DNA Banks for Endangered Animals
DNA Banks for Endangered Animals
DNA banks for endangered animals consist of samples of sperm , ova, embryos, tissue samples, and serum . These biological materials are frozen in liquid nitrogen at -196°C or -373°F, where they can be maintained indefinitely. About a dozen zoos and conservation groups around the world have begun collecting genetic material from endangered animals and preserving it. The goal of this type of collection is to preserve information stored in the genetic material of animals that may not exist in the future. This material contains information about the biochemistry, physiology , and even the environment in which the animals existed.
The material in DNA banks for endangered animals is usually collected during surgical procedures or soon after an animal dies. For example, before breeding season every year, veterinarians examine captive giant pandas to assess their health. At these times, gamete (sperm or ova) samples can be taken and stored in DNA banks. In instances when gametes cannot be obtained, tissue samples from skin cells or blood samples may be banked.
One of the challenges facing biologists building DNA banks for endangered animals is determining the best way to freeze, store, and then recover biological samples. Because animal cells are mainly composed of water, when they are frozen, ice crystals destroy much of the cell. Therefore, the water in the cells must be removed and replaced with a cryoprotectant fluid, which protects the cellular structures and molecules. Scientists must develop special protocols to infuse the cells with this cryoprotectant, and these protocols vary from species to species. In addition, the rate at which genetic material is frozen and thawed may vary from species to species. In some species, special treatments may be needed after thawing occurs. Development of these sensitive procedures requires careful experimentation.
A variety of zoos and conservation groups have collected and stored genetic material from endangered species. The largest DNA bank for endangered animals is housed at the San Diego Zoo and is called the Frozen Zoo®. Between its establishment in 1975 and 2005, the Frozen Zoo collected samples from more than 7,000 threatened and endangered species, including more than 13,000 samples of semen , oocytes (eggs), and embryos. The Cincinnati Zoo and Botanical Garden holds genetic material for more than 60 animal species and 150 plant species. The Audubon Society maintains a DNA bank for at least 35 different animal species, most of which are endangered. In 2004, three British institutions, the University of Nottingham, the Institute of Zoology, and London's Natural History Museum, announced the formation of the Frozen Ark project, the purpose of which is to develop a genetic repository of all endangered species on the World Conservation Union's (IUCN) Red List, a list that totals more than 7,200 species.
Most of the DNA banks for endangered animals are focused on conservation. A major use for the genetic material stored in these banks is to increase the genetic diversity of species at risk of becoming extinct. As populations of endangered animals shrink, the gene pool of the animals becomes more limited. This leads to inbreeding, which increases the population's risk of disease, birth defects, and the inability to survive natural disaster. Material from DNA banks can be used to infuse small populations with new genetic material, increasing their chances of survival. Another goal of DNA banks is to increase the population size of endangered species by producing new individuals. In 1999 at the Audubon Center for Research of Endangered Species, a domestic housecat gave birth to an African wildcat kitten that had been frozen as an embryo in a DNA bank. This was the first example of interspecies birth. In 2000, the Center produced test-tube Caracal cats from sperm that had been stored in their DNA bank. Material stored in DNA banks for endangered animals can also be used to understand animal physiology by analyzing the blood serum and tissue samples for hormones and other biochemical indicators. Information regarding the environment in which the animal lived may also be understood from biochemical markers, trace metals, and compounds from the environment found in tissue samples.
DNA banks are also used for forensic work with endangered animals. Between 1999 and 2001, researchers at the University of Trent in Ontario, Canada, developed DNA banks of endangered animals that are listed on the CITES (Convention on the International Trade of Endangered Species) list. They have developed a DNA bank of Gyrfalcons and Peregrine falcons so that wild birds can be distinguished from birds that have been bred in captivity. A DNA bank that includes genetic information of Amazon parrots helps to identify birds that are illegally traded. Genetic material from various species of sturgeon is also being deposited in DNA banks in order to identify caviar that is from fish on the CITES list. DNA banks of tigers have also been developed to identify materials found in Asian medicines. Finally, DNA banks of North American endangered duck and goose species are used for identification and for population management.
see also Gene; Wildlife forensics.