Physiological and metabolic responses of juvenile Lophiosilurus alexandri catfish to air exposure

The present study aimed to evaluate the physiological and metabolic stress responses of juvenile Lophiosilurus alexandri submitted to an air exposure test. The subjects consisted of 72 juveniles. Blood samples were taken at: 0hfish not exposed to air; 0.5hfish shortly after exposure to air for 30min (prior to returning to the tank); 1.5h (90min), 24, 48, and 96h after the initiation of exposure to air for 30min. After 96h, survivorship was 100%. Cortisol and glucose levels were higher at 0.5h, returning to baseline at 48 and 24h, respectively. Lactate dehydrogenase levels were highest at 1.5h after exposure to air, returning to normal values in 24h. Several changes were recorded in gasometric blood values and electrolytes. With regard to hematology and blood chemistry, exposure to air did not affect globular volume and AST throughout the 96h of the experiment. The values for alkaline phosphatase were highest at 0, 1.5, and 24h. Total protein was similar between 0 and 1.5h and lowest at 96h, while ALT was highest at 0.5h. Leukocytes were highest at 0.5, 1.5, 48, and 96h, while erythrocytes were highest at 96h. After 96h, juvenile L. alexandri were able to reestablish the main indicators of stress (cortisol, glucose and lactate dehydrogenase), while other indicators (hematological, biochemical, and gasometric) exhibited compensatory variation for normal physiological re-establishment.