Blind Cavefish Shed Light on the Dark Days of Mammalian Evolution

Like mammals, these cave-dwelling creatures have discarded a solar-powered system that repairs UV-damaged DNA

Pale, shrunken and blind, the Somalian cavefish lives a quiet life in the world’s most light-starved waters. With their ghastly pallor and no eyes to speak of, these pasty fish don’t seem to have much in common with mammals, but there’s far more to the humble cavefish than meets the eye.

Scientists reported yesterday in the journal Current Biology that cavefish could shed some much-needed light on a mysterious chapter of mammalian evolution: the loss of solar-powered DNA repair. Most organisms have mechanisms to repair their own DNA molecules activated by sunlight, but mammals lost the trait somewhere along the way—and so did the Somalian cavefish.

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Image Credit: (Hectonichus / Wikimedia Commons)

Feast your eyes on the blind Somalian cavefish, which has—like mammals—mysteriously lost the ability to use light to fix damaged DNA.

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Image Credit: (Luca Scapoli / University of Ferrara)

These blind Somalian cavefish are actually pretty easy on the eyes... even if they don’t have any themselves.

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Deep underground, in submerged caves, there is no light. Because there is no light, there is almost nothing for animals to eat. Yet life survives here.

The top predator in these sunless ecosystems is a tiny blind cavefish, only a few inches long. These fish are extremely rare, only found in the dark recesses of caves.