Cone mosaic development in the goldfish retina is independent of rod neurogenesis and differentiation.

The goldfish retina displays a characteristic arrangement of cone photoreceptors that develop in a stereotyped sequence according to spectral phenotype. It has been suggested that the earliest differentiating photoreceptor in the teleost, the rod photoreceptor, might play an instructive role in development of the cone mosaic. This hypothesis was tested, first by examining the expression pattern of a cone subtype-specific marker with respect to that of rod opsin, and then by killing the cells that generate rods and examining the cone mosaic that formed in the absence of new rods. We find that, although there is potential for interactions between developing cones and immediately postmitotic rods, a role for such interactions in cone mosaic pattern formation is not likely.