US-based Practical Fishkeeping reader Terry Wisener has successfully bred the genetically modified GloFish which many had suggested were sterile.
The transgenic Zebra danios glow in the dark thanks to a Red Fluorescent Protein (RFP) gene from a coral which has been inserted into the genome. The fish are being sold under license from the National University of Singapore (NUS), and have been trademarked under the name GloFish and marketed by Texas-based Yorktown Technologies. Two leading tropical fish suppliers, 5-D Tropicals and Segrest Farms, are distributing the fish to the aquatic trade.
The media had incorrectly reported that the GloFish, like the Taikong Corporation's TK1 transgenic fishes, were subject to a process of triploidisation to induce sterility.
Terry told PFK: "I live in Indiana, USA, and on January 14 I bought five GloFish at a local petshop, which turned out to be four males and one female. I have been raising fish as a hobbyist for over 30 years and thought I would give them a try.
"Two days after buying them, I had a nice tank full of baby danios clinging to the walls of the 10 gallon tank. The largest fry started glowing under a black light at 10 days old.
"At 23 days, I transferred them to a larger tank and counted 192 individuals."
Terry has also been successful in crossing his GloFish with other aquarium strains of the Zebra danio: "Crossing with short-fin spotted, long-fin gold, short-fin zebra, long-fin zebra, short-fin gold, and long-fin blue have all produced red and green glowing offspring (but not 100% of any one spawn)."
Alan Blake, Chief Executive Officer of Yorktown Technologies told PFK: "Aside from their brilliant colour, fluorescent Zebra fish are the same as other Zebra fish in every way. This includes everything from general care and temperature preferences to growth rate and life expectancy.
"Accordingly, our fish are able to breed just as any other Zebra fish. At the same time, we encourage people to remember that their sale is covered by a substantial number of patents and related intellectual property. Because of this, any breeding and subsequent sale of the fish is prohibited."