Daphnia has been widely used as an indicator species in aquatic biomonitoring for decades. Traditional toxicity assays based on lethality take a long time to assess, and the effect mode of contaminants is not clear. Because of the translucency of the Daphnia body and the application of fluorescent probes in cell staining, different intoxicated parts can be visualized. In this study, a double-staining method using two fluorescent dyes, Calcein AM (cell-permeant dye) and Propidium Iodide (cell-impermeant dye), was carried out on Daphnia magna exposed to six pathogens: Salmonella spp. (four strains) and Shigella spp. (two strains). The results showed that those bacteria caused different infections on daphnia depending on the age of this organism and bacterial concentrations. In detail, S. dublin and S. sonnei are the most harmful to Daphnia when they cause damage at smaller concentrations at the younger stage (3 weeks old). Interestingly, older Daphnia can give responses to nearly 10 CFU/ml to less than 100 CFU/ml of some bacteria strains. In another experiment, S. sonnei disturbed Daphnia after just 10 min of exposure, and Daphnia adapted to S. choleraesuis, S. typhi, and S. flexneri at the early stage (3 weeks old) after 1 h of exposure. Moreover, the damaged areas of the daphnia body were directly observed via a microscope, contributing to the understanding and the prediction of toxicity mechanisms.

数十年来，水蚤已被广泛用作水生生物监测的指示物种。基于致死性的传统毒性分析需要花费很长时间才能评估，并且污染物的影响方式尚不清楚。由于水蚤体的半透明性以及荧光探针在细胞染色中的应用，可以看到不同的中毒部位。在这项研究中，对暴露于六种病原体：沙门氏菌的大型蚤（Daphnia magna）进行了使用两种荧光染料，钙黄绿素AM（细胞渗透性染料）和碘化丙啶（细胞渗透性染料）的双重染色方法。（四个菌株）和志贺氏菌属。（两个菌株）。结果表明，这些细菌对水蚤造成了不同的感染取决于这种生物的年龄和细菌浓度。详细地讲，都柏林链球菌和索内链球菌在幼年期（3周龄）以较小浓度引起损害时，对水蚤的危害最大。有趣的是，较老的水蚤可以对某些细菌菌株产生接近10 CFU / ml的响应，而低于100 CFU / ml。在另一个实验中，S.宋内干扰水蚤只是10分钟暴露后，并水蚤适于猪霍乱，伤寒沙门氏菌，和志贺氏菌在曝光后1个小时的早期（3周龄）。而且，损坏的区域水蚤体通过显微镜直接观察，有助于了解和预测毒性机制。