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Abstract 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.

Resumo O estuário do Rio Paraíba, maior e mais importante do estado da Paraíba, nordeste do Brasil, sofre intensa degradação ambiental pela população humana no seu entorno, e possivelmente várias espécies de peixes estão ameaçadas neste habitat. Nós apresentamos uma lista de espécies de peixes capturadas neste estuário, com base em espécimes tombados na coleção da Universidade Federal da Paraíba. Quatro ordens de Chondrichthyes e 26 ordens de Osteichthyes foram identificadas. Um total de 187 espécies de peixes foi registrado, incluindo oito espécies de Chondrichthyes e 179 Osteichthyes, com 123 gêneros e 57 famílias. Em relação à riqueza, Perciformes dominou com 32 espécies, seguido por Acanthuriformes e Clupeiformes. Comparando estuários ao longo do nordeste brasileiro e considerando nosso longo período de amostragens, seria esperada uma riqueza maior. De acordo com a lista vermelha da IUCN, Urotrygon microphthalmum é tida como Criticamente Ameaçada e mais sete espécies são classificadas como Vulnerável: Rhizoprionodon porosus, Rhinoptera bonasus, Megalops atlanticus, Epinephelus itajara, Hyporthodus niveatus, Lutjanus cyanopterus e Cynoscion acoupa. Três dessas espécies também aparecem na mesma categoria na lista brasileira de espécies ameaçadas, tendo todas elas, suas populações em declínio. Em relação aos Elasmobranchii, Carcharhinus porosus é listada como Criticamente Ameaçada em nosso país e globalmente. Esse inventário abrange e organiza o conhecimento acerca da comunidade de peixes que ocorre nesse importante ecossistema, com inferências sobre hábitos de vida, guildas ecológicas e status de conservação das espécies de peixes.

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The effects of the rupture of a mining tailings dam were investigated using the gills and liver of Astyanax lacustris as a proxy for environmental quality. The fish were exposed for seven days to water sampled forming four groups: upstream of the dam rupture (P1), and 22 km (P2); 48 km (P3); and 70 km (P4) downstream from the dam rupture in the Doce River basin. The control group received dechlorinated tap water. The dissolved concentrations of metals were determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). We evaluated the histology of the gills and liver, as well as, immunohistochemistry for HSP70 and Na+/K+ ATPase (NKA) in the gills, and for P-gp in liver. In all sites we observed a mix of metals, with higher concentrations of Mn, Cd, As, and Cu/Cr in P1, P2, P3, and P4, respectively. All treatments groups showed histological changes in gills and liver, with the highest amount of these alterations found in the P2 group. Disorganization of the secondary lamellae, epithelial lifting, and mitochondria-rich cells (MRC) were observed in the gills. The parenchyma of the liver was rather disorganized, and hepatocytes and nuclei showed hypertrophy, vacuolization and cytoplasmic degeneration. A higher immunoreaction of HSP70 in P2 when compared with the other groups and lower labeling of HSP70 in the P4 was registered. In P2 and P3, NKA-positive cells were observed with hypertrophy and disorganization. Morphometric analyses of the liver revealed that all treatment groups presented a lower immunolabeling of P-gp when compared with the control group. Thus, the experimental approach revealed that the water from Doce basin can promote histological alterations in fish's liver and gills, as well as modulation of disruption of ionic balance, cellular responses to stress, and cell detoxification pathways.

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Abstract Herein we evaluated the histopathological alterations and expression patterns of multixenobiotic resistence (MXR) and autophagic proteins in liver samples of fish chronically exposed to anthropogenic contaminants in a highly polluted river, and then again after they had been transferred to good quality water. Two groups were established: euthanized on the day of capture (0 h), and maintained for 30 days in a tank (30 d). The fish of 0 h presented liver with vacuolated and hypertrophic hepatocytes. Also, it was observed strong immunostaining of cathepsin-D, LC3-II and P-gp. Necrosis and apoptosis were also observed throughout the liver. Conversely, the second group (30 d) showed recovery of the liver normal histology and weak immunoreaction of the studied proteins. So, our results indicated that there was a hepatic recovery in the fish kept in good quality water, as showed by the decreased expression of cathepsin-D, LC3-II, and the MXR (P-gp). Therefore, the alterations here observed could be proposed as potential biomarkers to be tested for following the impacts of remediation or mitigation measures to environmental impacts.

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RESUMO

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.

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