Tasmanian devils, the cute-but-scary marsupials found only in Tasmania and in Warner Brothers cartoons, are evolving to resist a lethal cancer that has threatened to wipe them out entirely. The transmissible cancer, called devil facial tumor disease (DFTD), is almost 100% fatal and has killed 80% of all Tasmanian devils in the past 20 years.
But the Tasmanian devil is fighting back, genetically at least, according to a new study from Washington State University, published in Nature Communications. The animals that survive the disease appear to be genetically different, with a resistance to the disease.
The Tasmanian devil is aggressive to other devils, and they often bite each other's faces. This can transmit DTFD. The problem is so bad that an "insurance population" is kept off-island in case the devils become extinct in their homeland.
The researchers compared stored devil DNA from before the outbreak with current DNA, collected from devils at outbreak sites. They found that these samples "exhibited significant changes in response to the strong selection imposed by the disease." Further, the majority of these mutations are in areas of the DNA related to cancer and immune functions in other animals, suggesting that the devils are indeed evolving resistance. Or rather, the resistance was already there, and the lucky devils that have it are surviving: The disease has only been around for a handful of generations, which is not long enough for evolution to really get involved in making completely defenses.
The next step is to breed resistant devils and use them to increase the genetic diversity of the off-island insurance population. And in future, says study lead Andrew Storfer, the knowledge gained here could be used to better understand the evolution of cancer transmissibility, notably in canine transmissible venereal tumor (CTVT) found in dogs.
In the meantime, though, things are looking up for the Tasmanian devil. "Overall," says Storfer, "the evolutionary response of Tasmanian devils observed here suggests hope for the continued survival of this species."
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