Abstract

Astyanax mexicanus is a teleost fish consisting of distinct surface dwelling (surface fish) and cave-adapted (cavefish) forms. The ancestors of cavefish were isolated in caves less than a million-year ago and have since adapted to this extreme environment. Cavefish differ from their surface counterparts in numerous morphological, physiological and behavioral traits, the most striking being that cavefish lack functional eyes and are de-pigmented. This makes this fish an outstanding model for microevolutionary studies. My PhD project aimed at understanding the loss of eyes in cavefish. Eyes first develop almost normally during embryogenesis, but after hatching, the lens enters apoptosis, which triggers the progressive degeneration of the entire eye. I studied the development of the lens, both its early specification and its later differentiation. Functional studies on some candidate genes allowed the identification of a major defect in cavefish lens that could account for lens apoptosis. Through a molecular evolution approach, the evolutionary forces at work during cavefish eye evolution were also investigated.