Investigating the Skate Retina by Identifying the purpose and function of Horizontal Cells
By: Yaqoub Yusuf
Department: Biology
Faculty Advisor: Dr. Ivan Anastassov
The visual systems of most vertebrate species tend to have two different kinds of light sensitive cells (i.e. photoreceptors): rods and cones. For example, human color vision in bright light is achieved by mixing and comparing neural signals from cone photoreceptors sensitive to different wavelengths of light. Rod photoreceptors, on the other hand, are sensitive to low light levels and help us see at night. Interestingly, our model system, the cartilaginous fish L. erinacea (Little skate), only possess rods. However, these rods are unique in that they can function across large ranges of light intensity. The purpose of this research is to understand how the skate retina accommodates for the functional duality of monotypic photoreceptors in the downstream circuitry. Specifically, we aim to describe how the diversity of horizontal cell types (neurons downstream of skate rods) and their structural characteristics contribute to the ability of the skate retina to transmit information at the first visual synapse across vastly different levels of illumination. Normally, only one horizontal cell type is dedicated to rod signaling in mixed rod/cone retinas, but previous studies have shown that there are two distinct horizontal cell types in the skate retina. We hypothesize that each one of these horizontal cell types is uniquely tuned to process information in dim or bright light conditions. Here, we analyze differences between internal and external skate horizontal cells by using serial section electron microscopy data to obtain 3D representations of cell structure and cell connectivity at the nanoscopic level.