah, I suppose that's true. all red on one side and all black on the other. would be a really cool animal.

Yep.  I’d LOVE to see one!  The gene for patches of color on white is separate from the genes for color, so it could happen and would be amazing.  I also lean towards that likely to be in that 1:100,000 range or less to get a true chimera with color patches divided side to side.  Because of how embryos merge, it could have only a small amount of black or only a small amount of orange.  Like only one leg could have an orange patch and the rest of the cat could be black patches on white or vice versa.  We tend to think of chimeras being perfectly split down the middle, but they aren’t always.  They can be uneven and sometimes extremely uneven.  But split perfectly down the middle - that would be truly epic!

And apologies to @Scapexghost for getting completely side-tracked into a calico cat genetics discussion instead of guppy genetics discussion.

SQUIRREL! 🐿️ 🥜 🌰 

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