Acute toxic effects of zinc and mercury on survival, standard metabolism, and metal accumulation in juvenile ridgetail white prawn, Exopalaemon carinicauda

Ridgetail white prawn (Exopalaemon carinicauda) is widely distributed in Chinese coastal zones, especially in the Yellow Sea and Bohai Sea. It is not only considered as an important economic species in China, but also taken as a potential indicator species for the environmental pollution in the estuaries. At present, the responses of this species to environmental toxicants, including trace metal are not well understood. In this study, the acute toxic effects of zinc (Zn) and mercury (Hg) on the survival, oxygen consumption, ammonia-N excretion, and metal accumulation were investigated in the juveniles of E. carinicauda. The median lethal concentrations (LC50) of Zn were 76.4, 44.0, 30.2, and 17.2 mg/L, respectively, after the juveniles were exposed in for 24, 48, 72, and 96 h, and the LC50 of Hg was 0.212, 0.096, 0.084, and 0.065 mg/L under the same exposure duration. The juveniles decreased the oxygen consumption by 51.4%, and increased ammonia-N excretion by 129% when they were exposed in Zn at the concentration of 76.4 mg/L compared with their controls without Zn exposure, therefore the O:N ratio decreased by 82.9% compared with the control. Hg exposure with the concentration of 0.212 mg/L caused the inhibition of oxygen consumption by 48.1% and increasement of ammonia-N excretion by 161%, and the atomic ratio of consumed oxygen to excreted ammonia-nitrogen (O:N ratio) decreased by 80.6% in the juveniles in comparison with the control. A concentration-dependent accumulation of heavy metals was observed in the gills, hepatopancreas and muscles of the experimental animals, with a maximum accumulation of 16.3 folds for Zn and 72.8 fold for Hg in the gills of the juveniles after 24 h exposure. The data obtained from the present study would provide useful information for help further understanding on the toxicological responses of this species to trace metals.