Whales get sun tans, burns too

Los Angeles TimesSeptember 29, 2013 

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A blue whale surfaces in the Pacific near Dana Point,Calif.: How whales’ skin reacts to UV rays varies among species. (AP Photo/Marc Carpenter,Capt. Dave's Dolphin & Whale Safari)

MARC CARPENTER — AP

We’re not the only ones who get summer tans. So do whales – and their DNA gets damaged in the process too, scientists say. The new findings, published in the journal Scientific Reports, could lead to better sunscreens and other sun protection products for humans.

The study authors already knew that the UV radiation in sunlight caused some whales’ skin to react like human skin, forming sunburn-like blisters. But was this response similar at a molecular level, too?

To find out, the team analyzed skin samples from the backs of 106 blue whales, 23 sperm whales and 55 fin whales during their annual migration from the Arctic Ocean to the sunnier Gulf of California, which lasts from February to April.

In all three species, the number of cells that produce the pigment melanin increased over this time period as UV radiation levels rose, similar to what happens in humans. Blue whales, the palest of the three species, showed the greatest increase in melanin-producing cells, or melanocytes, most likely because they had so few of them to begin with, said Mark Birch-Machin, a molecular biologist at Newcastle University in England and a co-author of the study.

On the other hand, the slightly darker sperm whales showed a more subtle increase in melanocytes, probably because they spend more time socializing at the sunlit ocean surface, Birch-Machin said. Their bodies had already produced more melanocytes as a result.

The number of melanocytes didn’t change in the pitch-black fin whales. They had the highest baseline level of these cells, which could be because they spend most of the year in the Gulf of California. “They’ve already become acclimatized to this amount of UV exposure,” Birch-Machin said.

The researchers also examined the DNA in the animals’ mitochondria, the tiny “battery packs” that provide energy to cells. Mitochondrial DNA is damaged in sunburned human skin. And the same is true for whales, the researchers found: Blue whales suffered the worst mitochondrial DNA damage, followed by sperm and fin whales. The results suggest that melanin protects whales against UV radiation, just like it does in humans.

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