Molecular and Synaptic Organization of a Vertebrate Retina with a Single Photoreceptor Type
Alexander Agredano
Department of Biology
Faculty Supervisor: Ivan A. Anastassov
Most vertebrates have a duplex retina, which consists of rods for dim light (scotopic) vision and cones for bright light (photopic) vision, allowing them to adapt to multiple lighting conditions. However, the Little Skate (Leucoraja erinacea) only has rod-like photoreceptors, yet it functions under both dim and bright environments. This unusual functional plascticity has only been observed in skate, making it the only “simplex” visual system known to exhibit these qualities. The majority of other vertebrates have duplex retinas consisting of rods and cones, which split the scotopic and photopic workload between each other. This study investigates the molecular organization of the skate retina using two approaches. First, we use immunofluorescence staining for key functional proteins, including Transducin, PSD-95, and SV2, revealing how different parts of the retina are organized and how they function. Additionally, 3D electron microscopy (EM) analysis of mitochondria via serial block-face imaging allows measurement of the Mitochondrial Complexity Index (MCI) across different cell types found within the skate retina. Since MCI is linked to synaptic strength, this analysis helps us understand how the shape and complexity of mitochondria relate to the energy needs of different retinal neurons. These findings suggest that the little skate retina shares conserved molecular features with other vertebrates, providing a foundation for future studies on retinal evolution and function.