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Sperm whale (Pyseter macrocephalus)

Sperm whales (tail flukes pictured) must contend with getting too much sun, as they can spend hours at the ocean's surface.

Photograph by Stephen Frink, Getty Images

Jane J. Lee

National Geographic

Published August 29, 2013

It's a good idea to apply sunscreen before heading to the beach if you don't want to burn and blister. But for marine animals like whales, that's not an option.

Species like sperm whales can spend up to six hours at the ocean's surface in between dives, baking in the sunlight. So how do they protect themselves from a serious case of sunburn?

It turns out that their bodies have similar defense mechanisms against the sun's ultraviolet (UV) radiation as people, according to a new study published August 30 in the journal Scientific Reports.

Researchers took more than a hundred skin biopsies from blue, fin, and sperm whales in the Gulf of California (map) from 2007 to 2009. They used crossbows loaded with modified arrowheads to retrieve plugs of skin from the marine mammals.

They found that blue whales—which have the lightest skin color of the three species—tanned during their summer sojourns before migrating back to their northern feeding grounds.

Sperm whales didn't tan. Instead, the whales, which can receive an "overdose" of UV radiation during their hours at the ocean's surface, have proteins that protect their cells from UV damage, said study co-author Mark Birch-Machin, a professor of molecular dermatology at Newcastle University in the United Kingdom.

This process is similar to how human bodies produce antioxidants in response to free radicals, molecules that can cause a lot of genetic and cellular damage.

And fin whales escaped sun damage thanks to their high levels of melanin—a skin pigment also shown to protect humans from UV radiation.

Uncharted Territory

Studying how whales react to UV-radiation damage has never been done before, making the new paper very useful, said Marie-Francoise Van Bressem, a veterinarian specializing in skin diseases in whales, dolphins, and porpoises at the Peruvian Centre for Cetacean Research in Lima.

Now that the ozone layer that shields Earth from UV radiation is diminishing, "it's important to know what the consequences are for whales and dolphins, especially for vulnerable or endangered species," added Van Bressem, who was not involved in the study.

Instances of skin disease among whales, dolphins, and porpoises—collectively known as cetaceans-are on the rise, she said. And although it's difficult to tell what causes many of these skin conditions, UV damage is one cause.

Even though whales have built-in defenses to UV radiation, high exposure can still be harmful.

"At what point does that [skin lesion] develop into skin cancer?" asked Birch-Machin. No one knows, he said.

But it's important to figure out, he said, since the skin damage researchers are already seeing could serve as an early warning sign of a serious disease like cancer. (Learn about cancers in beluga whales.)

Mirrors

Birch-Machin and colleagues studied the DNA contained in the whales' mitochondria—a cellular organ responsible for powering the cell—in order to assess damage caused by UV radiation.

"Mitochondrial DNA damage is directly linked to UV exposure, which is why UV ages us," said Birch-Machin.

"Because the mitochondria are the battery packs of the cell, basically, our batteries run down."

The research team found that older whales, and whales with less melanin content in their skin—like blue whales—had the greatest level of damage in their mitochondrial DNA (mtDNA). Fin whales, which had the greatest amount of melanin, had the least amount of mtDNA damage.

Looking at the genetic consequences—or mtDNA damage—of UV radiation has also never been looked at in whales before, Birch-Machin said. And it turns out that this aspect of whale aging mirrors human aging. (Related: "Do Whales Have Culture? Humpbacks Pass on Behavior.")

Early Warning Signs?

Birch-Machin would like to figure out whether the skin blistering seen on these whales would develop into skin cancer.

He and his colleagues would also be interested in looking at other hairless marine mammals, such as walruses, to see if they have similar issues with UV-radiation exposure.

Although Birch-Machin does a lot of work on UV damage in human skin, he's excited about the prospect of delving further into other species.

"Whales will reflect the UV dose that the ocean receives," he said. As "floating dosimeters," they are a signal for the health of the ocean.

Follow Jane J. Lee on Twitter

6 comments
Babu Ranganathan
Babu Ranganathan

NOT MADE BY NATURE! Just because something exists in nature doesn't mean it was invented or made by Nature. If all the chemicals necessary to make a cell were left to themselves, "Mother Nature" would have no ability to re-organize them into a cell. It takes an already existing cell to bring about another cell. The cell exists and reproduces in nature but Nature didn't invent or design it! Nature didn't originate the cell or any form of life.

Natural laws can explain how an airplane or living cell works, but it's irrational to believe that mere undirected natural laws can bring about an airplane or a cell. Once you have a complete and living cell then the genetic program and biological machinery exist to direct the formation of more cells, but how could the cell have originated naturally when no directing code and mechanisms existed in nature? All of the founders of modern science believed in God. Read my Internet article: HOW FORENSIC SCIENCE REFUTES ATHEISM 

Only evolution within "kinds" is genetically possible (i.e. varieties of dogs, cats, etc.), but not evolution across "kinds" (i.e. from sea sponge to human). How did species survive if their vital tissues, organs, reproductive systems were still evolving? Survival of the fittest would actually have prevented evolution across kinds! Read my Internet article: WAR AMONG EVOLUTIONISTS! (2nd Edition). I discuss: Punctuated Equilibria, "Junk DNA," genetics, mutations, natural selection, fossils, genetic and biological similarities between species.
 
Natural selection doesn't produce biological traits or variations. It can only "select" from biological variations that are possible and which have survival value. The real issue is what biological variations are possible, not natural selection. Only limited evolution, variations of already existing genes and traits are possible. Nature is mindless and has no ability to design and program entirely new genes for entirely new traits.

Visit my newest Internet site: THE SCIENCE SUPPORTING CREATION

Sincerely,
Babu G. Ranganathan*
(B.A. theology/biology)

Author of popular Internet article, TRADITIONAL DOCTRINE OF HELL EVOLVED FROM GREEK ROOTS

* I have had the privilege of being recognized in the 24th edition of Marquis "Who's Who In The East" for my writings on religion and science, and I have given successful lectures (with question and answer time afterwards) defending creation from science before evolutionist science faculty and students at various colleges and universities.

Charles Greenberg
Charles Greenberg

Hey babu, quick question, Why would you respond "NOT MADE BY NATURE!" if the word nature or the suggestion of it is not mentioned once in the article.  I believe everyone has a right to their own views but your post makes you look desperate.

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