Tanning sharks resistant to melanoma

Hammerhead shark pups held in a shallow clear seawater pond at the Hawaii Institute of Marine Biology darkened after several weeks. Photo / Thinkstock

Sharks may hold the key to preventing skin diseases in humans, according to new research.

Michael Sweet, a researcher in the School of Biology at Newcastle University's Newcastle Institute for Research on Sustainability, has found that while sharks can tan, they are resistant to melanoma.

"As far as I'm aware, sharks appear very robust to skin damage and disease," he told Discovery News. "I don't know what makes shark skin so special, but it definitely needs to be studied."

Previously research undertaken by Mr Sweet and his team has found melanomas detected in wild fish in Australia's Great Barrier Reef, with the likely cause environmental exposure to UV radiation. Sharks' skin, however, simply changed colour, from brown to black.

The study has been published in the scientific journal PLoS ONE.

Mr Sweet is keen to look into whether human activities could have an impact on fish melanoma.

"I believe many other fish species will be suffering from cancers, and the more we look, the more we shall see," he told Discovery News. "We need to do further work to confirm the UV link, and if this comes true, then I'm sure human activities are having a direct effect on these fish. As I'm sure you are aware, climate change has dramatically affected many ecosystems and many, many organisms."

Another recent study, undertaken by the California State University Shark Lab, also looked tanning sharks.

Hammerhead shark pups held in a shallow clear seawater pond at the Hawaii Institute of Marine Biology darkened after several weeks, where UV levels are 600 times greater than those in their regular habitat of Kaneohe Bay.

An opaque filter was placed over the pectoral fins of untanned sharks to cut out UV light, to determine whether the darkening was due to solar radiation.

"Areas of skin from under the opaque filter were untanned, whereas all other skin exposed to direct sunlight was considerably darker, resulting in distinct "tan lines", the researchers said.

"Our experiments demonstrated that the sharks were truly sun-tanning and that the response was, in fact, induced by the increase in solar radiation, particularly UV. These sharks increased the melanin content in their skin by 14 percent over 21 days, and up to 28 percent over 215 days."

The researchers said the only other animals known to suntan are mammals.