Visual pigments and oil droplets in the penguin,Spheniscus humboldti

Abstract

The photoreceptors of the penguin,Spheniscus humboldti, were examined using a microspectrophotometer. The cones could be divided into three classes based on their visual pigment absorbance spectra [λmax 403, 450 and 543 nm (Fig. 1)], and into five classes based on their visual pigment-oil droplet combination (Fig. 4). Oil droplets were of three types (Fig. 2). The rods contained a rhodopsin with λmax at 504 nm. No double cones were observed. The penguin should be capable of good wavelength discrimination in the blue-green region of the spectrum but with poor discrimination at longer wavelengths. It is concluded that the spectral properties of the cone types indicate that the photopic vision ofS. humboldti is adapted to the spectral qualities of its aquatic environment.