Trophic Relationships and Habitat Preferences of Delphinids from the Southeastern Brazilian Coast Determined by Carbon and Nitrogen Stable Isotope Composition

To investigate the foraging habitats of delphinids in southeastern Brazil, we analyzed stable carbon (δ13C) and nitrogen (δ15N) isotopes in muscle samples of the following 10 delphinid species: Sotalia guianensis, Stenella frontalis, Tursiops truncatus, Steno bredanensis, Pseudorca crassidens, Delphinus sp., Lagenodelphis hosei, Stenella attenuata, Stenella longirostris and Grampus griseus. We also compared the δ13C and δ15N values among four populations of S. guianensis. Variation in carbon isotope results from coast to ocean indicated that there was a significant decrease in δ13C values from estuarine dolphins to oceanic species. S. guianensis from Guanabara Bay had the highest mean δ13C value, while oceanic species showed significantly lower δ13C values. The highest δ15N values were observed for P. crassidens and T. truncatus, suggesting that these species occupy the highest trophic position among the delphinids studied here. The oceanic species S. attenuata, G. griseus and L. hosei had the lowest δ15N values. Stable isotope analysis showed that the three populations of S. guianensis in coastal bays had different δ13C values, but similar δ15N results. Guiana dolphins from Sepetiba and Ilha Grande bays had different foraging habitat, with specimens from Ilha Grande showing more negative δ13C values. This study provides further information on the feeding ecology of delphinids occurring in southeastern Brazil, with evidence of distinctive foraging habitats and the occupation of different ecological niches by these species in the study area.Peer reviewe

Brominated flame retardants and natural organobrominated compounds in a vulnerable delphinid species along the Brazilian coast

Guiana dolphins, Sotalia guianensis, are vulnerable to extinction along their distribution on the Brazilian coast and assessing chemical pollution is of utmost importance for their conservation. For this study, 51 carcasses of Guiana dolphins were sampled across the Brazilian coast to investigate legacy and emerging brominated flame retardants (BFRs) as well as the naturally-produced MeO-BDEs. PBDEs and MeO-BDEs were detected in all samples analyzed, whereas emerging BFRs were detected in 16 % of the samples, all in Rio de Janeiro state. PBDE concentrations varied between 2.24 and 799 ng.g-1 lipid weight (lw), emerging BFRs between 0.12 and 1.51 ng.g-1 lw and MeO-BDEs between 3.82 and 10,247 ng.g-1 lw. Concentrations of legacy and emerging BFRs and natural compounds varied considerably according to the sampling site and reflected both the local anthropogenic impact of the region and the diversity/mass of biosynthesizers. The PBDE concentrations are lower than what was found for delphinids in the Northern Hemisphere around the same sampling period and most sampling sites presented mean concentrations lower than the limits for endocrine disruption known to date for marine mammals of 460 ng.g-1 lw, except for sampled from Santa Catarina state, in Southern Brazil. Conversely, MeO-BDE concentrations are higher than those of the Northern Hemisphere, particularly close to the Abrolhos Bans and Royal Charlotte formation, that are hotspots for biodiversity. Despite the elevated concentrations reported for this group, there is not much information regarding the effects of such elevated concentrations for these marine mammals. The distinct patterns observed along the Brazilian coast show that organobrominated compounds can be used to identify the ecological segregation of delphinids and that conservation actions should be planned considering the local threats.A.F. Azevedo and J. Lailson-Brito thank the National Council for Scientific and Technological Development (CNPq) for grants PQ-1B and 1D, respectively; and UERJ (Prociência). We thank the students from Aquatic Mammal and Bioindicator Lab (UERJ - Brazil), Environmental Chemistry Lab (CSIC - Spain) and Radioisotope Lab (UFRJ - Brazil). L.G. Vidal thanks the Coordination for the Improvement of Higher Education Personnel (CAPES - Finance Code 001) for providing her PhD grant. The authors thank the ICMBio - Estação Ecológica de Tamoios (ESEC Tamoios) and APA de Guapi-Mirim/ESEC da Guanabara for supporting the collection of carcasses in Ilha Grande Bay.Peer reviewe

Molecular identification and microscopic characterization of poxvirus in a Guiana dolphin and a common bottlenose dolphin, Brazil

The poxviruses identified in cetaceans are associated with characteristic tattoo or ring skin lesions. However, little is known regarding the prevalence and progression of these lesions and the molecular characterization of cetacean poxviruses in the Southern Hemisphere. This manuscript describes the progression of poxvirus-like skin lesions in 5 free-ranging Guiana dolphins Sotalia guianensis. Additionally, 151 skin samples from 113 free-ranging cetaceans from Brazil, including 4 animals with tattoo skin lesions, were selected for poxvirus testing. Poxviral DNA polymerase gene PCR amplification was used to detect the virus in β-actin-positive samples (145/151). DNA topoisomerase I gene PCR was then used in Cetaceanpoxvirus (CePV)-positive cases (n = 2), which were further evaluated by histopathology and electron microscopy. Based on photo-identification, adult Guiana dolphins presented regressing or healed poxvirus-like lesions (2/2), while juveniles presented persistent (2/3) or healed and progressive lesions (1/3). CePV DNA was amplified in a common bottlenose dolphin Tursiops truncatus and in a Guiana dolphin. Intracytoplasmic inclusion bodies and viral particles consistent with poxvirus were identified by histology and electron microscopy, respectively. CePV-specific amino acid motifs were identified through phylogenetic analysis. Our findings corroborate previous studies that suggest the placement of poxviruses from cetaceans within the novel CePV genus. This is the first molecular identification of poxvirus in South American odontocetes

