- By Victoria Gil
- Science Correspondent, BBC News
“It’s gone,” whispers Gabby Drake, a veterinarian at Chester Zoo, holding a stethoscope to the feathered chest of a 28-year-old bright red tropical parrot.
The bird is a chattering lory, an elderly resident of Chester Zoo and a species listed by the International Union for Conservation of Nature (IUCN) as vulnerable to extinction.
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It is sad to see that this striking and characterful bird must be put to sleep. Their little clawed feet are gnarled and they suffer from arthritis too severe to treat.
But this is not the end of the unique genetic code contained in your cells. A few small pieces of its body will be attached to samples taken from 100 species. They will be frozen, stored indefinitely, at the UK’s largest organic living tissue bank, Nature’s Safe.
In vials filled with a cell-friendly, nutrient-rich antifreeze, the samples are stored at -196°C, the temperature at which all natural chemical processes in cells stop: they are suspended in animation.
The idea is that at some point in the future decades, maybe even centuries from now, they could be resurrected. This is a frozen backup solution in case of extinction.
Life takes its course
Conservationists say we are losing species faster than ever.
Amid a biodiversity crisis that the United Nations says threatens a million plant and animal species with extinction, some scientists are now scrambling to figure out what to put in the freezer for the ‘next’.
“It won’t prevent extinction, but it will definitely help,” says Tullis Matson, founder of Nature’s Safe.
Mr. Tullis is a tall, friendly man who makes no bones about his charity’s mission to preserve the living tissue of wild animals.
“This is where life begins again,” he smiles, showing me the image of a vial of cheetah skin cells under the microscope.
The screen is filled with densely packed skin cells, the building blocks of a body. The black dot in the middle of each connected spiky cell is a nucleus containing a unique set of genetic instructions that made, in this case, a now-deceased cheetah.
“This animal died in 2019,” says Tullis Matson. “We woke these cells up a few days ago, and now you can see they’re all over the screen. They’ve multiplied.”
Skin cells are very useful for this task, especially a type of connective tissue cell called a fibroblast.
They are essential for wound healing and repair, and after being taken out of the freezer and warmed to body temperature in a necessary nutrient bath, they divide and multiply beautifully on a plate.
One of the possible future uses of these cells is the cloning of new animals, using these thawed packages of DNA.
Animal cloning is not new. It was in 1996 when Scottish scientists cloned Dolly the sheep by fusing a cell from one sheep with an egg cell from another. It is a reproductive technology, born in the field of domestic animals and now oriented towards conservation.
US biotech company Revive and Restore recently produced a clone of the skin cells of an endangered black-footed ferret that had been dead for decades. Her eggs had been frozen in 1988.
The fusion of a ferret fibroblast with an egg cell created an embryo, and a clone, Elizabeth Ann the black-footed 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 truly “wild” horse alive, at a cost of $60,000 (37,242,815 FCFA). The clone, named Kurt, lives at the San Diego Zoo.
“It was actually cheaper for the zoo to clone a horse, to bring more genetic diversity into the US population of the species, than it was to ship a horse from a European zoo,” says scientist Dr. Ben Novak, director of Revive and Restore. .
What species should we freeze?
Genetic diversity is important. When the population of a species declines, it can lead to inbreeding. In mammals, offspring receive a set of genetic instructions from each biological parent. And if those parents are related, the genetic diseases they have are much more likely to be passed on.
According to Dr. Novak, cell banking is not the cheapest way to resuscitate genes.
“Conservationists are fighting to save the species, but we couldn’t save everything, the destruction is underway.”
“Getting ahead and banking things gives us the ability to do catering in the future,” he adds. “If we don’t, we’ll regret it later,” she continues.
Biobanks risk sending the message that we shouldn’t worry about saving species today “because we can freeze them for later”, says Professor Bill Sutherland, a conservation biologist at the University of Cambridge.
“And there’s the problem of prioritizing what gets stored,” he says. “It would be wonderful to get tissue from 20 snow leopards from 20 different places, but it would be very difficult.”
Instead, Nature’s Safe works closely with European zoos, including Chester Zoo.
When an animal needs to be put to sleep or dies unexpectedly, zoo veterinarians collect tissue for the bank.
“It’s a ray of light,” says Tullis Matson. “The death of this animal actually gives some hope for the future of this species, because we can freeze these genes,” he adds.
Although stockpiling what is available is not a perfect approach, it has allowed Nature’s Safe to obtain samples of species such as the mountain frog, a critically endangered amphibian that has been nearly wiped out by a fungal disease.
He also obtained tissue from a Javan green magpie, a bird on the brink of extinction in demand from the wild bird trade. (These almost garishly beautiful birds have remarkable and highly sought-after mimicry skills.)
Dr Sue Walker, chief scientist at Chester Zoo, says it’s about saving as much genetic material as possible. “If we don’t do it when the animal goes missing, we’ve lost it,” she says.
Earlier this year in Chester, Goshi, a nine-year-old female jaguar, was found dead in her enclosure. Veterinarian Gabby Drake carefully cut off the big cat’s left ear, put it in a cold pack and sent it to Nature’s Safe, before sending Goshi for an autopsy.
“Jaguars are not the most threatened big cats, but they are in decline and face the same human pressures as other large predators,” says Gabby.
“She was a fairly young animal and unfortunately she never had babies. It’s sad, but it’s good to know that her living tissue will endure.”
Today, a few pea-sized pieces of Goshi’s velvety black ear, cleaned, prepared and dipped in a protective nutrient solution, are housed in a box of liquid nitrogen growing in biodiversity.
Tullis Matson is optimistic about what science may allow in the future. “With gene-editing technology, we could even create new genetic diversity,” he speculates.
Looking at the now solitary male jaguar patrolling his enclosure, Chester Zoo’s Dr Sue Walker says it may be “decades before we have the technology to do what we want to do with these specimens”.
His hope, and that of most conservationists, is that it will never be necessary to use frozen cells from long-dead animals.
“But if we don’t collect them, those genetic elements will be lost forever,” she says. “We will have lost all this unique biodiversity.”