2023 34 B2

Defining the Anatomy of Rod Pathways in the Simplex Retina of L. erinacea

By: David Umbertus

Department: Biology

Faculty Advisor: Dr. Ivan A. Anastassov

The retina is a thin layer of tissue that lines the back of the eye and allows vertebrates to visualize the world around them. Most retinas use a duplex system of light sensitive cells (photoreceptors) known as rods and cones. Cones are used for photopic vision (daylight/color) and rods are used for scotopic vision (dim light). In most vertebrate retinas, rods utilize three distinct pathways to transmit visual information at different levels of light, called the primary, secondary, and tertiary pathways. These three distinct pathways that mediate rod signals vary in sensitivity to light, with the primary being the most sensitive, and the tertiary being the least sensitive. It is important to note that these pathways utilize some form of cone circuitry, at the very least in mammals. The little skate (L. erinacea) is a type of cartilaginous fish with a pure-rod, “simplex” retinal system (meaning, cones are not present). However, the skate retina can function in both dim and bright light conditions. Therefore, we are interested in understanding how this organism transmits information from the input to rods, and downstream to retinal ganglion cells, without the ability to piggy-back onto cone circuitry. To address this question we have performed segmentation and analysis of 3D reconstructions (using serial EM approaches) of rod pathway components in the skate retina.