Abstract: Objective　To evaluate the molluscicidal activity of surfactin against Oncomelania hupensis, so as to provide the experimental basis for use of Bacillus for killing O. hupensis. Methods　O. hupensis snails were collected from schistosomiasis⁃endemic foci of Wuhu City on September 2022, and Schistosoma japonicum⁃infected snails were removed. Then, 60 snails were immersed in surfactin at concentrations of 2, 1, 0.5, 0.25, 0.125 mg/mL and 0.062 5 mg/mL for 24, 48, 72 hours at 26 ℃, while ultrapure water⁃treated snails served as controls. The median lethal concentration (LC50) of surfactin against O. hupensis snails was estimated. O. hupensis snails were immersed in surfactin at a concentration of 24 h LC50 and ultrapure water, and then stained with propidium iodide (PI). The PI uptake in haemocyte was observed in O. hupensis snails using fluorescence microscopy. Results　The mortality of O. hupensis was 5.0% following immersion in surfactin at a concentration of 0.062 5 mg/mL for 24 h, and the mortality was 100.0% following immersion in surfactin at a concentration of 2 mg/mL for 72 h, while no snail mortality was observed in the control group. There were significant differences in the mortality of O. hupensis in each surfactin treatment groups at 24 ([χ]2 = 180.150, P < 0.05), 48 h ([χ]2 = 176.786, P < 0.05) and 72 h ([χ]2 = 216.487, P < 0.05), respectively. The average mortality rates of O. hupensis were 38.9% (140/360), 62.2% (224/360) and 83.3% (300/360) 24, 48 h and 72 h post⁃immersion in surfactin, respectively ([χ]2 = 150.264, P < 0.05), and the 24, 48 h and 72 h LC50 values of surfactin were 0.591, 0.191 mg/mL and 0.054 mg/mL against O. hupensis snails. Fluorescence microscopy showed more numbers of haemocytes with PI uptake in 0.5 mg/mL surfactin⁃treated O. hupensis snails than in ultrapure water⁃treated snails for 24 h, and there was a significant difference in the proportion of PI uptake in haemocytes between surfactin⁃and ultrapure water⁃treated snails ([χ]2 = 6.690, P < 0.05). Conclusion　Surfactin is active against O. hupensis snails, which may be associated with the alteration in the integrity of haemocyte membrane.

Key words: Oncomelania hupensis, Surfactin, Molluscicidal activity, Haemocyte

摘要： 目的　观察表面活性素对钉螺的影响，以期为应用芽胞杆菌杀灭钉螺提供实验基础。 方法　2022年9月，于芜湖市血吸虫病流行区现场采集钉螺。剔除血吸虫感染阳性钉螺后，采用室内浸杀法，以2、1、0.5、0.25、0.125 mg/mL和0.062 5 mg/mL表面活性素于26 ℃分别浸泡60只钉螺24、48 h和72 h，同时设超纯水对照组，观察表面活性素杀螺效果，计算钉螺半数致死浓度（LC50）。参考上述浸泡杀螺活性实验结果选择表面活性素实验浓度，分别以0.5 mg/mL浓度表面活性素（实验组）和超纯水（对照组）浸泡处理钉螺，采用碘化丙啶（PI）荧光法于荧光显微镜下观察钉螺血淋巴细胞PI摄取情况。结果　经0.062 5 mg/mL表面活性素浸杀24 h，钉螺死亡率为5.0%（3/60）；2 mg/mL表面活性素浸杀72 h，钉螺死亡率为100.0%（60/60）；而对照组未发现钉螺死亡，不同组间钉螺死亡率差异有统计学意义（[χ]224 h = 180.150，[χ]248 h = 176.786，[χ]272 h = 216.487，P均< 0.05）。浸杀24、48 h和72 h后，钉螺平均死亡率分别为38.9%（140/360）、62.2%（224/360）和83.3%（300/360），差异有统计学意义（[χ]2 = 150.264，P < 0.05）。表面活性素浸杀钉螺24、48 h和72 h LC50值分别为0.591、0.191 mg/mL和0.054 mg/mL。荧光显微镜下可见，经0.5 mg/mL表面活性素浸杀24 h后，实验组钉螺摄入PI染料的血淋巴细胞数显著高于对照组（[χ]2 = 6.690，P < 0.05）。结论　表面活性素具有杀灭钉螺活性，可能与其改变钉螺血淋巴细胞膜完整性有关。

关键词: 钉螺, 表面活性素, 杀螺活性, 血淋巴细胞