We investigated the activity of the multixenobiotic resistance (MXR) phenotype, a biological defense system in aquatic organisms, in the fish assemblages of two tropical estuaries with different degrees of environmental impacts, the Paraiba River and Mamanguape River Estuaries. The aim of this work was to compare the activity of the MXR phenotype of different fishes to test the hypothesis that each species has an inherent activity level and to use this activity as a bioindicator of aquatic contamination. We assessed the MXR activity of the gills, using rhodamine B (RB) accumulation assay. The results demonstrated a species‐specific difference in the MXR activity of fishes caught in the same estuarine zone. Also, the pelagic species Eucinostomus melanopterus, Eucinostomus argenteus, and Lutjanus jocu had higher RB accumulation, while the demersal species Sphoeroides testudineus and Sphoeroides greeleyi had the lowest RB accumulation, suggesting that the ecological characteristic of fish in the water column exerts an influence on MXR activity. Besides, we demonstrated the potential of using the gill MXR activity of the key estuarine species, the Brazilian silversides Atherinella brasiliensis, as a tool for biomonitoring estuaries.

中文翻译：

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河口鱼类组合在多异生物抗药性方面表现出物种特异性差异。

我们调查了两个异质口对热带环境的影响，即帕拉伊巴河和马曼瓜普普河口，这是水生生物的生物防御系统，即多异生抗药性（MXR）表型的活动。这项工作的目的是比较不同鱼类的MXR表型的活性，以检验每个物种具有固有活性水平的假设，并将该活性用作水生生物污染的生物指标。我们使用罗丹明B（RB）累积测定法评估了ill的MXR活性。结果表明，在同一河口区域捕获的鱼类的MXR活性在物种上存在差异。此外，中上层物种是黑尾叶桉，Eucinostomus argenteus和Lutjanus jocu具有较高的RB积累，而海生物种Sphoeroides testudineus和Sphoeroides greeleyi的RB积累最低，表明水柱中鱼类的生态特性对MXR活性有影响。此外，我们展示了利用主要河口物种ill巴西银sides Atherinella brasiliensis的illMXR活性作为生物监测河口的工具的潜力。