Platy changed sex?

[keansor]

I know this sounds bizaar, but I suspect one of my female platies has changed sex. I have previous read somewhere that occasionally female Swordtails can become males. I'm a bit concerned that the same thing may have happened to one of my female platies. When we originally bought our platies, we had two females and one male, however the anal fin on one of the females looked like a cross between between a female's and a male's. Although she has the size and colouring of our other female (who is VERY pregnant), she has taken to chasing the pregnant female around the way the male used to. The male now leaves her alone because he is significantly outsized by our possible sex changer. I'm concerned because if our ratio of males to females has changed, the poor girl won't get any peace. Has anyone heard of this happening to a platy before? Thanks for your help!

[Laura]

I recall a post where this question was thoroughly debunked, but I couldn't find it when I did a seach.  Perhaps a smarter mind than mine can find it.
For the typical livebearers, juvies appear as female before they exhibit their sexual characteristics.  Perhaps yours was a late bloomer?
Given that, I could have sworn that when I kept fancy guppies oh so long ago that this was my experience, but it's entirely possible that I was absolutely wrong (or had a late bloomer).

[keansor]

Here is an interesting discussion of sexual genetics in Swordtails and Platies; although I'm not sure I understand all of the ramifications. Can anyone lend a hand?

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T9H-4CNCT3Y-5&_user=10&_coverDate=07%2F31%2F2004&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=272fe4491228fd2989266ef81b02471e#toc4

[rmicroys]

Haven't seen that with my platys, but my swordtails are definitely all born female, and after they are about an inch long, the ones that are destined to become male morph.  Oddly, when I bought my three swords, they were near complete adult size, and I bought a small male and two larger females.  Turns out that they can even morph when fully grown - because one of the girls turned in to a dude and now terrorizes the little male