Failure of cortisol response in induced capture handling stress and carrageenin in Piaractus mesopotamicus Holmberg, 1887 (Osteichthyes: Characidae)

Abstract

In this assay the effect of consecutive stress handling and carrageenin injection (500 µg in 0.5 ml of saline solution) or 0.5 mL of saline on Piaractus mesopotamicus Holmberg, 1887 (Osteichthyes: Characidae) was evaluated. The fish were subjected to 30 s capture handling stress applied repeatedly at 60 min intervals over 6 h. Blood sampling was as following: time 0: basal blood sampling and first stress; time 1: injection with carrageenin or saline and sampling after 5 min; time 2: stress and sampling after 5 min; time 3: stress and sampling after 5 min; time 4: stress and sampling after 5 min; time 5: blood sampling after 90 min. Circulanting cortisol levels showed significant decrease in time 4 and 5 in both carageenin and saline injected fish. In saline injected fish, glucosis increased in time 2 while in carrageenin injected fish this fact occurred in time 3. An increase in the special granulocitic cells and lymphocitopenia in blood were observed in the time 2. Neutrophilia was reported in time 3.