Swordtail fry always all female

[Ogertron3000]

Like the title says, I have 1 male and 2 female swordtails. They breed constantly, I leave the fry in the tank as a survival of the fittest scenario. I now have numerous fry of all sizes/ages and for some reason every single one is female.

Just trying to figure out why this happens? I can only think of 2 possibilities, either something to do with the water conditions which somehow influences the sex of the fry or the male swordtail picks of the male fry so he can stay king of the castle?

I also have guppies in with them which also breed but very few of the babies actually make it to adult size. Im guessing this i most likely due to the swordtails being more aggresive and fast growing and eating them.

 

[Milingu]

For how long are you raising the swordtails?
I have some X. cortezi and it took a whole year for the males to devlop a visible genopodium and even longer to develop a sword. I raised them without any adult fish in the tank.
With common swordtails I had some late males that only showed male traits when they where big enough to compete with the other adult males.

If yours don't show any male traits after a year and after they reached adult size I would try to raise some without any adult male in the tank.

 

[Ogertron3000]

For how long are you raising the swordtails?
I have some X. cortezi and it took a whole year for the males to devlop a visible genopodium and even longer to develop a sword. I raised them without any adult fish in the tank.
With common swordtails I had some late males that only showed male traits when they where big enough to compete with the other adult males.

If yours don't show any male traits after a year and after they reached adult size I would try to raise some without any adult male in the tank.

The oldest ones are approx 4 months old. They are around half of the full grown adult size. Im not sure the correct name for it but the genital fin looks female too, not just the lack of swords.
It doesnt really bother me, my thinking is the more females the more fry eventually I am just curious why its happening. Maybe I should just be patient and wait and see. I didnt know it would take so long for the swords to grow on the males.
I will be putting a pair of rainbow cichlids in there when I can track them down, or convicts if I get too impatient so am happy to let the livebearers just do there thing until then. Im actually enjoying them a lot more than i expected to.

 

[Magnus_Bane]

Like the title says, I have 1 male and 2 female swordtails. They breed constantly, I leave the fry in the tank as a survival of the fittest scenario. I now have numerous fry of all sizes/ages and for some reason every single one is female.

Just trying to figure out why this happens? I can only think of 2 possibilities, either something to do with the water conditions which somehow influences the sex of the fry or the male swordtail picks of the male fry so he can stay king of the castle?

I also have guppies in with them which also breed but very few of the babies actually make it to adult size. Im guessing this i most likely due to the swordtails being more aggresive and fast growing and eating them.

I've honestly had the same issue with my mollies lately. Had over 40 of em born so far and each and every single one turned out to be female. Atm I only have the 1 male and 4 females. Fed the rest to my FH's. No clue on why it's happening either, totally stumped on why no males were born.

As for your situation ik that swordtails can freely swap gender on an almost daily basis. Not sure if that would make them all female tho. Seems a bit weird that all of em ended up the same gender and still refuse to have some turn into males.

 

[BIG-G]

Their has been a few studies that show sex ratio have been effected by temperature in guppies.

So I’d would guess that it may be true in other live bearers.

It would be an interesting project to try with swordtail or molly to determine if sex ratios are effected the same way.

 

[dr exum]

they can switch sexes -

i had a bunch of girls - then dominant female turned boy -

 

[Ogertron3000]

Thanks for the replies guys, all very interesting. Who knew the humble swordtail could be so mysterious.
I wonder if i took the male out then it might trigger one or more to switch sexes? It would be an interesting thing to try.
I ight get some more female guppies too, it might increase the survival rate of the guppy fry. The annoying thing is I dont like the swordtails I got all that much, just the stock standard orange ones, They were all that was available during our lockdown and now I have a tank full of them! I guess once I get the cichlids that will thin out the smaller fry a bit and keep the amount being born more manageable.

 

[Milingu]

I am not sure if they really switch sexes after a certain age. With small fry it might be possible since their gonads are not defined right away after birth.
I never had fry from any "female" that turned later out as male. They looked female including their anal fin before they developed a gonopodium.
I assume their gonadads were saying male all the time and they were simple not showing it.

So taking out the adult fully developed males might be worth a try.

 

[duanes]

With cichlids, it is well known that a higher or lower pH, or higher or lower temps can effect sex ratios in broods, so it is not out of the realm of possibilities that those type conditions could also have an effect on live bearers. One of the studies below suggest humic compounds could also be a cause.
In nature nitrate is almost non-existent as a component of natural waters, yet we as aquarists often accept nitrate concentrations or 20-40 ppm as normal healthy amount in our tanks. It might be an interesting experiment to alter temps, pH, or even nitrate concentrations (thru water changes) with your fry to see what happens with your broods.
The studies below can get a bit dry, I usually just read the first parts (intros) and the conclusions (discussion) and skip the middle, because the the majority of the rest is usually methods and detailed procedures, required by scientists to review and validate.
Sex inversion in domesticated strains of the swordtail ...www.tandfonline.com › doi › pdf
Xiphophorus helleri Heckel - Max Planck Institute for ...www.demogr.mpg.de › publications › files

 

[Magnus_Bane]

I am not sure if they really switch sexes after a certain age. With small fry it might be possible since their gonads are not defined right away after birth.
I never had fry from any "female" that turned later out as male. They looked female including their anal fin before they developed a gonopodium.
I assume their gonadads were saying male all the time and they were simple not showing it.

So taking out the adult fully developed males might be worth a try.

From my experience with swordtails is that it doesn't matter what age the fish is as long as the male and female ratio is out of wack the females should start turning into males and viscera. When I had mine I only had 3 of em, 1male 2 females, all were roughly 3½in when I got them and they constantly swapped gender. Only reason ik they were swapping gender was because each one had its own unique color compaired to the other 2 so when ya have only 1 orange one that was male yesterday and is suddenly female today it means it swapped gender lol. Really interesting to see that wild adaptation shows its self in a home like setting. From what I understand is that swordtails developed this adaption to avoid inbreeding and to avoid total extinction if one of the sexes were to die out for whatever reason. Even if thousands of em died within a single moment, as long as there is a small group left behind, regardless of gender, they should be able to bounce back with relative ease.

Honestly tho imo, even tho it is very interesting to see it can be very annoying if they do that while your trying to breed a small group like I was lol. Kinda bad when they can't even make up their own mind on who wants to be what gender at what time. Lol this is pretty much the only reason I refuse to try breeding swordtails again.