Abstract
The toxic effects of methylmercury (MeHg) on organisms have caused widespread concerns, but little has been reported on its effects in marine fish. This study investigated the acute and sub-lethal toxicities of MeHg chloride to large yellow croaker (Pseudosciaena crocea) embryos and larvae. Acute toxicity tests showed that the 48-h LC50 values of methylmercury to the embryos and larvae were 28.39 (21.33-33.98) and 18.27 (11.33-29.29) μg L -1 , respectively, while the 96-h LC50 value for larvae was 9.28 (4.41-14.49) μg L -1 , indicating that larvae were more sensitive to MeHg than the embryos. On the other hand, MeHg could cause low hatching success, increase larvae heart rate at concentrations ≥ 20 μg L -1 , as well as delayed hatching process, reduced survival and higher morphological malformations at concentrations ≥ 10 μg L -1 to the embryos and larvae. Results showed that the early life stages of large yellow croaker were sensitive to MeHg exposure.
Highlights
Mercury (Hg) has been shown to be a widespread and persistent metallic pollutant in estuarine and coastal waters all over the world (Satoh, 2000)
MeHg exposure had a significant impact on the Median effective time for hatch (MET) of large yellow croaker embryo (ANOVA, p < 0.05)
MeHg exposure had no significant effect on embryo’s heart rate (ANOVA, p > 0.05; Figure 2A), but the heart rate of larvae was significantly increased in the 5 μg L−1 (91 beats min−1) and 20 μg L−1 (86 beats min−1) treatments compared to the control (59 beats min−1; ANOVA Dunnett’s test, p < 0.05; Figure 2B)
Summary
Mercury (Hg) has been shown to be a widespread and persistent metallic pollutant in estuarine and coastal waters all over the world (Satoh, 2000). Mercury can be converted into various forms such as metallic elements, inorganic salts and organic compounds (Lee et al, 2017). Among these forms, methylmercury (MeHg) is the most toxic and it is mainly produced by sulfate-reducing bacteria from precipitated mercury sulfate compounds in marine ecosystems (Gochfield, 2003). MeHg can be readily absorbed by aquatic organisms and its concentration increases with the increasing trophic levels due to biomagnification, which threatens the health of marine biota and the stability of the ecosystem (Jewett et al, 2003).
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