RESUMO

Corbicula fluminea is an invasive bivalve responsible for several environmental and financial problems around the globe. Despite the invasive potential of this species, it suffers certain restrictions in lentic environments due to natural phenomena that significantly affect its population structure (e.g. water column fluctuation and sunlight exposure). The present study addresses how temporal decline of the water level in a Neotropical reservoir and exposure to sunlight affect the population structure of C. fluminea. Samplings were carried out twice in the reservoir of Furnas Hydroelectric Power Station (HPS) (Minas Gerais, Brazil), in 2011 and 2012. Population density, spatial distribution and mean shell length of C. fluminea were estimated for each year after sampling in 51 quadrats (0.0625m2) placed on three transects at different distances along the reservoir margins (0, 10 and 20 m from a fixed-point). We observed a predominance of C. fluminea in both years, with a simultaneous gradual decrease in density and richness of native species in the sampling area. Significant differences in density of C. fluminea were registered at different distances from the margin, and are related to the temporal variability of physical conditions of the sediment and water in these environments. We also registered a trend toward an increase in the density and aggregation of C. fluminea as we moved away from the margin, due to the greater stability of these areas (>10 m). The mean shell length of C. fluminea showed significant difference between the distinct distances from the margin and during the years, as well as the interaction of these factors (Distances vs.Years). These results were associated with the reproductive and invasive capacity of this species. This study reveals that these temporal events (especially water column fluctuation) may cause alterations in density, spatial distribution and mean shell length of C. fluminea and the composition of the native malacofauna in Neotropical lentic environments.

Assuntos

RESUMO

Corbicula fluminea is an invasive bivalve responsible for several environmental and financial problems around the globe. Despite the invasive potential of this species, it suffers certain restrictions in lentic environments due to natural phenomena that significantly affect its population structure (e.g. water column fluctuation and sunlight exposure). The present study addresses how temporal decline of the water level in a Neotropical reservoir and exposure to sunlight affect the population structure of C. fluminea. Samplings were carried out twice in the reservoir of Furnas Hydroelectric Power Station (HPS) (Minas Gerais, Brazil), in 2011 and 2012. Population density, spatial distribution and mean shell length of C. fluminea were estimated for each year after sampling in 51 quadrats (0.0625m2) placed on three transects at different distances along the reservoir margins (0, 10 and 20 m from a fixed-point). We observed a predominance of C. fluminea in both years, with a simultaneous gradual decrease in density and richness of native species in the sampling area. Significant differences in density of C. fluminea were registered at different distances from the margin, and are related to the temporal variability of physical conditions of the sediment and water in these environments. We also registered a trend toward an increase in the density and aggregation of C. fluminea as we moved away from the margin, due to the greater stability of these areas (>10 m). The mean shell length of C. fluminea showed significant difference between the distinct distances from the margin and during the years, as well as the interaction of these factors (Distances vs.Years). These results were associated with the reproductive and invasive capacity of this species. This study reveals that these temporal events (especially water column fluctuation) may cause alterations in density, spatial distribution and mean shell length of C. fluminea and the composition of the native malacofauna in Neotropical lentic environments.(AU)

Corbicula fluminea é um bivalve invasor, responsável por inúmeros problemas ambientais e econômicos ao redor do mundo. Apesar de sua capacidade de invasão, a espécie sofre certas restrições devido a fenômenos naturais em ambientes lênticos, afetando significativamente sua estrutura populacional (e.g. flutuação do nível da água e a exposição à luz solar). O presente trabalho avaliou como o decréscimo temporal do nível da água de um reservatório neotropical e a exposição solar, afeta a estrutura populacional de C. fluminea. Duas amostragens foram realizadas no reservatório da Usina Hidrelétrica (UHE) de Furnas (Minas Gerais, Brasil), em 2011 e 2012. A densidade populacional, o comprimento médio e a distribuição espacial da espécie para cada ano foram estimados após amostragem em 51 quadrats (0,0625m2) dispostos em três transectos em diferentes distâncias das margens do reservatório (0, 10 e 20 m em relação a um ponto fixo). Observou-se o predomínio de C. fluminea em ambos os anos, coincidindo com o decréscimo da densidade e riqueza de espécies nativas nas áreas de amostragem. Foram registradas diferenças significativas na densidade de C. fluminea entre as distâncias da margem, sendo atribuídas principalmente à variabilidade temporal do substrato e da água desses ambientes. Registrou-se também uma tendência em aumento da densidade e agregação com o aumento da distância da margem, devido à maior estabilidade dessas áreas (>10 m). Houveram diferenças significativas no tamanho médio das conchas de C. fluminea entre às distâncias da margem e durante os anos, assim como na interação desses fatores (Distâncias vs. Anos). Tais resultados foram associados à capacidade reprodutiva e invasiva da espécie. Esse estudo revelou que eventos temporais (principalmente, a flutuação do nível da água) em ambientes lênticos neotropicais provocam alterações na densidade, tamanho médio e distribuição de C. fluminea e na composição da malacofauna nativa.(AU)

