Abstract
Nocturnal and diurnal birds exhibit differences in retinal wiring, specifically with regard to "retinal pooling," or the number of photoreceptor cells providing information to a single ganglion cell in the retina. Diurnal birds have low retinal pooling, which acts to increase acuity, since each photoreceptor cell is responsible for a proportional angle of visual space. Nocturnal birds have high retinal pooling; if multiple photoreceptors provide information to a single ganglion cell, light sensitivity is increased. The optic nerve (CN II) is comprised of the ganglion cell axons delivering visual information to the brain. This study tests the hypothesis that nocturnal birds consistently exhibit a smaller optic nerve and chiasm than diurnal birds, based on area measurements. Whole bird heads are preserved in 4% paraformaldehyde, and the optic nerve and chiasm are dissected and mounted in modeling clay and photographed. Areas are measured from the photographs in SigmaScan. ANOVA and regression analysis of the comparative size of the optic nerve supports our hypothesis that nocturnal birds have consistently smaller optic nerve and optic chiasm areas.Grant Funding SourceAAA Student Travel Award
Published Version
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