Researchers have found coral, bar-cheeked, and blue spotted trout living in the Great Barrier Reef off the coast of Australia that are covered in lesions and dark patches—“a scalier version” of melanomas, ScienceNOW reported. Skin cancer can be induced in fish in the lab, as a model for human skin cancer, by breeding swordtails and platyfish to generate hybrid offspring, some of which carry a tumor gene from the platyfish but lack its regulator, making them more susceptible to various cancers. But this is the first time that the disease has been found in wild fish populations.
When marine biologists at the Australian Institute of Marine Science in Townsville first noticed the black patches on the fishes’ skin, they suspected it might be a fungal infection. But tissue samples analyzed by scientists at Newcastle University in the United Kingdom revealed no causative microbes, and no pollutants were identified in the Great Barrier Reef waters. Under a microscope, the answer became clear: the tightly clustered and pigmented cells suggested the fish had skin cancer. The researchers reported their results yesterday (August 1) in PLoS ONE.
"People have been working on coral trout for a long time, and it's interesting that this relatively recent observation might have a genetic component," Christopher Lowe, a marine biologist at California State University, Long Beach, told ScienceNOW. He noted that the wild fish could be interbreeding to produce a similar effect as the swordtail-platyfish crosses in the lab. But he and others suspect that UV radiation is also playing a big role, as the Great Barrier Reef sits below one of the largest hole in the ozone layer.