Assuntos

RESUMO

Corbicula fluminea is an invasive bivalve responsible for several environmental and financial problems around the globe. Despite the invasive potential of this species, it suffers certain restrictions in lentic environments due to natural phenomena that significantly affect its population structure (e.g. water column fluctuation and sunlight exposure). The present study addresses how temporal decline of the water level in a Neotropical reservoir and exposure to sunlight affect the population structure of C. fluminea. Samplings were carried out twice in the reservoir of Furnas Hydroelectric Power Station (HPS) (Minas Gerais, Brazil), in 2011 and 2012. Population density, spatial distribution and mean shell length of C. fluminea were estimated for each year after sampling in 51 quadrats (0.0625m2) placed on three transects at different distances along the reservoir margins (0, 10 and 20 m from a fixed-point). We observed a predominance of C. fluminea in both years, with a simultaneous gradual decrease in density and richness of native species in the sampling area. Significant differences in density of C. fluminea were registered at different distances from the margin, and are related to the temporal variability of physical conditions of the sediment and water in these environments. We also registered a trend toward an increase in the density and aggregation of C. fluminea as we moved away from the margin, due to the greater stability of these areas (>10 m). The mean shell length of C. fluminea showed significant difference between the distinct distances from the margin and during the years, as well as the interaction of these factors (Distances vs.Years). These results were associated with the reproductive and invasive capacity of this species. This study reveals that these temporal events (especially water column fluctuation) may cause alterations in density, spatial distribution and mean shell length of C. fluminea and the composition of the native malacofauna in Neotropical lentic environments.

Corbicula fluminea é um bivalve invasor, responsável por inúmeros problemas ambientais e econômicos ao redor do mundo. Apesar de sua capacidade de invasão, a espécie sofre certas restrições devido a fenômenos naturais em ambientes lênticos, afetando significativamente sua estrutura populacional (e.g. flutuação do nível da água e a exposição à luz solar). O presente trabalho avaliou como o decréscimo temporal do nível da água de um reservatório neotropical e a exposição solar, afeta a estrutura populacional de C. fluminea. Duas amostragens foram realizadas no reservatório da Usina Hidrelétrica (UHE) de Furnas (Minas Gerais, Brasil), em 2011 e 2012. A densidade populacional, o comprimento médio e a distribuição espacial da espécie para cada ano foram estimados após amostragem em 51 quadrats (0,0625m2) dispostos em três transectos em diferentes distâncias das margens do reservatório (0, 10 e 20 m em relação a um ponto fixo). Observou-se o predomínio de C. fluminea em ambos os anos, coincidindo com o decréscimo da densidade e riqueza de espécies nativas nas áreas de amostragem. Foram registradas diferenças significativas na densidade de C. fluminea entre as distâncias da margem, sendo atribuídas principalmente à variabilidade temporal do substrato e da água desses ambientes. Registrou-se também uma tendência em aumento da densidade e agregação com o aumento da distância da margem, devido à maior estabilidade dessas áreas (>10 m). Houveram diferenças significativas no tamanho médio das conchas de C. fluminea entre às distâncias da margem e durante os anos, assim como na interação desses fatores (Distâncias vs. Anos). Tais resultados foram associados à capacidade reprodutiva e invasiva da espécie. Esse estudo revelou que eventos temporais (principalmente, a flutuação do nível da água) em ambientes lênticos neotropicais provocam alterações na densidade, tamanho médio e distribuição de C. fluminea e na composição da malacofauna nativa.

Assuntos

RESUMO

Limnoperna fortunei is an invasive gonochoristic and byssate freshwater bivalve originary from Southeast Asia. It shows great adaptive-reproductive ability, so knowledge of the gonadal cycle is an important factor for the prevention and control of this bioinvasion. This species is highly damaging to natural and human environments. We analyzed the distribution and maturity state of reproductive follicles in the mantle of both male and females. Male results are not shown but, in general, they followed the same pattern as that of females. Routine histological techniques included serial longitudinal sections and transversal sections in three body regions (anterior, middle and psoterior). Oocytes with conspicuous nucleoli were measured on both types of sections to estimate the maturity stage in the different regions. ANOVA indicates that there were no significant differences in maturity ratio between the studied regions, so that a small number of sections would render precise results to assess maturity

