Why the Mexican cavefish gave up their eyes

illustration: silverbackblog.com
If you're a fish living in a cave, having eyes isn't going to be particularly useful to you. Eyes and the parts of the brain handling vision need a lot of energy to work in the form of food. In theory, evolution would have cave-dwelling fish do away with vision altogether. That could be what has happened to a species of fish known as the Mexican tetra.

That is the hypothesis described in a recent open-access paper published in Science Advances, where they calculate that for a 1-gram fish, vision could cover a whopping 15% of it's resting metabolic rate. Read more about it here.
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