P1.126 Wednesday, Jan. 4 The evolution of retinal morphology in birds HANCOCK, Jennifer A.*; BIKNEVICIUS, Audrone R.; Marietta College, Marietta, Ohio; Ohio University Heritage College of Osteopathic Medicine, Athens, Ohio email@example.com
Retinal morphology is highly variable in extant birds, ranging from the afoveate retina of the Oilbird (Steatornis caripensis) to the bifoveate retina of the Common Flamingo (Phoenicopterus roseus). In order to understand the distribution and evolution of avian retinal morphology, we collected known data on retinal features in 165 species of birds. Specifically, we recorded the number and location of the area centralis (a region of increased retinal cell density) and foveae (a depression within the area centralis) for each species. Configurations of the area centralis include: circular in shape and located in either the nasal or temporal retina; circular in shape and located in both the nasal and temporal retinal fields; a horizontal band that extends across the retina; and absent. The number of foveae similarly ranges from 0 to 2 per eye, and, when present, they may be located in the nasal, temporal or both retinal fields. These data were then mapped onto a phylogeny in order to reconstruct the evolution of retinal characters. The ancestral character state for birds was found to be a nasal unifoveate retina with a band-shaped area, and from this nine other retinal patterns evolved. The evolution of these retinal patterns appears complex, involving retentions of the primitive condition, directional changes toward different configurations and reversals.