Meeting Abstract
The eye is a precise and complex organ which has remained remarkably conserved despite changes in morphology as vertebrate lineages adapted to diverging life histories. The same distinguishing eye characteristics found in humans are also found in zebrafish and lamprey, implying that our eye (as it first arose) has remained nearly unchanged since at least the time that lamprey diverged, nearly 500 million years ago. Though development and structure have been well defined across vertebrates, our understanding of how the eye evolved remains poorly understood. Pacific hagfish (Eptatretus stoutii ) are in the unique position of straddling the boundary between eyed vertebrates and non-eyed chordates. Likewise, their eyes are difficult to categorize as they lack many of the diagnostic features shared by vertebrates including a lens, ocular musculature, and a 3-layered retina. These relatively simple features lead us to question: is the hagfish eye representative of a transitional species in the evolution of vertebrate eyes, or is it degenerate? We hypothesize that the lack of observable vertebrate-like organization in the adult hagfish retina may be due to a degeneration or re-distribution of retinal cell types during maturation and growth. Preliminary evidence suggests that juvenile hagfish show layering of the retina that more closely resembles that of vertebrates in comparison with adults. Using RNAseq, protein and gene expression assays, this project aims to further explore retinal cell-types and their organization within the hagfish retina in order to better interpret their morphology in the greater context of vertebrate eye evolution. We will capture any characters that aid us in revealing the hagfish eye as degenerate or ancestral, allowing us to place the hagfish in the context of the evolution of the vertebrate eye.
