Whales have been shown to increase the pigment in their skin in response to sunshine, just as we get a tan（黝黑色，棕褐色）. Research published today in Nature journal, Scientific Reports, reveals that not only do some species of whales get darker with sun exposure, incurring DNA damage in their skin just like us, they also accumulate damage to the cells in the skin as they get older.

Experts in the response of skin to UV radiation at Newcastle University were called in after marine biologists in Mexico noticed an increasing number of whales in the area had blistered skin. Analysing samples from three types of whales -- blue, sperm and fin -- they worked together to study the changes in the whale skin after their annual migration to sunnier climes（气候，地方）.

Mark Birch-Machin, Professor of Molecular Dermatology at Newcastle University and joint senior author of the paper said: "Whales can be thought of as the UV barometers of the sea. It's important that we study them as they are some of the longest living sea creatures and are sensitive to changes in their environment so they reflect the health of the ocean."

Migrating whales 'tan'

Over three years, the team of marine biologists from Trent University, Canada and Universities in La Paz and Querétaro, Mexico, took skin samples from the backs of three species of whales during their annual migration. Occurring between February and April the whales move to the sunnier Gulf of California, along the northwest coast of Mexico.

Blue whales, the jumbo-jet sized giants, have a very pale pigmentation. During migration time the team found a seasonal change with the pigment in their skin increasing as well as mitochondrial DNA damage. This internal damage to the mitochondria, the engines of the cells, is caused by UV exposure and is what we find in sunburned human skin.

Sperm whales with their distinctive rounded foreheads have a darker pigmentation, also migrate between February and April to the Gulf of California, but have a different lifestyle. They spend long periods at the surface between feeds and are therefore, exposed to more sun and UV.

The scientists found the sperm whales had a different mechanism for protecting themselves from the sun, triggering a stress response in their genes. Newcastle University researcher Amy Bowman added: "We saw for the first time evidence of genotoxic pathways being activated in the cells of the whales -- this is similar to the damage response caused by free radicals in human skin which is our protective mechanism against sun damage."

In contrast, the darkest whales, the deeply pigmented fin whales, were found to be resistant to sun damage showing the lowest prevalence（流行，普遍） of sunburn lesions in their skin.