Temperature Tolerances of Wild-Type and Red Transgenic Zebra Danios

Abstract

Seventy-nine transgenic red zebra danios Danio rerio (also known as zebrafish; transgenics also known as glofish) and 78 wild-type zebra danios acclimated to 20°C and 30°C had critical thermal maxima (±SD) of 38.8 ± 0.54°C and 41.3 ± 0.50°C (glofish) and 39.2 ± 0.34°C and 41.7 ± 0.35°C (wild-type), respectively. The critical thermal minima (±SD) were 7.2 ± 0.48°C and 10.0 ± 0.50°C (glofish) and 6.2 ± 0.28°C and 10.6 ± 0.53°C (wild-type), respectively. At both 20°C and 30°C acclimation temperatures, critical thermal maxima (CTMax) and critical thermal minima (CTMin) were significantly different between transgenic and wild zebrafish; however, differences were 1°C and less. The temperature tolerances would classify both varieties of zebra danios as eurythermal and place this species in the relatively rare category of fishes with a CTMax above 40.0°C. Compared with similar temperature tolerance data reported for other tropical fishes that have successfully been introduced into U.S. waters, the present data suggest both wild-type zebra danios and red glofish are capable of overwintering in some southern U.S. waters.