Battling extinction with test-tube tigers.Battling extinction with test-tube tigers A surrogate mother surrogate mother, a woman who agrees, usually by contract and for a fee, to bear a child for a couple who are childless because the wife is infertile or physically incapable of carrying a developing fetus. named Nicole has provided scientists with a moment to remember. The 9 1/2-year-old Siberian tigress gave birth on April 27 to three Bengal tiger cubs, the world's first "big cats" produced through in vitro fertilization in vitro fertilization (vē`trō, vĭ`trō), technique for conception of a human embryo outside the mother's body. Several ova, or eggs, are removed from the mother's body and placed in special laboratory culture dishes (Petri dishes); and embryo transfer embryo transfer n. After artificial insemination, the process by which the fertilized ovum is transferred at the blastocyst stage to the recipient's uterus. . The births have boosted biologists' hopes for preventing extinction of the world's five tiger subspecies subspecies, also called race, a genetically distinct geographical subunit of a species. See also classification. as well as a number of other endangered animals. Veterinarians at the Henry Doorly Zoo The Henry Doorly Zoo, located at 3701 South 10th Street, is a zoo in Omaha, Nebraska. It is accredited by the Association of Zoos and Aquariums (AZA) and a member of the World Association of Zoos and Aquariums (WAZA). in Omaha, Neb., delivered the cubs through Cesarean section. Two cubs later died, one from respiratory complications and the other from kidney failure. Zoo scientists do not think the deaths were related to the fertilization/implantation technique. Reproductive physiologists Ann Miller and Leslie Johnston of the National Zoo in Washington, D.C., tailored the technique to tigers in collaboration with researchers from the Henry Doorly Zoo and the Minnesota Zoological Gardens in Minneapolis. They also developed a miniaturized in vitro fertilization lab for use in Omaha and possibly in the wild. The team gave Bengal tigresses hormones that increase egg production, then removed the eggs for fertilization in a petri dish. The resulting embryos were placed in Nicole's reproductive tract. Only 3,000 to 5,000 tigers remain in the wild, most driven into isolated reserves by human encroachment, notes tiger specialist Ulysses Seal of Minneapolis, a consultant on the project. This fragmentation has separated potential mates and increased the chances of inbreeding inbreeding, mating of closely related organisms. Inbreeding is chiefly used as a means of insuring the preservation of specific desired traits among the offspring of purebred animals (see breeding). , he says. "One of our objectives in the long term will be to move genetic material from one reserve to another," Seal told SCIENCE NEWS. "Moving embryos rather than animals is much less dangerous for the animals." In vitro fertilization not only promises to bolster genetic stocks in zoos and reserves, but also might enable biologists to freeze embryos of species on the verge On the Verge (or The Geography of Yearning) is a play written by Eric Overmyer. It makes extensive use of esoteric language and pop culture references from the late nineteenth century to 1955. of extinction, he adds. |
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