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31.
The Cambro-Ordovician anomalocaridids are large ecdysozoans commonly regarded as ancestors of the arthropods and apex predators. Predation is indicated partly by the presence of an unusual “peytoia”-type oral cone, which is a tetraradial outer ring of 32 plates, four of which are enlarged and in perpendicular arrangement. This oral cone morphology was considered a highly consistent and defining characteristic of well-known Burgess Shale taxa. It is here shown that Anomalocaris has a different oral cone, with only three large plates and a variable number of smaller and medium plates. Its functional morphology suggests that suction, rather than biting, was used for food ingestion, and that anomalocaridids in general employed a range of different scavenging and predatory feeding strategies. Removing anomalocaridids from the position of highly specialized trilobite predators forces a reconsideration of the ecological structure of the earliest marine animal communities in the Cambrian. 相似文献
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Environmental sanitation programmes are vital for tackling environmental-related disease and ensuring human dignity in emergency situations. If they are to have maximum impact they must be planned in a rapid but systematic manner. An appropriate planning process comprises five key stages: rapid assessment and priority setting; outline programme design; immediate action; detailed programme design; and implementation. The assessment should be based on carefully selected data, which are analysed via comparison with suitable minimum objectives. How the intervention should be prioritised is determined through objective ranking of different environmental sanitation sector needs. Next, a programme design outline is produced to identify immediate and longer-term intervention activities and to guarantee that apposite resources are made available. Immediate action is taken to meet acute emergency needs while the detailed programme design takes shape. This entails in-depth consultation with the affected community and comprehensive planning of activities and resource requirements. Implementation can then begin, which should involve pertinent management and monitoring strategies. 相似文献
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The role of organic solutes in the osmotic adjustment processes of the marine macroalga Enteromorpha intestinalis (L.) Link was investigated in 1986, using fresh samples collected from mid-shore rock pools at Tayport, Fife, Scotland. Natural-abundance 13C nuclear magnetic-resonance spectroscopy revealed -dimethylsulphoniopropionate (DMSP) to be the only major low molecular weight organic osmolyte present. However, on transfer to a hypersaline medium (300% sea water; 100%=35 S), tissue sucrose and proline levels increased markedly, while DMSP remained constant. Recovery of optimal photosynthetic activity and increases in inorganic ion levels occurred over a similar time scale to the changes in sucrose and proline (within 48 h), indicating that these two organic solutes are involved in hyperosmotic adjustment in E. intestinalis while DMSP is not. Freshly-collected plants transferred to 300% sea water medium in the dark showed no significant increases in organic osmolytes. In contrast, starch-enrichment (16 d continuous illumination) led to enhanced synthesis of sucrose and proline in the light and in darkness, but tissue DMSP levels showed no variation throughout. These observations suggest that DMSP is not involved in short-term osmoacclimation in E. intestinalis. 相似文献
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Minimizing opportunity costs to aquatic connectivity restoration while controlling an invasive species
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Austin W. Milt Matthew W. Diebel Patrick J. Doran Michael C. Ferris Matthew Herbert Mary L. Khoury Allison T. Moody Thomas M. Neeson Jared Ross Ted Treska Jesse R. O'Hanley Lisa Walter Steven R. Wangen Eugene Yacobson Peter B. McIntyre 《Conservation biology》2018,32(4):894-904
Controlling invasive species is critical for conservation but can have unintended consequences for native species and divert resources away from other efforts. This dilemma occurs on a grand scale in the North American Great Lakes, where dams and culverts block tributary access to habitat of desirable fish species and are a lynchpin of long‐standing efforts to limit ecological damage inflicted by the invasive, parasitic sea lamprey (Petromyzon marinus). Habitat restoration and sea‐lamprey control create conflicting goals for managing aging infrastructure. We used optimization to minimize opportunity costs of habitat gains for 37 desirable migratory fishes that arose from restricting sea lamprey access (0–25% increase) when selecting barriers for removal under a limited budget (US$1–105 million). Imposing limits on sea lamprey habitat reduced gains in tributary access for desirable species by 15–50% relative to an unconstrained scenario. Additional investment to offset the effect of limiting sea‐lamprey access resulted in high opportunity costs for 30 of 37 species (e.g., an additional US$20–80 million for lake sturgeon [Acipenser fulvescens]) and often required ≥5% increase in sea‐lamprey access to identify barrier‐removal solutions adhering to the budget and limiting access. Narrowly distributed species exhibited the highest opportunity costs but benefited more at less cost when small increases in sea‐lamprey access were allowed. Our results illustrate the value of optimization in limiting opportunity costs when balancing invasion control against restoration benefits for diverse desirable species. Such trade‐off analyses are essential to the restoration of connectivity within fragmented rivers without unleashing invaders. 相似文献
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The establishment of protected areas is a critical strategy for conserving biodiversity. Key policy directives like the Aichi targets seek to expand protected areas to 17% of Earth's land surface, with calls by some conservation biologists for much more. However, in places such as the United States, Germany, and Australia, attempts to increase protected areas are meeting strong resistance from communities, industry groups, and governments. We examined case studies of such resistance in Victoria, Australia, Bavaria, Germany, and Florida, United States. We considered 4 ways to tackle this problem. First, broaden the case for protected areas beyond nature conservation to include economic, human health, and other benefits, and translate these into a persuasive business case for protected areas. Second, better communicate the conservation values of protected areas. This should include highlighting how many species, communities, and ecosystems have been conserved by protected areas and the counterfactual (i.e., what would have been lost without protected area establishment). Third, consider zoning of activities to ensure the maintenance of effective management. Finally, remind citizens to think about conservation when they vote, including holding politicians accountable for their environmental promises. Without tackling resistance to expanding the protected estate, it will be impossible to reach conservation targets, and this will undermine attempts to stem the global extinction crisis. 相似文献
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This paper examines the distribution of areas burned in forest fires. Empirical size distributions, derived from extensive fire records, for six regions in North America are presented. While they show some commonalities, it appears that a simple power-law distribution of sizes, as has been suggested by some authors, is too simple to describe the distributions over their full range. A stochastic model for the spread and extinguishment of fires is used to examine conditions for power-law behaviour and deviations from it. The concept of the extinguishment growth rate ratio (EGRR) is developed. A null model with constant EGRR leads to a power-law distribution, but this does not appear to hold empirically for the data sets examined. Some alternative parametric forms for the size distribution are presented, with a four-parameter ‘competing hazards’ model providing the overall best fit. 相似文献
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