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Genetically-engineered fish glow under UV light

According to a recent study in the journal Animal and Environmental Research, ‘GloFish’, a brand for genetically modified aquarium fish that can glow in black light, has escaped from eastern fish farms. south of Brazil and is beginning to breed in the wild.

GloFish is a patented and registered trademark of genetically modified fluorescent fish. They are made from a number of different fish species: the zebrafish (Danio rerio) which was the first GloFish to hit pet stores, and more recently the tetra (Gymnocorymbus ternetzi), the tiger barb (Puntius) tetrazona), rainbow shark (Epalzeorhynchos frenatum), and more recently betta have been added to the range. They are sold in a variety of colors, branded as “Starfire Red”, “Moonrise Pink”, “Sunburst Orange”, “Electric Green”, “Cosmic Blue” and “Galactic Purple”, although not all species are available in all colors.

Although not originally developed for the aquarium trade, it was one of the first genetically modified animals made available to the public. The rights to GloFish are owned by Spectrum Brands, Inc., which purchased GloFish from Yorktown Technologies, the original developer of GloFish, in May 2017.

Early development

The original zebrafish (or zebra danio, Danio rerio) is a native of rivers in India and Bangladesh. In 1999, Dr. Zhiyuan Gong and his colleagues at the National University of Singapore were working with a gene that encodes the green fluorescent protein (GFP), originally extracted from a jellyfish, that naturally produced bright green fluorescence. They inserted the gene into a zebrafish embryo, allowing it to integrate into the zebrafish’s genome, which caused the fish to be brightly fluorescent under both natural white light and ultraviolet light.

Shortly thereafter, his team developed a line of red fluorescent zebra fish by adding a gene from a sea coral, and orange-yellow fluorescent zebra fish, by adding a variant of the jellyfish gene. Later, a team of researchers at the National Taiwan University, headed by Professor Huai-Jen Tsai, succeeded in creating a medaka (rice fish) with a fluorescent green color, which, like the zebrafish, is a model organism used in biology.

Introduction to the United States market

GloFish were introduced to the United States market in late 2003 by Yorktown Technologies, after two years of research. The governmental environmental risk assessment was made by the U.S. Food and Drug Administration (FDA), which has jurisdiction over all genetically modified (GM) animals, including fluorescent zebra fish, since they consider the inserted gene to be a drug. The FDA determined in December 2003: Because tropical aquarium fish are not used for food purposes, they pose no threat to the food supply. There is no evidence that these genetically engineered zebra danio fish pose any more threat to the environment than their unmodified counterparts which have long been widely sold in the United States. In the absence of a clear risk to the public health, the FDA finds no reason to regulate these particular fish.

Vulnerability to predation

GloFish are more vulnerable to predation compared to the wild type, according to a study published in 2011. In experiments including habitat complexity, transgenic red fluorescent zebrafish were approximately twice as vulnerable as the wild type to predation by largemouth bass (Micropterus salmoides) and eastern mosquitofish (Gambusia holbrooki), two native predators that potentially resist invasion by introduced fish.

Evolutionary outcomes

According to an article published in 2015, wild-type males had a significant advantage over GloFish when it came to mating. According to the mating trials that were analyzed in the study, wild-type males sired twice as much as the genetically modified fish due to their more aggressive nature. In a previous study that was referenced, female zebrafish preferred the GloFish rather than wild-type males.

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