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Sex change in livebearers?
January 16, 2013
5:26 pm
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plesner
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I'm considering putting together one long article or several shorter ones dealing with some of the myths we hear in the hobby.

 

One topic I consider is the stories about sex change in livebearers, especially guppies and swordtails. I am aware, that a lot of the stories are based on things like late developing males or old females, which end up looking like males, due to a change in the balance between male and female hormones.

 

My question is: Are there any known incidences of actual sex changes in livebearers - that is either a functioning male becoming a functioning female or vice versa? The more solid the evidence the better. Scientific papers on the subject would be very welcome too.

January 16, 2013
6:03 pm
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torso
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Hi

I kept guppys - wild form, swardtails - green wild form and orange - cultivated form and Neoheterandria elegans changing sex. For swardtails I'm shure, that females becoming males are fertile. The situation ocurred, when there was only one male in the group left - N. elegans or  with guppies. So I don't have evidence that N. elegans or guppys schanging sex were fertile. But: it wouldn't make sense otherwise.

In any case the females changing sex were always the largest in the group and by far larger than the "normal" males.

Cheers Charles

PS: what's your name?

January 16, 2013
6:47 pm
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plesner
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I've never experienced an old female, which developed male characteristics being even interested in the 'real' females at all. Usually they die of old age 3-6 months later (or at least that is what happens to mine). The female will remain the same size she used to, but develop a sword and the anal fin will even resemble a gonopodium Thus they will by far be the largest 'males'.

 

In certain species of swordtails, there is usually only one male - that is only one fish with obvious external male characteristics. The other males continue looking like small females. If/when that male dies, one of the smaller males (probably the strongest one) begins to develop male characteristics in a fairly short time and becomes the alpha male.

 

As far as Neoheterandria formosa goes, I suppose it makes sense for female N. elegans to look like males. I keep this species and the females can be really hard on each other. I try to keep so many together, that the aggressions don't cause casualties, because there are many 'victims' for the aggressive female(s) to harrass.

 

My name is under my avatar.

January 16, 2013
7:27 pm
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torso
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Hi Plesner

My swordtail-females/males always had been kidding before.

Cheers Charles

January 17, 2013
10:42 am
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Matt
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As far as I know there's no scientific evidence to support this theory.

Where are you planning to publish Plesner?

Cake or death?
January 17, 2013
1:13 pm
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Bojan Dolenc
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Poeciliids present an amazing variety of mechanisms, which span from simple XX-XY or ZZ-ZW systems to polyfactorial sex determination. The gonosomes of poeciliids generally are homomorphic, but very early stages of sex chromosome differentiation have been occasionally detected in some species.

There are 2 types of males in the swordtails with polygenic autosomal sex determination mechanism: earyl males ("strong" males) and larger late males ("weak" males), which become sexually mature much more later.

January 17, 2013
6:38 pm
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plesner
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Matt said
As far as I know there's no scientific evidence to support this theory.

Where are you planning to publish Plesner?

I'm still only thinking about it. I'm considering one or more articles for a Danish site I use - Danish is my native language after all. As there are far more knowledgeable people in here, I thought I'd ask here.

January 17, 2013
6:39 pm
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plesner
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Bojan Dolenc said
Poeciliids present an amazing variety of mechanisms, which span from simple XX-XY or ZZ-ZW systems to polyfactorial sex determination. The gonosomes of poeciliids generally are homomorphic, but very early stages of sex chromosome differentiation have been occasionally detected in some species.

There are 2 types of males in the swordtails with polygenic autosomal sex determination mechanism: earyl males ("strong" males) and larger late males ("weak" males), which become sexually mature much more later.

Thanks Bojan. Would you happen to know of one or more good sources to read more about this topic?

January 17, 2013
8:31 pm
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Bojan Dolenc
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plesner said
Thanks Bojan. Would you happen to know of one or more good sources to read more about this topic?

Book: Genetics for Aquarists, Schroder - TFH

PDF: Sexual Behavior, Genes, and Evolution in Xiphophorus.

http://www.ikhebeenvraag.be/my.....hal-85.pdf

> Genetica: Variability of genetic sex determination in poeciliid fishes. J.-N. Volff and M. Schartl
http://www.springerlink.com/co.....070811552/

January 17, 2013
9:16 pm
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plesner
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Bojan Dolenc said 
Book: Genetics for Aquarists, Schroder - TFH

PDF: Sexual Behavior, Genes, and Evolution in Xiphophorus.

http://www.ikhebeenvraag.be/my.....hal-85.pdf

> Genetica: Variability of genetic sex determination in poeciliid fishes. J.-N. Volff and M. Schartl
http://www.springerlink.com/co.....070811552/

Thanks again Bojan. I only seem to be able to find the 1976 edition for sale. Will that be ok, or should I wait until I find the 1991 edition available somewhere?

 

Oh, and does someone in here have access to the text from Genetica?

 

January 18, 2013
8:13 am
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Matt
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Yes, think I do. Let me check. Also have some other stuff that might be useful for you.

Cake or death?
January 18, 2013
4:46 pm
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plesner
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Matt said
Yes, think I do. Let me check. Also have some other stuff that might be useful for you.

Thank you Matt. It's very much appreciated.

 

plesner

January 19, 2013
3:10 am
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nuchal man
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From my experience with a few wild swordtail types I would say what many say is females becoming males is simply subdominant males who are afraid to display female characteristics to avoid aggression. I've had fish that I swear were females with no visible gonopodium and female coloration that never spawned in breeding colonies and when the male died or they were moved to a larger tank, one of these female looking fish would develop a gonopodium and male coloration. I think this could also be related to the genetics of the fish as Bojan pointed out. I don't buy the theory that they switch sex and think it is more of an aquarium myth. Just my observations and opinion though.

October 22, 2013
10:48 am
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R-y Guy
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I never saw any livebearer"switching sex".Like said, they hide sex, and keeps on growing.It happens very often to fisf with highly developed hierarchy.(velifera) But swordtails, YES they can do it! Long time ago I had red swordtail who already gives birth twice, starts turning  to male. At last heshe looks like normal big-strong male with fully developed gonopodium and pretty long sword.I gived this fish to my friend,so I cant say becomes he father too? But I think its possible.

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