Fish are the sex-switching masters of the animal kingdom.
The habit of switching sex appears to have developed during fish evolution multiple times in separate families, and though in all of them a suite of genetic and hormonal triggers come into play, the enzyme aromatase appears to be the key.
“It can change ‘androgen’ hormones into the estrogenic hormones that can transform gonads into ovaries.” explains Professor Stefano Mariani of the University of Salford.
In freshwater fish, it is well established that chemical pollutants – such as the pesticide atrazine, fertilizer runoff from livestock operations, ethinyl estradiol (the active ingredient in the birth control pill) – have all skewed the sex populations of wild populations of fish.
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