University of Wisconsin researchers, in cooperation with the Baltimore Zoo, are preparing to use test tube fertilization techniques to aid in the preservation of endangered animals.
The researchers will take eggs from rare Indian lion-tailed macaque monkeys at the zoo and fertilize them in a plastic dish with macaque sperm. The embryos will then be flown from Baltimore to the Regional Primate Research Center in Madison for implant into rhesus monkeys, a nonendangered species, which will serve as surrogate mothers.
The scientists hope the experiment will produce more lion-tails and perhaps lead to techniques that can be applied to other endangered species.
Although the method has been used with considerable success in humans and cattle, researchers are just learning to make it reliable for use on other species. This is the first time their ability to help save a species from extinction will be tested, said Barry Bavister, the embryologist who pioneered the procedure and used it to develop the world's first test tube monkey at the University of Wisconsin-Madison.
Although protected by the Indian government, the lion-tail's habitat in the evergreen forests of southern India has been so reduced by human encroachment that the estimated population of 1,500 live in isolated pockets. About 300 live in captivity, 20 of them in Baltimore.
Researchers at the Baltimore Zoo first tried the procedure about four months ago with a nonendangered pig-tailed monkey. The test tube fertilization itself proved successful, but the container carrying the embryo to Madison leaked, robbing it of nourishment and making the embryo unsuitable for implanting.
If the next attempt using the pig-tailed monkey is successful, the project will go ahead with the valuable lion-tailed monkey and within a year the world could have its first endangered primate born to a surrogate of a different species.
Obtaining eggs with the best chance of successfully producing embryos is perhaps the trickiest aspect of the procedure, according to scientists.
Researchers have to know when to remove the eggs. If they take the eggs too early, it's not terribly troublesome -- the eggs can be put in culture where they will usually mature. But if removed too late, the eggs may have started to degenerate.
After the eggs have been fertilized, they are placed first in a medium of nutrients designed to support the small bundle of cells that will become an embryo. When the fertilized eggs have divided into about eight cells they are transferred to a richer medium where they will stay until ready to be placed in the womb.
Next the monkey embryos will be flown to the Primate Research Center in Madison where they will be implanted in surrogate mothers and brought to term.
Researchers hope the procedure, if perfected, might help to prevent inbreeding. When animals are inbred the offspring become more and more alike, genetic diversity is lost, and the colony is more vulnerable to disease, Bavister said. With in vitro fertilization, diversity could be increased by spreading closely related individuals around the globe, he said.
William Conway, a biologist at the Bronx Zoo in New York, sees the procedure as a means of enhancing long-term conservation efforts and helping to save larger numbers of endangered species.
"I calculate that under the best of conditions we might sustain as many as 1,000 species in all the world's zoos. But if the techniques of in vitro fertilization and [embryo freezing] can be mastered, we have a chance of greatly increasing these numbers," Conway said.
The fate of the lion-tailed macaques is tied to the forests they inhabit in India. Since the British arrived in the 1800s their range has been reduced by the clearing of wilderness for coffee, tea and cardamom plantations, as well as for road-building and other development projects.