A total of 85 interspecific hybrid F2 （Cyprinus carpio var.wuyuanensis ×Cyprinus pellegrini pellegrini） were cooled to specific temperatures and held at those temperatures over a maximum of 4 days in a water-recycled and temperature-controlled aquarium inside.As a result,the blood homeostasis of experimental fish changed violently as acute temperature changed from 16 ℃ to 10 ℃ and 4 ℃ at a rate of 1 ℃·h-1 according to the data we collected.Whole blood pH,also called extracellular pH（pHe） were very sensitive to temperature changes,where there was a significant difference between 10 ℃（7.41） and 16 ℃（7.17）(P<0.01),compared to other values of hematology and serum chemistry.When the water temperature was continually decreased to an extreme temperature of 4 ℃,the content of Na+ of serum decreased remarkably in comparison with that of 10 ℃ and 16 ℃,which was 85.2 mmol·L-1,113.3 mmol·L-1 and 118.7 mmol·L-1,respectively.The values of hematology and serum chemistry also altered in gentle temperature changes of（10±2） ℃ and（4±2） ℃.Most values of serum chemistry and pH changed significantly,whereas the values of blood plasma changed slightly.pH was up slowly in 4 days at（10±2） ℃ and down slowly in 3 days at（4±2） ℃.A variety of values of serum chemistry changed remarkably both at（10±2） ℃ and（10±2） ℃,but the values of TP,TG and ALB only changed significantly at（4±2） ℃.These results distinguished at least two mechanisms involved in cold-induced stress in hybrid F2.Cold-induced pH changes resulted in other values altered.What's more,pH correlated negatively with water temperature above 10 ℃,and the content of Na+.We also found that gentle temperature changes will be physiologically compensated for on day one at（10±2） ℃ and on day 2 at（4±2） ℃ in hybrid F2.
