OK, I can't find the original artical, but I did some poking around and gleaned the following:
Amateur opinion breaks down into:
- In an population with too few males, some females will change sex.
Swordtails don't change sex, but older females develop male traits (a false gonopdium and small sword). (Come give your Aunt Bunny a kiss....)
Some males just develop later.
Based on the one learned article I could find
(and make sense of), I have to believe that the last one is the case. The reason being is that I had previously held the first opinion, and believed that the way one could tell a male that had changed sex was that it had a largely female body size and shape. Whereas this article implies that males that grow to the female size and heft tend to develop later and exhibit a sensitive, 21st century approach to mating.
So they're not transsexuals, they're metrosexuals.
Quack Ergo Duck