A Curraa two-ton southern white rhinoceros, was killed by microscopic bacteria of the genus Clostridium this past November 25 in the Ol Pejeta park in Kenya. But his death following this unequal biological struggle has not been in vain. Curra was gestating the first embryo created in the laboratory and successfully implanted by the German consortium BioRescue in these animals. It is the only and meager door for the survival of the northern subspecies, of which only two females remain: Ours And your daughter Seeds. The experience of Curra As a surrogate mother she has shown, for the first time, that it is possible. Her legacy is the hope of avoiding another extinction.
Ours y Seedsboth descendants of Sudandied in 2018 of natural causes, survive in Ol Pejeta with the sad honor of being the only two survivors of the northern white rhino subspecies. Their imposing presence is a shameful reminder for humanity, which has led these animals to the critical danger of extinction due to hunting and climate change.
The BioRescue consortium, financed by the German Government and which includes a dozen international entities, began a scientific program 15 years ago to produce and preserve 30 fertilized embryos in laboratories in Berlin (Germany) at -196 degrees Celsius in liquid nitrogen. Cremona (Italy) from eggs and sperm from the last 12 northern white rhinos that had arrived alive this century in reserves and zoos. All but Ours y Seeds They have already died. In 2019, research work begins to develop an implantation technique in surrogate mothers.
“We are pursuing alternative scientific approaches to create new northern white rhino calves and ensure the greatest genetic diversity of their future population. All these strategies converge in the production of embryos in vitro and their successful transfer to surrogate mothers to create a pregnancy,” details Susanne Holtze, project scientist.
The scarce remnant of embryos and specimens from the north forces us to first try the southern subspecies, of which there are just over 10,000 animals left. In this way, ovules Elenorewho lives in the Belgian zoo of Pairi Daiza, are fertilized by intracytoplasmic injection (direct to the egg) in a laboratory in Italy with sperm from Athosfrom the Austrian Zoo Hellbrunn.
The complex fertile cycle of rhinos remained to be unraveled to determine the precise moment of the transfer. To detect it, Curra live with Ouwana vasectomized male used as an indicator. Scientists observe a mating, presumably sterile, except for a failed vasectomy, on September 17 and 18, which shows that Curra she is ready. BioRescue scientists and veterinarians, led by the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW), implant two embryos into Curra on September 24. Days later, Ouwan he loses sexual interest in her: she is pregnant.
Although embryo transfer is already a common technique in humans and in domestic and livestock species, it has never been achieved in rhinos. If the transfer worked, its viability was demonstrated, the only door for the survival of the lineage of Ours y Seeds. “It has been completely uncharted territory and everything from the approach to procedural protocols to the equipment required has had to be invented, developed and tested to be safe,” explains Thomas Hildebrandt, head of the BioRescue-Leibniz-IZW project.
Hildebrandt clarifies that the technique used is very similar to that used with people or cattle and horses. “But it needs a different technology”, he points out. “It is not an experiment because we do not harm the animals. “We just want to make babies, so technically everything is approved by the Kenya Wildlife Service, by the Kenyan Government, because it is not experimental.”
The implant is not carried out through the rhino’s reproductive organ, but through its previously disinfected digestive system. Through the rectum, they introduce a long catheter to take the embryo to the oviducts, where gestation begins. “The success rate is very high, although the technique is a challenge,” comments the scientist.
Everything is measured to the second and to the millimeter, from anesthesia to loading the implantation device with the embryo. “There are many very difficult and challenging elements to this procedure. However, our team is so well trained that we are already preparing the next implant,” says Hildebrandt, who plans to carry it out in May.
The white rhino requires a mating process that lasts more than an hour and requires up to six ejaculations to fertilize the egg naturally regarding six days following ovulation. “The female’s cervix is extremely long and convoluted,” explains the project leader. If the implant were performed through the uterus, it would cause irritation and damage that would prevent the success of the operation. With its technique of reaching the oviducts through the rectum, the intervention is reduced to 20 minutes.
The technique works and Curra She fulfills her role as surrogate mother perfectly. For 70 days, she gestates the embryo of a male that reaches 6.4 centimeters in length. Their chances of being born alive following a complete gestation period of between 16 and 18 months rose to 95%.
But, despite his pleasant life in Kenya and permanent monitoring, the enemy, this time, is invisible. An adverse climatic episode of torrential rains floods the Ol Pejeta reserve and disperses bacterial strains of Clostridium Paraclostridium bifermentans y Paenicolostridium sordellii that cause a fatal infection in Curra and his partner Ouwanwho died three days earlier.
Frank Göritz, head veterinarian of the project, regrets the outcome: “Witnessing the death of an animal you have worked with for so long for reasons you cannot control is depressing. We try to control all the factors that affect the well-being of animals, but in the wild you can’t do everything and sometimes your plans are frustrated. “It’s very sad, but we try to look forward and see it as a milestone for the mission.”
Immediately following the incident, the team established an emergency program of vaccination, isolation and reparcelling of the areas where the rhinos live, including the only two existing northern white ones.
The next step is to analyze samples of the fetal tissue at the German centers Max Delbrück for Molecular Medicine and Leibniz-IZW to ensure that the natural mating had been sterile and that the pregnancy had occurred by artificial implantation of the embryo. This January it is confirmed and the door opens to the hope of saving the northern white rhinoceros.
The German consortium announced this Wednesday that the new phase of rescue of the subspecies has already started, which involves the selection of a new surrogate mother, another decoy male and another implantation, which might already be with a northern white rhino embryo. within a period of two or three years.
The project director believes that it will not be inconvenient if the embryo and the surrogate mother are of different subspecies. A breeding was already achieved naturally in 1978 with a couple from the north and the south. “We are very confident that the northern white rhino embryos in our southern surrogate mother will be successful,” he says.
He adds: “We can produce between 20 and 25 northern white rhino calves in the next two or three years. Although there are only two females left, we cannot accept the extinction of this subspecies. Now we can say that we will achieve it. Success comes just in time to achieve it. We want the babies to live with Ours y Seeds for years to learn the social behavior of their species,” highlights Hildebrandt. The six-year grant from the German Federal Ministry of Education and Research (BMBF) ends in 2025, opening a parallel race to secure funding for the project following the endorsement that embryo implants are possible.
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