A ganglionic source of new eighth nerve neurons in a post-embryonic fish.

In the post-embryonic fish Astronotus ocellatus (the oscar) sensory hair cells and eighth nerve neurons are added to the peripheral statoacoustic system all during adulthood. Here we use 3H-thymidine to label S-phase precursors to new neurons in the statoacoustic ganglion. The neuronal precursor cells have small nuclei with little surrounding cytoplasm. They are surrounded by cells that appear to be part of a developmental sequence ending with mature eighth nerve neurons. Taken with our previous studies, these results demonstrate that hair cell and neuronal precursors in post-embryonic oscars are spatially segregated and morphologically distinct from one another.