COMPLETE SEX-REVERSAL IN THE VIVIPARO TELEOSTXIPHOPHORUS HELLERI

Abstract

1. Two cases of complete sex-reversal, from female to male, in adult Xiphophorus helleri have been described. 2. It is definitely known that both fish gave birth to normal young prior to sex-reversal. 3. It is also definitely known that both fish fertilized virgin females which gave birth to young with sex-ratio typical of the species. 4. The transformed fish is indistinguishable from a "normal" male except body form which is that of a female. 5. The entire ovary disintegrates except the epithelium of the ovarian cavity. From it cells proliferate and form sex cords in sex-reversal cases. 6. The epithelium of the ovarian cavity is derived from the peritoneal epithelium and at no time is infiltrated with primordial germ cells. 7. The position, structure and physiology of the testis of the transformed fish is identical to that of the "normal" males. The oviduct becomes the spermduct. 8. No tubercular lesions or lesions of any other disease were found in the arrhenoid fishes. 9. Chromosomes are not considered as having the function of sex determination and control. 10. Sex is determined and controlled by the sex hormones derived from the ovary and testes. 11. Any agent or condition which tends to decrease the capacity for hormone secretion becomes an immediate factor in sex-reversal.