Evolution Helped Blind Cave Fish Reduce Their Energy Consumption, Ensuring Survival

Biologic energy conservation seems to be something of a theme for the blind cave fish (Astyanax mexicanus), say researchers from Lund University.

As a response to being washed into a cave in northeastern Mexico and trapped there,these prehistoric fish had no choice but to adapt to a life spent in darkness. They evolved without eyes and also lost a large part of their brain's visual center along with their circadian rhythm, which would otherwise control metabolic functions, such as sleeping and eating cycles. Ultimately, they evolved to rely more on their sense of smell and taste while becaming much more sensitive to movement.

All of that cut down on the animal's total energy budget, which helped them to adapt and survive.

"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," Eric Warrant, a researcher in functional zoology at Lund University, said in the release.

"Our measurements in the Mexican cavefish show that the visual system requires between five percent and 15 percent of the animal's total energy budget, depending on the age of the fish. This is a tremendously high cost! Over evolution, this morph lost both eyes and visual cortex, without a doubt because of the unsustainable energy cost of maintaining a sensory system that no longer had any significance," Damian Moran, one of the study's researchers, said in a news release.

Their study was recently published in the journal Science Advances.

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