Hematological and Biochemical Responses of the Flowerhorn Fish to Hypoxia

Hematological and biochemical responses of the flowerhorn fish (Amphilophus trimaculatus x Amphilophus citrinelllus x Vieja synspilum) and their surviving strategies to hypoxia were investigated. Male and female flowerhorn fish were divided into five groups. Each group contained tree replications of five groups and was exposed to hypoxia by the substitution of nitrogen for oxygen for 12, 24 and 48 h, respectively. Blood sample was collected from the caudal vein and physiological-biochemical blood parameters analyzed. The results showed that hypoxia caused a significant increase in ventilation rate. Hematological parameters including red blood cell count, white blood cell count, hematocrit and hemoglobin concentration were significantly increased in fish exposed to hypoxia whereas mean corpuscular hemoglobin concentration remained the same. In addition, hypoxia caused significant increases in serum glucose, alanine amino-transferase, aspartate amino-transferase, creatine kinase and blood urea nitrogen. However, cholesterol and creatinine were significantly decreased. The effects of hypoxia on those parameters occurred in a time dependent manner. Changes in hematological parameters fully recovered after 1 week oxygen replenishment whereas biochemical parameters slowly returned to control levels. These suggest that acute hypoxia in the flowerhorn fish up to 48 h can affect physiology functions as indicated by changes in hematological and biological parameters. Alteration of most physiological functions can be restored by repayment of oxygen debt. The results also suggest that the flowerhorn fish coped with hypoxic condition by using both energy saving strategies and by attempting to increase the oxygen extraction capacity.