Great Barrier Reef Coral Trout Susceptible to Melanoma Skin Cancer

Australian and British scientists publish first account of skin cancer in wild fish

August 2, 2012

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Lesions were present on approximately 15% of the sampled population of Plectropomus leopardus; a) affected individual showing <10% coverage of body surface; b) P. leopardus with almost complete coverage >90%; c) healthy tissue under light microscope and d) the lesion. Photo and caption: PLOS One Journal.

Researchers with the Australian Institute of Marine Science and England's Newcastle University have found evidence of melanoma in wild populations of coral trout (Plectropomus leopardus) on Australia's Great Barrier Reef, according to a research paper published in the PLoS One journal. Scientists with the Australian Institute of Marine Science were initially at the reef performing shark prey surveys, when they noticed blotchy patches of skin on the coral trout, which when healthy exhibits bright orange skin.

The scientists then turned to Newcastle University scientists who were on the reef studying coral disease. When they ruled out infection, which was their first suspicion, the scientists put tissue samples under the microscope and determined that the reason for the discoloration was due to tumor formations on the skin of the fish. Samples of the fish tumors were compared against fish that were given melanoma in the lab, which looked to be virtually identical. The scientists sampled 136 fish, of which 20 of these fish (15 percent of the sample) had the lesions on the skin, with some fish showing 5 percent skin coverage and others showing complete coverage, giving the normally orange fish a black appearance. Scientists speculate that the fish are being exposed to UV radiation due to the location of the reef, which sits under the outer edge of the ozone hole over Antarctica.

“Further work needs to be carried out to establish the exact cause of the cancer but having eliminated other likely factors such as microbial pathogens and marine pollution, UV radiation appears to be the likely cause,” said Dr. Michael Sweet, lead researcher of the study.

“Studying disease in wild fish populations is very time-consuming and costly so it’s hard to say how long the disease has been around. However, what we do know is that it is now widespread in the coral trout population effecting three different species of this type of fish and we would not be surprised to find it in other species as well,” Sweet said.

The complete paper can be found at PLOS One.