CELL-PROLIFERATION AND HAIR CELL ADDITION IN THE EAR OF THE GOLDFISH,CARASSIUS-AURATUS

Cell proliferation and hair cell addition have not been studied in the ears of otophysan fish, a group of species who have specialized heari ng capabilities. In this study we used the mitotic S-phase marker brom odeoxyuridine (BrdU) to identify proliferating cells in the ear of one otophysan species, Carassius auratus (the goldfish). Animals were sac rificed at 3 h or 5 days postinjection with BrdU and processed for imm unocytochemistry. The results of the study show that cell proliferatio n occurs in all of the otic endorgans and results in the addition of n ew hair cells. BrdU-labeled cells were distributed throughout all epit helia, including the primary auditory endorgan (saccule), where hair c ell phenotypes vary considerably along the rostrocaudal axis. This stu dy lays the groundwork for our transmission electron microscopy study of proliferative cells in the goldfish ear (Presson et al., Hearing Re search 100 (1996) 10-20) as well as future studies of hair cell develo pment in this species. The ability to predict, based on epithelial loc ation, the future phenotype of developing hair cells in the saccule of the goldfish make that endorgan a particularly powerful model system for the investigation of early hair cell differentiation.