A new study has answered why the Mexican Cavefish made the choice to lose their eyes. Apparently fish with big eyes have low levels of energy.
A team of researchers from Sweden compared Mexican Cavefish collected from dark underwater caves to Mexican Cavefish collected from Mexican and American rivers (aboveground environments) and came to the realization that the specimens living in dark underwater caves are very cautious about how they use their energy.
Since food and oxygen are scarce in such hostile environments, Mexican Cavefish have to have the energy needed to catch prey when and if they come across it. But the research team also informs that the animals aren’t fussy, as they are even willing to eat the remains of other animals and plants.
While the specimens collected from Mexican and American rivers have hold on to their eyes and in fact have perfect vision, the ones collected from dark underwater caves have opted to let go of their eyes in favor of an extra boos of energy.
After the scientists studied the energy consumption associated with sight by calculating the amount of oxygen that the animals’ eyes require to function, as well as the amount of oxygen required by the the fish’s brain to process vision, they noticed that young Mexican Cavefish save 15 percent (15%) of their energy when they choose to go blind.
Damian Moran, field expert from Lund University (Sweden) and study leader, offered a statement informing that the photoreceptive cells and neurons are the ones to blame as they are constantly hungry for energy.
The choice makes sense for the Mexican Cavefish living in dark underwater caves as their environment favors “individuals with reduced visual capacity”. The absence of light keeps the animals from being able to use their eyes to spot food and predators, so they rely on other senses.
And this is not an uncommon practice. Eric Warrant, Lund University’s expert in Functional Zoology and study author, offered a statement of his own explaining that the Mexican Cavefish are not the only animals that have to consume high amounts of energy if they want to keep their eyes. He went on to stress that if the species didn’t trade its eyes for more energy, it would have to trade some other organ:
“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”.
Image Source: livescience.com