Color Blindness in Whales

Abstract

NEUROSCIENCE The exceptionally good color vision of most primates, including humans, is due to the presence of three types of color-sensitive cone photoreceptors in the retina of the eye (trichromatic vision). Most other mammals have two types of cones (detecting blue and green light), enough to perceive the world in color. Peichl et al. document, however, that whales and seals possess only one type of cone and thus are essentially color-blind. The retinas of these marine mammals, in addition to rod photoreceptors (responsible for black and white vision), contain only L (or long-wavelength) cones. In contrast, the close terrestrial relatives of whales and seals—hippopotamuses and otters, respectively—possess the usual S and L cones. The ancestors of modern whales and seals most likely lived in shallow coastal waters (in which light is red-shifted in comparison to the deep sea) where they seem to have lost their S cones. This clearly is a disadvantage for their present-day ocean-dwelling descendants, who may have needed to develop compensatory mechanisms (including perhaps acoustic communication) to overcome this evolutionary gene loss. — PRS Eur. J. Neurosci. 13 , 1520 (2001).