Using your eyes takes a lot of energy, especially if you’re a fish. The energy costs associated with good vision have led certain species of fish to just grow up without eyes, according to a group of researchers from Lund University in Sweden.
The Price of Sight for Cavefish
The recent study, published in the Science Advances journal, focuses on the eyeless Mexican Cavefish. While their above-ground fish counterparts have perfect vision, the cavedwellers in this species seem to have developed without eyes in order to save energy.
Researchers determined that developing young cavefish can save between five and fifteen percent of their energy if they grow up without eyes, numbers that were apparently much higher than the authors of the study expected to see. In the case of the Mexican Cavefish, the energy costs were calculated according to the oxygen consumption levels of their eyes and of the parts of their brains associated with vision.
Whereas the ground-dwelling fish live in a comparatively light- and nutrient-rich environment, fish that make their homes in darkness really have no use for sight. Rather, they find food and avoid predators using other senses. It makes much more sense for the cavefish, evolutionarily, to expend that energy elsewhere, especially considering what a high energy cost it really is for good eyesight. The fish repurpose the energy that would be spent on vision systems and use it instead to build other organs.
This calculated trade-off becomes particularly necessary due to the relatively low levels of resources present in cave environments. Their surroundings are nutrient-poor, that “if the animal didn’t sacrifice its eyes, it would have to sacrifice some other part of itself,” as Swedish zoologist Eric Warrant so poetically puts it.
The Work Is Never Done
Critics of the study argue that more hard evidence is needed in order to give backing to the energy theory. However, the findings still work to support existing assumptions about evolutionary processes in relation to species’ environments.
Furthermore, it might be interesting to take these questions regarding the price of sight, reinterpret them, and apply them to people. A good percentage of the energy spent on vision systems is consumed by the neurons that process the images. What could neuroscientists tell us about the energy costs associated with not just visual sight, but intellectual and philosophical sight? Do people who pursue different kinds of knowledge embody different physiological advantages or disadvantages as they go through life? How much energy does it really take to do a good job on your homework?
