Postnatal development of the organ of Corti in the wild house mouse, laboratory mouse, and their hybrid.

Length of the basilar membrane, number and distribution of cochlear receptors, and the width of the triad of outer hair cells were analyzed in the course of the postnatal development and in adult individuals in wild and laboratory house mice and in hybrids of these species. While in newborn animals the triad of outer hair cells was wide at the base and narrow at the apex, the opposite was true for adult animals. The parameter decreased at the base and increased at the apex during postnatal development. The center of differentiation of (the reticular lamina of) the organ of Corti was localized at 40-50% of the basilar membrane length from the base and corresponded to the region with the maximum density of inner hair cells. The reticular lamina in the apical half of the cochlea matured earlier than in the basal half. Distribution of receptors did not change after birth. The shortest basilar membrane and the slowest rate of maturation were found in wild mice. Hybrids had the longest basilar membrane and the highest rate of maturation. These facts are considered an effect of heterosis.