Evidence of melanoma in wild marine fish populations

The increase in reports of novel diseases in a wide range of ecosystems, both terrestrial and marine, has been linked to many factors including exposure to novel pathogens and changes in the global climate. Prevalence of skin cancer in particular has been found to be increasing in humans, but has not been reported in wild fish before. Here we report extensive melanosis and melanoma (skin cancer) in wild populations of an iconic, commercially-important marine fish, the coral trout Plectropomus leopardus. The syndrome reported here has strong similarities to previous studies associated with UV induced melanomas in the well-established laboratory fish model Xiphophorus. Relatively high prevalence rates of this syndrome (15%) were recorded at two offshore sites in the Great Barrier Reef Marine Park (GBRMP). In the absence of microbial pathogens and given the strong similarities to the UV-induced melanomas, we conclude that the likely cause was environmental exposure to UV radiation. Further studies are needed to establish the large scale distribution of the syndrome and confirm that the lesions reported here are the same as the melanoma in Xiphophorus, by assessing mutation of the EGFR gene, Xmrk. Furthermore, research on the potential links of this syndrome to increases in UV radiation from stratospheric ozone depletion needs to be completed.

The increase in reports of novel diseases in a wide range of ecosystems, both terrestrial and marine, has been linked to
many factors including exposure to novel pathogens and changes in the global climate. Prevalence of skin cancer in
particular has been found to be increasing in humans, but has not been reported in wild fish before. Here we report
extensive melanosis and melanoma (skin cancer) in wild populations of an iconic, commercially-important marine fish, the
coral trout Plectropomus leopardus. The syndrome reported here has strong similarities to previous studies associated with
UV induced melanomas in the well-established laboratory fish model Xiphophorus. Relatively high prevalence rates of this
syndrome (15%) were recorded at two offshore sites in the Great Barrier Reef Marine Park (GBRMP). In the absence of
microbial pathogens and given the strong similarities to the UV-induced melanomas, we conclude that the likely cause was
environmental exposure to UV radiation. Further studies are needed to establish the large scale distribution of the
syndrome and confirm that the lesions reported here are the same as the melanoma in Xiphophorus, by assessing mutation
of the EGFR gene, Xmrk. Furthermore, research on the potential links of this syndrome to increases in UV radiation from
stratospheric ozone depletion needs to be completed.

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