Response of the tambacu hybrid (Piaractus mesopotamicus Homberg, 1887 male x Colossoma macropomum Cuvier, 1818 female) to single and consecutive stimuli of capture

Abstract

The effect of two kinds of capture stress on the physiological and hematological response were evaluated in tambacu hybrid (Piaractus mesopotamicus male x Colossoma macropomum female). Throughout the consecutive stimuli stress (CS), the samples were collected before (T0) the stress induction to determine basal values and one hour after each stimulus (T1, T2, T3, T4, T5). These groups of fish were submitted to five stresses with intervals of one hour. In the fish submitted to single stress (SS), the samples were collected before the stimulus (T0) to determine basal values and 60 min (T1); 90 min (T2); 120 min (T3); 150 min (T4), and 180 min after stress (T5). Therefore, fish were submitted to just one stress. Through CS, fish showed reduced cortisol concentration at T2; increased glucose levels from T1 with maximum at T4; increased number of blood leucocytes at T3; the hematocrit and erythrocyte number increased from T4; the percentage of monocytes and neutrophils increased, and that of lymphocytes reduced at T2. No alteration was observed in the levels of cortisol and glucose through SS. On the other hand, increased leucocyte number occurred at T1 and reduction on erythrocyte number, at T2. Thrombocyte number, hemoglobin rate and hematocrit did not alter but an increase on neutrophil percentage and a decrease on lymphocyte percentage from T1 were also observed. The study showed the quick response of tambacu hybrids to stress when compared to their parent Piaractus mesopotamicus.