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. K E Y W O R D S biomarker, Brazilian silverside, P-glycoprotein, MXR, rhodamine B, tropical estuaries SUPPORTING INFORMATION Additional supporting information may be found online in the Supporting Information section. How to cite this article: Macêdo AKS, da Silva JRP, dos Santos HB, Thomé RG, Vendel AL, Amado EM. Estuarine fish assemblages present a species-specific difference in the multixenobiotics resistance activity. J. Exp. Zool. 2019;331: 530-539. https://doi.
The Paraiba River estuary is the largest and most important estuary of Paraiba state, northeastern Brazil. It is under intense environmental degradation by the surrounding human population, and possibly several fish species are at risk in this habitat. Scientific sampling of the ichthyofauna started in the late 1970's and proceeded until recently. We present a list of fish species captured in this estuary, based on voucher specimens housed at the Federal University of Paraiba collection. Four orders of Chondrichthyes and 26 orders of Osteichthyes were identified. A total of 187 fish species, including eight species of Chondrichthyes and 179 Osteichthyes, with 123 genera and 57 families were identified. Perciformes dominated in terms of richness (32 species), followed by Acanthuriformes and Clupeiformes. Comparing estuaries along the Brazilian northeastern coast and considering our large time sampling span, a higher richness would be expected. According to the IUCN Red List, Urotrygon microphthalmum is considered Critically Endangered and more seven species are classified as Vulnerable: Rhizoprionodon porosus, Rhinoptera bonasus, Megalops atlanticus, Epinephelus itajara, Hyporthodus niveatus, Lutjanus cyanopterus, and Cynoscion acoupa. Three of these species also appear in the same category in the threatened Brazilian list, all of which have declining population trends. Concerning the Elasmobranchii, Carcharhinus porosus is listed as Critically Endangered in our country and globally. This inventory organizes and broadens knowledge on the fish community that occurs in this important ecosystem, with inferences about life habits, ecological guilds and conservation status of the fish species.
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