DEVELOPMENT OF THE OLFACTORY ORGAN IN ZEB RAFISH - AN ELECTRON-MICROSCOPIC AND IMMUNOCYTOCHEMICAL STUDY OF EARLY DIFFERENTIATION GROWTH

The present study describes the ontogeny of the olfactory organ of the zebrafish, Brachydanio rerio. Scanning and electron microscopy was us ed to show the formation of the olfactory placode from the cells of a subepidermal cell layer, their differentiation into receptor cells, su pporting cells, basal cells and ciliated nonsensory cells, and the ope ning processes of the olfactory pit by which later the incurrent and e xcurrent nostrils are built. The expression pattern of HNK-1- and subs tance P-immunoreactivity was investigated with respect to the origin o f the olfactory placode.