Assuntos

RESUMO

Limnoperna fortunei is an invasive gonochoristic and byssate freshwater bivalve originary from Southeast Asia. It shows great adaptive-reproductive ability, so knowledge of the gonadal cycle is an important factor for the prevention and control of this bioinvasion. This species is highly damaging to natural and human environments. We analyzed the distribution and maturity state of reproductive follicles in the mantle of both male and females. Male results are not shown but, in general, they followed the same pattern as that of females. Routine histological techniques included serial longitudinal sections and transversal sections in three body regions (anterior, middle and psoterior). Oocytes with conspicuous nucleoli were measured on both types of sections to estimate the maturity stage in the different regions. ANOVA indicates that there were no significant differences in maturity ratio between the studied regions, so that a small number of sections would render precise results to assess maturity

Assuntos

RESUMO

Limnoperna fortunei is an invasive gonochoristic and byssate freshwater bivalve originary from Southeast Asia. It shows great adaptive-reproductive ability, so knowledge of the gonadal cycle is an important factor for the prevention and control of this bioinvasion. This species is highly damaging to natural and human environments. We analyzed the distribution and maturity state of reproductive follicles in the mantle of both male and females. Male results are not shown but, in general, they followed the same pattern as that of females. Routine histological techniques included serial longitudinal sections and transversal sections in three body regions (anterior, middle and psoterior). Oocytes with conspicuous nucleoli were measured on both types of sections to estimate the maturity stage in the different regions. ANOVA indicates that there were no significant differences in maturity ratio between the studied regions, so that a small number of sections would render precise results to assess maturity

Assuntos

RESUMO

Limnoperna fortunei is an invasive gonochoristic and byssate freshwater bivalve originary from Southeast Asia. It shows great adaptive-reproductive ability, so knowledge of the gonadal cycle is an important factor for the prevention and control of this bioinvasion. This species is highly damaging to natural and human environments. We analyzed the distribution and maturity state of reproductive follicles in the mantle of both male and females. Male results are not shown but, in general, they followed the same pattern as that of females. Routine histological techniques included serial longitudinal sections and transversal sections in three body regions (anterior, middle and psoterior). Oocytes with conspicuous nucleoli were measured on both types of sections to estimate the maturity stage in the different regions. ANOVA indicates that there were no significant differences in maturity ratio between the studied regions, so that a small number of sections would render precise results to assess maturity

Assuntos

RESUMO

Pomacea canaliculata (Lamarck, 1822) (Mollusca Gastropoda) shows a large native distribution range in South America, reaching as far south as 37º S (Buenos Aires, Argentina). This species was deliberately introduced into Southeast Asia around 1980 and subsequently underwent a rapid intentional or accidental dispersal into many countries in the region. It was also introduced into North and Central America and Hawaii. In this contribution we record the presence of P. canaliculata in Patagonia, assessing the possible influence of climatic change in the new establishment of this species there. Three samplings (between September 2004 and April 2005) were carried out at 38º 58' 20.2" S-68º 11' 27.3" W. In the sampling we found two adult specimens of P. canaliculata and numerous egg clutches. Pomacea canaliculata is naturally distributed in the Plata and Amazon Basins. The southern boundary of this species has been established as the isotherms of 14 ºC and 16 ºC in Buenos Aires province, and precipitations of 900 to 600 mm/year. This study also analysed variations in annual temperature and precipitation in Patagonia. Average temperatures show an increase over the years, although not constantly. Important modifications in precipitation regime in northern Patagonia, triggered by global climatic changes, could be beneficial for the settlement of populations of P. canaliculata in this new area, where precipitation increased enough to reach values similar to those in the southernmost area of distribution of this species.

Assuntos

RESUMO

Pomacea canaliculata (Lamarck, 1822) (Mollusca Gastropoda) shows a large native distribution range in South America, reaching as far south as 37º S (Buenos Aires, Argentina). This species was deliberately introduced into Southeast Asia around 1980 and subsequently underwent a rapid intentional or accidental dispersal into many countries in the region. It was also introduced into North and Central America and Hawaii. In this contribution we record the presence of P. canaliculata in Patagonia, assessing the possible influence of climatic change in the new establishment of this species there. Three samplings (between September 2004 and April 2005) were carried out at 38º 58' 20.2" S-68º 11' 27.3" W. In the sampling we found two adult specimens of P. canaliculata and numerous egg clutches. Pomacea canaliculata is naturally distributed in the Plata and Amazon Basins. The southern boundary of this species has been established as the isotherms of 14 ºC and 16 ºC in Buenos Aires province, and precipitations of 900 to 600 mm/year. This study also analysed variations in annual temperature and precipitation in Patagonia. Average temperatures show an increase over the years, although not constantly. Important modifications in precipitation regime in northern Patagonia, triggered by global climatic changes, could be beneficial for the settlement of populations of P. canaliculata in this new area, where precipitation increased enough to reach values similar to those in the southernmost area of distribution of this species.

