How do blind cavefish find their way? The answer could be in their bones.

A study has found asymmetry in the cranial bones of Mexican cavefish 

Date: May 24, 2017
Source: University of Cincinnati

Imagine living in perpetual darkness in an alien world where you have to find food quickly by touch or starve for months at a time.

The limestone caverns of Mexico's Sierra del Abra Tanchipa rainforest contain deep cisterns cloaked in utter blackness. This is where researchers at the University of Cincinnati traveled to find a little fish (Astyanax mexicanus) that has evolved to feast or endure famine entombed hundreds of feet below the ground.

"They have been able to invade this really extreme environment. They are exposed to darkness their entire life yet they're able to survive and thrive," said Amanda Powers, a UC graduate student and lead author of a study on blind cavefish published in May in the journal PLOS One.

"They've evolved changes to their metabolism and skull structure. They've enhanced their sensory systems. And they can survive in an environment where not many animals could," she said.

Mexican cavefish are bizarre, not merely blind but born with eyes that regress until they are completely lost as adults. The bones of their once-round eye orbits have collapsed. In place of eyes, their empty sockets store fat deposits that are covered in the same silvery, nearly translucent scales as the rest of their pale, unpigmented bodies.

The UC study examined one biological adaptation that might help to explain how these fish navigate and find food without benefit of sight -- asymmetry. Researchers examined juvenile and adult cavefish to understand how their skulls change during their lives.

Most fish are symmetrical -- their left and right sides are virtually identical and streamlined to provide the most efficient locomotion in the water.



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