Underwater and Aerial Visual Acuity in the Asian “Clawless” Otter (Amblonyx cineria cineria)

Abstract

Gentry and Peterson¹ have compared data obtained from a sea otter (Enhydra lutris) on an underwater size discrimination task with data obtained by Schusterman et al.² using two sea lions (Zalophus californianus). Although Gentry and Peterson did not test the sea otter's vision in air, they concluded that its performance was inferior to that of the sea lion because the “pinniped eye” is emmetropic underwater with adaptations for aerial vision and that the “otter eye” (Lutra) was emmetropic in air with adaptations for underwater vision³. Such an interpretation of the difference between otters and sea lions emphasizes different dioptric mechanisms and ignores neural structure and organization at the retinal level, as well as at the level of the cortical projection areas.