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排序方式: 共有237条查询结果,搜索用时 562 毫秒
41.
Bennett PM Jepson PD Law RJ Jones BR Kuiken T Baker JR Rogan E Kirkwood JK 《Environmental pollution (Barking, Essex : 1987)》2001,112(1):33-40
We investigate whether long-term exposure to heavy metals, including immunosuppressive metals like mercury (Hg), is associated with infectious disease in a wild cetacean. Post-mortem investigations on 86 harbour porpoises, Phocoena phocoena, found dead along the coasts of England and Wales revealed that 49 of the porpoises were healthy when they died as a consequence of physical trauma (most frequently entrapment in fishing gear). In contrast, 37 porpoises died of infectious diseases caused by parasitic, bacterial, fungal and viral pathogens (most frequently pneumonia caused by lungworm and bacterial infections). We found that mean liver concentrations of Hg, selenium (Se), the Hg:Se molar ratio, and zinc (Zn) were significantly higher in the propoises that died of infectious disease compared to healthy porpoises that died from physical trauma. Liver concentrations of lead (Pb), cadmium (Cd), copper (Cu) and chromium (Cr) did not differ between the two groups. Hg, Se, and the Hg:Se molar ratio were also positively correlated with age. The association between Zn concentration and disease status may result from Zn redistribution in response to infection. Further work is required to evaluate whether chronic exposure to Hg may have presented a toxic challenge to the porpoises that succumbed to infectious disease. 相似文献
42.
Summary Various butterflies select young foliage on which to lay their eggs; volatiles emitted by young and old leaves have been compared (by sorption enrichment, followed by GC-MS) to gauge possible qualitative and quantitative differences between the two age groups. The plants investigated are cabbage (Brassica oleracea), two milkweeds (Asclepias syriaca andA. curassavica), the bitter orange (Citrus aurantium) and the lime (C. aurantiifolia). The chemical compounds identified belong to three classes, isoprenoids, fatty acid derivatives and benzenoids. Quantitative differences were found between young and old leaves, of which a few may be characteristic of young leaves only. Thirty-four single trials withDanaus plexippus exposed to volatiles from young and old leaves are recorded. 相似文献
43.
Diet induced differences in carbon isotope fractionation between sirenians and terrestrial ungulates
Carbon isotope differences (Δ13C) between bioapatite and diet, collagen and diet, and bioapatite and collagen were calculated for four species of sirenians,
Dugong dugon (Müller), Trichechus manatus (Linnaeus), Trichechus inunguis (Natterer), and the extinct Hydrodamalis gigas (Zimmerman). Bone and tooth samples were taken from archived materials collected from populations during the mid eighteenth
century (H. gigas), between 1978 and 1984 (T. manatus, T. inunguis), and between 1997 and 1999 (D. dugon). Mean Δ13C values were compared with those for terrestrial ungulates, carnivores, and six species of carnivorous marine mammals (cetaceans = 1;
pinnipeds = 4; mustelids = 1). Significant differences in mean δ13C values among species for all tissue types were detected that separated species or populations foraging on freshwater plants
or attached marine macroalgae (δ13C values < −6‰; Δ13Cbioapatite–diet ∼14‰) from those feeding on marine seagrasses (δ13C values > −4‰; Δ13Cbioapatite–diet ∼11‰). Likewise, Δ13Cbioapatite–collagen values for freshwater and algal-foraging species (∼7‰) were greater than those for seagrass-foraging species (∼5‰). Variation
in Δ13C values calculated between tissues and between tissues and diet among species may relate to the nutritional composition of
a species’ diet and the extent and type of microbial fermentation that occurs during digestion of different types of plants.
These results highlight the complications that can arise when making dietary interpretations without having first determined
species-specific Δ13Ctissue–diet values.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
44.
We investigated a case of massive feto-maternal bleeding by using negative magnetic cell sorting (MACS) and fluorescent in situ hybridization (FISH). A 37-year-old pregnant woman had an uncomplicated amniocentesis for advanced maternal age at 16 weeks' gestation. The fetal karyotype was 46, XY. At 19 weeks' gestation, she had a minor car accident and slight vaginal bleeding. A subsequent Kleihauer-Betke test showed a 140 ml feto-maternal haemorrhage. Serial sonographic examinations indicated a normal fetus and placenta. We performed FISH analysis on maternal peripheral blood at 25 weeks. Anti-CD45 and MACS were used to deplete maternal leucocytes, enriching the proportion of fetal nucleated erythrocytes present. The isolated cells were analysed by using dual-colour FISH with X and Y specific probes. Approximately 65 800 nucleated cells were obtained after MACS depletion. A total of 234 cells were analysed by FISH. The results revealed that 70 of the nucleated cells (30 per cent) were male with one X and one Y signal. Among these cells, six male metaphases were observed in spontaneously dividing cells. 相似文献
45.
