Beyond social bonding: Sex-specific regulation of familiarity-dependent mate choice by oxytocin in medaka

Oxytocin (OXT) contributes to social recognition and selective social behavior, but its effects depend on sex and behavioral context. Medaka ( Oryzias latipes ) reveal this dependence within a single species: wild-type females preferentially accept visually familiarized males, whereas wild-type males court females relatively independently of familiarity. Disruption of the oxt – oxtra pathway produces contrasting phenotypes. Mutant females show high receptivity even without visual familiarization, whereas mutant males show reduced courtship toward socially unfamiliar females and enhanced mate guarding toward familiar females. These findings distinguish recognizing familiarity from using it to guide mating behavior. A recent preprint reports similar behavioral and TN-GnRH3 circuit abnormalities in OXT-signaling-deficient and c1qb -mutant females, supporting a working model involving C1q-associated circuit refinement at an undetermined stage. How OXT signaling regulates microglial function remains unresolved, as does the circuit mechanism underlying the male phenotype. We propose that OXT calibrates the behavioral influence of familiarity within sex-specific mating circuits. This model accommodates female selectivity and broader male courtship without assigning OXT a uniformly affiliative function. Future studies will require separate assays of recognition and behavioral valuation, together with temporally and cell-type-restricted manipulations.