Can guppies change sex?

[Barbvday]

I have not seen it personally but I’ve heard that female only tanks can sometimes have a female turn into a male? Is that the case?

 

[Chick-In-Of-TheSea]

@Guppy Guy @Guppysnail ?

[sumplkrum]

On rare occasions I do find a male fish in with my separated females.

I can't confirm that they actually change sex though. Small fish can be difficult to sex and some of them develop late.
I chalk it up to human error. "I thought I saw a gravid spot, but it must have been late developing male that fooled me."

I've never seen any evidence of older fish changing sex. I imagine if it was possible an adult could change ... but adults are drastically different physiologically.

[PineSong]

I have experienced juveniles that look female developing male characteristics more than one month after the other males in their litter. I have seen this with platies and with guppies.
I do not think it is truly a case of female fish becoming male, I think they just look female by default and are late bloomers.

I’ve never seen a fish that I put in the boys tank later appear to be female.

I did read an article that said platies have more options for sex chromosomes than just X and Y. They have a W option and the fish that have a W chromosome can develop either way according to environmental factors, maybe? I don’t recall the details.

[TheSwissAquarist]

@PineSong I have also experienced this, and I expect that overbreeding has caused some genetic deficiencies (de-fish-encies😁) which mean that some guppies are just late bloomers.

[bryanisag]

Insert: "life finds a way" meme here

[Barbvday]

On 7/27/2022 at 6:36 AM, TheSwissAquarist said:

@PineSong I have also experienced this, and I expect that overbreeding has caused some genetic deficiencies (de-fish-encies😁) which mean that some guppies are just late bloomers.

That’s what I was thinking… most likely just misgendering young fish rather than actual sex changes.

[gardenman]

I've never seen it with guppies, but I've seen it with swordtails. The difference in body size, shape, and structure with most fancy guppies makes it a harder transition than for swordtails and platies. By the time they're more than a few months old, most female guppies will be significantly larger than the males with a stockier build.

It's common for some marine fish to change genders, sometimes several times, depending on the population of their section of the reef. A male fish can become female if there are too many males and then the next year be a male if there aren't enough males.

[PineSong]

On 7/27/2022 at 6:36 AM, TheSwissAquarist said:

@PineSong I have also experienced this, and I expect that overbreeding has caused some genetic deficiencies (de-fish-encies😁) which mean that some guppies are just late bloomers.

You know, IDK whether it would even be a deficiency--it may be genetically advantageous in some circumstances.

I think about it like this: A fish that I think is female goes into my female guppy tank, then develops as a male and I don't immediately notice. (This happened to me last week, so it's fresh in my mind.) That male now has access to 40 females and can impregnate all of them, thereby producing thousands of offspring. Evolutionary win!

His early-blooming male littermates are safely tucked away in the male guppies tank, where they have no chance of reproducing unless there is something particularly striking about them that I want to breed. Therefore, almost no chance of reproducing. Evolutionary defeat!

I picture my high school: some guys could grow full-on lumberjack beards by senior year. Other guys  could barely  grow peachfuzz by age 18 but have full beard possibilities by age 30. Maybe that difference is irrelevant in our society because both bearded and non-bearded men are equally likely to reproduce.

But in another society it might be better to have early-developing genes if that means you can start breeding earlier in life and therefore produce offspring for more years.

And then let's say you live in a warrior society where once you have a full beard you move to the front lines....in that society men without beards might live longer and produce more offspring, and being an early bloomer would be genetically disadvantageous.

With guppies being able to have a new generation every 6 months, if they have been in captivity since 1859, that's 326 generations--I don't know enough about genetics to know if that's enough time for late blooming to be selected as a favorable trait. Maybe @Biotope Biologist would know.

 

 

[TheSwissAquarist]

On 7/27/2022 at 4:40 PM, PineSong said:

You know, IDK whether it would even be a deficiency--it may be genetically advantageous in some circumstances.

I think about it like this: A fish that I think is female goes into my female guppy tank, then develops as a male and I don't immediately notice. (This happened to me last week, so it's fresh in my mind.) That male now has access to 40 females and can impregnate all of them, thereby producing thousands of offspring. Evolutionary win!

His early-blooming male littermates are safely tucked away in the male guppies tank, where they have no chance of reproducing unless there is something particularly striking about them that I want to breed. Therefore, almost no chance of reproducing. Evolutionary defeat!

I picture my high school: some guys could grow full-on lumberjack beards by senior year. Other guys  could barely  grow peachfuzz by age 18 but have full beard possibilities by age 30. Maybe that difference is irrelevant in our society because both bearded and non-bearded men are equally likely to reproduce.

But in another society it might be better to have early-developing genes if that means you can start breeding earlier in life and therefore produce offspring for more years.

And then let's say you live in a warrior society where once you have a full beard you move to the front lines....in that society men without beards might live longer and produce more offspring, and being an early bloomer would be genetically disadvantageous.

With guppies being able to have a new generation every 6 months, if they have been in captivity since 1859, that's 326 generations--I don't know enough about genetics to know if that's enough time for late blooming to be selected as a favorable trait. Maybe @Biotope Biologist would know.

 

 

Are you a University professor in biology 🙃? 
 

I do agree though that it would be genetically advantageous to mask one’s male sex for a while (especially as males tend to be more colorful and therefore are more likely to be eaten). That said there would be no need to do so in a controlled environment (aquarium).

[Biotope Biologist]

Y’all I think are definitely there intuitively. 

 

Guppy females and non dominant males in the wild will display their cryptic camouflage to hide from predators. Typically the dominant male(s) of the group are considered stronger and can outrun predatory fish. They are usually older, younger males will hide with the females to escape predation and male-male competition. This leads to some sneaking around. The males that appear female avoid detection from the competing males and can slip into the courtship mix unnoticed to spread their genetics. It’s a very interesting tactic that has evolved multiple times in different species.

 

As for physically being able to change sex. It should be exceedingly rare. But it is possible. I believe it takes extreme external factors for this to happen in most animals. Other fish species with different hierarchy systems can change their sex based on sexual competition. But those are specific species. See clownfish or sheepshead wrasse.

 

This article is worth a read. It’s rare in scientific articles but the ‘methods’ section actually describes  the natural history of the sexual selection in guppies. Worth a read for those who are active breeders:

https://www.researchgate.net/profile/Mullica-Jaroensutasinee-2/publication/12840816_Operational_sex_ratio_influences_female_preference_and_male-male_competition_in_guppies/links/5ac0a9c20f7e9bfc045c6480/Operational-sex-ratio-influences-female-preference-and-male-male-competition-in-guppies.pdf

[Guppy Guy]

While I have no scientific behind this, here is my 2 cents.

I have never seen a guppy change sex after it is born, but I did see where the water temperature they are born in could affect it. I have not seen this in my tanks though.