A team of marine biologists from James Cook University and University College London found that blind cavefish living in dark caves in Mexico produce cells that respond to light. In their paper published in the journal Proceedings of the Royal Society Bthe team describes their study of several samples of blind cavefish.
Previous research has shown that fish living in the waters of a complex cave in parts of Mexico and the US all evolved from the same species of fish in the surface river. And because the fish in different caves have evolved independently over different periods of time, from tens of thousands to millions of years, they have different features related to adaptation to living in the dark. Those who have had less time to develop, for example, still have eyes, although most do not function anymore. Those who progressed for longer periods lost their eyes completely.
Previous research has also shown that as fish develop, their circadian rhythms gradually disappear and sleep time decreases significantly. Most also developed a stronger sensitivity to vibrations, which allowed them to sense the movement of the water around them—useful for navigation and finding food.
Not much is known about fish because they are notoriously difficult to study. However, the team working on this new research wondered how the fish changed as they lost their internal daily cycle. To find out, they turned to Astyanax mexicanus, a blind species of cavefish that is receptive to reproduction in a lab setting. They took samples grown from fish caught in several caves by other research teams and matched them to create additional specimens for their study. They then collected cell samples and tested them for sensitivity to light. They also compared what they found to the species from which all the others came.
In testing the cells, the research team found that many species of fish produce cells that are sensitive to light, despite being completely blind. They noted that the source species had the strongest sensitivity. The researchers also found that some fish species were able to enter their internal clocks back into the light/dark cycle.
Inga A. Frøland Steindal et al, Blind fish have cells that see light, Proceedings of the Royal Society B: Biological Sciences (2023). DOI: 10.1098/rspb.2023.0981
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Citation: Biologists determine that blind cavefish cells respond to light (2023, July 17) retrieved on July 17, 2023 from https://phys.org/news/2023-07-biologists-cavefish-cells – responsive.html
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