Wild Zebrafish Outcompete GMO Zebrafish For Sex

When it comes to mating, genetically modified zebrafish get run out of town by their wild counterparts.

GloFish were out hustled by their wild counterparts when it came to mating. Photo by Glofish.com
GloFish were out hustled by their wild counterparts when it came to mating. Photo by Glofish.com

While the issue of GMOs in the food supply rages on, one thing has been determined in the GMO Glowfish, those genetically modified zebrafish  (Danio rerio) that come in a rainbow of colors; they cannot compete with wild zebrafish when it comes to sex. That is right, the GMO Glofish are sexually weaker than their wild caught counterparts when it comes to mating.


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According to a press release put out by Purdue University, researchers at the university conducted a study of the sexuality of the GloFish and their wild counterparts and found that while the female zebra danio preferred to mate with the genetically-modified neon red male fish over the brown wild zebra danio, the wild zebrafish consistently chased off the genetically modified variants to the point that the rate that the red transgenic trait appeared in offspring disappeared over 15 generations of more than 18,500 fish and was completely gone from all except one of the 18 populations.

“The females didn’t get to choose,” said William Muir, a co-author of the study. “The wild-type males drove away the reds and got all the mates. That’s what drove the transgene to extinction.”

The wild zebrafish and the genetically modified GloFish were identical in every other aspect, including health fertility and lifespan, which the researchers did not expect given than genetically modifying an organism usually leads it to be less fit in the wild. Where it counted, in the mating ritual, was the only aspect in which the genetically modified fish lost out, the one trait that would ensure the survival of the genetically modified gene.

“Darwin was right: Survival of the fittest works,” Muir said. “If we make a transgenic organism that has reduced fitness in the wild, evolution takes over and removes it. Nature experiments with mutations all the time, and it only saves the best of the best.”

So what does this mean for genetically modified fish? The GloFish has been approved for sale and can be found in many fish stores throughout the United States. However, genetically modified fish for human consumption has not yet been approved for sale in the United States. One company, AquaBounty is hoping that its genetically modified salmon will make it to the table in the U.S.


John B. Virata has been keeping fish since he was 10 years old.  He currently keeps an 80 gallon cichlid tank, a 20 gallon freshwater community tank and a 29 gallon BioCube with a Percula clown, a huge blue green chromis, and a firefish all in his kitchen, and a 55 gallon FOWLR tank with a pair of Ocellaris clowns, two blue green chromis, a six line wrasse, a peppermint shrimp, assorted algae and a few aiptasia anemones in his living room. Follow him on Twitter @johnvirata

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