Platy Changing Sex And Changing Species?

[Lonnie]

Almost two years ago I bought two blue female platies from Wal-Mart. I have them in a 10 gallon aquarium with swordtails and other platies. Today I was setting in my easy chair watching my fish swim around. I noticed a slight curvature in the tail fin of one of my blue female platies. I thought it was rather odd that I hadn't noticed it before. I kept my eye on her. Then I saw what almost made me have a heart attack. A gonopodium! She now has a gonopodium. I have never seen a fish change its sex before. I did not think that platies changed their sex. She was a blue female platie when I bought her and now her tail is developing a sword like a male swordtail.   I have had platies and swordtails for 3 years and have never seen this phenomenon.   Thank you,  Lonnie

 

[fluttermoth]

to the forum, Lonnie
 
Platies and swordtails often appear to change sex, but they don't really. You can have males that are late developers, so look female when you buy them, or you can have females that take on male characteristics as they get old and are producing less female hormones.
 
Platies and swordtails are very closely related, and can (and will!) interbreed. Many pet store fish are actually platy/swordtail hybrids.
 
Oddly, it's been found in experiments, that female platies prefer males with swords, even though males of their own species don't have them; given the choice, they would rather mate with a swordtail than a platy!
 
So what you're seeing isn't at all unusual

 

[Lonnie]

It really surprised me to see this take place in my aquarium.  I would imagine this particular female has gotten older and is no longer producing female hormones etc...   Though I purchased her as a platy and have had her over a year.  She is taking on the characteristics of a male swordtail.  

 

[Akasha72]

wow, I didn't know that female platies prefer swordtail males! I've learnt something there. Nor did I know they can appear to change sex as they age. I did have 2 young platies that I bred myself that I thought were female but turned out to be male, some seem to take a while to make up their mind. 
 
If your fish, Lonnie, has been with you over a year then maybe it's an age thing as fluttermoth suggests. None of my platies lived longer than 3 years so allowing for growing time/time at the lfs yours could be over 2 years old now

 

[fluttermoth]

It really surprised me to see this take place in my aquarium.  I would imagine this particular female has gotten older and is no longer producing female hormones etc...   Though I purchased her as a platy and have had her over a year.  She is taking on the characteristics of a male swordtail.  

 
'She' is almost certainly a late developing male swordtail x platy then