Eye Growth and Differentiation in the Blind Cavefish Astyanax mexicanus: A Study in the Evolution of Development

Abstract

Modern biological studies often employ a synthesis of multiple fields to accomplish a unified research goal. For instance, evolution of development (evo-devo) answers questions concerning the emergence of unique organismal phenotypes resulting from changes in evolutionary and developmental forces. I am interested in studying these forces on a microevolutionary scale. To accomplish this, I use the teleost fish Astyanax mexicanus. This species, indigenous to Mexico, is comprised of two forms: a surface stream dwelling form (surface fish) and a cave dwelling form (cavefish). Cavefish, which are the evolutionary descendent of surface fish, have evolved a number of constructive and regressive features as a result of being exposed to the subterranean environment, including loss of functional eyes and melanin pigment. Thus, Astyanax is ideal for comparative studies on a microevolutionary scale.

I am interested in studying changes in eye development between surface fish and cavefish, and how this may relate to the evolution of the two forms. I initially utilized a comparative approach, using candidate gene, cell proliferation, and cell death studies. I extended these studies to include differential gene expression analyses as a means to better understand differences between surface fish and cavefish development. To further this understanding, I ultimately performed surface fish to cavefish lens transplants and surface fish lens deletions to study the effect of the lens on eye development. Finally, I integrate these data into a theory concerning eye development in Astyanax and put these developmental phenomena in the context of evolution.