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51.
Nestmate recognition is a critical element in social insect organization, providing a means to maintain territoriality and
close the colony to parasites and predators. Ants detect the colony chemical label via their antennae and respond to the label
mismatch of an intruder with aggressive behavior. In the fire ant, Solenopsis invicta, worker ability to recognize conspecific nonnestmates decreases if the colony queen is removed, such that they do not recognize
conspecific nonnestmates as different. Here, we tested the hypothesis that the presence of the colony queen influences the
concentration of octopamine, a neuromodulator, in worker ants, which in turn has an effect on nestmate recognition acuity
in workers. We demonstrate that queenless workers exhibit reduced brain octopamine levels and reduced discriminatory acuteness;
however, feeding queenless workers octopamine restored both. Dopamine levels are influenced by honeybee queen pheromones;
however, levels of this biogenic amine were unchanged in our experiments. This is the first demonstration of a link between
the presence of the colony queen, a worker biogenic amine, and conspecific nestmate recognition, a powerful expression of
colony cohesion and territoriality. 相似文献
52.
M. R. Phillips E. J. Abraham A. T. Williams C. House 《Journal of Coastal Conservation》2007,11(3):159-170
Fifteen beaches from the Swansea Bay coastal sediment cell, South Wales, UK, were analysed via function analysis, involving
assessment of specific environmental and socio-economic indicators. These were allocated scores from field surveys and extensive
desktop studies, which included beach awards, relevant shoreline management plans, planning and conservation designations
and current legislation. Normalised scores allowed production of a conservation/development matrix, enabling beach location
in conservation, development or conflict fields, which results appropriately identified. Conservation field beaches tended
to have a low density residential hinterland with little or no commercialisation. Conversely, beaches that leant towards the
development field had a high density residential hinterland and were highly commercialised. Evaluation showed the importance
of planning legislation in conflict areas and identified locations of development potential, where significant environmental
consequences would be unlikely. This representation could be used for evolution of conservation/development status within
coastal areas, enabling policy adjustment as necessary. It will also enable future sustainability assessment and it is suggested
that indicators could be modified to reduce environmental emphasis and provide a more uniform socio-economic consideration. 相似文献
53.
Ultrastructural and chemical characterization of egg surface of honeybee worker and queen-laid eggs 总被引:3,自引:0,他引:3
Tamar?Katzav-GozanskyEmail author Victoria?Soroker Josef?Kamer Claudia?M.?Schulz Wittko?Francke Abraham?Hefetz 《Chemoecology》2003,13(3):129-134
Summary. Worker policing in honeybees predicts the
evolution of a mechanism to discriminate between queenand
worker-born eggs. Although it has been postulated that
this discrimination is based on an egg recognition
pheromone, neither the chemistry nor the glandular source
were elucidated. To verify whether egg discrimination might
be based on structural differences, we compared the ultrastructure
surface of queen-laid diploid and haploid eggs to
that of worker-laid eggs using SEM. Only small differences
between the different types of eggs were found. Thus, at
least based on the fine structure of the egg surface, queen
eggs are indistinguishable from worker-laid eggs.To explore the chemosensory hypothesis for egg discrimination,
we conducted a detailed comparative chemical
analysis of the different egg types. The coating of all egg
types was dominated by linear alkanes, but queen eggs,
diploid and haploid, differed from those of workers on two
accounts: 1. The diversity of compounds found on queenlaid
eggs was much greater than found on worker-laid eggs,
mainly due to the number of hydrocarbons. 2. Acetates of
some fatty alcohols, alkenes and especially monomethylalkanes
were characteristic to queen eggs. The origin of the
two latter substances and the acetates is still unknown.
Whether these compounds constitute the signal that enables
police workers to discriminate between queen- and workerborn
eggs remains to be investigated. 相似文献
54.
The model of Dewanji and Kalbfleisch for the estimation of time to tumour onset from a serial-sacrifice experiment is extended to include a marker state prior to the onset of the tumour. There are two versions of the model, one where a tumour is allowed to develop without the onset of marker, the other where a tumour develops after the marker but in which the marker later becomes unobservable. 相似文献
55.
The limits to economic growth due to resource scarcity can be alleviated only by the development of backstop substitutes. This paper combines resource-based economic growth with R&D to reduce the cost of backstop technologies. Characterizing the entire dynamics of optimal growth and R&D processes, we find that an economy's growth prospects depend on its type, as determined by its production technology and learning ability, and by its knowledge–capital endowment. A wide variety of growth patterns emerges, ranging from cases in which an economy that without R&D eventually stagnates (converges to a steady state) is diverted by R&D onto a path of sustained growth, to cases in which R&D is not warranted. Resource scarcity is shown to encourage R&D due to the increased reliance on the backstop technology. 相似文献
56.
