If you want a disco, take a dive to the depths of the ocean. You’ll find flashing clams, blinking jellyfish, glowing turtles, and neon sharks. But it seems we’re far from discovering all the party-goers: Scientists have now found two examples of fluorescent eels, and they look pretty awesome.
Described in the journal PLOS ONE, scientists actually happened upon their first glowing eel back in 2011 rather by accident. While studying biofluorescent coral around Little Cayman Island in the Caribbean, marine biologist David Gruber and his fellow expeditioners caught a tiny eel glowing green in one of their photographs, which was as intensely fluorescent as the surrounding corals.
Although the researchers weren’t sure what the exact species was, they identified it as a type of false moray eel belonging to the family Chlopsidae, which are similar in appearance but smaller than true moray eels. Still, in spite of a lack of ID, the find was amazing: It was the first image of a brightly green fluorescent vertebrate in the wild, the authors believe.
Intrigued and inspired by the find, the team subsequently embarked on a number of expeditions across the Caribbean and South Pacific, looking for more examples of biofluorescent marine animals. And it’s been a fruitful endeavor: Last year, Gruber’s group published a paper documenting more than 180 species of biofluorescent fishes.
Unlike bioluminescent animals, in which a reaction converts chemical energy into light energy that is then emitted, biofluorescent species don’t employ reactions to obtain their glow. Instead, they absorb high-energy blue wavelengths of light and re-emit them at lower wavelengths, such as green or orange. Since most wavelengths of light, other than blue, are filtered out with increasing ocean depth, this means that an environment that would otherwise be dominated by blue can achieve some color.
The proteins responsible for the glow in some biofluorescent animals have been described, but following the eel discovery, Gruber and colleagues managed to identify two that were previously unknown. These were found in a plain false moray eel, and another as yet unclassified false moray belonging to the same group as the former, National Geographic reports.
False moray in white (top) and green fluorescence (bottom). Gruber et al., PLOS ONE 2015.
The scientist then examined the genetic sequences responsible for these proteins in order to probe their possible origins, comparing the stretches of DNA to those found in other animals, which revealed an interesting evolutionary history. It turns out that long ago, these fluorescent proteins used to live in the brain and bind fatty acids, but somewhere along the line a gene duplication event occurred. The doubled sequence then came under strong positive selection, suggesting the resulting protein began serving an important function, and after some refinement ultimately gave rise to the fluorescent protein we see today.
Although it’s unclear at this stage what role fluorescence is playing in these eels, previous hypotheses for biofluorescence in marine animals have included communication and mating, possibly attracting mates or signaling reproductive status.
[H/T: National Geographic]