Genetic diversity in two threatened species of guitarfish (Elasmobranchii: Rhinobatidae) from the Brazilian and Argentinian coasts: an alert for conservation

The guitarfishes Pseudobatos horkelii and Pseudobatos percellens meet the criteria for threatened status as Critically Endangered (CR) and Endangered (EN), respectively. Both species occur in the Southern Atlantic Ocean. Considering the lack of data on the genetic structure of these species, the present study evaluated the genetic variability and population structure of the P. horkelii and P. percellens in the southern region of Brazil and the northern coast of Argentina, based on sequences of mitochondrial DNA, Control Region (D-loop). Samples of P. horkelii (n = 135) were analyzed in six localities situated in Northern Argentina, along the Brazilian states’ coast. The mean of nucleotide diversity was 0.0053, the ΦST was 0.4277 and demographic analysis of P. horkelii suggests the existence of stability of the populations, with D = 0.9929, FS = 2.0155, SSD = 0.0817, R = 0.2153. In P. percellens (n = 101) were analyzed from six Brazilian localities along the coast of Santa Catarina, Paraná, and São Paulo. The mean nucleotide diversity was 0.0014 and ΦST value of 0.2921, the demographic analysis indicates a high migration rate of P. percellens among the localities evaluated, with D = 0.5222, FS = 0.3528, SSD = 0.01785, R = 0.3890.As raias violas Pseudobatos horkelii e Pseudobatos percellens, são listados como “Criticamente em Perigo” (CR) e “Em Perigo” (EN), respectivamente. Ambas as espécies ocorrem no Sul do Oceano Atlântico. Considerando a falta de dados sobre a estrutura genética dessas espécies, o presente estudo avaliou a variabilidade genética e a estrutura populacional de P. horkelii e P. percellens na região sudeste do Brasil e litoral norte da Argentina, com base em sequências de DNA mitocondrial, região de controle (D-loop). Amostras de 135 indivíduos de P. horkelii analisados em seis localidades, situadas no norte da Argentina e ao longo da costa dos estados brasileiros. A média da diversidade nucleotídica foi de 0.0053, o índice ΦST foi de 0.4277 e a análise demográfica de P. horkelii, indicou a existência de estabilidade das populações, com D = 0.9929, Fus = 2.0155, SSD = 0.0817, R = 0.2153. Em 101 exemplares de P. percellens, foram analisados em seis localidades brasileiras ao longo do litoral de Santa Catarina, Paraná e São Paulo. A diversidade nucleotídica média foi de 0.0014 e o valor ΦST de 0.2921, a análise demográfica indicou uma alta taxa de migração de P. percellens entre as localidades analisadas, com D = 0.5222, FS = 0.3528, SSD = 0.01785, R = 0.3890.Fil: Cruz, Vanessa P.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Adachi, Aisni M. C. L.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Oliveira, Pablo H.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Ribeiro, Giovana S.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Paim, Fabilene G.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Souza, Bruno C.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Rodrigues, Alexandre S. F.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Vianna, Marcelo. Universidade Federal do Rio de Janeiro; BrasilFil: Delpiani, Sergio Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Díaz de Astarloa, Juan Martín. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Marinas y Costeras. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Marinas y Costeras; ArgentinaFil: Rotundo, Matheus M.. Universidade Santa Cecília; BrasilFil: Mendonça, Fernando F.. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Oliveira, Claudio. Universidade Estadual Paulista Julio de Mesquita Filho; BrasilFil: Lessa, Rosangela P.. Universidad Federal Rural Pernambuco; BrasilFil: Foresti, Fausto. Universidade Estadual Paulista Julio de Mesquita Filho; Brasi

Structure and Genetic Variability of the Oceanic Whitetip Shark, Carcharhinus longimanus, Determined Using Mitochondrial DNA

