A year after introducing the first pair of rare African black-footed kittens conceived through in vitro fertilization, the scientists at the Audubon Center for Research of Endangered Species in Algiers have announced the arrival of another kitten that, genetically, is their sister, and the first kitten of her type to be carried in the womb of a domestic cat. The same parents contributed to the frozen embryos that produced the two males born last year and this year's female.
A black-footed cat served as the surrogate mother for last year's litter. Researchers next sought to show that vastly more plentiful domestic cats can serve as surrogate mothers in efforts to save the small wild cat from extinction.
"Being able to use domestic cats adds another extra dimension to that, being able to produce more," said Earle Pope, acting director of the center. Only 53 of the cats, which are native to South Africa, live in zoo collections in the United States.
Domestic and African black-footed are different species of cat but members of the same group of felines. Their similar sizes and gestation lengths, Pope said, appear to be what made the pregnancy and birth physically possible even though the genetic makeup of the kitten differed from the mother.
"They're considered to be of the same lineage," he said. "Somewhere back a couple of million years ago, they're descended from the same ancestor."
The kitten, named Crystal, was born on Feb. 6 to domestic cat Amelie without any human assistance in the birth itself. It exhibits all the characteristics of a black-footed cat despite being nurtured by a domestic cat mother, Pope said.
"It's not changed genetically in any way," from other black-footed cats, he said. "It is totally a black-footed cat in behavior."
Researchers handle the kitten almost every day as they study it, but she remains decidedly unadapted to human contact.
"It just wants you to leave it alone and stay away from it," Pope said. "It gets along beautifully with the domestic cat mother. They don't know, or do not care, that it's a different species."
Scientists started gathering the genetic material that eventually created the kitten in 2003, when they collected and froze a sperm sample from a black-footed cat named Ramses that lived at a research center in Nebraska. In 2005, they thawed the sperm and combined them with eggs from Zora, a cat living at Audubon. That produced 11 embryos, which went into deep freeze.
The center thawed some of the embryos to produce last year's brothers and thawed more on Dec. 2 to produce Crystal.
The embryos can be frozen indefinitely, preserving their genetic information for years if kept at exactly the right temperature, Pope said.
The researchers weren't certain the pregnancy with the domestic cat would work, however, because their attempts to implant cloned black-footed cat embryos in domestic cats have failed so far. Cloned embryos are created by combining cellular material to create new eggs, not by using eggs taken in their entirety from black-footed cat females.
Solving the problem of using cloned embryos will be one of the next steps in the center's long history of breakthrough genetic work, which includes a previous birth of another type of wild kitten to a domestic cat, the first wildcats born to cloned parents, the cloning of sand cats, caracal cats and African wildcats and even a kitten born with eyes, gums and a tongue that glow green under ultraviolet light. That showed it is possible to introduce a new gene to an animal without hurting it, which has medical ramifications for humans in the development of gene therapy. The center also works on reproduction programs for endangered birds: Mississippi sandhill cranes and whopping cranes.
Audubon Senior Scientist Martha Gomez said she has created cloned embryos using egg cells from domestic cats and replacing their nuclei with material from skin cells of African black-footed cats. Using skin cells potentially expands the methods of producing kittens even further because the cells are numerous and can be saved from animals that have died.
But none of the pregnancies have lasted, Gomez said. The arrival of Crystal narrows the field of possible causes by proving domestic cats can carry black-footed kittens. Gomez said she now can focus on fixing flaws in the genetic information of the cloned embryos.
"It's the embryos," she said, "the quality of the embryos."
In addition to working out the glitches in the cloning process, Gomez said the center next will explore using domestic cats as surrogates for a more distantly related type of threatened wild cat, the rusty spotted cat, also from Africa.
"This is exciting," she said about the birth of Crystal, "because now we can go forward in research."