How the genes of Cedric and Spirit can help save the Tasmanian devils
The names of Cedric and Spirit can be added to the list of outstanding stars of the Tasmanian devil community - alongside Taz from Taz-Mania, the instantly recognizable cartoon caricature of these bizarre marsupials. Cedric and Spirit are the names given to two Tasmanian devils, by scientists who have fully sequenced the pairs' genome, in order to help save their brethren from extinction. The pioneering conservation research is being published today in Proceedings of the National Academy of Sciences.
Tasmanian devils are the largest carnivorous marsupials in the world, since the demise, last century, of the dog-like Tasmanian tiger. They are only found on the island of Tasmania, off of the south coast of Australia, and are renowned for their rending screech, ferocious build, powerful bite and frenzied feeding habits. But now they are facing a foe even more ferocious than themselves - a face-eating cancer that is spread from animal to animal, and which may have wiped out half the population since 1996.
Devil Facial Tumor Disease (DFTD) is a nasty and infectious cancer that first disfigures its victims, and then causes them to die from suffocation or starvation. It appears to have started with a single individual, and is spread by the normal social interaction of Tasmanian devils - touching, mating and biting. The only option open to scientists, to prevent the species from being wiped out, is to hold back a number of individuals in zoos in isolation, to act as a disease-free 'firebreak'.
But deciding which individuals to select is tricky, as maximizing genetic diversity is important for the devils, once the firestorm of DFTD has passed. This is where Cedric and Spirit come in. These two individuals come from opposite ends of the island, with Cedric having shown some resistance to strains of DFTD.By sequencing all 3.3 billion base pairs of their genes, the scientists hoped to glean information on what might be enabling some devils to resist DFTD.
The team - from Pennsylvania's Penn State University, San Diego's Venter Institute and a number of other institutes in the US, Australia and Denmark - were able to sequence the genes exceptionally quickly, by using a new genetic technique developed by Roche Diagnostics and 454 Life Sciences. As well as Cedric and Spirit, the team were also able to capture snatches of the genetic diversity of 175 other devils - both alive, and stuffed, in museum cases across the world.
Lead author, Stephan Schuster, refers to the use of the genetic resources stored in museums as 'museomics', and believes this is an overlooked, but increasingly valued, tool for conservationists. 'Museums are treasure troves of specimens collected in the last 250 years," he said. The sampling approach leaves collections intact, says: "in fact, we can get DNA from hair shafts of a museum specimen.'
The results of all this genetic sequencing have shown two things - first, the genetic diversity of living Tasmanian devils is low, meaning that careful selection of individuals to save is even more important. And the museum pieces have revealed that this low diversity is historical - Tasmanian devils have long been short of genetic diversity, and DFTD has not introduced a genetic 'choke-point' in the evolutionary history of the animals.
Schuster is hoping that this delving into the genetic past will help to keep the descendants of Cedric and Spirit alive-and-kicking in the Tasmanian wilds in the future. 'To plan for the future, you have to be willing to understand the past. It's important to examine museum specimens, as well as the population history of species over the last 10,000 to 50,000 years, and to use that genetic data to formulate a plan. The idea is to save a species, not to do a 'post-mortem' on it,' he concluded.
Top Image Credit: © Cloudia Newland
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