Information regarding population structure and genetic connectivity is an important contribution when establishing conservation strategies to manage threatened species. The oceanic whitetip shark, Carcharhinus longimanus, is a highly migratory, large-bodied, pelagic shark listed by the IUCN (International Union for Conservation of Nature) Red List as "vulnerable" throughout its range and "critically endangered" in the western north Atlantic. In 2014, the species was protected globally under Appendix II of CITES (Convention on International Trade in Endangered Species), limiting and regulating trade. This study used partial sequences of mitochondrial DNA (mtDNA) control region to determine the population genetic structure of oceanic whitetip sharks across the Atlantic and Indian Oceans. 724 base pairs were obtained from 215 individuals that identifed nine polymorphic sites and defined 12 distinct haplotypes. Total nucleotide diversity (pi) was 0.0013 and haplotype diversity (h) was 0.5953. The Analysis of Molecular Variance (AMOVA) evidenced moderate levels of population structure (phi(ST) = 0.1039) with restricted gene flow between the western and eastern Atlantic Ocean, and a strong relationship between the latter region and the Indian Ocean. Even though the oceanic whitetip is a highly migratory animal the results presented here show that their genetic variability is slightly below average of other pelagic sharks. Additionally, this study recommends that at least two populations in the Atlantic Ocean should be considered distinct (eastern and western Atlantic) and conservation efforts should be focused in areas with the greatest genetic diversity by environmental managers

Identification and phylogenetic inferences on stocks of sharks affected by the fishing industry off the Northern coast of Brazil

The ongoing decline in abundance and diversity of shark stocks, primarily due to uncontrolled fishery exploitation, is a worldwide problem. An additional problem for the development of conservation and management programmes is the identification of species diversity within a given area, given the morphological similarities among shark species, and the typical disembarkation of processed carcasses which are almost impossible to differentiate. The main aim of the present study was to identify those shark species being exploited off northern Brazil, by using the 12S-16S molecular marker. For this, DNA sequences were obtained from 122 specimens collected on the docks and the fish market in Bragança, in the Brazilian state of Pará. We identified at least 11 species. Three-quarters of the specimens collected were either Carcharhinus porosus or Rhizoprionodon sp, while a notable absence was the daggernose shark, Isogomphodon oxyrhyncus, previously one of the most common species in local catches. The study emphasises the value of molecular techniques for the identification of cryptic shark species, and the potential of the 12S-16S marker as a tool for phylogenetic inferences in a study of elasmobranchs

Regional movements of the tiger shark, Galeocerdo cuvier, off northeastern Brazil: inferences regarding shark attack hazard

An abnormally high shark attack rate verified off Recife could be related to migratory behavior of tiger sharks. This situation started after the construction of the Suape port to the south of Recife. A previous study suggested that attacking sharks could be following northward currents and that they were being attracted shoreward by approaching vessels. In this scenario, such northward movement pattern could imply a higher probability of sharks accessing the littoral area of Recife after leaving Suape. Pop-up satellite archival taus were deployed on five tiger sharks caught off Recife to assess their movement patterns off northeastern Brazil. All tags transmitted from northward latitudes after 7-74 days of freedom. The shorter, soak distance between deployment and pop-up locations ranged between 33-209 km and implied minimum average speeds of 0.02-0.98 km.h(-1). Both pop-up locations and depth data suggest that tiger shark movements were conducted mostly over the continental shelf. The smaller sharks moved to deeper waters within 24 hours after releasing, but they assumed a shallower (< 50 m) vertical distribution for most of the monitoring period. While presenting the first data on tiger shark movements in the South Atlantic, this study also adds new information for the reasoning of the high shark attack rate verified in this region,State Government of Pernambuco and Petrobras (Brazil); Fundacao para a Ciencia e Tecnologia (Portugal) [MCTES/FCT/SFRH/BD/37065/2007

Elasmobranchs from Patos lagoon estuary : occurrence of catches and population structure

