Mapping the Rod Photoreceptors of the Little Skate, Leucoraja erinacea, a Unique Retina Model
Amir Chirar
Department of Biology
Faculty Supervisor: Ivan A. Anastassov
The Little Skate, Leucoraja erinacea, contains a simplex retina, comprised solely of rod photoreceptors. These rod cells display hybrid characteristics of cone photoreceptors, displaying cone-like terminals and having the ability to change sensitivity and signaling to act like cone cells, allowing it to see in both photopic and scotopic light. How these cells manage to reliably change signaling is still largely unknown, thought it has been shown that in other vertebrates, adjacent photoreceptors can cause signaling changes in their neighbors. Therefore, it is possible that these rod cells communicate to mediate their change in function, likely through chemical or electrical synapses. Here we report novel findings of invaginating synapses identified between adjacent Little Skate photoreceptors, as well as evidence of gap junctions. Invaginating synapses were explored through 3D reconstructions of rod cell terminals from serial block-face EM data. Gap junctions were similarly identified through EM analysis, as well as through in-situ hybridization to identify connexin mRNA transcripts present in rod photoreceptors. Additional chemical synapsing sites, such as basal synapses or lone invaginating synapses were also identified through EM data. These findings indicate that Little Skate rod cells form significant inter-photoreceptor synapses, more so than previously reported.