(…) Organization of the visual system in Cetacea still remains unclear in many respects. Of special interest are data on ganglion cell distribution in the retina. It is related closely with visual acuity (Van Buren, 1963; Frisen and Frisen, 1976).
To understand the organization of the best vision zones of Cetacea, it is necessary to have analogous data on other representatives of this order. The objective of this study was to investigate the spatial distribution of ganglion cell density in three Cetaceans, differing in their taxonomy and ecology: the harbor porpoise, Phocoena phocoena, the grey whale, Eschrichtius gibbosus, and the Amazon river dolphin, Inia geoffrensis. (…)