RESUMO
In order to investigate the feasibility of using ultraviolet (UV) irradiation to prevent the invasive Asian mussel, Limnoperna fortunei, from colonizing components of the cooling systems of industrial and power plants, the mobility and mortality of its larvae were assessed after exposure to different doses of UVC (λ = 254 nm) in laboratory conditions. Total (100%) mortality was achieved with a dose of 149 mJ cm(-2) at 23 °C and 103 mJ cm(-2) at 25.8 °C. Immediately after exposure, larvae were alive but had reduced mobility. The proportion of active larvae increased after 24 h, but fell again at 48 and 72 h to levels similar to those immediately after exposure. The highest mortality rates were always recorded at the last observation, 72 h after exposure. These results indicate that the larvae of L. fortunei are highly sensitive to UVC, suggesting that UV irradiation has the potential to control fouling by this mussel when the water is relatively clear. However, application of UV-based technologies in plants that use cooling water from water bodies with high loads of suspended solids (eg the Paraná-Uruguay basin, with ca 160 mg l(-1) of suspended solids and absorbance values around 0.255) is unlikely to be effective without prior filtration of the water.
Assuntos
Incrustação Biológica/prevenção & controle , Bivalves/efeitos da radiação , Raios Ultravioleta , Animais , Bivalves/crescimento & desenvolvimento , Filtração , Larva/efeitos da radiação , Centrais Elétricas , Água/químicaRESUMO
We explored possible links between vector activity and genetic diversity in introduced populations of Limnoperna fortunei by characterizing the genetic structure in native and introduced ranges in Asia and South America. We surveyed 24 populations: ten in Asia and 14 in South America using the mitochondrial cytochrome c oxidase subunit I (COI) gene, as well as eight polymorphic microsatellite markers. We performed population genetics and phylogenetic analyses to investigate population genetic structure across native and introduced regions. Introduced populations in Asia exhibit higher genetic diversity (H(E)â=â0.667-0.746) than those in South America (H(E)â=ââ0.519-0.575), suggesting higher introduction effort for the former populations. We observed pronounced geographical structuring in introduced regions, as indicated by both mitochondrial and nuclear markers based on multiple genetic analyses including pairwise Ф(ST), F(ST), bayesian clustering method, and three-dimensional factorial correspondence analyses. Pairwise F(ST) values within both Asia (F(ST)â=â0.017-0.126, Pâ=â0.000-0.009) and South America (F(ST)â=0.004-0.107, Pâ=â0.000-0.721) were lower than those between continents (F(ST)â=â0.180-0.319, Pâ=â0.000). Fine-scale genetic structuring was also apparent among introduced populations in both Asia and South America, suggesting either multiple introductions of distinct propagules or strong post-introduction selection and demographic stochasticity. Higher genetic diversity in Asia as compared to South America is likely due to more frequent propagule transfers associated with higher shipping activities between source and donor regions within Asia. This study suggests that the intensity of human-mediated introduction vectors influences patterns of genetic diversity in non-indigenous species.
Assuntos
Bivalves/genética , Variação Genética/genética , Animais , Ásia , Bivalves/classificação , Genética Populacional , Filogenia , Dinâmica Populacional , América do SulRESUMO
The acute upper lethal temperature (AULT) at different rates of increase was evaluated as a tool for the design of cheaper and environmentally friendlier control strategies for the invasive bivalve Limnoperna fortunei. Survivorship of 6 ± 2 mm and 20 ± 2 mm mussels acclimated to 12, 23 and 28 ° C and subjected to different heating rates (1 ° C per 5, 15 and 30 min) was estimated in the laboratory. The temperatures required to kill 50% (LT(50)) and 100% (SM(100)) of the mussels, and the mean death temperature (MDT) varied between 42.2 and 51 ° C over 54 experiments. Heating rates significantly (p < 0.001) affected LT(50), SM(100), and MDT. AULT was not affected by mussel size and acclimation temperatures. Limnoperna appears to be more resistant to high temperatures than Dreissena polymorpha, a mussel invasive in the USA and Europe. Lethal temperatures of L. fortunei are within the current thermal operational industrial capacities, suggesting that heat treatment is a viable alternative for controlling its fouling in utility systems.
Assuntos
Aclimatação , Incrustação Biológica/prevenção & controle , Mytilidae/fisiologia , Centrais Elétricas , Temperatura , AnimaisRESUMO
Since its introduction in South America around 1990, the freshwater mussel Limnoperna fortunei has become a major fouling pest for most industrial plants that use raw river or lake water, chiefly for cooling purposes. We assessed the tolerance of the mussel to upper lethal temperatures as an economical and environmentally innocuous method of controlling its fouling in industrial installations. Survival of juvenile (7 ± 2 mm in length) and adult (21 ± 2 mm) individuals, acclimated to 12 and 28 °C, was evaluated under laboratory conditions. At 38-43 °C, all mussels die after 0.7 to 17.5 h, regardless of acclimation temperature and size class. At 34-36 °C, total mortality takes 25.0 to 644.3 h, regardless of the size of the animals, but mussels acclimated at 12 °C die significantly faster that those acclimated at 28 °C. Comparison of these results with the range of conditions currently used in the industry indicates that heat treatment is a viable alternative for an efficient control of this Asian mussel in fouled systems.