David M. Mushet Laurie C. Alexander Micah Bennett Kate Schofield Jay R. Christensen Genevieve Ali Amina Pollard Ken Fritz Megan W. Lang 《Journal of the American Water Resources Association》2019,55(2):307-317
We describe a collection of aquatic and wetland habitats in an inland landscape, and their occurrence within a terrestrial matrix, as a “freshwater ecosystem mosaic” (FEM). Aquatic and wetland habitats in any FEM can vary widely, from permanently ponded lakes, to ephemerally ponded wetlands, to groundwater‐fed springs, to flowing rivers and streams. The terrestrial matrix can also vary, including in its influence on flows of energy, materials, and organisms among ecosystems. Biota occurring in a specific region are adapted to the unique opportunities and challenges presented by spatial and temporal patterns of habitat types inherent to each FEM. To persist in any given landscape, most species move to recolonize habitats and maintain mixtures of genetic materials. Species also connect habitats through time if they possess needed morphological, physiological, or behavioral traits to persist in a habitat through periods of unfavorable environmental conditions. By examining key spatial and temporal patterns underlying FEMs, and species‐specific adaptations to these patterns, a better understanding of the structural and functional connectivity of a landscape can be obtained. Fully including aquatic, wetland, and terrestrial habitats in FEMs facilitates adoption of the next generation of individual‐based models that integrate the principles of population, community, and ecosystem ecology. 相似文献
46.
Courtney G. Flint Elizabeth Wynn Travis Paveglio Amanda Boyd Cathy Bullock 《Journal of the American Water Resources Association》2019,55(5):1306-1322
Water is a salient issue in the Intermountain West of the United States (U.S.), with concerns ranging from water scarcity and drought to intermittent flooding and water quality risks. This paper investigates coverage of water issues across seven newspapers in the core of the U.S. Intermountain West region. Newspapers have the potential to set agendas and influence perceived salience of issues among consumers. The Intermountain West region shares common concerns about water supply and demand, climate change, and water quality. We investigate whether or not local daily newspaper coverage of water issues provides a more local or regional sensitivity. Findings from this exploratory study reveal differences in water coverage across local daily newspapers. The overall volume of water‐related articles differed across newspapers as did proportion of articles on specific water topics and connecting issues. Coverage of local issues was more dominant than might be expected given mass media trends, but water geography in articles extended across the U.S. and the world in every newspaper studied. Variations in newspaper coverage of water issues suggests more local nuance persists despite the experience of common water issues across the region. 相似文献
47.
Thomas W. Crawford Daniel J. Marcucci Andrew Bennett 《Journal of Coastal Conservation》2013,17(3):431-443
Coastal barrier environments are heavily influenced by human activities yet there are few examples of landscape ecological work investigating human dimensions of settlement disturbance patterns and processes. We investigated the impacts of residential development on vegetation cover for a remote roadless coastal barrier in Carova, North Carolina that is subject to policies from the federal to local levels and addressed three research questions: How has the region’s the policy history influenced patterns of residential parcel development? What are the spatial and temporal patterns of parcel development? How has development impacted patterns of barrier vegetation cover? We traced the influences of the federal 1982 Coastal Barrier Resources Act (CBRA) designed to discourage development in risky coastal areas as well as state/local coastal policies and employed remote sensing change detection, NDVI analysis and spatial analysis and regression techniques. Results showed an acceleration of new housing structures since 1990, contrary to the intended effects of CBRA. An estimated vegetation cover loss of 437 m2 was associated with each newly developed parcel. NDVI varied along spatial and temporal gradients with more recent development having lower NDVI than older development. Recently developed parcels were larger in area, closer to the beach, and contained houses with larger footprints compared to older developed parcels. Our approach represents a place-based analytical framework for coastal barrier landscapes. Beyond the Carova case study, adopting such an approach coupling natural and human systems for the entire eastern US barrier system requires defining a comprehensive set of coastal barrier spatial units to enable typological classification and subsequent systematic investigation to inform debates regarding coastal ecosystem services and sustainability. 相似文献
48.
49.
Quantifying species recovery and conservation success to develop an IUCN Green List of Species
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H. Resit Akçakaya Elizabeth L. Bennett Thomas M. Brooks Molly K. Grace Anna Heath Simon Hedges Craig Hilton‐Taylor Michael Hoffmann David A. Keith Barney Long David P. Mallon Erik Meijaard E.J. Milner‐Gulland Ana S.L. Rodrigues Jon Paul Rodriguez P.J. Stephenson Simon N. Stuart Richard P. Young 《Conservation biology》2018,32(5):1128-1138
Stopping declines in biodiversity is critically important, but it is only a first step toward achieving more ambitious conservation goals. The absence of an objective and practical definition of species recovery that is applicable across taxonomic groups leads to inconsistent targets in recovery plans and frustrates reporting and maximization of conservation impact. We devised a framework for comprehensively assessing species recovery and conservation success. We propose a definition of a fully recovered species that emphasizes viability, ecological functionality, and representation; and use counterfactual approaches to quantify degree of recovery. This allowed us to calculate a set of 4 conservation metrics that demonstrate impacts of conservation efforts to date (conservation legacy); identify dependence of a species on conservation actions (conservation dependence); quantify expected gains resulting from conservation action in the medium term (conservation gain); and specify requirements to achieve maximum plausible recovery over the long term (recovery potential). These metrics can incentivize the establishment and achievement of ambitious conservation targets. We illustrate their use by applying the framework to a vertebrate, an invertebrate, and a woody and an herbaceous plant. Our approach is a preliminary framework for an International Union for Conservation of Nature (IUCN) Green List of Species, which was mandated by a resolution of IUCN members in 2012. Although there are several challenges in applying our proposed framework to a wide range of species, we believe its further development, implementation, and integration with the IUCN Red List of Threatened Species will help catalyze a positive and ambitious vision for conservation that will drive sustained conservation action. 相似文献
50.