Going Dark

Three million years without sunlight has made a big impact on these Somalian cavefish, which live in complete darkness in underwater caves. Not only have they lost their eyes and skin pigmentation, but evolving in the dark has had an impact on the inner workings of their cells too. Cavefish obviously don’t suffer damage to their DNA from the ultraviolet rays in sunlight in their deep, dark homes, so they’ve lost the main light-dependent molecular repair ‘toolkit’ that other surface-dwelling animals rely on to fix these faults, known as photoreactivation DNA repair. However, they still retain a different mechanism known as nucleotide excision repair, which can be switched on if the cavefish are exposed to light. Comparing these processes in cavefish with the DNA repair systems in daylight-living zebrafish helps to illuminate the changes that have happened during their evolutionary journey over millions of years in such a strange environment.

Written by Kat Arney

Kat Arney

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Dr Kat Arney is an award-winning science writer, broadcaster and public speaker, and is the founder and Creative Director of First Create The Media.

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• Image by Hectonichus via Wikimedia
• Research by Haiyu Zhao et al, Institute of Biological and Chemical Systems, Karlsruhe Institute of Technology, Eggenstein-Leopoldshafen, Germany
• Image originally published with a Creative Commons Attribution Attribution-ShareAlike 3.0 Unported (CC BY-SA 3.0)
• Research published in PLOS Genetics, February 2021