Alexis Pashkevich Timur Pavluk Abraham Bij De Vaate 《Environmental monitoring and assessment》1996,40(2):143-156
Before using macroinvertebrates in water quality assessment in the Chusovaya River (Russia, the Urals, 50°55N, 60° E), preliminary results of three sampling methods were compared: handnet, circular shovel and a standardized artificial substrate sampler. The artificial substrate consisted of glass marbles ( 20 mm). To compare the efficiency of these sampling methods the total numbers of taxa found at each location per sampling data were considered to be 100%. The highest efficiency was reached with the artificial substrate sampler. 75–100% of the taxa at the different locations were collected with this sampler. Only 5–19% and 10–20% of the taxa at each location per sampling date were collected with the circular shovel in the sand and gravel substrate respectively, being the lowest efficiency. Intermediate results were obtained with the hand net. 23–38% of the taxa were collected with this net. Based on these results and requirements placed upon sampling methods in general, the standardized artificial substrate sampler has been considered to be an optimal sampling device for macroinvertebrates in biological monitoring. 相似文献
57.
Land use and socioeconomic influences on a vulnerable freshwater resource in northern New England, United States 总被引:1,自引:0,他引:1
Firooza Pavri Anna Springsteen Abraham Dailey Jean D. MacRae 《Environment, Development and Sustainability》2013,15(3):625-643
Land use and cover conversions as well as climatic factors drive current and future threats to freshwater systems. Research from the United States and across the globe has focused on already threatened and degraded freshwater systems, whose recovery requires significant investments. Attention must also be directed to monitoring freshwater systems that may appear robust, yet are likely to face enhanced vulnerabilities in the future due to climate and land use and cover changes. Such proactive monitoring can help identify problems early and provide potential solutions. In this study, we consider the case of Sebago Lake and its watershed in southern Maine; a region that has experienced significant population growth and development activity. Land use, socioeconomic change and water quality trends are monitored over a 20-year period using Landsat imagery, census, water quality and precipitation data. Our results indicate that Developed Land within the watershed has increased from 5.4 % of the total land area in 1987 to 8.9 % in 2009 with associated increases in population and housing activity. Sebago Lake’s water quality indicators from 1990 to 2010 show a directional trend concomitant with this change. The increase in Developed Land is likely to place additional pressures on water quality in the future. The analysis also indicates that precipitation trends play an important role in water quality variability for Sebago Lake. Predicted changes to climatic factors including enhanced spring time precipitation or earlier ice-out conditions combined with further land use change may play an influential role in determining water quality. The analysis highlights emerging areas of concern and reiterates the essential role of proactively monitoring vulnerable systems to help mitigate future threats. 相似文献
58.
Houtman CJ Booij P Jover E Pascual del Rio D Swart K van Velzen M Vreuls R Legler J Brouwer A Lamoree MH 《Chemosphere》2006,65(11):2244-2252
The identity of compounds responsible for estrogenic and dioxin-like activities in sediment from the harbour of the small town Zierikzee in Zeeland, The Netherlands, was investigated using a bioassay directed fractionation approach with the in vitro estrogen and dioxin responsive reporter gene assays ER- and DR-CALUX. For identification of compounds exhibiting activity in the bioassays, either one or two-dimensional GC in combination with quadrupole (MSD), ion trap (ITD) or time-of-flight mass spectrometric detection (ToF-MS) was used, depending on the biological and chemical characteristics and the complexity of the fractions. The natural estrogenic hormone 17-β-estradiol and its metabolite estrone were identified with GC–ITD as the main contributors to the estrogenic activity. After successive rounds of fractionation, the dioxin-like activity could be explained by the presence of various polycyclic aromatic hydrocarbons identified with GC–MSD and two-dimensional comprehensive GC × GC–ToF-MS. Some estrogenic activity of a relatively non-polar nature remained unidentified. 相似文献
59.
Wolf-Rainer Abraham Heinrich Lünsdorf Carsten Strömpl Balbina Nogales Edward R. B. Moore Kenneth N. Timmis 《Water, Air, & Soil Pollution: Focus》2003,3(3):57-64
A moorland soil site polluted with PCB showed a high diversity ofmetabolically active bacteria. Beside frequent types of 16S rRNAsequences similar to those of the species ofSphingomonasand the Acidobacterium phylum an unusual high number ofsequences from the genus Burkholderia were found. Burkholderia was also the main genus in isolates enriched onbiphenyl or various chlorobenzoates. In microcosm experimentssterilized surfaces exposed to PCB polluted soil always showed thepresence of clay aggregates formed by bacteria attached to thesubstratum. The bacteria use the PCB loaded clay colloids astransport medium for the water insoluble substrate to get accessto the carbon source. This is a novel mechanism of how bacteria dealwith hydrophobic substrates. 相似文献
60.