Scientists say they are close to being able to genetically modify a rare Australian mammal to save it from going extinct as a result of the presence of the non-native cane toad.
The northern quoll, a small carnivorous marsupial weighing up to about 1kg and belonging to the same family as the Tasmanian devil, has suffered huge population declines and range decreases as a result of habitat loss and the impact of a whole range of introduced species.
But the cane toad, native to South and Central America and brought to Australia in the 1930s to deal with a sugar cane pest, is perhaps the quoll’s ultimate nemesis. Along with other members of the Bufonidae family, including the European common toad, cane toads possess a neurotoxin to which no Australian species has resistance because they evolved on a continent entirely free from this group of amphibians.
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As a result, many species – not just northern quolls but native reptiles such as goannas and tiger snakes – frequently die when they predate on the toads, which are large and slow-moving animals, making them easy meals.
Now experts in gene-editing from the University of Melbourne and a ‘de-extinction’ company called Colossal Biosciences say they can introduce genetic resistance to the toxin by taking DNA from a species of South American lizard and ‘edit’ that into the cells of a northern quoll. They have already managed to do this with the cells of the closely related dunnart, another endemic marsupial.
The problem conservationists face, explains Andrew Pask, professor of genetics and developmental biology at the University of Melbourne, is that not only have they been unable to control cane toads in any effective way, the toads are rapidly spreading into the few remaining parts of Australia where quolls are still found.
“The northern quoll is one of our most endangered species and is predicted to go extinct within the next decade,” he says. Trying to remove cane toads hasn’t worked because they are such prodigious breeders. “In a standard spawning event, a cane toad can lay 20,000 eggs, and they do that multiple times a year, so they are just unstoppable,” Pask adds.
Conferring resistance within the quolls to the toxin would not only allow them to safely eat any toads they come across, but it could also create a situation where they effectively control and reduce populations of the invasive amphibian, potentially improving the conservation status of other species.
Jack Ashby, a zoologist with an expertise in Australian mammals and assistant director of Cambridge University’s Museum of Zoology, says it was an interesting idea, but needed serious thought.
“Genetically modifying a wild species has very serious ethical considerations,” Ashby says. “To what extent this is the last hope for the northern quoll is a big question. Is a genetically modified quoll better than no quoll? We need to have a solid understanding of the ethics of changing a wild species (before anything occurs).”
The northern quoll used to be widespread across a broad swathe of the top half of Australia, but today it can only be found in a few isolated areas in Western Australian, Northern Territory and Queensland. Once genetically modified quolls have been created, the idea would be to test whether the strategy works in a contained environment before releasing them properly into the wild. It’s thought the modified animals would come to dominate as they would have such a competitive advantage.
Pask says the technology had the potential to be used to solve other conservation conundrums. “(Creating) resistance to devil facial tumour disease in Tasmanian devils is another thing we are looking at,” he says. “Chlamidia resistance in koalas could be another. The gene-editing technology that we have makes these things possible.”
Find out more about the study.
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