Cone Photoreceptors, Color Specificities

Abstract

Cone photoreceptors (cones) in the vertebrate retina mediate color vision. Cones are composed of four parts; an outer Segment, an inner segment, a cell body, and a synaptic terminal (pedicle) (Fig. 1). The outer segment is made of numerous infoldings of the plasma membrane, which contains a photosensitive substance (visual pigment). Microspectrophotometric studies have shown that individual cones contain one of the three different visual pigments whose absorbances are maximal for red, green, and blue lights. Three sets of visual pigments are commonly found in vertebrates; for example, the absorbance maxima lie at 625, 530, and 455 nm in the goldfish; 623, 522, and 462 nm in the turtle; 567, 514, and 461 in the pigeon; 567, 535, and 415 in the monkey ( Macaca); and 558, 531, and 419 nm in the human. These varieties of absorbance maxima are probably related to the adaptation to the light environment of the habitats.