- Written by Victoria Gill
- Science reporter, BBC News
“It’s gone,” whispered Gabi Drake, a veterinarian at Chester Zoo, holding a stethoscope over the feathered chest of a 28-year-old tropical red parrot.
The bird is a talkative bird – an elderly resident of Chester Zoo, and a species listed by the International Union for Conservation of Nature (IUCN) as endangered.
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It is sad to see that this striking bird must sleep. His little paws clawed tangled up and he suffers from arthritis that is difficult to treat.
But this is not the end of the unique genetic code contained in his cells. A few small pieces of his body will join samples from 100 species. It will be frozen – stored indefinitely – in the UK’s largest live organic tissue bank, Nature’s Safe.
In vials filled with a nutrient-rich, cell-friendly antifreeze, samples are stored at -196°C, the temperature at which all normal chemical processes of cells stop — suspended in animation.
The idea is that at some point in the future — decades, maybe even centuries from now, it could be revived. This is a frozen backup solution in case of extinction.
Life resumes its course
Conservationists say we are losing species faster than ever.
Amid a biodiversity crisis that the United Nations says threatens one million plant and animal species with extinction, some scientists are now scrambling to figure out what to put in the freezer in the future.
“It won’t prevent extinction, but it will definitely help,” says Tullis Matson, founder of Nature’s Safe.
Mr. Tullis is a tall, friendly guy who doesn’t speak up about his charity’s mission to conserve living tissue for wild animals.
“This is where life begins again,” he beamed, showing me a picture of a vial of leopard skin cells under a microscope.
The screen is filled with densely packed skin cells – the basic building blocks of the body. The black dot in the middle of each connected spinous cell is a nucleus containing a unique set of genetic instructions that made, in this case, a now-deceased leopard.
“This animal died in 2019,” says Tolis Matson. “We woke up to these cells a few days ago — and you can see now, they’re all over the screen. They’ve multiplied.”
Skin cells are very useful in this endeavor, especially a type of connective tissue cell called fibroblasts.
They are essential for wound healing and repair, and after being taken out of the freezer and warmed to body temperature in a bath of necessary nutrients, they divide and multiply nicely in a plate.
One potential future use of these cells is to clone new animals, using thawed bundles of DNA.
Animal cloning is not new. In 1996 Scottish scientists cloned Dolly the sheep, merging a cell from a sheep with an egg from another. It is a breeding technique that was born in the field of pets and is now geared towards conservation.
US biotech company Revive and Restore recently produced a clone of the skin cells of an endangered black-footed ferret that died decades ago. Her eggs were frozen in 1988.
The fusion of a ferret fibroblast with an egg led to the formation of an embryo, and a clone – Elizabeth Ann the black-legged ferret – was born in December 2020.
They used the same basic approach to clone a Przewalski’s horse – a species believed to be the last true “wild” horse alive – at a cost of $60,000 (FCF37,242,815). The clone, named Kurt, lives at the San Diego Zoo.
“It was cheaper for the zoo to clone a horse – to bring more genetic diversity to the US population of the species – than to ship a horse from a European zoo,” says scientist Dr. Ben Novak.
What types should we freeze?
Genetic diversity is important. When the number of species decreases, this can lead to inbreeding. In mammals, the offspring receives a set of genetic instructions from each biological parent. And if these parents are related to each other, the genetic diseases they suffer are more likely to be passed on.
According to Dr. Novak, cell banking is not the most economical way to revive genes.
“Conservators are fighting to save species, but we haven’t been able to save everything – destruction is underway.”
“Going forward and banking gives us the ability to serve food in the future,” he adds. “If we don’t, we’ll regret it later,” he continues.
Biobanks risk sending the message that we don’t need to worry about saving species today “because we can freeze them for later,” says Professor Bill Sutherland, a conservation biologist at the University of Cambridge.
“There is a question of prioritizing what is stored,” he says. “It would be great to get tissues from 20 snow leopards from 20 different places, but it would be really hard.”
Instead, Nature’s Safe works closely with European zoos, including Chester Zoo.
When an animal needs to sleep or dies unexpectedly, zoo vets collect tissues for the bank.
“It’s a ray of light,” says Tolis Matson. “The death of this animal gives some hope for the future of this species, because we can freeze these genes,” he adds.
Although dealing with what is available is not an ideal approach, it has enabled Nature’s Safe to obtain samples of species such as the mountain frog, an endangered amphibian that has been nearly wiped out due to a fungal disease.
It also obtained tissues from the green Javan bird, a bird that is on the verge of extinction due to the demand for the wild bird trade. (These beautiful, glowing birds have wonderful and much in-demand mimicry skills.)
It’s about making as much genetic material available as possible, says Dr Sue Walker, chief scientist at Chester Zoo. “If we don’t do it when the animal is gone, we’ve lost it,” she says.
Earlier this year in Chester, Gucci, a nine-year-old female jaguar, was found dead in her enclosure. Veterinarian Gabe Drake carefully cut out the left ear of the big cat, put it in a cold pack and sent it to Nature’s Safe, before sending Goshi for an autopsy.
“Jaguars are not the most endangered of the big cats, but they are in decline and facing the same human pressures as other large predators,” Gabe says.
“She was a fairly young animal and never had any children, unfortunately. It’s sad, but it’s good to know that her living tissue will last.”
Today, a few pea-sized pieces of Goshi’s black velvet ear — cleaned, primed, and bathed in a protective nutrient solution — are housed in a liquid nitrogen box where biodiversity grows.
Tullis Mattson is optimistic about what science might allow in the future. “By using gene-editing technology, we may even be able to create new genetic diversity,” he speculates.
Given the now solitary tigers that patrol its surroundings, says Dr. Sue Walker of Chester Zoo, it may be decades before we have the technology to do what we want to do with these specimens.
His hope, as most conservationists do, is that using frozen cells from long-dead animals will never be necessary.
“But if we don’t collect them, those genetic elements are lost forever,” she says. “We would have lost all of this unique biodiversity.”
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