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On November 5th, 2015, the Fundão dam collapsed in Minas Gerais, southeastern Brazil, releasing millions of cubic meters of mud containing mining residue into the Doce River. Two weeks later, the mud arrived to the marine environment, triggering changes in franciscana dolphin habitat, Pontoporia blainvillei, from Franciscana Management Area Ia. This is an isolated population of the most endangered cetacean species in the South Atlantic Ocean. Organohalogen compounds (OHCs) may pose a threat to this endangered population because of their endocrine disrupting properties. Hence, this study sought to determine if there were differences in the bioaccumulation profile of OHC (PCBs, DDTs, Mirex, HCB, HCHs, PBDEs, PBEB, HBBZ and MeO-BDEs) in franciscana dolphins before and after dam collapse and to build a temporal trend. Blubber of 33 stranded individuals was collected in Espírito Santo state for organohalogen assessment between 2003 and 2019. Differences were found between franciscana dolphins collected prior to and after the disaster. Additionally, significant temporal trends for organochlorine pesticides and natural and anthropogenic organobromine were detected. The increase in pesticide concentrations after 2015 is suggestive of their reavailability in the environment. The decline in organobromine over time could be due to their debromination in the marine environment and alterations in the composition of their natural producers. PCBs remained stable during the period of the study. Our findings show an increase in endocrine disruptor concentrations, which is of great concern for this endangered population.

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Rough-toothed dolphins, Steno bredanensis, are closely associated with coastal waters in the Southwestern Atlantic Ocean, increasing the exposure to multiple stressors, such as chemical pollution. Persistent organic pollutants (POPs) are known to affect the health of cetacean species. To comprehend the potential impacts of POPs on populations' viability, it is necessary to distinguish populations and predict their risk of long-term exposure. Blubbers of rough-toothed dolphins (n = 28) collected along the southeastern (SE) and southern (S) Brazilian coast were screened for polychlorinated biphenyls (PCBs) and pesticides in a gas chromatograph coupled to a mass spectrometer. Based on the contamination profile, a discriminant function analysis separated the rough-toothed dolphins into three ecological populations: two coastal and one offshore. POP concentrations were the highest reported for the species worldwide and highest among the delphinids in Brazilian waters, reaching 647.9 µg g-1 lw for PCBs. The SE population presented 212.9 ± 163.0, S population presented 101.0 ± 96.7, and OCS/S population presented 183.3 ± 85.3 µg g-1 lw (mean ± SD) of PCBs. The potential risk of effects triggered by elevated PCB concentrations was assessed in an individual-based model. A risk of severe decline in population size is projected for the three populations in the next 100 years, especially in SE Brazil, varying between 67 and 99%.

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The franciscana (Pontoporia blainvillei) is the most threatened small cetacean in the South Atlantic. In this study we report the development of 13 microsatellite markers for franciscanas through next-generation sequencing, and the characterization of those loci in 38 samples from the species' northernmost population (Espírito Santo, Brazil). Besides providing diversity indices for the new, specific loci, we also report on the transferability of heterologous loci which had not been screened in franciscanas before, and review all loci used in previous studies. Expected heterozygosity in the new loci ranged between 0.107 and 0.595, and all but one were in Hardy Weinberg Equilibrium. These are the first microsatellite loci isolated from franciscanas, and they are an important addition to heterologous markers that were available previously.

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The taxonomy of common dolphins (Delphinus sp.) has always been controversial, with over twenty described species since the original description of the type species of the genus (Delphinus delphis Linnaeus, 1758). Two species and four subspecies are currently accepted, but recent molecular data have challenged this view. In this study we investigated the molecular taxonomy of common dolphins through analyses of cytochrome b sequences of 297 individuals from most of their distribution. We included 37 novel sequences from the Southwestern Atlantic Ocean, a region where the short- and long-beaked morphotypes occur in sympatry, but which had not been well sampled before. Skulls of individuals from the Southwestern Atlantic were measured to test the validity of the rostral index as a diagnostic character and confirmed the presence of the two morphotypes in our genetic sample. Our genetic results show that all common dolphins in the Atlantic Ocean belong to a single species, Delphinus delphis. According to genetic data, the species Delphinus capensis is invalid. Long-beaked common dolphins from the Northeastern Pacific Ocean may constitute a different species. Our conclusions prompt the need for revision of currently accepted common dolphin species and subspecies and of Delphinus delphis distribution.

