Many temperate freshwater habitats are at risk for contamination by run-off associated with the application of road de-icing salts. Elevated salinity can have various detrimental effects on freshwater organisms, including greater susceptibility to infection by parasites and pathogens. However, to better understand the net effects of road salt exposure on host–parasite dynamics, it is necessary to consider the impacts on free-living parasite infectious stages, such as the motile aquatic cercariae of trematodes. Here, we examined the longevity and activity of cercariae from four different freshwater trematodes (Ribeiroia ondatrae, Echinostoma sp., Cephalogonimus sp. and an unidentified strigeid-type) that were exposed to road salt at five different environmentally relevant concentrations (160, 360, 560, 760 and 960 mg/ml of sodium chloride). Exposure to road salt had minimal detrimental effects, with cercariae activity and survival often greatest at intermediate concentrations. Only the cercariae of Cephalogonimus sp. showed reduced longevity at the highest salt concentration, with those of both R. ondatrae and the unidentified strigeid-type exhibiting diminished activity, indicating interspecific variation in response. Importantly, cercariae seem to be relatively unaffected by salt concentrations known to increase infection susceptibility in some of their hosts. More studies will be needed to examine this potential dichotomy in road salt effects between hosts and trematodes, including influences on parasite infectivity.

中文翻译：

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路盐对自由生活吸虫感染阶段的影响

许多温带淡水栖息地面临与道路除冰盐应用相关的径流污染的风险。盐度升高会对淡水生物产生各种不利影响，包括更容易受到寄生虫和病原体的感染。然而，为了更好地了解道路盐分暴露对宿主 - 寄生虫动态的净影响，有必要考虑对自由生活寄生虫感染阶段的影响，例如吸虫的活动水生尾蚴。在这里，我们检查了四种不同淡水吸虫尾蚴的寿命和活性（河豚,棘口虫sp.,头孢属sp。和一种身份不明的 strigeid 型）暴露于五种不同的环境相关浓度（160、360、560、760 和 960 mg/ml 氯化钠）的路盐中。暴露于路盐的有害影响最小，尾蚴活动和存活通常在中等浓度下最大。只有尾蚴头孢属sp。在最高盐浓度下显示出寿命降低，两者的R. ondatrae和未鉴定的strigeid型表现出活性降低，表明反应的种间变异。重要的是，尾蚴似乎相对不受盐浓度的影响，盐浓度会增加一些宿主的感染易感性。需要更多的研究来检验宿主和吸虫之间道路盐效应的这种潜在二分法，包括对寄生虫感染性的影响。