HANCOCK, Jennifer A.*; BIKNEVICIUS, Audrone R.; Ohio University; Ohio University: Phylogenetic analysis of foveation in birds

The fovea is a specialized area of the retina thought to function to increase visual acuity. Among vertebrates there are a number of different retinal configurations including afoveate, unifoveate and bifoveate. Afoveate and unifoveate retinae are found throughout vertebrates, however, bifoveate retinae have only be recorded in birds and anoline lizards. Some avian studies have hypothesized functional significance of the different retinal arrangements based on ecology and visual requirements, yet no study has evaluated foveation in birds using a phylogenetic comparative analysis. This study will assess the evolutionary history of foveation in birds using information from the avian literature. Eight general retinal arrangements have been reported, including variations in fovea number, fovea position and area of increased photoreceptor densities. For example, all species that have been examined in the basal group within Aves, the paleognathous birds, have a unifoveate retina with the fovea located on the nasal side of the fundus. In contrast, the three species that have been examined to date within the Family Rallidae have three distinct retinal arrangements.