With global animal populations declining by 69% since 1970, underscoring a dire biodiversity crisis, experts are turning to an innovative solution to help avoid species extinction. Similar to how frozen eggs offer humans the option of delaying reproduction, the technology of cryogenically freezing animal genetic samples could also be the key to halting the decline of various species.

Researchers highlight the huge potential of cryogenic libraries, which can store various genetic materials of animals at ultra-low temperatures, in protecting dwindling animal populations around the world. The study was supported by several global conservation agencies, and the researchers recommend that future sampling of species should be prioritized and a global cryobank database established to facilitate collaborative conservation efforts and potentially reintroduce threatened species into their natural habitats.

A recent paper published in the journal ZooBiology highlights the far-reaching promise of cryobanks or live cell banks in addressing global conservation challenges.

These living cell banks preserve animals' genetic material, such as DNA, embryos, semen and living tissue, at ultra-low temperatures. These cells can be cultured for a variety of purposes, including genetic analysis, assisted reproductive technology, ensuring the genetic diversity of animal populations, and even potentially reintroducing species into their natural habitats.

In the study, researchers analyzed the contents of the San Diego Wildlife Alliance's (SDZWA) Frozen Zoo, the world's largest and most diverse repository of living genetic samples, to develop a framework for prioritizing species for future sampling. The researchers also used aggregated data from the Species360 Zoological Information Management System (ZIMS), the world's largest database of species knowledge, to identify opportunities for future genetic sample collection.

The findings show that the SDZWA frozen zoo currently stores 965 different species, including 5% of amphibians, birds, mammals and reptiles, while further collection of samples from zoos and aquariums could significantly increase this proportion to 16.6%, resulting in an additional 707 endangered species.

Additionally, 50% of genetic samples from species currently listed as extinct in the wild are already preserved in the SDZWA cryozoological park, but sampling from the zoo could increase this number to 91%, potentially providing a vital lifeline to these endangered species.

The study's lead author, Dr Andrew Mooney from Dublin Zoo and Trinity College Dublin's School of Natural Sciences, highlighted the significance of the study, saying: "This study not only highlights the efforts of Dublin Zoo and Trinity College Dublin's School of Natural Sciences in protecting endangered species, but also provides valuable lessons for both Dublin Zoo and Trinity College Dublin's School of Natural Sciences."

"This study not only highlights the incredible work done to date by the San Diego Zoo Wildlife Alliance, but also exemplifies the collective potential of the global zoo and aquarium community to further advance global cryobanking programs and conservation priorities. As wildlife populations continue to decline around the world, there has never been a more critical time to collect and preserve genetic samples from endangered species. Frozen samples offer unparalleled conservation opportunities, however, we must come together and collect samples now before it is too late." "

Yvonne Buckley, Professor of Zoology in the Department of Natural Sciences at Trinity College, said:

"We are in the midst of a biodiversity extinction crisis, with more than a million species likely to be threatened with extinction in the coming decades. While our priority is to prevent species from declining in the wild, cryopreservation provides a means to protect critical genetic diversity and reintroduce it into populations to increase their fitness and resilience."

Johanna Staerk of the Species360 Conservation Science Alliance, co-author of the study, said:

"This study highlights the huge potential of cryopreservation in protecting endangered species, and the role of zoos and aquariums in conservation. Given the difficulty of obtaining genetic samples from wild species, zoos and aquariums provide ideal resources to collect genetic samples to ensure the future survival of species."

Oliver A. Ryder, Kleberg Endowment Director of Conservation Genetics at the San Diego Zoo Wildlife Alliance said:

"Cryozoology's cryopreservation of viable cells over four decades has provided a vast and impactful resource for genomics-based biodiversity discovery and demonstrated the possibilities of cell-based genetic rescue. There is an urgent need for countries around the world to expand their efforts and establish distributed biobank networks to make cell-based genetic resources available in an equitable manner and provide conservation options for future generations."

Marlys Houck, curator of the San Diego Zoo Wildlife Alliance's Frozen Zoo and co-author of the study, said:

"Dr. Kurt Beniske created the Frozen Zoo in 1975, and hundreds of samples are added to it every year. Thanks to his foresight, we have cell lines of species and individuals stored decades ago, some of which have not yet been reproduced. Their genetic diversity is not represented in current populations, but can be genetically rescued in the future by samples from the Frozen Zoo."

In addition to recommending a framework for which species should be prioritized for genetic sampling, the study authors also encourage the establishment of a global database of cryobanks to facilitate collaboration in the conservation of genetic diversity.

The research is the result of a workshop held during the 2016 meeting of the IUCN Conservation Planning Specialist Group (CPSG) and was organized by the Species360 Conservation Science Alliance in partnership with Oliver Ryder of Frozen Zoo.

The role of cryogenic gene banks in saving species from extinction

The powerful role of cryopreservation in conservation is demonstrated in efforts to save the now functionally extinct northern white rhinoceros. With only two female white rhinos left alive, scientists are using samples from frozen zoos to save the subspecies from disappearing forever through assisted breeding techniques.

While the case of the northern white rhino represents a last-ditch attempt to save the subspecies, the study authors stress the importance of being proactive in prioritizing species and building a global cryodatabase to ensure conservation action can be taken faster.

Cryopreservation may be the only lifeline to save endangered species, such as northern white rhinos and killer whales, for which living cell cultures are available. Unfortunately, these possibilities will never be realized for the recently extinct Yangtze finless porpoise and Christmas Island lizard, as there are no live biological samples for them.

However, there are still sampling opportunities for most species. Considering that 71% of species listed as "least concern" on the IUCN Red List of Threatened Species are at risk of extinction due to the effects of climate change, storing genetic samples now could help protect these species in the future.