VISUALEYES COST

To See or Not to See: The Metabolic Cost of Having Eyes and its Role in the Evolution of Vision

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 Obiettivo del progetto (Objective)

'The evolution and regression of vision in animals has long interested scientists, and researchers have strived to identify the proximate (how did eyes evolve or regress?) and ultimate (why did eyes evolve or regress?) explanations for the appearance and disappearance of eyes. This Marie Curie proposal will use the Mexican blind cavefish to test whether the metabolic cost of the eye has been a significant selective force in the evolution and regression of vision. The Mexican blind cavefish is model species used in developmental biology, and is useful in the study of visual evolution as it has eyed, surface-dwelling ecomorphs, and non-eyed, cave-dwelling ecomorphs. I will measure the energy demand (oxygen consumption rate) of the eye in eyed ecomorphs using both in vivo and in vitro techniques. In vivo oxygen consumption measurements of the eye will be performed on anaesthetised individuals using oxygen microsensors. The energetic demand of the eye will be compared to the whole body metabolic rate of eyed and non-eyed individuals to infer a metabolic cost of vision. The in vitro oxygen consumption measurements of isolated retina will be performed on a specially constructed device where the incoming light intensity can be varied. The retinal oxygen consumption rate will be measured over a range of light intensities to quantify how the cost of the eye changed as Mexican blind cavefish diversified from surface habitats into caves. It is hypothesised that the energy requirements of the retina will be higher in the dark than that in the light. This project will offer an energetic explanation as to why eyes would be disadvantageous in the absence of light, and why selection would act to regress eyes in dark habitats. By understanding the metabolic cost of eyes, we can also learn about the energetic advantages that must have been gained by evolving vision.'