Sex Reversal in Livebearers

Hi guys, here's Diego from Italy. Just a question for you []:

Do u know something about sex reversal in livebearers?Did u ever hear or read
something about that?
Do u also know how pH,temperatures or population density can have an
influence on sex ratio?
Can u indicate me any scentific article or so?

Take care Diego

hi diego well i've learnt that swordtails can reverse sex but only from female to male. the ph also effects the sex of fry . i've got this book and theres a page about it, i'll type it up for u(sigh)....
Sex reversal in swordtails:
the reproductive habits of the livebearing fishes are particulary interesting, and have attracted the attention of scientists across the world. in the swordtail , in particular, the phenomenon of sex reversal has been frequently noted by scientists and hobbyists.
in most higher animals, the sex of each individual is determined at the moment of fertilisation of the egg
However, this is not the case with the swordtail. each immature fish could develop into a male or female, depending on wheter the male or the female reproductive organs develop first.(loads more to go!)these will secretefemale hormones and the fish will develop into a female; the opposite occurs if the male testes develop first. later on in life(half way there!), however, if the female ovaries regress and sease to function, the once female fish can turn into a functional male. female to to male changes are not uncommon, but male to female have rarely, if ever, been observed in swordtails. also of interest is the fact that external factors such as ph can effect the sexual  development of some fishes(nearly there!).it has been shown that low ph values(5-6) a greater proportion of male fish develops in the brood of the swordtail, and also in many dwarf cichilds. at higher alkaline ph values(7+, the sex ratio within the broods of these fishes is weighted towards the females!


hope this helps!!!!!

very interesting. i have on several occasions had broods heavily weighed to one sex or the other. i had a tank of xiphophorus xiphidium that produced only females until i moved them to a higher tank (warmer) then got a higher ratio of males. not sure about pH as mine is always above 7.5

Sex bias is a problem that I always have in my swordtails. I got 6 Xiphophorus alvarezi last year and they have all turned into males!!

I have been keeping them in unheated tanks, so it has been quite cool and the pH is about 7.5 also. So I will have to try keeping them in warmer tanks.

I actually thought that it was physically impossible for fish to change sex, although common sense suggests that the conditions during gestation could effect the sex.

Keith, have your results occurred when raising the fry? Or when you changed the conditions that the gestating mother was kept in?

WHEN MOVING THE ADULTS TO WARMER/COOLER CONDITIONS.
I ALSO HAVE PROBLEMS WITH THE ALVEREZI AS ALL MINE HAVE TURNED OUT TO BE MALES APART FROM ONE. NOW HAVE A TANK OF MAYAE (PMH) WITH 14 MALES AND ONE FEMALE.
SO I WILL NEED TO MOVE THEM BOTH FOR THE WINTER TO COOLER TANKS.
I NOTICE THAT YOU HAD YOUR ALVEREZI IN UNHEATED TANKS, HMM, THIS IS STRANGE[:-bigeyes2] AS I WAS CONVINCED THE REASON FOR ALL MY MALE ALVEREZI WAS THE TEMP.[:-idea]
WHAT TO DO, WHAT TO DO.[}:)]

Shows what I know!!

I did a search on google for Sex Reversal in fish

http://news2.news.wisc.edu/whyfiles/shorties/071salmon_sex/

http://www.amonline.net.au/fishes/faq/sexchange.htm

And then sex reversal in poeciliidae

http://www.blackwell-synergy.com/doi/abs/10.1046/j.1365-2109.2002.00699.x?journalCode=are

very interesting articles. brings about the question of additives and other nasties in our tap water, do they have any effect on sex ratios in fish? or humans for that matter!

[Attached Image:]

Here is a pic of a female gold sailfin molly  (Velifera ) she is around 3 inch  and changing sex  . not a very good pic wrong setting on camara now batteries have died  will take a better one asap Attached Image:

When you say she is changing sex, has she produced any young (i.e. has she ever been a viable female), or is she just a late developing male?

large fish that looks like female with the black spot can turn into males. but never if they have produced fry! the black spot is a possible signal to other males that this fish is not a threat (yet!)

I understand that to be true also and that scientific records of sex reversal have been found to be compromised by the presence of other females etc. I have not heard of any poeciliids that have been scientifically proven to have been a viable female and a viable male, although I wouldn't like to say that it never happens, especially knowing some of the amazing ways poeciliids have evolved.

Who knows Widget, you may have a late developing male or it may be a very significant event indeed. Although I would need convincing that it was the latter.

Found it. This is quite an interesting article on sequential hermaphroditism (sex reversal to the rest of us).

http://www-personal.umich.edu/~roldfiel/OldfieldFAF2005.pdf

I know of no cases of proven sex reversal in poeciliidae. In fact only one species of freshwater fish (Crenicara punctulata)
has been shown to exhibit post-maturational sex change (female to male).

ref:
Ohm, D. 1980. Evidence of protogynous hermaphroditism in a South
American cichlid Crenicara punctulata. Newsletter I.A.F.E. 3: 51-53

Carruth, L. L. (2000). Freshwater Cichlid Crenicara Punctulata
Is a Protogynous Sequential Hermaphrodite. Copeia(1): 71-82.

Yes, it is maturation that is the important thing.

There is plenty of information on fish appearing to change sex, but really they just mature far later giving the impression that they are changing sex.