These fish could be harbingers of a major human health crisis

Bad news, everyone. Researchers have discovered that 15% of the coral trout living in Australia's great Barrier Reef are suffering from what's been described as a scalier version of melanoma, a deadly form of skin cancer. That's unsettling for a number of reasons, but there are two big ones that should immediately give you pause.

1) This is the first case of melanoma ever documented in a wild fish population.
2) The Great Barrier Reef is directly beneath a gaping hole in Earth's ozone layer.

In other words, this is the first (disturbingly strong) evidence that fish are developing skin cancer from ultraviolet radiation outside of a research laboratory. Three coral trout with black patches of skin characteristic of melanoma can be seen up top. A healthy coral trout, pictured below, shows what these fish normally look like. Writes Science NOW's Krystnell Storr:

Scientists know how to give fish skin cancer in the lab. They breed a swordtail and a platyfish, both common pets, to create offspring that are more sensitive to UV light. The reason is genetic. Platyfish have a so-called tumor gene and a regulator to control it, whereas swordtails have neither. When the two mate, their offspring will sometimes inherit only the tumor gene without the regulator, leading to increased incidence of various cancers.

The researchers blame the disease [in the wild fish] on a couple of factors. The Great Barrier Reef lies directly below the largest hole in the ozone layer, which means the region receives significantly more UV radiation than other place on Earth. In addition, they believe that the three fish species may be crossbreeding with each other, resulting in offspring that are more prone — due to the loss or mutation of certain genes — to UV-induced skin cancer.

These fish could be harbingers of a major human health crisis

"Further work needs to be carried out to establish the exact cause of the cancer," explains coral disease researcher Michael Sweet, who led the study, "but having eliminated other likely factors such as microbial pathogens and marine pollution, UV radiation appears to be the likely cause." Sweet and his team's findings are published in the latest issue of PLoS ONE. You can read the report in its entirety here, free of charge.

The ozone layer, people. We need it. Just ask anybody living in Australia, where a staggering 2 in 3 people will be diagnosed with skin cancer before the age of seventy. That's higher than anywhere else on Earth. Coincidence? Hardly. The same reason you want to avoid overexposure to sunlight is the same reason Australia's cancer incidence is so astonishingly high: the UV radiation pouring through the ozone hole above Australia is incredibly harmful. It's so harmful that in 2009, the World Health Organization declared it a class I carcinogen.

Let this shocking revelation about wild fish populations be a reminder to us all to be smart about our sun exposure: avoid large doses of sunlight, wear sunscreen and protective clothing, and mind the gap(s in the ozone). Your skin will thank you for it.

[PLoS ONE via Science NOW + LA Times]

Images by Michelle Heupel and Michael Sweet