From narrow and overlapped to wide and segregated: The isotopic niche of a tropical cetacean community

Species in sympatry can coexist due to some degree of niche partitioning. Four cetacean species, Guiana (Sotalia guianensis), franciscana (Pontoporia blainvillei), Atlantic spotted (Stenella frontalis), and rough-toothed dolphins (Steno bredanensis), frequently occur in Ilha Grande Bay (RJ), with three of them presenting residence pattern. This tropical bay is considered a biodiversity hotspot and preserved by marine protected areas, though located in a highly developed region of the Southwestern Atlantic Ocean. To verify niche partitioning and segregation in these species and to explore the trophic structure of this cetacean community, their isotopic niches were investigated through carbon (δ13C) and nitrogen (δ15N) stable isotopes in the muscle of specimens stranded in the region between 2012 and 2022. The rough-toothed dolphin had the largest niche area and high segregation. On the other hand, there was a high niche overlap between the species that have site fidelity patterns in the bay. The Atlantic spotted dolphin had the highest values for almost all the Layman metrics, a large niche area, and trophic diversity; the Guiana dolphin explored a diverse variety of resources, and the franciscana dolphin presented the narrowest and most overlapped niche and the lowest niche diversification. This is the first study to access the trophic ecology of this cetacean community. Our results indicate that the region is an important foraging area for three of the studied species, with a high diversity and availability of resources that might enable the high niche overlap observed for resident species. The findings for the threatened and small franciscana population in this recently discovered habitat bring concern. Therefore, the area deserves conservation attention to prevent anthropogenic stressors from interfering in the relationship balance between these sympatric predators

Distinct bioaccumulation profile of pesticides and dioxin-like compounds by mollusk bivalves reared in polluted and unpolluted tropical bays: Consumption risk and seasonal effect.

Mariculture activity has increased its production along the Atlantic Coast of Brazil over the last years. This protein source for human consumption may also represent risks due to the exposure to bioaccumulated contaminants in the tissues of organisms reared in polluted shallow waters. This study evaluated the bioaccumulation of pesticides and dioxin-like compounds in two commercial marine bivalve species reared at different sites along the Rio de Janeiro State coast (SE-Brazil). We observed distinct contamination profiles in bivalve tissues reared at each sampling site, which may be related to human activities historically developed in those areas. A pronounced tendency for higher contamination levels in animals sampled in the last month of winter (September) is discussed as being likely due to environmental issues, rather than biological factors. Based on Minimal Risk Level. Maximum Residue, Acceptable Daily Intake and Toxic Equivalent, bivalves are classified as safe for human consumption

Elementos traza (HgT, Cd, Cu y Ag) en el delfín común de pico corto (Delphinus delphis) y el delfín de Fraser (Lagenodelphis hosei) del atlántico sudoccidental

Entre la amplia variedad de contaminantes encontramos, dentro de los denominados elementos traza, el mercurio total (HgT), el cadmio (Cd), el cobre (Cu) y la plata (Ag). Su principal vía de absorción para los vertebrados marinos es la dieta. Los odontocetos están en la cima de las cadenas tróficas y dado que acumulan gran cantidad de compuestos a lo largo de la vida, son considerados bioindicadores de contaminación del ecosistema. Algunos trabajos indican que no existe una acumulación diferencial de elementos traza entre sexos, pero sí una relación con la edad y la talla. El objetivo del presente estudio fue analizar las concentraciones de elementos traza en el hígado y riñón de 31 delfines comunes (Delphinus delphis) y 6 delfines de Fraser (Lagenodelphis hosei) varados en las costas de los Golfos norpatagónicos entre 1996 y 2012. Asimismo, evaluar las concentraciones de estos contaminantes en relación al sexo, la edad y el largo estándar.Fil: Durante, Cristian Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Manhães Moura Reis, B.. Universidad Estadual de Río de Janeiro; BrasilFil: Loizaga de Castro, Rocio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; ArgentinaFil: Lailson Brito Jr, J.. Universidad Estadual de Río de Janeiro; BrasilFil: Crespo, Enrique Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico. Centro para el Estudio de Sistemas Marinos; Argentina. Universidad Nacional de la Patagonia "San Juan Bosco"; ArgentinaXI Congreso de la Sociedad Latinoamericana de Especialistas Mamíferos AcuáticosValparaisoChileSociedad Latinoamericana De Especialistas Mamíferos Acuático