The Physiology and Molecular Ecology of Vision in Hawaiian Seabirds

Abstract

Spectral sensitivity is considered highly similar among bird species, despite well documented differences in the spectral sensitivities of other vertebrate species (i.e. fish) based on ecology and light environment. Seabirds function across complex light environments; displaying diurnal, crepuscular, and nocturnal activity, foraging in open ocean water to various depths, forming nesting colonies anywhere from barren rocky cliffs to burrowing in dense forests, all while simultaneously coping with the visual transition between air and water - all factors known to shape vision. Because studies of vision in birds primarily focus on land birds, seabirds are understudied yet an ideal group to test the assumption that vision is similar among birds. In this dissertation I challenge the prevailing idea that avian vision is similar among species through the physiological characterization of vision in Hawaiian seabirds and propose a novel molecular framework for the modulation of color vision across all avian species. The aims of this work are threefold: 1) Quantify physiological differences in spectral and temporal response to light using electroretinograms from adult and juvenile birds in three target species of endangered and locally threatened birds in Hawai’i (Pterodroma sandwichensis, Puffinus newelli, and Ardenna pacifica); 2) Using retinal transcriptomes from A. pacifica, identify a novel molecular mechanism in bird eyes capable of rapidly modulating light response; 3) Explore expression patterns and ecological correlations of this novel molecular mechanism using retinal transcriptomes from 17 species of Hawaiian sea- and waterbirds. Here, I present physiological evidence of species-specific variation in spectral, temporal, and absolute sensitivity in vision between three closely related seabird species. Additionally, I present molecular evidence of novel alternative splicing of visual proteins and describe the functionality of alternative splicing as a method for rapid adaptation of vision in birds. Finally, I identify the widespread use of alternative splicing of visual proteins in avian species and propose potential applications of alternative splicing in avian vision beyond the species in this dissertation. Unanswered questions about the specific drivers and functionality of alternative splicing of visual proteins lay the groundwork for a novel field of research and an abundance of opportunities for future studies of avian vision and visual ecology.