Biology Is Weird — Eyesight or superpowers?
We can all agree there’s nothing cooler than losing a vital sense and turning it into a superpower. We see you Daredevil. It makes it totally worth it. Sure, I can’t see, but I can hear your heart beating from miles away and I can smell lies. Vison is a pretty cool thing, no doubt, but in the grand scheme of things, we’d all trade it for superpowers.
Well, evolution made that decision for some of our underwater friends. Many species of cavefish have been found to have evolved beyond sight. These creatures spent so many years in the dark that they got rid of the functionless eyes so that they could redirect energy to more deserving members of their body.
The most popular (i.e. my favorite) of the blind fish crew is the Mexican tetra, scientifically known as ‘Astyanax mexicanus’. This freshwater fish actually comes in two forms, the ‘Eyed Form’ and the ‘Blind Cave Form’, the latter of which we are talking about. Scientists theorize that several schools of the Mexican tetra found their way into underwater caves, got trapped and began to live and breed there and due to natural selection, they evolved over time from their bright-eyed, silvery grey selves to blind, pale fishies.
The interesting thing about these blind fish is the fact that they’re not technically blind, they just don’t have eyes. The blind tetras are born with eyes but their eyes regress until the sockets collapse and become a scale-covered fat store.
These fish have three superpowers. They can memorize their surroundings and rely on this memory to get around, their lateral lines are extremely sensitive to any and all vibrations or pressure changes in the water and they are scavengers through and through, eating both plants and smaller animals.
In captivity, these cavefish know to stay on edge. Literally. They have been observed to move clockwise round the edges of their tank while their careless, sightful cousins either hide or swim haphazardly. Despite their evolutionary changes, the two forms of the Mexican tetra breed with each other easily and produce fertile young. It goes to say, it doesn’t matter what’s on the outside, only what’s on the inside.
My first question for the fish was, “Why did you lose your eyes instead of gaining night vision?” The response was simple, and quite condescending might I add. Losing their eyesight was the best thing to happen to them. It gets depressing looking at the same cave walls all the time, they eat anything and sometimes it’s better to not see what it looks like and they don’t have to stare and mourn their pigment less bodies. Just kidding.
Eyesight is totally useless in the caves, because there’s no period of even a little external light. It’s pitch black 24/7. Besides, seeing as they are basically trapped in caves, they don’t have any natural predators in the wild that they’d have to avoid or evade. On a sadder note, there is less food available to them and so they had to get rid of unnecessary body processes for maximum energy conservation. It was basically be dead or be blind, the choice is obvious.
That is it for today. If anybody loses their eyes, please write and tell me if you gained superpowers. Much love to everyone without their eyesight or with heavy vision impairment, the Mexican tetra teaches us that we can adapt and thrive no matter what. I hope you learned something or at least smiled once, thank you for coming to my Ted talk.
