Sexually dimorphic role of oxytocin in medaka mate choice

Significance In some monogamous species, the oxytocin system facilitates mating preference for a familiar individual, irrespective of sex. In contrast, in nonmonogamous species, the mating strategy mostly differs between males and females; males tend to compete with rival males and court indiscriminately, whereas females choose their mates selectively. Here, we studied the role of oxytocin in mate choice in medaka fish, a nonmonogamous species. Analysis of oxytocin system mutants in medaka revealed that the oxytocin system regulates mate preference in a sex-specific manner, indicating that the oxytocin system is required for mate choice in both sexes, regardless of the differences in the mating strategy between monogamous and nonmonogamous species.