A frozen zoo is a storage facility in which genetic materials taken from animals (e.g. DNA, sperm, eggs, embryos and live tissue) are stored at very low temperatures (−196 °C) in tanks of liquid nitrogen. Material preserved in this way can be stored indefinitely and used for artificial insemination, in vitro fertilization, embryo transfer, and cloning. There are a few frozen zoos across the world that implement this technology for conservation efforts. Several different species have been introduced to this technology, including the Pyrenean ibex, Black-footed ferret, and potentially the white rhinoceros.
Overview
Gathering material for a frozen zoo is rendered simple by the abundance of sperm in males. Sperm can be taken from an animal following death. The production of eggs, which in females is usually low, can be increased through hormone treatment to obtain 10–20 , dependent on the species. Some frozen zoos prefer to fertilize eggs and freeze the resulting embryo, as embryos are more resilient under the cryopreservation process. Some centers also collect skin cell samples of endangered animals or extinct species. The Scripps Research Institute has successfully made skin cells into cultures of special cells called induced pluripotent stem cells (IPS cells). It is theoretically possible to make sperm and egg cells from these IPS cells.
Several animals whose cells were preserved in frozen zoos have been cloned to increase the genetic diversity of endangered species, . 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
At the United Arab Emirates' Breeding Centre for Endangered Arabian Wildlife (BCEAW) in Sharjah, the embryos stored include the extremely endangered Gordon's wildcat ( Felis silvestris gordoni) and the Arabian leopard ( Panthera pardus nimr) (of which there are only 50 in the wild).
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.
The Frozen Ark is a frozen zoo established in 2004 and jointly managed by the Zoological Society of London, the London Natural History Museum, and the University of Nottingham. This organization operates as a charity with many different departments including the DNA laboratory, consortium, taxon expert groups, and the database. In the DNA laboratory, samples are contained after collection from scientists, and different research projects are conducted there. The consortium acts as a bridge to bring together different, but important, groups from zoos, aquariums, museums, and universities. The taxon expert groups monitor the major phyla and lists like the IUCN Red List. The database is the essential piece as it holds all reports and records needed to perform all of the other functions for the charity. The hope for the future is for zoos and aquariums to be able to collect samples from their threatened and/or endangered species in house to help with conservation efforts. The collection and freezing of these samples allows for the distribution of gametes among populations. Samples can be collected from living hosts and from deceased hosts as well.
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.
Drawbacks
Applications
Gaur
Banteng
Przewalski's horse clone
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 genetic variation in the captive Przewalski's horse population, and in anticipation of the development of new cloning techniques, tissue from the stallion was cryopreserved at the San Diego Zoo's Frozen Zoo. Breeding of this individual in the 1980s had already substantially increased the genetic diversity of the captive population, after he was discovered to have more unique than any other horse living at the time, including otherwise-lost genetic material from two of the original captive founders. To produce the clone, frozen skin were thawed, and grown in cell culture. An oocyte was collected from a domestic horse, and its nucleus replaced by a nucleus collected from a cultured Przewalski's horse fibroblast. The resulting embryo was induced to begin division and was cultured until it reached the blastocyst stage, then implanted into a domestic horse Surrogacy mare, which carried the embryo to term and delivered a foal with the Przewalski's horse DNA of the long-deceased stallion.
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. There is a breeding herd in the San Diego Zoo Safari Park. Once the foal matured, he was relocated to the breeding herd at the San Diego Zoo Safari Park, 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.
Black-footed ferret
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. , being weighed on the 18th of February 2021 (at 70 days old)]] 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.
Pyrenean ibex
Potential candidates
White rhinoceros
See also
- Cryoconservation of animal genetic resources
- Cryopreservation
- Ex-situ conservation
- Genetic pollution
- Genetic erosion
- Genepool
- Endangered species
- List of conservation topics
- Extinction
- SVF Foundation
- Svalbard Global Seed Vault
- National Ice Core Laboratory
- Amphibian Ark
- Coral reef organizations
- Rosetta Project
- Colossal Biosciences
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