Instances of sex inversion in the domesticated swordtail, Xiphophorus helleri Heckel (Pisces, Osteichthyes)

3 protogynous hermaphrodites were found in a domesticated strain of Xiphophorus helleri, confirming much doubted observations by older authors. It therefore seems that sex determination may vary between strains, certain strains being strictly gonochoristic but others being capable of true hermaphroditism.