Scientists say they have sufficient genetic material to recover the northern white rhino. But that does not mean it will be an easy process.
Just two northern white rhinos remain on the planet. Both of them are female, named Najin and her daughter Fatu. The last male, Sudan, died in 2018.
Bringing a species back
Researchers at the San Diego Zoo Wildlife Alliance in California examined skin cells extracted from 12 distinct northern white rhinos preserved in their Frozen Zoo. Using a computer model, they simulated the outcome of utilizing the genetic material from these rhinos to produce sperm and egg cells. What next? The cells, transformed into embryos, could be carried by a closely related subspecies, the southern white rhino (Ceratotherium simum simum).
“The beauty of having this consistent resource of genomes in the Frozen Zoo is that we can continually pull new individuals out and reintroduce them into the population,” Aryn Wilder, a researcher in Conservation Genetics at the San Diego Zoo Wildlife Alliance, told New Scientist.
The research discovered that this approach could work, offering hope to bring back other white rhinos. But over multiple generations.
According to their simulations, the northern white rhinos were not inbred after 10 generations. Inbreeding occurs when individuals within a population mate with close relatives, lowering genetic diversity. In this case, the results showed that the mating pairs in each generation were genetically diverse. This mimics natural reproductive patterns that prevent inbreeding in a healthy population. Shortly, the genetic diversity of the northern white rhinos remained intact, indicating the population’s sustainability.
What is behind the process?
Skin cells, for example, are collected and stored in a bank. These cells can then be reprogrammed into induced pluripotent stem cells (iPSCs). iPSCs are unique because of their ability to differentiate into any type of cell in the body. Once they generate iPSCs, researchers can direct them to differentiate into primordial germ cells. “One hurdle is that the primordial germ cells require support cells for growth and maturation,” Wilder told . “For endangered species like the northern white rhino, we will need to generate these support cells from the iPSCs,” she added.
The other side of the coin
The researchers still need to overcome many challenges, such as chemically inducing frozen skin cells into functional sperm and egg stem cells. There is uncertainty about whether surrogates from the closely related southern white rhino species will be capable of carrying embryos to term successfully. This is a significant concern because success depends on the ability to gestate and birth healthy offspring.
“There is so much more to conserving rhinos than genetic diversity in cell lines,” Terri Roth, Adjunct Professor at the Center for Conservation and Research of Endangered Wildlife at Cincinnati Zoo and Botanical Garden, added. “But good news on any front is still worth celebrating in these tough times.”
