Scientists Create Gene-Edited ‘Peter Pan’ Tadpoles That Could Control Invasive Cane Toads Through Cannibalism To combat one of Australia’s most troublesome species, researchers are developing hungry tadpoles that never grow up In hopes that they could control destructive cane beetles, people introduced cane toads to Australia in 1935. Instead, the amphibian's population exploded, and today, cane toads number roughly 200 million. Joshua Prieto / SOPA Images / LightRocket via Getty Images Scientists in Australia have genetically modified invasive cane toad eggs to create “Peter Pan” tadpoles that never grow up—they don’t ever metamorphose into adults. Cane toad tadpoles already have an appetite for eggs of their own species, but these modified versions may eat several times as many, making them a potential solution for controlling the destructive amphibian’s numbers. Cane toads were purposely introduced to Queensland in 1935 to control cane beetles that were damaging cane crops. But that plan backfired, and they’ve since become an even bigger problem. With very few predators, the toads quickly spread across northern Australia. Now, they wreak havoc on the local environment, outcompeting native species with their enormous appetites. There are an estimated 200 million cane toads in the region, where their poison kills native marsupials and reptiles that try to eat them. A single cane toad can lay a clutch of more than 30,000 eggs, so manual control methods have struggled to keep up with their population growth. Instead, biologists are turning to gene editing. Rick Shine, an evolutionary biologist at Macquarie University in Australia, has been creating the Peter Pan tadpoles with his team. The scientists removed a gene that controls the production of thyroxine, a hormone that regulates the amphibians’ metamorphosis. “Since cane toad tadpoles cannibalize cane toad eggs, they would be a terrific cane toad controller,” Shine explained to Elisabeth Marie at Australian Geographic last November. “They also don’t eat the eggs of native frogs much at all and have almost no poison until they metamorphose.” After knocking out the gene, “we seem to have ended up with these sort of quite large, relatively long-lived, voracious cannibals that are just ideally suited to control the numbers of their own species,” adds Shine to Peter de Kruijff at the Australian Broadcasting Corporation (ABC).Cane toad tadpoles are already cannibalistic, but these gene-edited versions are even bigger and hungrier for eggs. The new tadpoles are not merely cannibals: “To our delight, they are super-cannibals,” write the researchers. The trials suggest Peter Pan tadpoles can eat up to four times the number of eggs as standard cane toad tadpoles do, though that work has yet to be peer-reviewed. Other scientists also say the method has potential. “It builds off basic toad biology to potentially deliver a new tool for managing toads,” says Ben Phillips, a population biologist at Curtin University who was not involved in the research, to the ABC. “It has promise as a local control measure in places where breeding sites are limited, so it is worth developing further.” So far, the Peter Pan tadpoles have only been tested in controlled settings in Western Australia and the Northern Territory. The first field trials are expected to start later this year, after a risk assessment. The researchers will need to determine whether the gene-edited tadpoles could impact native birds, fish and turtles. “Adequate research to demonstrate there is no possibility of negative consequences for native wildlife will be required before any permits for wild release can be considered,” says a spokesperson for the Northern Territory’s Department of Lands, Planning and Environment to the ABC. In a way, though, the researchers say they aren’t creating any organisms that don’t already exist—Shine noted to Australian Geographic that some cane toad tadpoles already happen to never metamorphose in the wild. They intend to make that occur at a higher rate. “We’re very carefully testing reactions of native fauna to our non-metamorphosing tadpoles before we talk about releasing them in the wild,” Shine told the Economist in January. “We’re trying not to repeat the folly of 1935.” The researchers also have to figure out another problem: how to scale the method. The gene-edited tadpoles never get old enough to reproduce, so their populations won’t sustain themselves in the wild. And it’s impractical for the scientists to manually modify thousands of eggs. One option would be to add thyroxine to a body of water with Peter Pan tadpoles to make some of them grow into adults. Then, those toads might breed and lay eggs with the modification. “Then we would have 20,000 or 30,000 Peter Pan tadpoles per clutch,” explains Shine to the ABC. “It wouldn’t really take very many adult toads with that genetic change for us to have a vast supply of the sorts of tadpoles we’d like.” As of now, that strategy hasn’t successfully coaxed the Peter Pan tadpoles to mature into adults, but Shine has faith that they can get there with more research. “When I first thought of the idea, it seemed like a ‘moonshot’ that would probably be impossible, but could be incredibly exciting if it worked,” said Shine to Australian Geographic. “That dream is now close to reality.” “We can use cane toads to control themselves.” Get the latest stories in your inbox every weekday.