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The fishery for Calophysus macropterus, an Amazonian necrophagous catfish, is highly detrimental to river dolphins and caimans, which are deliberately killed for use as bait. In the Brazilian Amazon, this fishery has increased over the last decade, in spite of the rejection of scavenger fishes by Brazilian consumers. It was suspected that C. macropterus fillets were being sold in Brazilian markets, disguised as a fictitious fish (the "douradinha"). We collected 62 fillets from "douradinha" and other suspiciously named fish from 4 fish-processing plants sold at 6 markets in Manaus, in the Brazilian Amazon, and sequenced the cytochrome b gene to identify fillets to species. Sixty percent of fillets labeled "douradinha" or with other deceptive names were actually C. macropterus. Six other fish species of low commercial value were also found. The presence of dolphin tissue in the stomach contents of C. macropterus was confirmed by mtDNA control region sequencing. Our results formed the scientific basis for a moratorium on the fishing and fraudulent selling of C. macropterus, issued by the Brazilian Ministries of the Environment and Fisheries. Exposure of this fraud via the mass media can help end the illegal use of dolphins as bait in Brazil.

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Franciscanas are the most endangered dolphins in the Southwestern Atlantic. Due to their coastal and estuarine habits, franciscanas suffer from extensive fisheries bycatch, as well as from habitat loss and degradation. Four Franciscana Management Areas (FMA), proposed based on biology, demography, morphology and genetic data, were incorporated into management planning and in the delineation of research efforts. We re-evaluated that proposal through the analysis of control region sequences from franciscanas throughout their distribution range (N = 162), including novel sequences from the northern limit of the species and two other previously unsampled localities in Brazil. A deep evolutionary break was observed between franciscanas from the northern and southern portions of the species distribution, indicating that they must be managed as two Evolutionarily Significant Units (ESU). Furthermore, additional FMAs should be recognised to accommodate the genetic differentiation found in each ESU. These results have immediate consequences for the conservation and management of this endangered species.

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Molecular data have provided many insights into cetacean evolution but some unsettled issues still remain. We estimated the topology and timing of cetacean evolutionary relationships using bayesian and maximum likelihood analyses of complete mitochondrial genomes. In order to clarify the phylogenetic placement of Sotalia and Steno within the Delphinidae, we sequenced three new delphinid mitogenomes. Our analyses support three delphinid clades: one joining Steno and Sotalia (supporting the revised subfamily Stenoninae); another placing Sousa within the Delphininae; and a third, the Globicephalinae, which includes Globicephala, Feresa, Pseudorca, Peponocephala and Grampus. We also conclude that Orcinus does not belong in the Globicephalinae, but Orcaella may be part of that subfamily. Divergence dates were estimated using the relaxed molecular clock calibrated with fossil data. We hypothesise that the timing of separation of the marine and Amazonian Sotalia species (2.3 Ma) coincided with the establishment of the modern Amazon River basin.

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We tested the zinc-finger sex chromosome-linked genes Zfx/Zfy and the sex-determining region Y (Sry) genes for gender determination of biopsy samples from marine and riverine tucuxi dolphins (Sotalia guianensis and S. fluviatilis). We also evaluated the performance of these genes with decomposed carcasses, for which sexing cannot rely on the direct examination of the reproductive tract. Both systems proved reliable for sexing 46 fresh and decomposed samples, making them especially useful when biopsy darting is coupled with photo-identification studies.