Sex Changing Fish

[The-Wolf]

This recent topic has me wondering
can certain livebearers truly change sex or are they just slow to develop their true sexual organs?
are there any scientific papers/studies done on this subject?

 

[helterskelter]

No they cant change sex, how ever you get late developers and molly and swordtails this happens quite often.

Some male are suppressed by larger more dominate males and as life it not easy they take the rought of not devloping early so to try to breed they take the longer route of growing as large as possible and then becoming alpha male via size.

I've seen swords take as long as 12 months to and molly simular time but usually around 10 months.

I've not see any papers on this subject will will bring it up on my forums

 

[helterskelter]

Ok just posted it

http/www.livingfish.co.uk/forum/topic.asp?TOPIC_ID=976

I'll try to copy the posts back if i see anything interesting there.

 

[dane261]

am i right to say a clowm fish when paired up one will become a female


cheers dane

 

[helterskelter]

Yes, a few marine fish will, clowns start as all male and then devleope into a female (sure that the right way.)

Posts from my site.

Xiphophorus kallmani, nigrensis and Limia perugiae are said to not change sex, but all males are reluctant to mature until other males have been removed.

 

[juanveldez]

there was also a debate on this topic within the cichlid community a few years back in fact there was an article in the ACA( American Cichlid Association)'s journal about it. I will have to look for it but if I remember correctly it was concerning Midas's living in the Niciraguan lakes.

 

[andywg]

There are quite a number of fish in marine seas which change sex. Anthias will often change sex with a large female becoming a male. Clownfish start out as male and the more dominant tends to change to female.

Some others change sex during life. The ribbon moray (Rhinomuraena quaesita) matures from a black juvenile into a blue male. As it grows it then changes colour to a blue female.

As both damsels and clowns are from the Order Perciformes, I would not be surprised to see cichlids being able to change sex.

 

[annka5]

How does it work on a chromosome level? They can't just "grow" or "lose" a chromosome, so is it just suppressed chemically?

Are there any cases where the male (eg) clownfish has paired and fathered babies before changing to a female clown fish and giving birth to babies? Or is it that they appear to be male, and live as if they are male, but biologically are female, then develop the female characteristics later?

I'm not being skeptical of what you're saying, I'm just not clear on what happens re: chromosomes etc.

 

[Lynden]

I have personally witnessed a fully adult (1.5'') female guppy transform into a male over a period of a few weeks. First, the colour on her tail spread to the caudal pundicle, then her anal fin rays gradually thickened and compressed to form a gonopodium. "She" then began to mate with "her" female tankmates. This was of course when I tried to keep an all-female group (bought them as feeder fish; never bothered to get a male). The guppy was later killed by breeding convicts while being used as a target fish.

I clearly never realized that this topic was usually dismissed as a myth. I have also raised guppies (from birth) of both sexes in the past, so I realize the difference between simple late blooming and true protogynous hermaphrodites. Obviously this ability would be very helpful in the wild, as a "stranded" group of females could build a new population.

 

[The-Wolf]

Lynden has hit the nail on the head.
this is what I was referring too.

I remember being told about guppies doing this when kept in all female groups
and it was explained as a survival mechanism for when there are too few males about.

 

[Musho3210]

are clowns born males or born genderless? Like without either sex organ?

 

[nadajdui]

Wow, this topic is amazing! I had no idea about any of this. Would it be possible for a male guppy to turn into a female?

 

[Mordinbar]

I am unsure whether or not it would be possible tor a male to turn into a female. This is somewhat off topic, but it may apply. A few days ago I was reading a paper dicussing the social rearing issues with transgendered human babies. It was discussing how for a child to become male, not only must the Y chromosome be present, but the hormonal levels and development must be complete and proper for the fetus to develop male genitalia. The argument presented, was that 'male' children born with incomplete genitalia can actually be forced to revert to females by removing and altering the genitalia so the hormonal levels are changed. This will actually allow the child to pass through puberty as a female (aka menstruation) and it will proceed to be a functionally reproductive female. The point of the paper was the belief that Female was the base sex and that to become a male required specific hormonal attributes that could potentially be developed. So to generally apply this as was stated above, I could see the development of male hormones in the female guppies that would allow them to grow male sex organs and morphological characteristics, but I am not sure if the opposite would be nearly as possible. And while I do know the anthias and damsels are capable of it, Im just throwing this out there as kind of a devils advocate idea.

Again like I said, this is slightly off topic but I believe it applies in a general sense.

-Mord

I will see If I can track down the paper so I can reference it here if anyone is interested.

Here is the Title/Author of the paper: How to Build a Man by Anne Fausto-Sterling

There is a link to it on Google Scholar, but it is broken currently

 

[dwarfgourami]

About the chromosome thing. John Dawes in his book of Livebearing Fishes (paperback edition, 1995, pp. 68-69) explains it as follows:

"While the sex of a mammal can usually be relatively easily determined by looking at the chromosomes of a living cell, things are not quite as clear-cut when it comes to fish.
Certain species...have clear-cut, identifiable sex chromosomes- the autosomes. They are also morphologically indistinguishable between the sexes. This means that in most fish the male and female cells cannot be distinguished, as they can in mammals, by their possession of X or Y chromosomes.
This is because sex determination in fish is polygenic or polyfactorial. As both these terms indicate, numerous genetic interactions are at work when it comes to determining the sex of an individual fish.
First put forward by Winge in 193, the polygenic theory allocates sex determination not only to those genes that may be located on the genuine sex chromosomes, but also to a host of others that occur on the autosomes. This applies both to species in which the sex chromosomes are identifiable and to those in which they are not. In the end, it is not just a question of whether a fish has identifiable sex chromosomes or not; it is more a question of the ratioof male to female factors determining the sex of an individual.
The sex chromosomes are assumed to carry superior sex genes that have greater mae or genetic power than the other male and female genes located on the autosomes. These male and female factors are often referred to as M and F determinants respecively...What appears to happen is that the M and F factors within the sex chromosomes themselves determine which genetic switches are going to be turned on. If a predominance of male type switches are turned on, then the fish in question will develop into a male, and vice versa. This may explain to an extent why environmental factors appear to play such a publicised role in sex determination of certain fishes."

He then goes on (p. 69) to discuss sex reversal. This has been well documented in clown fish and wrasses, but there are as yet no cases of sex change in guppies and swordtails that are scientifically documented.

In Lynden's case, for this to carry scientific weight, he would need to prove that his female was a genuine female. Saying "I am experienced and I know what a female looks like" is not scientific proof. Looking for sex chromosomes is not an option, dissection is not an option- he would really need to show that this individual female had given birth (on its own, not with other females who might be the real mother) and then turned into a male, i.e. a fish that was able to impregnate other virgin females. As far as I know, the situation is still the same as when Dawes wrote: noone has carried out these experiments under sufficiently controlled conditions.

 

[The-Wolf]

He then goes on (p. 69) to discuss sex reversal. This has been well documented in clown fish and wrasses, but there are as yet no cases of sex change in guppies and swordtails that are scientifically documented.

perfect answer to the question
thanks DG