Chilling Conservation at the Frozen Zoo
The Frozen Zoo® continues to grow in new and exciting ways and make fundamental contributions to conservation research initiatives. Like a bank in which deposits and withdrawals are ongoing, new cell cultures, sperm samples, and other tissues with reproductive potential, DNA preparations are being added on a regular basis.
In 2012, 184 new cell cultures were established and characterized (as of November) and are now maintained in liquid nitrogen freezers at -321º F, bringing the total number of cell cultures to over 9,000 individuals.
Over 30 new species of birds, reptiles and mammals were added in 2012 including Audubon’s crested caracara, Roti Island snake-necked turtle, giant horned lizard, Caribbean flamingo, scarlet ibis, white crowned shrike, crested screamer and giant river otter. Our efforts to establish and bank amphibian cells in support of conservation efforts continued as we strive to increase the number of individuals and taxa archived in the Frozen Zoo®.
We have utilized cells frozen in 1979 from a male gorilla born at the San Diego Zoo Safari Park for a study examining variation in the DNA sequences of the Y-chromosome. Northern white rhino cells grown from cultures frozen in 1992 were provided to collaborators working on stem cell development for endangered species. Studies aimed at adding stem cells derived not from embryos, but from adult cells are now underway, offering new opportunities for the Frozen Zoo® to contribute to animal health and population sustainability.
Frozen viable cell cultures from over 9,000 individual animals, comprising nearly 1,000 species are included in the collection. Banked DNA and tissue samples from rare and endangered species provide material for new studies that help point the way forward for managed populations and assist in monitoring and planning for sustainability of wild populations.
Data derived from our Frozen Zoo® resources builds a database for forensic analysis to identify species origin. Genetic barcodes (short regions of a gene specific to a single species) are used to monitor illegal trafficking in wildlife products by making it possible to identify the species used in animal products such as leather shoes and handbags or meat traded at urban markets in countries where bushmeat harvest is common.
The resources in the Frozen Zoo® can be used to develop genetic barcodes on a wide variety of species to aid in identification of commercial animal products.
Nearly 15,000 sperm samples from 1,232 individual males of 309 species are currently stored in the Frozen Zoo®. The collection includes sperm from endangered species, which can be thawed to produce offspring through artificial insemination or other advanced reproductive techniques.
Chicks of several bird species have hatched following artificial insemination with frozen semen, including the endangered Chinese monal pheasant. Because sperm from each species requires specially designed freezing and thawing methods, samples from related nonendangered animals are collected to develop optimal cryopreservation methods by comparing pre- and post-freezing viability.
Recently, the sperm of the critically endangered Fiji banded iguana was successfully frozen despite the fact that very little is known about preserving the sperm of any reptile species.
In addition to sperm, oocytes (eggs) of 381 females of 177 species remain safely frozen until needed for fertilization and embryo transfer for the production of young. New technologies such as vitrification (very rapid freezing) are currently being explored to enhance the viability of stored oocytes and embryos. Under the right conditions, frozen cells remain viable for many decades or even longer. For example, we recently injected southern white rhinoceros oocytes with sperm frozen for more than 20 years and documented successful fertilization.