Sequestration The production of chemical defenses is often assumed to be expensive because it requires resources that might otherwise have been used for growth and reproduction. One way for a species to avoid such cost is to sequester compounds produced by its prey. Sequestration was first discovered in the monarch butterfly. Monarch caterpillars feed on milkweeds and sequester the plant's cardenolides. Milkweeds produce toxic cardenolides that deter most vertebrate herbivores, but monarchs have evolved the ability to tolerate and sequester these compounds. When blue jays were fed monarchs, the birds soon regurgitated and learned to associate this unpleasant response with eating monarchs. To help advertise their chemical nastiness and perhaps to increase the learning response of birds, monarchs evolved aposematic coloration. Other species of butterflies, such as the viceroy and the queen butterflies, mimic monarchs, affording them protection from predators that have already learned to avoid orange and black butterflies. Nudibranchs are a class of sea slugs that lack the protective shell that most of their gastropod relatives possess. Because they lack the physical defense of a shell, they must protect themselves from other mechanisms, and have ingenious ways of doing so. Most nudibranchs do not produce their own defenses. Rather, they sequester the defenses of their prey. For example, aeolid nudibranchs are famous for sequestering functional nematocysts from their cnidarian prey. They transfer nondischarged nematocysts from their gut to their skin, thereby protecting themselves frompredators such as fish. Nudibranchs also sequester secondary metabolites from their invertebrate prey, which effectively protect them from predatory fishes.
Endangered Species on the Cloning List The world's first successful cloning of an animal belonging to an endangered species by interspecies nuclear transfer was carried out by researchers at Advanced Cell Technology (ACT), in Worcester, Massachusetts, who cloned a baby gaur, an oxlike animal found in India, Indochina, and Southeast Asia. Using skin cells from the gaur as a source of genetic material, internuclear transfer by microinjection of an egg cell obtained from a cow and subsequent implantation into the uterus of a cow serving as a surrogate mother resulted in the birth of a cloned ox named Noah on January 8, 2001. Unfortunately, the cloned animal died just two days later from a common dysentery infection, apparently unrelated to the cloning procedure or gestation in a different species. In November, 1999, the first successful transplantation of a frozen embryo froman African wildcat, an endangered animal species, into a surrogate mother of another species, the common housecat, was carried out by Betsy Dresser and colleagues of the Audubon Center for Research of Endangered Species (ACRES). Other interspecies embryo transfer successes include a mouflon sheep born to a domestic sheep, a red deer born to a white-tailed deer, and a bongo antelope born to a common African antelope called an eland. Endangered species that could benefit fromthe new interspecies cloning technologies include the cheetah, which is close to extinction due to the loss of its natural habitat, and the panda, which has already been the subject of assisted reproductive technologies in captivity. In August, 1999, Hua Mei was born at the San Diego Zoo following successful artificial insemination. Research efforts on interspecies embryo transfer involving pandas have been largely focused on American black bears as egg donors and surrogate mothers. The first donor panda cells used in these experiments were frozen cells obtained from the late Hsing Hsing and Ling Ling.
