Phagocytic activity, respiratory burst, cytoplasmic free-Ca2+ concentration and apoptotic cell ratio of haemocytes from the black tiger shrimp, Penaeus monodon under acute copper stress

The aim of this study was to investigate the cellular toxicity of copper-induced injury to the black tiger shrimp Penaeus monodon. The 24 h, 48 h, 72 h and 96 h LC50 (median lethal concentration) of Cu2+ on P. monodon (11.63 ± 1.14 g) were found to be 3.49, 1.54, 0.73 and 0.40 mg L− 1, respectively. Total haemocyte count (THC), phagocytic activity, respiratory burst (RB), cytoplasmic free-Ca2+ (cf-Ca2+) concentration and apoptotic cell ratio of shrimp were determined after exposure to different concentrations of Cu2+ (0, 0.05, 0.5, 1.5 and 3.5 mg L− 1) for 0, 6, 12, 24 and 48 h. There was no significant effect on the analytic indicator of shrimp exposed to 0.05 mg L− 1 Cu2+. THC decreased after Cu-exposure to 0.5 mg L− 1 for 48 h, 1.5 mg L− 1 for 24 h and 3.5 mg L− 1 for 12 h. Phagocytic activity decreased in P. monodon following 48 h exposure to 3.5 mg L− 1 Cu2+. RB was induced after 6 h exposure to 0.5, 1.5 and 3.5 mg L− 1 Cu2+. cf-Ca2+ concentration increased after 48 h exposure to 0.5 mg L− 1 Cu2+, and 12 h exposure to 1.5 and 3.5 mg L− 1 Cu2+. The percentage of apoptotic cells increased to 9.5%, 16.3% and 18.6% respectively following 48 h exposure to 0.5, 1.5 and 3.5 mg L− 1 Cu2+. These results indicate that Cu can induce oxidative stress, elevation of cf-Ca2+ and cell apoptosis, and inhibit phagocytic activity in the shrimp P. monodon, and the lethal injury of Cu2+ to P. monodon may be mainly due to the sharp reduction of THC caused by ROS-induced apoptosis.