Final Report Summary - VISUALEYES COST (To See or Not to See: The Metabolic Cost of Having Eyes and its Role in the Evolution of Vision)
Project objectives
A 24-month Marie Curie IEF project was undertaken to study the energy expenditure of eyes and the role of energy as a factor in the evolution of eyes. The Mexican cavefish was used as a study organism as this species has naturally occurring eyed and non-eyed forms. The non-eyed forms live in caves in north-eastern Mexico. One hypothesis for the reason they lost their eyes is that eyes are energetically expensive and natural selection favoured individuals living in food-limited caves with successively smaller eyes.
Project tasks
Methods were developed to measure the whole body energetic expenditure of both eyed and non-eyed forms, and also the expenditure of isolated brains and eyes. The eyed forms and non-eyed Mexican cavefish were found to differ in the way their metabolism varied throughout the day. Eyed forms showed a daily (circadian) rhythm in metabolism typical of animals. Non-eyed forms did not have a circadian rhythm in metabolism, which allowed this type of Mexican cavefish to substantially lower its daily energy expenditure. This loss of a circadian rhythm in metabolism is a new phenomenon not previously observed in animal physiology studies. This work has been submitted for peer review.
Project results
A side project that evolved from the fundamental science project was a collaboration with medical researchers on improved techniques for culturing retina outside of the host animal. We discovered that stretch is an important force in maintaining the intergrity of the retina. This finding has both fundamental and applied science implications and was published in the journal Investigative Ophthalmology and Visual Science. The energy expenditure of the eye and visual centres of the brain were found to be a significant portion (2-6 %) of the total body energy expenditure of eyed Mexican cavefish. Non-eyed Mexican cavefish therefore make significant energy savings in their food-limited caves by having lost their visual sense. The significant energy expenditure of the visual system in Mexican cavefish lends weight to the idea that organs made of nervous tissue are energetically expensive and under pressure are likely to become smaller where food is limited
A 24-month Marie Curie IEF project was undertaken to study the energy expenditure of eyes and the role of energy as a factor in the evolution of eyes. The Mexican cavefish was used as a study organism as this species has naturally occurring eyed and non-eyed forms. The non-eyed forms live in caves in north-eastern Mexico. One hypothesis for the reason they lost their eyes is that eyes are energetically expensive and natural selection favoured individuals living in food-limited caves with successively smaller eyes.
Project tasks
Methods were developed to measure the whole body energetic expenditure of both eyed and non-eyed forms, and also the expenditure of isolated brains and eyes. The eyed forms and non-eyed Mexican cavefish were found to differ in the way their metabolism varied throughout the day. Eyed forms showed a daily (circadian) rhythm in metabolism typical of animals. Non-eyed forms did not have a circadian rhythm in metabolism, which allowed this type of Mexican cavefish to substantially lower its daily energy expenditure. This loss of a circadian rhythm in metabolism is a new phenomenon not previously observed in animal physiology studies. This work has been submitted for peer review.
Project results
A side project that evolved from the fundamental science project was a collaboration with medical researchers on improved techniques for culturing retina outside of the host animal. We discovered that stretch is an important force in maintaining the intergrity of the retina. This finding has both fundamental and applied science implications and was published in the journal Investigative Ophthalmology and Visual Science. The energy expenditure of the eye and visual centres of the brain were found to be a significant portion (2-6 %) of the total body energy expenditure of eyed Mexican cavefish. Non-eyed Mexican cavefish therefore make significant energy savings in their food-limited caves by having lost their visual sense. The significant energy expenditure of the visual system in Mexican cavefish lends weight to the idea that organs made of nervous tissue are energetically expensive and under pressure are likely to become smaller where food is limited