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A northern white rhino, named Najin, at Ol Pejeta Conservancy in Kenya in 2015. (Tony Karumba / AFP / Getty Images)
A 28-year-old rhino named Najin and his daughter, Fatu, are the only Northern white rhinos on the planet. They live at Ol Pejeta Conservancy in Kenya under constant armed guard. Both animals are infertile. In March, veterinarians euthanized Sudan, Najin's father and the last male rhinoceros of their species. Once Najin and Fatu die, their subspecies go the same way.
But the genes of the northern white rhinos could survive. In a new study published Wednesday in Nature Communications, researchers used in vitro fertilization to create viable rhinoceros embryos.
An international team of zoologists, veterinarians, and other researchers collected unfertilized eggs from southern white rhinos, a closely related subspecies with a population of about 20,000 individuals. In one dish, scientists used northern white rhinoceros sperm to fertilize southern white rhinoceros eggs, producing hybrid embryos.
Two hybrid embryos were frozen for future implantation, the researchers said. They anticipate, after developing the proper technique, that it will be possible to transfer embryos to female southern white rhinos in the years to come. A hybrid calf provides some genetic continuity for the northern white rhinoceros even after extinction.
"It's a very ambitious and very courageous effort to save some of the genetics of a spectacular animal," said conservation biologist Stuart Pimm. from Duke University, who studies the extinctions and has not been involved in this project.
Northern white rhinos are not evolutionary failures. Rhinos have failed, as Thomas B. Hildebrandt, biologist and author of the study, said Tuesday, because their skins were not bullet-proofed. They have failed because rhinoceros horns, the gram for the gram, are worth more than gold – seeking high prices as status symbols or for their medicinal powders. (The horns, mainly composed of a protein called keratin, are as medically useful as nails.)
Hildebrandt, professor at the Leibniz Institute for Zoological and Wildlife Research in Berlin, and his colleagues do part of a project that has stored genetic material of the northern white rhinoceros for decades. Oliver Ryder, a conservation geneticist at the San Diego Zoo, took skin samples from Sudan in 1986 as part of a rhinoceros cell bank. According to Hildebrandt, scientists began freezing northern white rhinoceros sperm in 2008, either 300 milliliters or about the volume of a soda can
. A two-tonne wild animal
"It's a technological feat," said David E. Wildt, senior researcher at the Smithsonian Conservation Biology Institute, who was not involved in this research. The study's authors used a 60-inch (patent-pending) instrument to insert a needle through the anus of the South-anesthetized white rhinos and into the ovarian tissue. An ultrasound monitor provided the only orientation for egg collectors.
Embryos are viable and "beautiful," Wildt said. He adds: "It's the first step of a long journey to produce live offspring."
Veterinarians have successfully used in vitro fertilization in horses, cattle and other animals, but never as fat as a white rhinoceros. Yet such techniques are the "only way" to save the northern white rhinoceros genes, said biologist Terri Roth, director of the Center for Conservation and Threatened Wildlife Research at the Cincinnati Zoo. These genes could benefit white rhinos that move in their parents' old habitats, or confer benefits to live rhinoceroses during epidemics.
The odds are against a complete revival of the white rhino, according to Roth, who oversaw the first successful reproduction of a Sumatran rhinoceros in captivity in 2001. "Even though the moon and the stars were lining up" and that a rhinoceros surrogate gave birth to a hybrid calf, "this still has not brought back the subspecies".
Ryder from the San Diego Zoo, along with Hildebrandt and other reproductive biologists, devised a plan in Vienna in 2015 to save the subspecies. It will be possible to bring back a complete Northern White Rhino, predicts Ryder, which would require an egg and sperm.
Hildebrandt and his colleagues plan to harvest eggs from Najin and Fatu, and the researchers are "extremely confident" that they will succeed. The highest risk is not lacking in acquiring eggs, says Hildebrandt, but to adult rhinos. The animals must be anesthetized for two hours, "which is a pretty risky situation."
One of Hildebrandt's co-authors is Katsuhiko Hayashi of Kyushu University, a pioneering reproductive biologist who turned mouse cells into eggs. The team aims to replicate this success with rhinoceros stem cells. Until now, they have generated 12 lines of rhinoceros stem cells, said Hildebrandt.
All scientists who spoke with The WashingtonPost agreed that biological techniques can complement the protection of rhinos on the ground. Funds allocated for laboratory research generally do not come from the same sources as funds for other conservation purposes. "We should come to that with everything we have," Roth said.
"It's a big puzzle." Susie Ellis, executive director of the Rhino International Foundation, said, "There is no single solution." never been saved by the high-tech approach alone. "Science is" very important, "but it needs to be paired with" working with local communities and politicians. "
Pimm, as excited as she is. it was about this result, offered a warning.We can not afford to adopt a cavalier attitude towards extinction, as if the animals were something to bring back to our liking, he said. "The main event must be: We must stop the poaching of rhinos."
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