YOUR WEEKLY DOSE OF WOWZERS AND WONDER FROM THE NATURAL WORLD
When you live in the dark all of your life, your eyes become less of a necessity.
This week’s featured fish has done away with their eyes completely!
We’re talking about the Blind Mexican Tetra—also known as the Blind Mexican Cave Fish!
The tiny Mexican Tetra is native to the waters of the Rio Grande, Nueces, and Pecos Rivers, as well as the central and eastern regions of Mexico.
There are variations of the fish which have eyes and live in rivers and open waters.
However, the blind version of the tetra—first documented in the 1930s—is found at a few different underwater cave sites in the San Luis Potosi and Tamaulipas regions of Mexico.
Some have non-functioning eyes while others have no eyes at all!
Researchers have found that this evolutionary change is likely a result of these creatures trying to survive in dark, food-scarce caves.
When you’re never sure where your next meal might come from, every bit of energy counts.
Instead of wasting energy using eyes in water that is pitch black, these fish slowly evolved over generations to develop highly advanced skulls and lines on their body.
These two genetic modifications help them to detect the slightest changes in water pressure.
Meanwhile, their unused eyes slowly disappeared!
While in the egg, baby cave fish often have eyes. In most cases, however, they disappear before hatching.
Fish living near the openings of caves may retain their eyes, but they will likely have limited vision.
Blind Mexican Cave Fish are largely scavengers, eating the animal or plant remains that settle on the floor of their cave ponds.
However, they’ll also eat insects and other small creaturesthat happen to swim by.
Their small size means that they’re a tasty snack for a huge range of bigger fish, birds, and other animals.
However, their enhanced senses give them an advantage when it comes to detecting threats.
If they avoid predators, blind cave fish are quite hardy and typically live for around a decade—quite a long time for such a tiny fish.
This—combined with their schooling nature—makes them popular options for personal aquariums around the world.
If you're interested in seeing one of these critters in person, you’re far more likely to encounter one at your local pet store or aquarium than you are to see one in the wild.
Most pet blind cave fish can be traced back to a single group of fish collected from the Cueva Chica Cave in the Sierra del Abra cave system in Mexico in 1936.
Researchers have found a genetic difference in blind cave fish which causes them to gain twice as much weight as their sighted river-dwelling counterparts on the same diet.
The skulls of Mexican Cave Fish slowly twist to the left as they grow older. While researchers still don’t know exactly why this happens, they suspect it helps them to better detect changes in their surroundings and map their dark cave homes.
When finding a mate, cave fish flap their gills and mouths, creating tiny ripples and changes in the water for potential partners to detect!
Dive deep under the jungle floor to see a blind Mexican tetra in its natural habitat!