Fish genetically engineered to glow blue, green, or red under blacklight have been a big hit among aquarium lovers for years.
But the fluorescent pet is not restricted to glass displays anymore. The red- and green-glowing versions, more vivid than normal zebrafish even in natural light, have escaped fish farms in southeastern Brazil and are multiplying in creeks in the Atlantic Forest, a new study shows.
It is a rare example of a transgenic animal accidentally becoming established in nature, and a concern for biologists, who worry the exotic fish could threaten the local fauna in one of the most biodiverse spots on the planet.
“This is serious,” says ecologist Jean Vitule at the Federal University of Paraná, Curitiba. Vitule, who was not part of the research, says the ecological impacts are unpredictable.
He worries, for example, that the fluorescence-endowing genes from the escapees could end up being introduced in native fish with detrimental effects, perhaps making them more visible to predators. “It’s like a shot in the dark,” he says.
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The transgenic fish seem to achieve sexual maturity earlier than their forebears, which allows them to reproduce more and spread faster.
