Physiological and molecular responses in the silver carp (Hypophthalmichthys molitrix) larvae after acute mercury exposure.

Abstract

The current study was performed to examine the acute toxicity of mercuric chloride (HgCl2) on the silver carp (Hypophthalmichthys molitrix) larvae. Probit analysis was used to determine the median lethal concentration (LC50). The LC50 values of Hg2+ for the fish larvae at 24, 48, 72, and 96h were 267.72, 252.97, 225.57, and 97.80μg/L, respectively. The safe concentration of Hg was 9.78μg/L for fish larvae. Based on the 96h LC50, fish were exposed to four different groups including 0, 6.11, 12.23, and 24.45μg/L for 96h to assess the effects of different concentrations of Hg2+ on antioxidant capacity, energy metabolism parameters, and related gene expression. The findings revealed that there were no significant differences in the activities of superoxide dismutase (SOD) and total antioxidant capacity (T-AOC) in fish larvae among all the groups (P < 0.05). In the 12.23μg/L group, fish larvae had a maximum in catalase (CAT) activity. The creatine kinase (CK) activities of fish larvae in control and 6.11μg/L groups were significantly lower than those groups (P < 0.05). A high concentration of Hg2+ significantly upregulated the mRNA levels of heat shock protein 70 (HSP70) and metallothionein (MT) genes in fish larvae. Furthermore, the IBR index value showed the highest value in the 24.45μg/L group. Overall, this study provides an increased understanding of the effects of Hg-acute toxicity on silver carp larvae.