Purdue University researchers say that while males of a genetically modified zebrafish that glow in the dark are more attractive to females, their wild cousins end up with more breeding success.
Glofish are a GM version of zebrafish with a transgene from a sea anemone, which gives them a neon glow.
Animal science professors, William Muir and Richard Howard conducted a long-term study of mating success in mixed populations of wild zebrafish and Glofish. Although female zebrafish strongly preferred the neon-red males to their brown wild counterparts, the females were coerced into spawning with the wild males who aggressively chased away their transgenic rivals.
As a result, the rate at which the red transgenic trait appeared in offspring fell rapidly over 15 generations of more than 18,500 fish and ultimately disappeared in all but one of 18 populations. “The females didn’t get to choose,” Muir said in a Purdue release. “The wild-type males drove away the reds and got all the mates. That’s what drove the transgene to extinction.”
Except for their mating competitiveness, wild-type males and Glofish males were similar in fitness — that is, their health, fertility and lifespan — which was unexpected since genetically modifying an organism often decreases its ability to flourish, Muir said.
“Natural selection has had billions of years to maximize an organism’s fitness for its environment,” he said. “Changing its genetics in any way almost always makes an organism less fit for the wild. You’ve ‘detuned’ it.”