Mercury (Hg2+) effect on enzyme activities and hepatopancreas histostructures of juvenile Chinese mitten crab Eriocheir sinensis

We studied the effects of mercury (Hg²⁺) on antioxidant and digestive enzyme activities in terms of LC₅₀ value and on hepatopancreas histostructures of juvenile Chinese mitten crabs Eriocheir sinensis in 40-day exposure to various concentrations of Hg²⁺ (0, 0.01, 0.05, 0.10, 0.20, and 0.30 mg/L). The results show that the activities of superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase (CAT) significantly increased in the concentrations of 0.01 and 0.05 mg/L, while that of enzyme decreased in 0.10, 0.20 and 0.30 mg/L treatments. Meanwhile, Hg²⁺ disrupted the histostructures of the hepatopancreas, causing decreases in activities of pepsin, tryptase, amylase, and cellulose, which are synthesized in the hepatopancreas. Moreover, as the Hg²⁺ concentration increased, the survival rate of the crabs decreased, worst at 56.57% in 0.30 mg/L. Therefore, although crabs are able to tolerate low levels of mercury pollution, high levels lead to cellular injury and tissue damage in hepatopancreas, which then loses some of its vital physiological functions such as absorption, storage, and secretion.