Ruffed cells identified in the adult zebrafish olfactory bulb

The morphology and distribution of ruffed cells was examined in the olfactory bulb of adult zebrafish, Danio rerio, using retrograde tract tracing and Golgi-Kopsch techniques. The neurons had variable-shaped soma that ranged in size from 7 to 15 microm in diameter. There was an obvious protrusion of the membrane, a ruff, near the initial portion of the axon, and the cells appeared to be distributed primarily in the glomerular layer and superficial internal cell layer. This cell type has been described for a number of teleosts, but not for other animal groups. While the presence of ruffed cells in all teleosts has been suggested, the existence of this cell type in zebrafish was uncertain until now. This new evidence may provide additional insight into olfactory coding and processing in this key model system.