Socially Induced Inhibition of Genetically Determined Maturation in the Platyfish, Xiphophorus maculatus

Maturation in Xiphophorus maculatus (Pisces; Poeciliidae) is under control of the sex-linked P gene. However, when two individuals are reared together the socially dominant individual delays the maturation of the subordinate. Nevertheless, it is not a requirement that a fish be socially dominant to become mature. The data suggest that inhibition of maturity takes place when an individual is not dominant at a time near the genetically determined age of maturation. Two hypotheses are offered to explain these results.