Low-temperature tolerances of tropical fish with potential transgenic applications in relation to winter water temperatures in Canada

Abstract

Application of fluorescent protein transgenes in tropical freshwater fish is used in research (e.g., in zebrafish) and in the commercial ornamental aquarium trade. To assess the overwinter potential of such fish in Canada, we examined the minimum temperature tolerance of three wild-type species (zebrafish, Danio rerio (Hamilton, 1822); black tetra, Gymnocorymbus ternetzi (Boulenger, 1895); tiger barb, Puntius tetrazona (Bleeker, 1855)) used as fluorescent models in the aquarium trade, as well as four lines of green fluorescent protein (GFP) transgenic and wild-type zebrafish used in research. Both tetra and barb had lower temperature tolerance limits that were higher than surveyed winter temperatures in Canada, and the lower tolerance limits of zebrafish lines was only within the range of a few surveyed lakes in some years. One line of GFP zebrafish had a lower temperature tolerance limit that was significantly higher than those of other lines, suggesting that some fluorescent transgene constructs may alter tolerance to extreme temperatures. When lines of zebrafish were reared at 8, 10, or 28 °C for 4 months, all lines were capable of producing viable embryos after cold rearing. These results indicate that tropical transgenic fish models used in research and in the aquarium trade are not expected to persist over winter in Canadian water systems.