Trichromatic color vision in the salamander (Salamandra salamandra)

Abstract

Spectral sensitivity functions were measured between 334 nm and 683 nm in Salamandra salamandra by utilizing two behavioral reactions: the negative phototactic response, and the prey catching behavior elicited by a moving worm dummy. The action spectrum of the negative phototactic response revealed 3 pronounced maxima: at 360–400 nm, at 520–540 nm, and at 600–640 nm. In the range around 450 nm, there was a “reaction gap” where sensitivity could not be measured. The action spectrum of the prey catching behavior was entirely different: maximal sensitivity was found at 500 nm and at 570 nm. Between 500 nm and 334 nm sensitivity decreased continuously for about 1 log unit (Fig. 6).

Experiments under chromatic adaptation using the prey catching behavior indicate that the relatively high sensitivity in the ultraviolet range is not due to a separate ultraviolet photoreceptor, but is based on the responses of a photoreceptor maximally sensitive at about 500 nm.

Color discrimination was tested by moving a colored worm dummy within a differently colored surround of equal subjective brightness. The salamanders were able to discriminate blue from green, and green from red (Fig. 10). The results can be explained by assuming a trichromatic color vision based on 3 photoreceptor types maximally sensitive around 450 nm, 500 nm and 570 nm (Fig. 12).