Spectral sensitivity of the freshwater turtle Pseudemys scripta elegans: evidence for the filter-effect of colored oil droplets.

Spectral sensitivity was measured in the light adapted state for two individuals (S1 and S2) of Pseudemys scripta elegans using a behavioral training technique. The curves have three pronounced maxima at 450 nm, at 570 nm (S1) or 540 nm (S2), and at 640 nm. The spectral sensitivity functions can be described by the over-envelope of the effective cone sensitivity functions which are determined by the absorption spectra of the cone photopigments (lambda max at 450, 518 and 620 nm) and by the filter properties of the colored oil droplets.