Retinopetal cells exist in the optic tectum of steelhead trout.

The existence of retinopetal cells in the tectum of various teleost fishes as been claimed by several authors. Others, however, have been unable to verify such observations and attribute the findings of retrogradely labelled tectal cells to methodological problems. In this study cobalt-lysine and HRP have been used as neuronal tracers. Evidence is provided for the presence of retinopetal cells in the tectum of steelhead trout. Dendritic arborizations of some of the cells are extremely elaborate. In salmon no such findings were made.