Abstract: The purpose of this study was to explore the effect of cold acclimation on mitochondrial DNA (mtDNA) copies number and development ability at low temperature of zebrafish embryos. The zebrafish was raised under 27℃ until adulthood, and acclimatized under 22℃ for 6 months. Fertilized embryos of acclimation group and wild-type group zebrafishes were collected after mating, then observed the embryogenesis of embryos while developing under lower temperatures which were 22℃ and 20℃ from 0 hpf stage. DNA of the 0 hpf, 8, 12 and 24 hpf embryos was extracted, detected and analyzed comparatively by Absolute Quantification PCR. The results showed that in 0 hpf, the mtDNA copies number of cold acclimation group was significantly lower than that of 27℃ non-acclimation group, and kept the same trend in the later 3 stages, but the gap was narrowing. Meanwhile, the embryos which endured cold acclimation at 22℃ showed higher survival rate than that at 27℃ non-acclimation group. And the embryos could survive under 20 ℃ cold stress. 

Key words: cold acclimation, zebrafish, mtDNA, embryogenesis