Subterranean Fishes of the World

3210

2013

AIM 2013

More than seventy years after Conrad H. Waddington first introduced the concept of canalization in evolutionary biology, and fifteen years after its uncovered nature as the heat shock protein 90 (HSP90), the actual role of HSP90 and its canalizing effect in evolution and speciation remain controversy. The theory of HSP90 keeping standing genetic variation poised for activation by an environmental stressor until subsequent selection of adaptive alleles in new environments can occur, however, remains a gripping and compelling concept for evolution. The cavefish model system Astyanax mexicanus has many characteristics which makes it a good candidate for studying a potential role of HSP90 in ecological evolution. The prime reason being, that the river forms had suddenly to live in and adapt to a new and rather extreme environment, the cave. Here, we test the role of HSP90 in eye and orbit size of surface and cave Astyanax mexicanus, two important and most likely adaptive traits in cave evolution. We show that HSP90 influences eye and orbit size variation in natural populations of surface Astyanax, suggesting corresponding underlying standing genetic variation in these river populations. Additionally and most importantly we provide evidence for selection of particular alleles affecting orbit size which are regulated by HSP90 during transition from surface to cave forms, making a scenario likely in which HSP90 has contributed to cavefish evolution. Finally we discuss potential environmental stressor scenarios in the cave environment and analyze their impact upon HSP90 regulation in surface fish development.

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