Too much sun can be bad for your skin, and while you and I can cover up, apply sunscreen or just get out of the sun to avoid its powerful rays, whales can't exactly do that. But new research reveals that some whales actually do the equivalent of tanning – applying a base coat of color so the sun will not be as harmful later on.
The news, published last week in the journal Scientific Reports, comes from a multi-year study of whales in the Gulf of California. A team of researchers studied blue, sperm and fin whales and found that each species has its own strategy for avoiding too much sun damage.
That damage, by the way, can be quite severe for an animal as big as a whale. The research began when marine biologists in Mexico noticed that more and more whales in their area had blisters on their skin. They called in UV radiation experts from Newcastle University in the U.K. and other institutions to study the blisters and the whales' behavior.
The researchers spent three years studying the whales, "tagging" them with crossbows that removed tiny portions of skin for the exam. They looked at the content of melanin in the whales' skin – that's the same pigment found in our own skin — as well as examined the skin for signs of damage to the mitochondrial DNA, which would be a sign of damage from UV radiation (in other words, sunburn).
The fin whales, it turned out, had the darkest skin and therefore the highest melanin content. As a result, they had the least amount of mitochondrial DNA damage and were found to be the most resistant to UV damage.
Blue whales, however, had the lowest melanin content of the three species. The researchers found that the blue whales actually got darker as the seasons changed. Although the skin darkened from exposure to the sun, the change did not necessarily provide greater levels of protection. The researchers found that the blue whales' skin also showed signs of UV damage.
As for sperm whales, they had a completely different mechanism. Their skin, the researchers found, contains a protein that protects it from UV damage. This species spends more time at the surface of the water, so the species has apparently adapted to withstand that constant exposure.
Some researchers have linked the whales' skin blisters to increased levels of solar radiation. This could have long-term implications for many whale species, says the study's joint senior author, Karina Acevedo-Whitehouse, who is currently senior lecturer at the Universidad Autónoma de Querétaro, Mexico. "There has been an increase in the number of reports on blister-type skin lesions in various whale species in areas of high UV radiation. It's important that we study the effect of UV radiation on whale skin and the mechanisms that these species use to counteract such damage, both from an evolutionary approach and from a conservation perspective."
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