| During seedling production of Coelomactra antiquata (Spengler,1802), the phenomena of death and delayed metamorphosis of larvae often occur when the larvae develop to the stages of settlement and metamorphosis. So settlement and metamorphosis limit the product of commercial culture. Factors and chemical inductions of settlement and metamorphosis of Coelomactra antiquata larvae were studied in this paper.The results indicate that:1. The settlement and metamorphosis rates of Coelomactra antiquata larvae were higher when the salinity is 28 × 10-3; Larvae of Coelomactra antiquata prefered to the environment of less illumination when it settles. When the illumination intensity was 114.8 Lux, the settlement and metamorphosis rates were higher than other illuminations intensities; Bacteria which could do good to water quality improved the settlement and metamorphosis rates of Coelomactra antiquata larvae.2. EPI has significant effect on the settlement and metamorphosis of Coelomactra antiquata larvae as well as GABA. Maximum inductions of settlement(92.8%) and metamorphosis(88.3%)were achieved by 10-4 M EPI. however, the settlement and metamorphosis rates were 80.1% and 32.8% respectively in black control.Maximum inductions of settlement(87.6%) and metamorphosis(86.9%) were produced by 10-5 M GABA, while the settlement and metamorphosis rates were 79.5% and 30.8% respectively in black control.L-DOPA also has some effect on the inductions of settlement and metamorphosis Coelomactra antiquata larvae.Maximum inductions of settlement(84.9 %) and metamorphosis(73.3 %) were achieved by 10-6 M L-DOPA,in contrast, the settlement and metamorphosis rates were 82.3% and 62.6% respectively in black...
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