Protein gene product 9.5-immunoreactive neurons in the retina of striped dolphin (Stenella coeruleoalba) and Fraser dolphin (Lagenodelphis hosei).

This study demonstrates immunocytochemically that protein gene product 9.5 (PGP 9.5), a neuronal marker, is expressed by various populations of retinal cells in Stenella coeruleoalba (striped dolphin) and Lagenodelphis hosei (Fraser dolphin): one in the retinal ganglion cells and the other in the inner nuclear layer, resembling horizontal and amacrine cells. The specific distribution of PGP 9.5 in a dolphin closely resembles that in rodents and carnivores; however, some differences arise among these animals. In a dolphin's retina, for example, only a few of giant ganglion cells are immunoreacted while almost all the small ganglion cells are stained strongly. The processes of horizontal cells, identified according to their localization, appear not to connect entirely in a dolphin. Instead, PGP 9.5 positive cells are widely distributed in the small to moderate ganglion cells and have distinct processes which are ramified extensively in the outer plexiform layer in rodents and carnivores. The high levels of PGP 9.5 expressing in the inner part of dolphin retina, including ganglion cells and their axons as well as distinct sublamination in the inner plexiform layer, indicate that this molecule markedly influences the retinal system, possibly in visual connection. Although mammals have various visual behavior, i.e., living marine vs. terrestrial environment, and active during daytime vs. in the night, the retina is a common model to characterize the neurochemical properties.