Why Don’t Fish Get Sunburnt?

Scientists have discovered that many animals can produce their own sunscreen [A.J. Hall]

With the summer months quickly approaching, the annual sun worshipping rituals that typically come along with the season will soon be in full swing. The only caveat, all of that fun in the sun exposure comes at a cost—a potentially steep and deadly cost as well, if the gradual increases in melanoma cases over the past 20 years is taken into consideration.

So, with all of this sun exposure being potentially detrimental to humans, how is it that many animal species are able to spend their entire lives outdoors with very little concern of overexposure to the sun? Scientists from Oregon State University (OSU) think they may have just found the answer: they make their own sunscreen.

While at first glance this might seem like an obvious conclusion, the OSU team has dug deep into the question to uncover the molecular pathways that many animals use to generate ultraviolet protective compounds. The researchers found that many fish, amphibians, reptiles, and birds can natural produce a compound called gadusol, which provides protection against UV radiation.   

“Humans and mammals don't have the ability to make this compound, but we've found that many other animal species do,” said Taifo Mahmud, Ph.D., professor at the OSU College of Pharmacy, and lead author on the research.

The findings from this study were published recently in eLife through an article entitled “De novo synthesis of a sunscreen compound in vertebrates”

Dr. Mahmud and his team also believe that the ability by so many diverse species to generate UV-protective compounds must have evolved long ago in some prehistoric single-cell organisms, which provided a selection advantage over time and spread through the animal kingdom.        

“The ability to make gadusol, which was first discovered in fish eggs, clearly has some evolutionary value to be found in so many species,” explained Dr. Mahmud. “We know it provides UV-B protection, it makes a pretty good sunscreen. But there may also be roles it plays as an antioxidant, in stress response, embryonic development and other functions.”

It was originally thought by many scientists that marine fish were acquiring gadusol compounds from dietary sources or some symbiotic origin. However, the OSU team unexpectedly discovered that many fish can synthesize gadusol de novo.

Additionally, the investigators were able to isolate the gadusol genes from fish and engineer them into yeast cells to produce the compound in much larger volumes. This will allow the researchers to test gadusol in many different ways, as well as open up entire new avenues of research into UV blocking compounds.  

“The discovery of the gadusol pathway in vertebrates provides a platform for understanding its role in these animals, and the possibility of engineering yeast to efficiently produce a natural sunscreen and antioxidant presents an avenue for its large-scale production for possible use in pharmaceuticals and cosmetics,” concluded the scientists.