Swords keep turning male?

Kendramc

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I know that swordtails can change from female to male, but I though this generally happened when there was a shortage of males. I'm pretty sure I'm on my way to the four most mature swords all being male.

A while back, I got two new swords, a male and a pregnant female. After she had her fry, she became a he. I had lost all of my other mature swords by this point, just these two left with a handful of fry from various females who had since died, so my only adults were male. The oldest fry (from a different female) was male, the next oldest appeared to be female. I noticed the other day that either I was wrong or she is become a he too (see photo).

So I guess I have two questions. 1) do swords go from male to female? And what could be causing so many to switch to male?

Ok, third question. Should I go and pick up a few more females?

Thanks.
 

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Well, swords won't change from male to female. But certain specimens can change from female to male. For phenotypically, all swords start off as being female during the embryonic state. Yes, also females that got pregnant and produced fry can become male. But not all females are able to change into male. When we talk about sword females, we are talking about XX females. But it depends on the allele combination wether they are able to change sex. The sex change ability will only go for females that have the allele combination of the Aa genotype. But they'll always start off as being phenotypically female. These aa females within the XX combination are born with both male and female gonads. AA genotypes within the XX combination are initial females and will remain female all their lives. An aa genotype within the XX combination are initial males just like XY males. But aa males (XX combination) are mostly late males. They become large and will show the male characteristics when they're fullgrown. But there are also late males by suppression by dominant males. So, there are two ways why late males are in order.
Females that have changed into male will be fully functional males and they'll keep their gravid spot but that's not functional anymore. Neither can they become pregnant again.

What also happens is when we are dealing with an old female that won't be reproductive anymore, is that she will show some male characteristics. But this won't be a sex change. When an old female isn't reproductive anymore, there will be a hormone change (just like humans when she's hitting menopause) which causes an over activity of the MSX genes that are responsible for morphological change in fin tissue. This will result in a more elongated anal fin (Someone may get the impression that it's changing into a gonopodium but it's not) and elongated outer finrays on the bottom side of the tail. Such a female remains female.

There are also YY males and YY females in swordtails. But this goes for most swordtails that are only derived from a wild swordtail. For a lot of fancy swordtails are derived from crossing swordtail to platy. And while sex change in platies also occur, there's a "but" that we have to put in there when we look at the story given before. This is because sex change in real platies happens in a different way. Besides the X and Y chromosome, we also are dealing with a third chromosome "W" .
So, we're looking at X, Y and W as the basic sex chromosomes in platies. XX combination will be born female and remains female. WX are born female and have the ability to change sex but won't be functional males. WY are born female and have the ability to change sex and become fully functional males.

I'd also like to add that the socalled pseudo gravid spot in male platies, that that phenomenon has got nothing to do with a real gravid spot. if such a pseudo gravid spot will develop in a male platy, that it mostly develops when they juvenile to almost adulthood. Such a pseudo gravid spot is just a black marking on the same area where a female has got her gravid spot. But the gravid spot of a female is a more translucent part of the skin while the pseudo gravid spot is a black marking in the skin that has developed. Once a pseudo gravid spot occurs, it will never fade again.

Also if you keep those pregnant swords at a too high temperature during the pregnancy, more males will be born. Same goes for platies. This is not a 100% guarantee but most of the time, it does work.
 
Well, swords won't change from male to female. But certain specimens can change from female to male. For phenotypically, all swords start off as being female during the embryonic state. Yes, also females that got pregnant and produced fry can become male. But not all females are able to change into male. When we talk about sword females, we are talking about XX females. But it depends on the allele combination wether they are able to change sex. The sex change ability will only go for females that have the allele combination of the Aa genotype. But they'll always start off as being phenotypically female. These aa females within the XX combination are born with both male and female gonads. AA genotypes within the XX combination are initial females and will remain female all their lives. An aa genotype within the XX combination are initial males just like XY males. But aa males (XX combination) are mostly late males. They become large and will show the male characteristics when they're fullgrown. But there are also late males by suppression by dominant males. So, there are two ways why late males are in order.
Females that have changed into male will be fully functional males and they'll keep their gravid spot but that's not functional anymore. Neither can they become pregnant again.

What also happens is when we are dealing with an old female that won't be reproductive anymore, is that she will show some male characteristics. But this won't be a sex change. When an old female isn't reproductive anymore, there will be a hormone change (just like humans when she's hitting menopause) which causes an over activity of the MSX genes that are responsible for morphological change in fin tissue. This will result in a more elongated anal fin (Someone may get the impression that it's changing into a gonopodium but it's not) and elongated outer finrays on the bottom side of the tail. Such a female remains female.

There are also YY males and YY females in swordtails. But this goes for most swordtails that are only derived from a wild swordtail. For a lot of fancy swordtails are derived from crossing swordtail to platy. And while sex change in platies also occur, there's a "but" that we have to put in there when we look at the story given before. This is because sex change in real platies happens in a different way. Besides the X and Y chromosome, we also are dealing with a third chromosome "W" .
So, we're looking at X, Y and W as the basic sex chromosomes in platies. XX combination will be born female and remains female. WX are born female and have the ability to change sex but won't be functional males. WY are born female and have the ability to change sex and become fully functional males.

I'd also like to add that the socalled pseudo gravid spot in male platies, that that phenomenon has got nothing to do with a real gravid spot. if such a pseudo gravid spot will develop in a male platy, that it mostly develops when they juvenile to almost adulthood. Such a pseudo gravid spot is just a black marking on the same area where a female has got her gravid spot. But the gravid spot of a female is a more translucent part of the skin while the pseudo gravid spot is a black marking in the skin that has developed. Once a pseudo gravid spot occurs, it will never fade again.

Also if you keep those pregnant swords at a too high temperature during the pregnancy, more males will be born. Same goes for platies. This is not a 100% guarantee but most of the time, it does work.
Ahem 🧐 yes...what he said
 
That was a very thorough explanation. Thanks. I'm going to take it as the big female probably wasn't going to reproduce anymore so she changed, the young one probably was always male just didn't show until recently, and I should probably go get myself a few new females and keep the temp a bit lower to get more female fry. Is that a reasonable summary?
 
That's the kind of thing you read on this forum that really makes you feel small and puny. Don't get me wrong ! That's good stuff. Really good stuff. Where else but on The Great TFF Forums do you have instant access to knowledge like that ?
Always ready to learn! Definitely get schooled here anyway....
 
Btw, why can't a female that has turned into a male not turn back to female? Because, once the anal fin has changed into a gonopodium, the male hormones will overrule. And once the structure of the anal fin has changed, it's irreversible.
 
Btw, why can't a female that has turned into a male not turn back to female? Because, once the anal fin has changed into a gonopodium, the male hormones will overrule. And once the structure of the anal fin has changed, it's irreversible.
Ah yes, the male organ does tend to overule almost everything else on this planet 🧐
 
With all that out of the way lets get back to his questions:
So I guess I have two questions. 1) do swords go from male to female? And what could be causing so many to switch to male?
There are a number of possible enviromental factors that could trigger the change. Water temperature, TDS, and water flow should be considered. Water temperature has been shown to affect the sex of shrimp during development. And there is good reason to believe that seasonal changes in in TDS and water flow might also affect breading. However in most cases this has not been extensively tested in the lab.

You could change one thing in your tank and try again if you want. But that could take years. Another roach would be to find out wre these fish are caught and collect as much information about the weather and chemistry oof the water and try identifying what in your tanks is different than the natural environment. And then change that and try again.
 

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