Heterogeneous Maturation of Retina of the Pied Flycatcher Ficedula hypoleuca

A method is developed to determine the moment of establishment of functional maturity of cones by the appearance of their lipid droplet. Using this method, the process of differentiation of photoreceptor layer cells is traced and general regularities are elucidated of growth and maturation of the bifoveal retina of chicks of the pied flycatcher Ficedula hypoleuca. Development of retina occurs heterochronously; the first colored lipid droplets determining mature photoreceptors are photooptically revealed locally in the temporal retina area at the 5th day; at the 7th day, the lipid droplets appear within the limits of the central fovea; then the maturation wave moves from the temporal and central fovea towards periphery of retina. By the 14th day the entire area of retina turns out to be filled with mature photoreceptors. It is suggested that the predominant early maturation of photoreceptor cells of the temporal area is due to a necessity of the forestalling development of the retina parts providing the short-focus binocular vision that is the most important for establishment of chick alimentary behavior and start of hunting on their own after flight from the nest.