Researchers have discovered why many animal species can spend their whole lives outdoors with no apparent concern about high levels of solar exposure: they make their own sunscreen.
The findings, published today in the journal eLife by scientists from Oregon State University, found that many fish, amphibians, reptiles, and birds can naturally produce a compound called gadusol, which among other biologic activities provides protection from the ultraviolet, or sun-burning component of sunlight.
The researchers also believe that this ability may have been obtained through some prehistoric, natural genetic engineering.
The gene that provides the capability to produce gadusol is remarkably similar to one found in algae, which may have transferred it to vertebrate animals - and because it's so valuable, it's been retained and passed along for hundreds of millions of years of animal evolution.
"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, a professor in the OSU College of Pharmacy, and lead author on the research.
The genetic pathway that allows gadusol production is found in animals ranging from rainbow trout to the American alligator, green sea turtle and a farmyard chicken.
"The ability to make gadusol, which was first discovered in fish eggs, clearly has some evolutionary value to be found in so many species," Mahmud said. "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."
In their study, the OSU researchers also found a way to naturally produce gadusol in high volumes using yeast. With continued research, it may be possible to develop gadusol as an ingredient for different types of sunscreen products, cosmetics or pharmaceutical products for humans.
A conceptual possibility, Mahmud said, is that ingestion of gadusol could provide humans a systemic sunscreen, as opposed to a cream or compound that has to be rubbed onto the skin.
The existence of gadusol had been known of in some bacteria, algae and other life forms, but it was believed that vertebrate animals could only obtain it from their diet. The ability to directly synthesize what is essentially a sunscreen may play an important role in animal evolution, and more work is needed to understand the importance of this compound in animal physiology and ecology, the researchers said.