Day-Glow Fish Found Illuminating Ocean Reefs

There is also evidence that turning red could serve as a kind of camouflage.

Ichthyologists appear to have been blind for decades to a fluorescent crimson glow that naturally comes from many fish at depths where the sun’s red light cannot penetrate.

The fish experts had long believed that the underwater creatures probably could not even see the color red, because the sea entirely filters out that wavelength of light at depths greater than 30 feet.

But researchers at the University of Tübingen in Germany accidentally saw fish glowing red when they used a filter to block out the brighter green and blue light waves, leaving only red ones.

Nico Michiels and his team found at least 32 species of reef fish, glowing in various hues of ruby, rust, crimson and cherry.

They say the fluorescence can only be seen at short distances, and believe it may be used for communication — possibly for mating or to signal danger.

Analysis of dissected fish revealed that the fluorescence originates in guanine crystals, a chemical compound that is added to nail polish and car paint to provide added luster.

The study was published in the British-based open-access journal BMC Ecology.

Photo: Nico Michiels - University of Tübingen