The role of a flat cornea in the amphibious behaviour of the blackfoot penguin (Spheniscus demersus)

Abstract

The refractive state of the eye of the blackfoot penguin (S. demersus) was measured in air and under simulated aquatic conditions. Contrary to the literature that states that penguins are adapted for vision under water and are therefore myopic in air, S. demersus was emmetropic in air and moderately hyperopic under water. Study of corneal curvature and pupil response indicated that a mechanism of compensation for amphibious activity involving a split aperture was not present. A relatively flat cornea minimizes the refractive change induced when moving from air to water or vice versa. The hyperopia that persists in water may be lessened through accommodation or as a result of the spectral quality of the aquatic environment (blue, blue-green).