Toxicity Test Assay of Waterborne Methylmercury on the Japanese Flounder (Paralichthys olivaceus) at Embryonic-Larval Stages

Methylmercury (MeHg) is a widespread pollutant in aquatic ecosystems, but its toxicity to the early life stages of marine fish has not been adequately investigated. This study used acute toxicity tests on embryonic-larval stages of a marine flounder Paralichthys olivaceus to determine the LC50 values for embryos and larvae and evaluate the responses of several biological endpoints to subacute MeHg exposure. Under exposures (0-15gL(-1)) below LC50 values (<15.3gL(-1) for embryos and 16.3g L-1 for larvae)(,) embryos were more sensitive to MeHg than were the larvae. MeHg exposures at13g L-1 increased morphological deformities and mortality, reduced growth and yolk absorption rate of the embryonic-larval flounder. These endpoints were sensitive to MeHg and their responses were dose-dependent. They could be used as bioindicators for assessing MeHg toxicity to the ELS of the flounder. Embryonic-larval flounder could be a useful fish for ecotoxicological assessment of MeHg in marine ecosystems.