Spectral sensitivity of the turtle, Pseudemys.

Abstract

The erg. of the turtle was recorded, using conventional techniques. Records were examined in regard to wave form, changes with stimulus intensity, and relative spectral sensitivity. With 1 animal, a study of spectral sensitivity based on its performance in a discrimination box also was made. The erg. manifested a series of positive waves in addition to a smooth, positive B wave component. Waves became more numerous and of larger amplitude with stimuli of increasing intensity. Erg. spectral sensitivity measured in the dark-adapted eye was found to be greatest for long wave-length stimuli, regardless of whether the whole response or the individual waves were considered. Spectral sensitivity on a behavioral basis was markedly different and maximizes at a shorter wave length. These results are in agreement with the hypothesis that turtles possess both photopic and scotopic retinal mechanisms.