Effects of neuroactive compounds, ions and organic solvents on larval metamorphosis of the mussel Mytilus coruscus

Abstract

Responses of mussel (Mytilus coruscus) larvae to neuroactive compounds, ions and organic solvents were investigated through a series of bioassays. In the 24-h exposure assays, epinephrine, dopamine, serotonin, actylcholine and γ-aminobutyric acid induced larval metamorphosis at 10−6 to 10−4M concentrations. In addition, epinephrine and dopamine, an epinephrine precursor, both exhibited inductive activity, indicating that the epinephrine biosynthesis pathway may play an important role in the process of larval metamorphosis in this species. The ions, NH4+ at 10−3M induced 8% metamorphosis, excess K+ at 5×10−2M induced 20% metamorphosis, and Ca2+ did not induce larval metamorphosis in all concentrations tested. Ethanol and methanol both induced metamorphosis in the 24-h exposure assays. Effects of exposure time on larval metamorphosis were further investigated for epinephrine, NH4+ and ethanol. Experiments revealed that efficacy of these chemicals varied with exposure time. Epinephrine at 10−4M induced a maximum of 31% larval metamorphosis after 1h exposure. NH4+ at 10−2M induced a maximum of 43% larval metamorphosis after 3h exposure. Ethanol at 0.5M yielded a maximum of 35% metamorphosis after 24h exposure. Thus, the above compounds were shown to be effective inducers of larval metamorphosis, and may be used to improve M. coruscus larval production for the Chinese aquaculture industry. The findings provide new insights on the biochemical mechanism controlling larval metamorphosis in this species.