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Monday, January 17, 2022

Explained: How IVF is reversing an imminent extinction

The death of Sudan, who was earlier at the Dvur Králové Zoo in the Czech Republic, left the world with only two northern white rhinos, Najin, 30, and Fatu, 19 — both female.

By: Express News Service | New Delhi |
Updated: January 20, 2020 8:45:17 am
Explained: How IVF is reversing an imminent extinction Female northern white rhinos Fatu right, and Najin, 30, in August 2019. (AP Photo)

Researchers said last week that they had created another embryo — the third — of the nearly extinct northern white rhino, a remarkable success in an ongoing global mission to keep the species from going extinct.

“It’s amazing to see that we will be able to reverse the tragic loss of this subspecies through science,” a report by The Associated Press quoted Kenya’s wildlife minister, Najib Balala, as saying in a statement issued by the Kenya Wildlife Service and conservationists from Kenya, the Czech Republic, Germany, and Italy.

FUNCTIONALLY EXTINCT SINCE 2018: The Kenyan conservancy looking after the last male northern white rhino was forced to euthanise it in March 2018. The 45-year-old rhino, Sudan, was suffering from age-related complications that had eaten at his bones and given him skin wounds.

The death of Sudan, who was earlier at the Dvur Králové Zoo in the Czech Republic, left the world with only two northern white rhinos, Najin, 30, and Fatu, 19 — both female. Sudan had steadfastly refused to mate with either, and conservationists had even tried to raise $9 million for a fertility treatment by putting him on Tinder with a profile that read: “I don’t mean to be too forward, but the fate of the species literally depends on me”, and “I perform well under pressure.”

Najin and Fatu, mother-daughter pair in a species that in the 1960s numbered some 2,000 individuals, live at the Ol Pejeta Conservancy near Mount Kenya, where Sudan too, lived. The northern white is one of the two subspecies of the white (or square-lipped) rhinocerous, which once roamed several African countries south of the Sahara. The other subspecies, the southern white is, by contrast, the most numerous subspecies of rhino, and is found primarily in South Africa. There is also the black (or hook-lipped) rhinocerous in Africa, which too, is fighting for survival, and at least three of whose subspecies are already extinct.

The Indian rhinocerous is different from its African cousins, most prominently in that it has only one horn. There is also a Javan rhino, which too, has one horn, and a Sumatran rhino which, like the African rhinos, has two horns.

REVERSING THE EXTINCTION: In July 2018, scientists reported a major breakthrough — IVF for rhinos. They created a test-tube embryo by fertilising the egg of a southern white female with the frozen sperm of a northern white male. Immediately, there was hope for the northern white subspecies — if eggs from Najin and Fatu could be fertilised by the available frozen sperm from four (now dead) northern white males.

The task of collecting oocytes from Najin and Fatu was difficult and delicate, but in September 2019, researchers announced they had created two embryos, the decisive turning point in the effort to save the northern white. The success announced last week was the third. Four eggs were collected from Najin and six from Fatu; all three viable embryos were, however, created using Fatu’s eggs.

The embryos have been preserved in liquid nitrogen, and will be transferred to a southern white surrogate. Neither of the two living northern white females can carry a pregnancy. Since the gestation period for a rhino could be 18 months, the first northern white calf is expected to arrive in the world in 2022. The ultimate goal, scientists say, is to create a herd of perhaps five northern white rhinos that could be returned to the wild. That, however, could take several decades, given that the task of collecting eggs from Najin and Fatu will likely become increasingly more complex and risky as they grow older.

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