Frozen zoo: how scientists are trying to save animals from extinction

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When UC San Diego researcher Kurt Benirschke began collecting skin samples from rare and endangered animals in 1972, he had no clear plan for what to do with them. He believed that tools would one day be developed to save these animals. A few years later, he moved his collection to the San Diego Zoo and named it the “Frozen Zoo,” according to CNN.

Frozen zoo: how scientists try to save animals from extinction

Photo: GreenZone COP 27 Egypt

“It is known that there was a poster hanging over the Frozen Zoo with the quote: “You must collect things for reasons that you do not yet understand,” says Oliver Ryder, a geneticist at the San Diego Zoo and one of the first employees of Benirschke . – We felt we were the custodians of this growing collection, which will have value for the future that we could not appreciate at the time.”

Benirschke passed away in 2018, but his legacy lives on. Today, the Frozen Zoo is the world's largest animal cryobank, which stores samples of more than 10,500 animals of 1220 species.

For a long time it was a one-of-a-kind project. However, in recent years, similar conservation efforts have sprung up around the world, and tools are now available that Benirschke did not yet have. At the same time, the clock is ticking for many endangered species.

“Irreplaceable Repository for Very Rare Animals”

According to the WWF Living Planet Report 2020, since 1970, mammal populations birds, amphibians, reptiles and fish have declined by an average of 68% – animals and plants are threatened with extinction in the coming decades and centuries.

At the current rate of biodiversity loss, some scientists believe that preserving specimens of species that may not exist tomorrow is no longer a visionary task, but a scientific necessity.

“As we accumulated efforts, we realized that we were collecting an irreplaceable repository very rare animals,” says Ryder. – Because we have cages at the Frozen Zoo, we can now apply new techniques and new technologies to expand our understanding and learn more information that is directly relevant to preventing species extinction.”

Ryder says many important milestones have been achieved in genetics since Frozen Zoo was founded, starting with the cloning of the first animal, a sheep named Dolly, in 1996. Since 2001, four endangered species have been cloned using genetic material from the Frozen Zoo: the Indian gaur, a humpbacked Asian wild bull; banteng, a type of cattle from Southeast Asia; the Przewalski's horse, once found throughout Mongolia and recently extinct in the wild, and the black-footed ferret, which was thought to be extinct in the wild until it reappeared in 1981, but was then almost wiped out by an epidemic.

Genetic salvation

While cloning isn't perfect – a cloned Indian gaur only lived for 48 hours – it's a useful tool to help save an endangered species, as it can increase genetic diversity. When a species' population declines, the remaining animals are forced to interbreed, and the genetic pool shrinks, further threatening survival. But cloned black-footed ferrets, for example, were born in 2020 from specimens collected in 1988, meaning their genetic profile was much more diverse than the current population.

“In animal species, genetic diversity is what gives them resilience, the ability to recover from natural disasters, attacks by viruses, attacks by diseases. This is because the more different types of genetics a species has, the more likely some of them will survive,” explains Brandon Noble, professor of regenerative medicine at the University of Westminster in London and chairman of The Frozen Ark. , a British animal cryobank.

Frozen Ark was founded in 2004 with the same purpose as the Frozen Zoo, but with a different structure: it is not a separate collection tied to one institution, but a distributed network of more than two dozen institutions such as zoos, museums and universities around the world, each sharing its collection and knowledge.

Although Frozen Ark has more specimens than the frozen zoo – 48,000 of the 5,500 species – about 90% of them are made up of DNA, not living cells, which are used differently and must be stored at much lower temperatures.< /p>

DNA samples cannot be used to clone an animal, but they are necessary to draw up a genetic blueprint for species that may become extinct. “This information can be used for a range of different scientific studies, from cancer research to understanding recovery processes such as limb regrowth,” says Lisa Yohn, professor of wildlife medicine at the University of Nottingham and scientific consultant at Frozen Ark. – By saving these resources, we will allow not only current scientists, but also future generations of scientists to make all kinds of new discoveries.

A cell with any other name

Freezing cells involves a more subtle process than with DNA, to avoid the formation of ice crystals when cells are frozen to -196 Celsius. Different cells also require different freezing procedures; for example, amphibian cells are difficult to freeze properly and are therefore severely underrepresented in cryobanks. And some of the technologies that would make the best use of cell lines still need to be improved.

“A lot of the things we want to do we can’t do yet,” says Tallis Matson of Nature’s Safe, a UK-based cryobank that collects living cells and gametes (sperms and eggs). He predicts that within the next 10-30 years it will be possible to turn these cells into pluripotent stem cells that can be reprogrammed to produce sperm and eggs.

As soon as this becomes possible, sperm and eggs can be created embryo and then implanted into a surrogate of an endangered species, again providing much-needed genetic diversity.

This method also opens the prospect of resurrecting completely extinct species using surrogates of the most genetically similar surviving animals. “We have cells from extinct species, but we don't do it for that reason,” says Ryder. – We've been asked to conserve the cells of some of the last individuals of a species – or literally the last individual – and we're doing it, but we don't really expect to be able to bring the species back from extinction by a single animal.”

Troubles ahead< /h4>

The accelerating climate crisis will put additional pressure on ecosystems, making the work of cryobanks even more important. “I consider cryopreservation to be the absolute cornerstone of conservation. We are now facing the sixth mass extinction and we need to be able to give future generations a way to bring these species back to life,” Matson says.

Many of the challenges facing these projects are of a practical nature. “Saving the Frozen Zoo far into the future is one of the biggest challenges,” says curator Marlys Hawke. – We want to keep collecting more samples, ensuring that the ones we already have will stay there after our lives. This includes securing dedicated funding for liquid nitrogen for DNA freezing and replacing cryotanks as they age.”

One of the main challenges will be convincing conservation agencies that cryobanking is a viable strategy and worthy of funding. “Many of us do this without any tangible support other than donations or grants, without government support,” says Jon. – Cryobanking is increasingly being recognized as a vital resource, so it is a little unclear why there is no financial support.”

Finally, all researchers agree that greater collaboration between all cryobanks is needed to achieve success. “The task is huge, no one can do it on their own,” Matson says. – A million species are in danger. We need 50 different genetic samples from each, that is 50 million samples; for each of them, we need five vials for each sample, so we need to store hundreds of millions of samples.”

Ryder says he is working on creating a global network to store the materials already collected.

“If we had a conversation with future generations, they would say, 'Please save as much biodiversity as possible now,'” he adds. – And they would say do it by all means available.