'Doomed' northern white rhino can be resurrected
Frozen cells will be able to bring the species back from the brink of extinction, claim scientists
There may only be two northern white rhinos left alive, but scientists say there is hope yet to bring the 'doomed' beasts back from the brink of extinction. Experts had worried that resurrecting the subspecies using frozen cells could create a heavily inbred population. New research shows the species has enough diversity in its DNA to survive this 'genetic bottleneck'. During such a bottleneck only a small number of animals contribute to the gene pool leading to a weaker species that struggles against disease outbreaks and environmental changes.
The closely-related southern white rhino recovered from a similar position following a sharp drop in numbers driven by poaching and habitat destruction. In the early 20th century the subspecies was the world's most endangered rhino with just 20 left alive, but there are now more than 20,000 in the wild. Scientists said the northern white could make a similar recovery through conservation efforts that make use of frozen cell lines.
The world's last male northern white rhino, Sudan, died in Kenya at the age of 45 in March, survived by two females - his daughter Najin and granddaughter Fatu. Without a male to breed with, scientists had hoped to use a small stock of frozen sperm to perform rhino IVF on Sudan's surviving kin and save the species. In vitro fertilization is used in the cattle industry to breed more robust herds, and a Cape buffalo was conceived through IVF for the first time in 2016.
Because Najin and Fatu are two weak to carry a pregnancy to term, scientists would implant the resulting embryo in a southern white. Because the females are related scientists had worried the resulting population could end up heavily inbred. Scientists could coax nine frozen cell lines, saved from dead rhinos, to become egg and sperm cells for IVF treatments but even this would leave little genetic diversity.
In the new study, researchers investigated whether the northern white could recover using frozen cells stored at San Diego Zoo. Scientists sequenced the full genome of these cell lines, which represent 8 unrelated northern whites, and compared them to the genomes of southern whites. They confirmed the theory that the two rhinos are subspecies rather than distinct species.
This is good news if researchers are to use a southern white to carry an IVF implanted northern white to term in future, as doing so through a separate rhino species would be less likely to succeed. Semen from dead northern white rhinos is stored in various locations around the world. Supporters think the work could be used to help other endangered species, while some conservationists believe the focus should be on other critically endangered species, including the Javan and Sumatran rhinos, that have suffered because of poaching and human encroachment on habitats.