The lasting impact of Toki-o Yamamoto's pioneering chapter on fish sex determination and differentiation: A retrospective analysis of its contributions to reproductive biology and influences on aquaculture and fisheries sciences

In 1969, Professor Toki-o Yamamoto published a landmark review on sex differentiation in fishes, which provided the first comprehensive synthesis of the various influences on sexual phenotype, clarified the nomenclature, and sought to define the mechanisms that determine sex. Yamamoto's review highlighted the genetic basis of sex determination and the influence of sex steroids on gonadal sex differentiation. He argued that genetic sex determination was influenced by the net effect of sex chromosomes, when present, and contributions of female- and male-influencing alleles. Yamamoto also demonstrated that sex steroid treatments could override underlying genetic controls, resulting in sex reversal (e.g., XX-genotype males or XY-genotype females) in gonochoristic species. His comprehensive review has since stimulated a wide range of fields including aquaculture and fisheries sciences, genetics, and aquatic toxicology. This retrospective discusses Yamamoto's scientific legacy and remarkable life, which was devoted to studying the reproductive biology of fishes.