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A headwater or river capture is a phenomenon commonly invoked to explain the absence of reciprocal monophyly of genetic lineages among isolated hydrographic basins in freshwater fish. Under the assumption of river capture, a secondary contact between populations previously isolated in different basins explains the observed genetic pattern. However, the absence of reciprocal monophyly could also arise under population isolation through the retention of ancestral of polymorphisms. Here, we applied an approximate Bayesian computation (ABC) framework for estimating the relative probability of scenarios with and without secondary contact. We used Cnesterodon decemmaculatus as a study model because of the multiple possible cases of river capture and the demographic parameters estimated in a previous mitochondrial DNA study that are useful for simulating scenarios to test both hypotheses using the ABC framework. Our results showed that, in general, mitochondrial DNA is useful for distinguishing between these alternative demographic scenarios with reasonable confidence, but in extreme cases (e.g. recent divergence or large population size) there is no power to discriminate between scenarios. Testing hypotheses of drainage rearrangement under a statistically rigorous framework is fundamental for understanding the evolution of freshwater fish fauna as a complement to, or in the absence of, geological evidence.

The Sinos River is an important water supply in Southern Brazil and receives industrial, agricultural, and domestic effluents which may affect aquatic biota. Water physicochemical and microbiological analyses, biomarker responses (scaled mass index (SMI), gill histopathology, and micronucleus and nuclear abnormality (MN and NA) frequencies), and metal bioaccumulation in muscle were assessed in the fish species Bryconamericus iheringii (Characidae) captured at three sampling sites (S1, S2, and S3) in four sampling periods. The mean values of five parameters (total phosphorus, thermotolerant coliforms, aluminum, iron, and lead) exceeded the limits established by the Brazilian legislation at the three sampling sites. Although physicochemical analysis indicated higher impacts at S3, in some samples, significantly higher MN frequencies and bioaccumulation of manganese in fish muscle were observed at S1, whereas low SMI and higher concentrations of aluminum and zinc in fish muscle were found at S2. Histopathological alterations in gills were observed in fish collected at the three sampling sites; however, no spatial differences were observed, indicating similar environmental conditions with respect to this biomarker. Moreover, temporal variation of biomarker responses and metal bioaccumulation were found at all sampling sites. Furthermore, the consumption of fish from the Sinos River should be avoided given the concentrations of chromium (all samples), cadmium, and lead in fish muscle above the threshold for safe human consumption.

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Manganese is an essential element for many physiological processes. However, in prolonged exposures or at high concentrations it may present toxicity to several organs, which has made it an object of study in pharmacological, behavioral, neurological and environmental research in different organisms. Thus, it was aimed to evaluate the damage caused by acute and chronic exposures to this element, through the histopathological analysis of the zebrafish (Danio rerio) intestine. Samples were embedded in paraffin for further processing in rotating microtome, and the slides were stained with Alcian Blue and hematoxylin for observation and analysis under light microscopy. The results demonstrated the potential of the metal to cause histological changes in this organ, such as fusion of villi (in 0.5 and 4.0 mg L-1), and to increase by more than 50% the number of goblet cells (in 8.0 and 16 mg L-1) in the region analyzed, mainly in the highest concentrations of Manganese Chloride and in chronic exposures, characterizing a possible inflammation of the intestinal epithelium. Thus, the histological analysis of intestines demonstrated to be a reliable alternative for the toxicological evaluation. It is important to monitor the concentrations of this and other metals in the water bodies, given their toxicity.

The Paranhana River, located in Southern Brazil, is one of the major tributaries of the Sinos River basin and receives mainly industrial and domestic effluents. In the present study, water physicochemical and microbiological analyses, condition factor, micronucleus test, gill histopathology and metal bioaccumulation in the muscle of the native fish Bryconamericus iheringii collected at two sites (S1 and S2) of the Paranhana River under different degrees of anthropogenic pressures were assessed in four sampling campaigns. Data from water quality parameters, condition factor, mucous cells proliferation in fish gills and bioaccumulation of chromium and manganese in muscle evidenced higher impacts at S2, whereas a higher genotoxic potential was observed at S1. Gill histopathological alterations were found in fish captured at both sampling sites. Temporal variations in all biomarkers analyzed and bioaccumulation of manganese and nickel were observed at S1, whereas only variations in condition factor, gill alterations and bioaccumulation of manganese and aluminum were found at S2. Our study evidences that S1 is under minor anthropogenic impacts and that the high urbanization at S2 reflects in a poor water quality. Nonetheless, the human consumption of fish from the Paranhana River should be avoided given the high concentrations of cadmium, chromium and lead.

The analysis of metal concentrations in feathers and the micronuclei (MN) and other nuclear abnormalities (NA) test in birds are tools used for evaluating the impacts that anthropogenic actions have been causing to the environment and organisms. Here we used these biomarkers to investigate the response of birds to disturbances observed in three areas with different environmental characteristics (natural, agricultural and urban) in southern Brazil. We obtained a diverse sample (108 individuals from 25 species and 17 families) without signi cant differences in metal concentrations, frequency of MN and AN between sampling points.The concentrations of zinc (Zn) and copper (Cu) were signi cantly different between trophic guilds (Zn: p = 0.0006, Cu: p = 0.04) and age classes (Zn: p = 0.01, Cu: p = 0.03). Omnivore birds contributed to the increase in the number of MN (∆AICc: 0.00; w = 0.40) and NA, which was also in uenced by age classes and body condition index (BCI) (∆AICc: 0.00; w = 0.34; ∆AICc: 0.89; w = 0.22; ∆AICc: 1.15; w = 0.19; ∆AICc: 1.33; w = 0.18). We showed that in a diverse sample of birds, the variables analyzed affected each biomarker in distinct ways.

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