Faced with extinction, the devils fight back
Research finds clues that Tasmanian devils are adapting to the cancer that threatens their existence. Andrew P Street reports.
In a very welcome piece of good news about Tasmanian devils (Sarcophilus harrisii), new University of Tasmania research on the contagious facial tumour disease currently afflicting wild populations seems to indicate that the marsupials are evolving to live with the cancer, according to a new paper in the journal Bioessays.
The researchers looked at animals at risk of catching transmissible cancer, known as devil facial tumour disease (DFTD), which has been driving the species toward possible extinction over the past two decades, and found unexpected signs of immunity, including elevated levels of certain immune system molecules which reduce their likelihood of getting the disease.
“Active immune responses to DFTD and even tumour regression have recently been observed in several animals, showing a very promising sign that could be exploited for the management of the species,” says lead author Beata Ujvari from Deakin University’s School of Life and Environmental Sciences in Melbourne, Australia.
The researchers say the adaptations made by the devils in response to the disease can be described as an “evolutionary arms-race between malignant cells and their hosts”.
“All the evidence suggests that devils have the capacity to adapt to this transmissible cancer at genetic and phenotypic levels,” explains co-author Rodrigo Hamede, from the University of Tasmania. “We have been observing natural selection in action, and this has happened in a very short amount of time.”
Part of the devil's arsenal is promiscuity: since individuals mate with multiple partners they maintain a diverse genetic pool which in turn increases the chances of responding to DFTD.
However, while the devils have been evolving, so has the disease. A second strain, DFT2, was described three years ago and future mutations seem inevitable. However, the threat of the species' imminent extinction in the wild appears to have been paused – for now, at least.