Por serem predadores de topo, elasmobrânquios significativamente influenciam o ecossistema dependendo de como usam o habitat. Para melhor compreender como o habitat é usado, este estudo descreve a ocorrência de elasmobrânquios no estuário da Lagoa dos Patos e sua estrutura populacional. No total, 581 indivíduos de 19 espécies foram amostrados. CPUE apresentou correlação com salinidade ( rs = 0.96; P < 0.00001), mas não com profundidade ( rs = 0.24, p = 0.218) ou temperatura superficial da água ( rs = -0.32, p = 0.101). Os maiores valores ocorreram na primavera e verão, quando a salinidade aumenta no estuário, assim como a abundância na Plataforma Sul devido à época de parto. Essa combinação de variáveis indica um uso esporádico do estuário. As espécies mais representativas foram Sphyrna lewini (6.71), Pseudobatos horkelii (2.39), Sphyrna zygaena (1.25) e Carcharhinus brevipinna (0.98). Seus padrões populacionais são similares aos encontrados na plataforma continental, indicando que o estuário da Lagoa dos Patos é um bom representante da biodiversidade do sul do Brasil. Este estudo ajuda a compreender a ocorrência de elasmobrânquios em diferentes habitats ao longo dos seus ciclos de vida.As high-trophic level predators, elasmobranchs significantly influence the ecosystem, according to how they use the habitat. To understand better how they use the habitat, this study describes the occurrence of elasmobranchs in Patos lagoon estuary and their populational structure. In total, 581 individuals from 19 species were captured. CPUE presented correlation with salinity ( rs = 0.96; P < 0.00001), but no correlation with depth ( rs = 0.24, p = 0.218) or water surface temperature ( rs = -0.32, p = 0.101). The highest values were during spring and summer, when salinity levels are known to get higher in the estuary, along with increases in the abundance in the South Platform due to parturition season. This combination of variables indicates a sporadic use of the estuary. The most representative species were Sphyrna lewini (6.71), Pseudobatos horkelii (2.39), Sphyrna zygaena (1.25) and Carcharhinus brevipinna (0.98). Their populational patterns were similar to those found in offshore waters, indicating that the Patos lagoon estuary is a good representative of the biodiversity from Southern Brazil. This study helps to understand elasmobranch occurrence in different habitats throughout their life cycle

The population genomic structure of green turtles (<i>Chelonia mydas</i>) suggests a warm-water corridor for tropical marine fauna between the Atlantic and Indian oceans during the last interglacial

The occasional westward transport of warm water of the Agulhas Current, “Agulhas leakage”, around southern Africa has been suggested to facilitate tropical marine connectivity between the Atlantic and Indian oceans, but the “Agulhas leakage” hypothesis does not explain the signatures of eastward gene flow observed in many tropical marine fauna. We investigated an alternative hypothesis: the establishment of a warm-water corridor during comparatively warm interglacial periods. The “warm-water corridor” hypothesis was investigated by studying the population genomic structure of Atlantic and Southwest Indian Ocean green turtles (N = 27) using 12,035 genome-wide single nucleotide polymorphisms (SNPs) obtained via ddRAD sequencing. Model-based and multivariate clustering suggested a hierarchical population structure with two main Atlantic and Southwest Indian Ocean clusters, and a Caribbean and East Atlantic sub-cluster nested within the Atlantic cluster. Coalescent-based model selection supported a model where Southwest Indian Ocean and Caribbean populations diverged from the East Atlantic population during the transition from the last interglacial period (130–115 thousand years ago; kya) to the last glacial period (115–90 kya). The onset of the last glaciation appeared to isolate Atlantic and Southwest Indian Ocean green turtles into three refugia, which subsequently came into secondary contact in the Caribbean and Southwest Indian Ocean when global temperatures increased after the Last Glacial Maximum. Our findings support the establishment of a warm-water corridor facilitating tropical marine connectivity between the Atlantic and Southwest Indian Ocean during warm interglacials