Pomacea canaliculata (Lamarck, 1822) (Mollusca Gastropoda) mostra um grande alcance de distribuição natural na América do Sul, chegando até os 37º S (Buenos Aires, Argentina). Esta espécie foi introduzida propositalmente no sudeste da Ásia, por volta de 1980 e, mais tarde, se submeteu a uma dispersão de forma rápida intencional ou acidental em muitos países da região. Também foi introduzido na América do Norte, América Central e Havaí. Nesta contribuição se confere a presença de P. canaliculata na Patagônia e se considera a influência das alterações climáticas no novo estabelecimento desta espécie no local referido. Três coletas (entre setembro de 2004 até abril de 2005) foram realizadas (38º 58' 20.2" S and 68º 11' 27.3" W). Nelas encontraram-se dois exemplares adultos de P. canaliculada e numerosas desovas. P. canaliculata distribui-se naturalmente nas regiões das Bacias do Prata e Amazonas. O limite sul desta espécie foi estabelecido nas isotermas de 14 ºC e 16 ºC na província de Buenos Aires, com precipitações de 900 a 600 mm. Também são analisadas as variações na temperatura anual e a precipitação na Patagônia. As médias de temperatura mostram um aumento no decorrer de dois anos. Modificações importantes no regime de precipitação no norte da Patagônia poderiam ser benéficas para o estabelecimento das populações de P. canaliculata nesta nova área, onde as precipitações aumentaram o suficiente até atingir os valores similares aos da região mais austral citada para a distribuição desta espécie.

Assuntos

RESUMO

Pomacea canaliculata (Lamarck, 1822) (Mollusca Gastropoda) shows a large native distribution range in South America, reaching as far south as 37º S (Buenos Aires, Argentina). This species was deliberately introduced into Southeast Asia around 1980 and subsequently underwent a rapid intentional or accidental dispersal into many countries in the region. It was also introduced into North and Central America and Hawaii. In this contribution we record the presence of P. canaliculata in Patagonia, assessing the possible influence of climatic change in the new establishment of this species there. Three samplings (between September 2004 and April 2005) were carried out at 38º 58' 20.2" S-68º 11' 27.3" W. In the sampling we found two adult specimens of P. canaliculata and numerous egg clutches. Pomacea canaliculata is naturally distributed in the Plata and Amazon Basins. The southern boundary of this species has been established as the isotherms of 14 ºC and 16 ºC in Buenos Aires province, and precipitations of 900 to 600 mm/year. This study also analysed variations in annual temperature and precipitation in Patagonia. Average temperatures show an increase over the years, although not constantly. Important modifications in precipitation regime in northern Patagonia, triggered by global climatic changes, could be beneficial for the settlement of populations of P. canaliculata in this new area, where precipitation increased enough to reach values similar to those in the southernmost area of distribution of this species.

Pomacea canaliculata (Lamarck, 1822) (Mollusca Gastropoda) mostra um grande alcance de distribuição natural na América do Sul, chegando até os 37º S (Buenos Aires, Argentina). Esta espécie foi introduzida propositalmente no sudeste da Ásia, por volta de 1980 e, mais tarde, se submeteu a uma dispersão de forma rápida intencional ou acidental em muitos países da região. Também foi introduzido na América do Norte, América Central e Havaí. Nesta contribuição se confere a presença de P. canaliculata na Patagônia e se considera a influência das alterações climáticas no novo estabelecimento desta espécie no local referido. Três coletas (entre setembro de 2004 até abril de 2005) foram realizadas (38º 58' 20.2" S and 68º 11' 27.3" W). Nelas encontraram-se dois exemplares adultos de P. canaliculada e numerosas desovas. P. canaliculata distribui-se naturalmente nas regiões das Bacias do Prata e Amazonas. O limite sul desta espécie foi estabelecido nas isotermas de 14 ºC e 16 ºC na província de Buenos Aires, com precipitações de 900 a 600 mm. Também são analisadas as variações na temperatura anual e a precipitação na Patagônia. As médias de temperatura mostram um aumento no decorrer de dois anos. Modificações importantes no regime de precipitação no norte da Patagônia poderiam ser benéficas para o estabelecimento das populações de P. canaliculata nesta nova área, onde as precipitações aumentaram o suficiente até atingir os valores similares aos da região mais austral citada para a distribuição desta espécie.

Assuntos

Assuntos