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Bigger not always better
 By Chris Sigurdson
Call it "Biotechnology--with your eyes open." Well aware of the promising potential of biotechnology for modified crops with novel uses, Purdue Agriculture scientists also are charged with investigating the possible risks. Animal scientist Bill Muir has found one.
 Muir, a geneticist who works with populations of animals, and his colleague, Purdue biologist Rick Howard, found that releasing a transgenic fish into the wild could damage native populations, even to the point of extinction.
A transgenic organism is one that contains genes from another species. The Purdue research is part of an effort by Purdue and the U.S. Department of Agriculture to assess the risks and benefits of biotechnology and its products, such as genetically modified fish. The study was published in the Proceedings of the National Academy of Science.
The researchers used medaka, a minute Japanese fish, to examine what would happen if genetically modified male medakas were introduced into a population of unmodified fish. The research was conducted in banks of aquariums in a laboratory setting, and the results were modeled for farm-raised fish of economic importance, such as salmon or tilapia.
The results warn that transgenic salmon and tilapia could present a significant threat to native wildlife. "Transgenic fish are typically larger than the native stock, and that can confer an advantage in attracting mates," Muir says. "If, as in our experiments, the genetic change also reduces the offspring's ability to survive, a transgenic animal could bring a wild population to extinction in 40 generations." Extinction results from a phenomenon that Muir and Howard call the "Trojan gene hypothesis." By basing their mate selection on size rather than fitness, female fish choose the larger, genetically modified but genetically inferior males, thus inviting the hidden risk of extinction.
The study demonstrates scientists policing science, Muir says. "I hope people understand that scientists are investigating the risks of biotechnology as well as the benefits, so decisions can be made with as much information as possible. It's important to understand the risks so they can be addressed."
The dominance of sexual preference over Charles Darwin's classic theory of survival of the fittest is not unknown to wildlife specialists and geneticists. Muir likes to use the example of the male bird of paradise with its long swells of gloriously colored plumage as an example. "The male bird of paradise with the longest, thickest tail attracts the most females. Subsequent offspring also exhibit the long tail and also compete well for females. Unfortunately, the birds with the biggest tails also have the biggest problem escaping predators who appreciate large birds pinned in place by their plumage. Obviously, the bird with the most sex appeal is the also the worst choice as a fit mate. Not unlike high school, some might say."
The researchers' next goal is to replicate the study with larger fish of economic importance in a larger environment. They're looking for an indoor swimming pool where they can raise tilapia and check the results of the medaka study.
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