A new study has finally found an answer for why the Mexican Cavefish decided to go blind. It turns out that the animal traded its eyes to save some energy.
Researchers from Lund University (Sweden) say that fish living in caves have to be very careful with how they use their energy as food is often scarce, and when they find it they have to be able to catch it. The Mexican Cavefish have adapted to this environment and have decided to lose their eyes to gain an extra bit of much needed energy that allows them to get the upper hand on their prey.
The field experts came to this conclusion after studying specimens of Mexican Cavefish that live in the rivers of Mexico and Texas, above-ground. These members of the species have perfect vision, as their environment has plenty of food and the animals do not need the energy boost that their cave dwelling peers do.
The researchers took some of these Mexican Cavefish into the lab and measured their sight related energy consumption. The approach they took was to calculate oxygen consumption of the animals’ eyes, as well as that of the parts of their brains related to vision.
The results showed that young, developing Mexican Cavefish can save 15 percent (15%) of their energy if they decide to go blind. Damian Moran, study leader and field expert from Lund University, gave a statement explaining that the culprits are the photo-receptive cells and neurons, as they are always hungry for energy.
He went on to add that the environment that these animals live in has a very limited supply of food and oxygen, and that if favors “individuals with reduced visual capacity”, especially since the absence of light makes it impossible for them to use their eyes to detect food and predators. They have to rely on other senses anyway.
Eric Warrant, study author and expert in Functional Zoology from Lund University, gave a statement of his own informing that the Mexican Cavefish is not the only species that requires a high amount of energy to keep its eyes, and that if the animal didn’t sacrifice its eyes, it would have to sacrifice some other part of itself.
He said that “Animals with large and well-developed eyes, necessary for their survival, pay a high price for them. As all animals have a strictly limited energy budget, a major investment in the visual system only occurs at a cost to other organ systems”.
The research team also showed that blind Mexican Cavefish have a midbrain that’s significantly smaller. This is the area that linked to vision.
The species has been classified as omnivorous and willing to eat whatever they can find. This includes the remains of dead animals and plants.
The study is not without its critics as William Jeffery, biologist from the University of Maryland (College Park), not involved in the study, also gave a statement saying that while the study backs up the widely accepted theory that fish living in caves lose their sight to save energy, the study fails to offer any undeniable evidence that proves the theory.
The findings were published a few days ago, on September 11, 2015, in the journal Science Advances.