Frozen zoo
A frozen zoo is a storage facility in which genetic materials taken from animals (e.g.
Overview

The first frozen zoo was established at the
Gathering material for a frozen zoo is rendered simple by the abundance of
Several animals whose cells were preserved in frozen zoos have been cloned to increase the genetic diversity of endangered species, as of 2021[update]. One attempt to clone an extinct species was made in 2003; the newborn Pyrenean ibex died of a development disorder which may have been linked to the cloning, and there are not enough genetic samples in frozen zoos to re-create a breeding Pyrenean ibex population.
Facilities
The Frozen Zoo at the San Diego Zoo's Institute for Conservation Research currently stores a collection of 8,400 samples from over 800 species and subspecies.[12] It has acted as a forebear to similar projects at other zoos in the United States and Europe.[13][14] However, there are still less than a dozen frozen zoos worldwide.[2]
At the United Arab Emirates'
The Audubon Center for Research of Endangered Species, affiliated with the University of New Orleans, is maintaining a frozen zoo. In 2000 the Center implanted a frozen-thawed embryo from the highly endangered African wildcat into the uterus of a domestic house cat, resulting in a healthy male wildcat.[15]
The
The University of Georgia's Regenerative Bioscience Center is building a frozen zoo. RBC Director Steven Stice and animal and dairy science assistant professor Franklin West created the facility with the thought of saving endangered cat species. The scientists have already extracted cells from a Sumatran tiger, which could be used for artificial insemination. Artificial insemination provides a remedy for animals who, due to anatomical or physiological reasons, are unable to reproduce in the natural way. Reproduction of stored genetic material also allows for the fostering of genetic improvements, and the prevention of inbreeding. Modern technology allows for genetic manipulation in animals without keeping them in captivity. However, the success of their restoration into the wild would require the application of new science and a sufficient amount of previously collected material.[11]
Drawbacks
Due to the very low temperatures required, varying levels of stress are put on the DNA samples.
Applications
Gaur
A gaur that died of natural causes had some skin cells frozen and added to the San Diego Frozen Zoo. Eight years later, DNA from these cells was inserted into a domestic-cow egg to create an embryo (trans-species cloning), which was then implanted in a domestic cow (Bos taurus). On 8 January 2001, the gaur, named Noah, was born in Sioux Center, Iowa. Noah was initially healthy, but the next day, he came down with clostridial enteritis, and died of dysentery within 48 hours of birth. This is not uncommon in uncloned animals, and the researchers did not think it was due to the cloning.[22]
Banteng
The
Przewalski's horse clone

In 2020, the first cloned
The somatic cell donor was a Przewalski's horse stallion named Kuporovic, born in the UK in 1975, and relocated three years later to the US, where he died in 1998. Due to concerns over the loss of
The cloned horse was named Kurt, after Dr. Kurt Benirschke, a geneticist who developed the idea of cryopreserving genetic material from species considered to be endangered. His ideas led to the creation of the Frozen Zoo as a genetic library.[31] There is a breeding herd in the San Diego Zoo Safari Park.[32] Once the foal matured, he was relocated to the breeding herd at the San Diego Zoo Safari Park,[32] so as to pass Kuporovic's genes into the larger captive Przewalski's horse population and increase the genetic variation of the species. In 2023, a second horse, named Ollie, was cloned from the same cell line.[27]
Black-footed ferret
To help mitigate inbreeding depression for two endangered species, the Black-footed ferret(Mustela nigripes), Revive & Restore facilitates on-going efforts to clone individuals from historic cell lines stored at the San Diego Zoo Wildlife Alliance Frozen Zoo. The program seeks to restore genetic variation lost from the living gene pool.
On December 10, 2020, the world's first cloned black-footed ferret was born. This ferret, named Elizabeth Ann, marked the first time a U.S. endangered species was successfully cloned.[33][34]
The cells of two 1980s wild-caught black-footed ferrets that never bred in captivity were preserved in the San Diego Wildlife Alliance Frozen Zoo. One of them was cloned to increase genetic diversity in this species in December 2020. More clones of both are planned. They will initially be bred separately from the non-cloned population.[35]
Pyrenean ibex

The Pyrenean ibex went extinct in 2000. In 2003 frozen cells from the last one (a female killed by a falling branch) were used to clone 208 embryos, of which 7 successfully implanted in goats, and one made it to term. That one ibex died of respiratory failure just after birth; quite possibly as a result of the cloning process, its lungs had not developed properly. There may not be enough individuals' cells preserved to create a breeding population.[36][37] Despite the death of the ibex, DNA analysis revealed that the offspring was a legitimate clone from its last living descendent.[38]
Potential candidates
White rhinoceros
Over the years, concerns over population declines of the northern white rhinoceros (Ceratotherium simum cottoni) have increased with the increasing value of their horns to poachers. Specifically, the population has declined nearly seventy percent from 2011 to 2019.[39] Processes like SCNT can help aid in conservation efforts towards the revival of their population. Researchers are looking towards induced pluripotent stem cells (iPSC), as they hold limitless possibilities.[40] With the lack of natural mating occurring within the species due to the limited number of them, this sub-species provides researchers the opportunity for iPSC intervention. Other methods, including artificial insemination with fresh semen (AI), have been used successfully in another sub-species, the Southern White Rhinoceros (Ceratotherium simum simum).[41] Frozen-thawed semen has been tested and has seen some successes, helping solve issues with reproduction of the species as a whole.[41]
See also
- Cryoconservation of animal genetic resources
- Cryopreservation
- Ex-situ conservation
- Genetic pollution
- Genetic erosion
- Gene pool
- Endangered species
- List of conservation topics
- Extinction
- SVF Foundation
- Svalbard Global Seed Vault
- National Ice Core Laboratory
- Amphibian Ark
- Coral reef organizations
- Rosetta Project
References
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- ^ Williams, Shawna (September 14, 2018). "Conservation Biologist and Placenta Expert Kurt Benirschke Dies; He established the San Diego Zoo's cryopreserved Frozen Zoo". The Scientist. Retrieved 2 December 2018.
- ^ a b Harris, Paul (August 28, 2010). "The Frozen Zoo aiming to bring endangered species back from the brink". The Guardian. Retrieved 2 December 2018.
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