Meet Watchfrogs: GM frogs and fish detect endocrine disrupting chemicals in wastewater

Xenopus laevis by Tim Vickers
African Clawed Frogs (Xenopus laevis), one of the species that the French company Watchfrog has genetically engineered to aid in detection of endocrine disrupting chemicals in wastewater. Photo by Tim Vickers

If there is one topic that can elicit even more uproar than GM crops, it is GM animals. Witness the hue and cry over the AquaAdvantage salmon, which could be the first GM animal approved by the FDA–if the approval process, which began almost 20 years ago, is ever completed.

Anti-GMO critics claim that if GM salmon escape and interbreed with wild salmon it could lead to the “extinction of the wild population in less than 40 fish generations.” Never mind that the salmon are sterile and would be farmed in inland facilities. The FDA has assessed GM salmon’s potential to escape and survive in the wild and determined that it is negligible.

Other anti-GMO groups claim that GM salmon is not safe for human consumption, that its flesh may be toxic or dangerously allergenic–“at least 19 percent more allergenic than natural salmon,” claimed  Mother Jones. But that “19 percent” figure is a misleading representation of data which they admit is insufficient to assess the fish’s actual potential to cause an allergic reaction.

While the AquaBounty “frankenfish” has received a steady stream of media attention and criticism from activist web sites, the public is generally unaware that a whole suite of GM animals is already in use. You just won’t find them at your local grocery store.


One “glowing” example is the use of GM animals to screen wastewater for endocrine disrupting chemicals (EDC), which can have adverse effects on the development and reproduction of organisms. Scientists at the French company Watchfrog have genetically engineered frogs and fish, introducing a jellyfish gene called “green fluorescent protein” that causes them to glow when the animals are exposed to EDC. The result: a practical and commercially viable tool for evaluating water safety.

With sufficient exposure, an EDC interact with the body’s endocrine system, often by mimicking a naturally occurring hormone or blocking a hormone action. Better-known examples of EDC are ethinylestradiol, a component of the birth control pill, or some pesticides like permethrin. These chemicals make their way into wastewater when we excrete them into our toilets or apply them to our lawn.

The adverse effects of EDC on development and reproduction of animals in the lab and the wild are well established. These can include altered sexual development and limb deformities. The effects of EDC on human health are harder to ascertain, because the types of controlled experiments that would be necessary to do so would be unethical. Nevertheless, it is widely agreed that for the sake of both wildlife and human health, we should limit the release of EDC into the environment- especially the water supply.

Wastewater treatment plants are required to monitor the treated water they release (effulent) in order to ensure that treatment is effective. EDC and other pollutants must be removed or reduced to acceptable levels. In vitro assays (tests) can detect the presence and quantity of individual chemicals. But some of these chemicals may cause different responses when an animal is exposed to a combination of them. An in vitro assay gives no information about the biological effect of a chemical. But an “in vivo” assay, which is performed on whole, living organisms, answers that question directly.


Watchfrog has created in vivo assays that use transgenic frog (Xenopus laevis) and fish (Oryzias latipes) embryos. Frogs and fish are known to be especially sensitive to EDC, and Watchfrog has taken advantage of this sensitivity. The GM frog and fish embryos can be exposed to water samples and the green fluorescent protein gene introduced into the animals makes their response to any EDC in the water samples easy to observe: the more polluted the sample, the more they glow. These assays give wastewater managers a practical way to assess the biological effect, or safety of wastewater.

Related article:  GMOs in pipeline promise consumer-friendly traits but attacks by familiar critics abound

Watchfrog’s in vivo assays are just one example of the use of GM animals for non-food purposes. “Pharming” or the use of transgenic animals to produce biopharmaceuticals, such as insulin or erythropoietin, is more common. A gene for the desired protein is introduced into an animal, which then produces the protein in a bodily fluid such as milk. These types of GM animals receive much less attention from anti-GMO groups and the media because the two major concerns about GM animals– their suitability for human consumption and potential for escape and breeding in the wild– do not apply to them. These are highly valuable, usually domestic, animals that are housed exclusively in a lab.

Except, that is, when they are sold at your local Petco. The mega pet store and other retailers are now selling transgenic zebrafish and other fish species. GloFish® are genetically engineered to glow under UV lights because sometimes humans enjoy looking at “trippy” things like lava lamps and fluorescent tetras.

GM animal products may or may not ever make it onto grocery store shelves, but that doesn’t mean they aren’t already benefiting humans. Whether they are ensuring water safety, producing valuable pharmaceuticals or simply diverting the eye, GM animals are already becoming part of our daily lives.


Meredith Swett Walker is a science writer based in western Colorado. She studied behavioral endocrinology at the University of Texas at Austin and received a Ph.D. in organismal biology and ecology from the University of Montana-Missoula.

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