殺蟲劑(Malathion, Cypermethrin, Paraquat)對圓水蚤(Daphnia pulex)之急毒性及趨光行之探討

目的：探討殺蟲劑對於環境中水生動物可能造成之影響，以水蚤趨光泳動行為當作環境有毒物質偵測指標，應用於許多環境評估與毒性偵測之層面，本研究參考文獻所提及之多項理論基礎，自行開發設計水蚤趨光泳動行為模式觀察槽體，偵測市面上常用之三種殺蟲劑對圓水蚤之急毒性及其趨光泳動行為之影響。方法：以本研究室自行培養五代以上之圓水蚤(Daphnia pulex)為試驗體材，圓水蚤培養液採用自行配製的仿自然水體（硬水），選取具代表性的三種殺蟲劑(Malathion, Cypermethrin, Paraquat)配製系列濃度，進行一系列的試驗活動包括，圓水蚤稚蟲急毒性試驗、水蚤泳動行為試驗、水蚤影像記錄、水蚤泳動路徑分析及試驗結果之統計分析等。結果：圓水蚤浸泡殺蟲劑之二十四小時之50%有效影響濃度(24h-EC50)值，顯示以具有神經毒性的有機磷類殺蟲劑(Malathion)對圓水蚤毒性最高，其濃度為0.12 ng/L (ppb)，合成除蟲菊(Cypermethrin)對圓水蚤毒性濃度為5.4 mg/L (ppm)，除草劑的Paraquat濃度為12.5 mg/L (ppm)。圓水蚤對殺蟲劑的48h-EC50值，顯示以Malathion毒性最高(0.05 ppb), Cypermethrin毒性次之(2.3 ppm), Paraquat毒性較低(7.3 ppm)水蚤泳動行為試驗分析結果顯示水蚤浸泡殺蟲劑Paraquat於試驗第十分鐘，濃度25 ppm之組別其水蚤泳動速度與其他組別有顯著之差異(P<0.001)；Malathion於試驗第十分鐘，濃度1 ppb之圓水蚤泳動速度與其他組別有顯著之差異(P<0.001)；Cypermethrin於試驗第十分鐘，濃度2.5 ppm之圓水蚤泳動速度與其他組別有顯著之差異(P<0.001)。結論：本研究數據顯示出於特定濃度與暴露時間可偵測出水蚤之24h-EC50值，水蚤泳動行為之價測敏感度於試驗五～十五分鐘可達到最高敏感度，與文獻指出之試驗時間符合，此試驗數據對於未來之水蚤泳動行為模式試驗可作為參考反應時間。

英文摘要 Purpose: This study investigates the influences of three commonly used pesticides on the phototactic swimming behavior of the water flea, Daphnia pulex, an index of acute toxicity. Methods: In this study we measured the effect of three representative pesticides on laboratory cultivated fifth generation water fleas in a medium of hard water similar to that found in nature. We carried out a series of experiments using variety of densities and measured acute toxicity in Daphnia pulex neonates, observed water flea swimming behavior by image recording, and analyzed swimming path Results: The 24h-EC50 values detected by Daphnia pulex showed that the Malathion had the highest nerve toxicity of 0.l2ng/L, followed by Cypermethrin (5.4mgIL) and Paraquat (12.5mg/L). The 48h-EC50 values detected by Daphnia pulex showed that Malathion had the highest toxicity (0.05ngIL), followed by Cypermethrin (2, 3mg/L) and Paraquat (7.3mgIL). Analysis of water flea swimming behavior showed that, at the 10(superscript th) minute of the pesticide Paraquat test, the water flea swimming speed in the group with a density of 25 ppm was significantly different (P<0.001) from those in the other groups. At the 10(superscript th) minute of the pesticide Malathion test, swimming speed in the group with a density of 1 ng/L was significantly different (P<0.001) from those of the other groups. At the 10th minute of the pesticide Cypermethrin test, swimming speed in the group with a density of 2.5 mg/L was significantly different (P<0.001) from the other groups. Conclusion: The methods used herein can be applied to detect the 24h-EC50 value of water flea at the particular density and exposure time. The sensitivity of swimming behavior was highest between the 5(superscript th) and the 15(superscript th) minute, The results of this study can be used as a reference when assessing reaction time in the swimming of water fleas exposed to various pollutants.