Early development

An ordinary Zebra Danio

The original zebrafish (or zebra danio, Danio rerio) is a native of rivers in India and Bangladesh. It measures three centimeters long and has gold and dark blue stripes. In 1999, Dr. Zhiyuan Gong^[3] 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. Their goal was to develop a fish that could detect pollution by selectively fluorescing in the presence of environmental toxins. The development of the constantly fluorescing fish was the first step in this process, and the National University of Singapore filed a patent application on this work.^[4] 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.

The scientists from NUS and businessmen Alan Blake and Richard Crockett from Yorktown Technologies, L.P., a company in Austin, Texas, met and a deal was signed whereby Yorktown obtained the worldwide rights to market the fluorescent zebrafish, which Yorktown subsequently branded as "GloFish". At around the same time, a separate deal was made between Taikong, the largest aquarium fish producer in Taiwan, and the Taiwanese researchers to market the green medaka in Taiwan under the name TK-1. In the spring of 2003, Taiwan became the first to authorize sales of a genetically modified organism as a pet. One hundred thousand fish were reportedly sold in less than a month at US$18.60 each. The fluorescent medaka are not GloFish, as they are not marketed by Yorktown Technologies, but instead by Taikong Corp under a different brand name.

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.^[5]

Marketing of the fish was met by protests from a non-governmental organization called the Center for Food Safety. They were concerned that approval of the GloFish based only on a Food and Drug Administration risk assessment would create a precedent of inadequate scrutiny of biotech animals in general. The group filed a lawsuit in US Federal District Court to block the sale of the GloFish. The lawsuit sought a court order stating that the sale of transgenic fish is subject to federal regulation beyond the FDA's charter, and as such should not be sold without more extensive approvals. In the opinion of Joseph Mendelson, the Center for Food Safety's legal director:

It's clear this sets a precedent for genetically engineered animals. It opens the dams to a whole host of nonfood genetically engineered organisms. That's unacceptable to us and runs counter to things the National Academy of Sciences and other scientific review boards have said, particularly when it comes to mobile GM organisms like fish and insects.^[6]

The Center for Food Safety's suit was found to be without merit and dismissed on March 30, 2005.

Subsequent developments

In addition to the red zebrafish, Yorktown Technologies released green and orange-yellow versions of the zebrafish in mid-2006. In 2011, blue and purple zebrafish were released. These lines of fish incorporate genes from sea coral.^[1] In 2012, Yorktown Technologies introduced a green version of a GloFish derived from a different species of fish, the black tetra.^[1] This was followed by a green version of a tiger barb. In 2013, Yorktown Technologies introduced orange, pink, and purple Tetras, which made Tetras the first GloFish to be available in pink. This was followed in 2014 by the release of red and blue Tetras. The colors are trademarked as "Starfire Red", "Moonrise Pink", "Sunburst Orange", "Electric Green", "Cosmic Blue", and "Galactic Purple".

Other fish released include the GloFish shark, available in orange, green, and purple. Though these fish are not scientifically related to sharks, they are based on the albino rainbow shark.^[7] In February 2020, green GloFish bettas also known as Globettas were released, with three different variations. These variations include female, (young) male, and premium (adult) male.

A "Galactic Purple" Glofish shark

Despite the speculation of aquarium enthusiasts that the eggs of the fluorescent fish were pressure treated to make them infertile, it has been found some GloFish are indeed fertile and will reproduce in a captive environment.^[8] However, the GloFish Fluorescent Fish License states "Intentional breeding and/or any sale, barter, or trade, of any offspring of GloFish fluorescent ornamental fish is strictly prohibited.".^[9]

Sale or possession of GloFish was made illegal in California in 2003 due to a regulation that restricts genetically modified fish. The regulation was implemented before the marketing of GloFish, largely due to concern about a fast-growing biotech salmon. The regulations were lifted in 2015 due to a growing body of evidence and the findings of the Food and Drug Administration and the Florida Department of Agriculture and Consumer Services. GloFish are now legal in California for importation and commercial sale.^[10]

The import, sale and possession of these fish is not permitted within the European Union. On November 9, 2006, however, the Netherlands’ Ministry of Housing, Spatial Planning and the Environment (VROM) found 1,400 fluorescent fish, which were sold in various aquarium shops.^[11]

In January 2009, the U.S. Food & Drug Administration formalized their recommendations for genetically engineered animals.^[12] These non-binding recommendations describe the way in which FDA regulates all GM animals, including GloFish.^[13]

Research published in 2014 assessed the environmental safety associated with GloFish. One paper concluded that there is little risk of invasiveness into the environment.^[14] A second study concluded that there is no difference in risk between GloFish and wild-type danios.^[15]