Study on the Acute Toxicity of Alternanthera philoxeroides to Brachydanio rerio

[Objective]The purpose of this study is to estimate the acute toxicity of extract from Alternanthera philoxeroides to fish (Brachydanio rerio) in order to guide the extraction of molluscacide from A.philoxeroides.[Methods] The acute toxicities of the extract of A.philoxeroides on B.rerio were determined with the static test method at normal temperature.The median lethal concentration(LC50) and 95% confidence limit were calculated by using Karber method.[Result]Determinations showed that the LC50 of extracts from A.philoxeroides on B.rerio for 24 h and 48 h were 587 and 497 mg/L,respectively;and its mass concentration of safely was 107 mg/L.The mortality rate of fish(B.rerio) increased with the rise of molluscacide concentration and the extension of action time.[Conclusion] The extract of A.philoxeroides showed a middling acute toxicity to B.rerio,and the mass concentration of safely was low than the concentration killing snail.