Primeiro clone de animal extinto na história

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An extinct animal has been resurrected by cloning for the first time—though the clone died minutes after birth.

Findings revealed January 23 in the journal Theriogenology describe the use of frozen skin in 2003 to clone a bucardo, or Pyrenean ibex, a subspecies of Spanish ibex that went extinct in 2000.

Scientists had cloned endangered species before, but not one that had officially died out.

(Related: "Scientists Clone First Endangered Species: A Wild Sheep" [October 29, 2001].)

Study co-author Jose Folch, of the Center for Agro-Nutrition Research and Technology in Aragon, Spain, said his team plans to try cloning another this ibex this year or next.

"We are not especially disappointed for the death of the cloned newborn," Folch explained in an email, because such deaths in cloning experiments are common.

"We will try to improve the technology in order to increase the efficiency of the cloning process."

But David Wildt, a senior scientist at the Smithsonian's National Zoological Park in Washington, D.C., who did not participate in this study, warned that the successful cloning wouldn't be the first step in creating a real-life Jurassic Park.

"The public should not leap to the conclusion that we are on the edge of cloning woolly mammoths or dinosaurs," he said. "Even if such embryos could be constructed, there are no appropriate surrogate mothers for long-dead species."

Success and Setbacks

For 200 years, hunting had thinned the Pyrenean ibex population, and the last living bucardo died in 2000, hit by a falling branch.

Using frozen skin samples taken from this lone specimen in 1999, Folch and his colleagues made clone embryos by inserting the bucardo's DNA into domestic goat eggs emptied of their original genetic material.

The clones were then implanted into other subspecies of Spanish ibex or goat-ibex hybrids.

If the environment in which an embryo develops is not a close match, problems can occur during pregnancy. Of the 208 embryos the researchers implanted, only seven goats became pregnant, and just one bucardo made it to term.

The newborn bucardo died of respiratory failure immediately after birth. Dissection revealed the animal had lung abnormalities, although all its other organs looked normal.

Such abnormalities are common in cloning—while a clone's DNA might be identical to its donors', the act of shuffling DNA from one cell to another can lead to irregularities during development.

A Step Forward

Smithsonian's Wildt called the work a "highly noteworthy scientific accomplishment."

"Offspring was produced from an animal well known to have suffered a recent extinction."

The bucardo story "is fascinating, because resurrection-by-cloning was the only option," Wildt said.

But there are "vastly more effective and logical approaches" at conserving virtually all living wildlife species, he added, including re-establishing wild habitats, captive breeding by natural means, and artificial insemination.

"The strong recovery of the black-footed ferret and giant panda are two excellent examples" of species that have come back from the brink thanks to conservation efforts, Wildt said.

(Related: "Ferrets Slinking Back From Brink of Extinction in U.S." [August 9, 2007].)

Reproductive biologist Bill Holt at the Zoological Society of London, who did not participate in this study, added that generating just one or a few animals via cloning "will not necessarily produce a viable population that would survive into the future."

Even if all resulting offspring were healthy, he said, the fact that they only have a few genetic samples of the bucardo to work with would mean there would be no genetic diversity in the population, as in inbred groups.

"They would be very susceptible to disease or even climatic change and may not be able to survive for very long."