Physiological responses of juvenile Colossoma macropomum after different periods of air exposure

Abstract

The objective of this work was to evaluate the physiological responses of juvenile Colossoma macropomum exposed to air for different periods of time. Juveniles weighing 74.78 ± 17.39 g were acclimated for 15 days in 30-L tanks in a recirculating aquaculture system (RAS) at a density of 6 animals/tank. The animals were then fasted for 24 h prior to the air exposure test and six juveniles were captured for blood collection to establish basal levels of the parameters. Next, 24 animals were exposed to air for 30 min and the other 24 for 60 min. Blood samples were taken from six animals of each exposure treatment immediately after exposure (IAE), and the other animals returned to their tanks. Subsequent blood samples were taken for six animals (n = 6) per exposure time at 1 h (1hAE), 24 h (24hAE) and 48 h (48hAE) after air exposure. No mortality was recorded. Hematocrit and hemoglobin did not vary according to air exposure time, collection time or the interaction between these two factors. There was an interaction of the factors times of exposure to air and times of collection for glucose where was higher for the 60 min exposure compared to the 30 min exposure at the 1hAE collection, while after 24hAE the levels did not differ from basal. For lactate there was also an interaction between the factors being higher for the 60 min exposure compared to the 30 min exposure at IAE and 1hAE. Blood pH varied among the collections, with a lower value at 1hAE for the 60 min exposure. The parameters PvCO2 (venous carbon dioxide partial pressure) and PvO2 (venous oxygen partial pressure) were inversely proportional; while PvCO2 increased, PvO2 decreased after collection 1hAE. Values of HCO3− (bicarbonate) differed between exposure times and varied among collections. The electrolytes Cl− (Chloride) and K+ (Potassium) varied among collections in relation to basal, however, they did not differ between exposure times. The value for Na+ (Sodium) for the 60 min exposure at IAE was higher than basal, and only 24hAE was different from basal for both exposures. Ca2+ (Calcium) values differed between exposure times (30 and 60 min) in the 24hAE collection, however, values did not differ from basal. Exposure to air caused physiological, biochemical, gasometric and electrolytic in juvenile C. macropomum. These animals can be considered resistant to this stress due to their ability to restore physiological.