An Overview of the Penguin Visual System

Abstract

Penguins require vision that is adequate for both subaerial and submarine environments under a wide range of illumination. Here we provide a structured overview of what is known about their visual system with an emphasis on how and how well they achieve these goals. Amphibious vision is facilitated by a relatively flat cornea, the power in air varying from 10.2 dioptres (D) to 41.3 D depending on the species, and there is good evidence for emmetropia both above and below water. All penguins are trichromats with loss of rhodopsin 2, a nocturnal feature, but only deeper diving penguins have been noted to have pale oil droplets and a preponderance of rods. Conversely, the diurnal, shallow-diving little penguin has a higher ganglion cell density (28,867 cells/mm2) and f-number (3.5) than those that operate in dimmer light. In most species studied, there is some binocular overlap, but this reduces upon submergence. However, gaps in our knowledge remain, particularly with regard to the mechanism of accommodation, spectral transmission, behavioural measurements of visual function in low light, and neural adaptations to low light. The rarer species also deserve more attention.

Extended ozone depletion and reduced snow and ice cover—Consequences for Antarctic biota

“…Few studies have reported effects of UV radiation due to the ozone hole on Antarctic vertebrates, with most studies restricted to animals in zoos (located at low–mid‐latitudes and where animals are kept under artificial light sources, Bliss et al., 2015; Karentz & Bosch, 2001; Woodhouse et al., 2016). A recent review on penguin visual systems shows that UV light may be relevant for sexual behavior in some penguin species (Hadden & Zhang, 2023). These studies show that penguin species vary in the extent to which UV radiation penetrates their eyes, with king penguin lenses absorbing almost all radiation below 370 nm while in gentoos more light is transmitted into the eyes (Hadden et al., 2023).…”