Pigment types, densities and concentrations in cone oil droplets of Emydoidea blandingii.

The peak optical densities (Dp) of colored oil droplets in the retinal cones of the turtle, Emydoidea blandingii, were found to range from 1.2 to 8.8 for yellow droplets, 3.2 to 11.4 for orange, and 8.8 to 58 for red. The yellow droplets' spectra matched that of zeaxanthin, the red and orange matched astaxanthin. One type of clear droplet absorbed negligibly in the visible spectrum. A second type had a Dp approximately 0.9 somewhere between 370 and 400 nm. The accessory cone had no oil droplet, but its ellipsoid contained a pigment with the absorption spectrum of zeaxanthin and Dp approximately 1.1.