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61.
Elva J. H. Robinson Thomas O. Richardson Ana B. Sendova-Franks Ofer Feinerman Nigel R. Franks 《Behavioral ecology and sociobiology》2009,63(5):779-636
Ant colonies are factories within fortresses (Oster and Wilson 1978). They run on resources foraged from an outside world fraught with danger. On what basis do individual ants decide to leave the safety of the nest? We investigated the relative roles of social information (returning nestmates), individual experience and physiology (lipid stores/corpulence) in predicting which ants leave the nest and when. We monitored Temnothorax albipennis workers individually using passive radio-frequency identification technology, a novel procedure as applied to ants. This method allowed the matching of individual corpulence measurements to activity patterns of large numbers of individuals over several days. Social information and physiology are both good predictors of when an ant leaves the nest. Positive feedback from social information causes bouts of activity at the colony level. When certain social information is removed from the system by preventing ants returning, physiology best predicts which ants leave the nest and when. Individual experience is strongly related to physiology. A small number of lean individuals are responsible for most external trips. An individual’s nutrient status could be a useful cue in division of labour, especially when public information from other ants is unavailable. 相似文献
62.
Donelle M. Robinson Andrea S. Aspbury Caitlin R. Gabor 《Behavioral ecology and sociobiology》2008,62(5):705-711
Selection should favor strategies that reduce costs associated with spermatogenesis. This is especially true when males are
sympatric with closely related species, and must avoid heterospecific matings, as in the unisexual–bisexual species complex
of mollies. Male sailfin mollies, Poecilia latipinna, are sexually parasitized by Amazon mollies (P. formosa), and produce more sperm in the presence of female sailfin mollies than in the presence of Amazon mollies. We tested the
hypothesis that male sailfin mollies differentially expend sperm when mating with either conspecific or heterospecific females.
We measured sperm expenditure by determining the amount of sperm males have remaining after mating. Male sailfin mollies had
more sperm available after mating with female sailfin mollies than after mating with Amazon mollies. While this result could
indicate higher sperm expenditure to Amazon mollies, males mating with female sailfin mollies had more sperm available after
mating than their baseline sperm reserves. Spermiation, the last stage of spermatogenesis, could be triggered by physical
contact with females, and could increase sperm availability during mating. We examined the relationship between sperm availability
and the amount of time that males mated with females. We found that sperm availability increased as mating trial time increased
with female sailfin mollies, but not with Amazon mollies. Spermiation in the presence of conspecific female stimuli could
reduce physiological costs associated with spermatogenesis while increasing the amount and quality of sperm available for
sperm competition. We suggest that future studies examining sperm priming and expenditure should consider the potential for
spermiation. 相似文献
63.
The organisms living on and in the sea floor, the benthos, represent an important ecological group. Although some (shellfish) have an economic value, most do not, and so little long-term data are available. We have identified three sources of historic benthic data for the North Sea, a regional sea that has been subjected to multiple human impacts for at least several hundred years. Each dataset has its limitations, but by their use together some issues emerge. Wider community shifts were observed in the shorter term and a number of extirpations at the scale of the North Sea were seen over longer time scales. The extirpated taxa share a number of characteristics consistent with an effect of fisheries such as fragile morphology. We must concentrate now on furthering our understanding of the ecological significance of shifts in dominance of particular functional units and protecting those habitats and species most vulnerable to fisheries-driven extirpation. 相似文献
64.
Effects of short-term pH fluctuations on cadmium, nickel, lead, and zinc availability to ryegrass in a sewage sludge-amended field 总被引:7,自引:0,他引:7
In this field experiment, sewage sludge was applied at 0, 5, 10, and 50tha(-1), and the availability of Cd, Ni, Pb, and Zn was assessed both by ryegrass uptake and by DTPA extractions. The aim was to investigate the role of important soil parameters, particularly pH, on heavy metal availability. It was found that metal uptake and extractability increased significantly in the 50tha(-1) treatment. In the 16th week of the experiment there was a significant, although temporary, increase in DTPA-extractable Cd, Ni, and Zn concentrations. Metal concentrations in ryegrass were also significantly elevated in week 20 compared to the subsequent cuttings. These fluctuations in both DTPA and ryegrass uptake occurred only at 50tha(-1) and were probably induced by a sudden pH decrease measured in the same treatment in week 16. This suggests that soils which have received high applications of sewage sludge may be prone to fluctuations in metal availability. 相似文献
65.
Robinson DR Luke-Boone R Aggarwal V Harris B Anderson E Ranum D Kulp TJ Armstrong K Sommers R McRae TG Ritter K Siegell JH Van Pelt D Smylie M 《Journal of the Air & Waste Management Association (1995)》2007,57(7):803-810
Fugitive emissions account for approximately 50% of total hydrocarbon emissions from process plants. Federal and state regulations aiming at controlling these emissions require refineries and petrochemical plants in the United States to implement a Leak Detection and Repair Program (LDAR). The current regulatory work practice, U.S. Environment Protection Agency Method 21, requires designated components to be monitored individually at regular intervals. The annual costs of these LDAR programs in a typical refinery can exceed US$1,000,000. Previous studies have shown that a majority of controllable fugitive emissions come from a very small fraction of components. The Smart LDAR program aims to find cost-effective methods to monitor and reduce emissions from these large leakers. Optical gas imaging has been identified as one such technology that can help achieve this objective. This paper discusses a refinery evaluation of an instrument based on backscatter absorption gas imaging technology. This portable camera allows an operator to scan components more quickly and image gas leaks in real time. During the evaluation, the instrument was able to identify leaking components that were the source of 97% of the total mass emissions from leaks detected. More than 27,000 components were monitored. This was achieved in far less time than it would have taken using Method 21. In addition, the instrument was able to find leaks from components that are not required to be monitored by the current LDAR regulations. The technology principles and the parameters that affect instrument performance are also discussed in the paper. 相似文献
66.
An Ecology-Based Method for Defining Priorities for Large Mammal Conservation: The Tiger as Case Study 总被引:2,自引:0,他引:2
67.
Nicholas Andrew Robinson 《Conservation biology》1995,9(1):114-125
On mainland Australia, the eastern barred bandicoot, Perameles gunnii , is confined to a relic wild population numbering less than 100 individuals in the city of Hamilton. Animals derived from this population are being bred in captivity in order to promote their recovery. The species also exists in Tasmania, where tittle is known of its conservation and taxonomic status. Mitochondrial DNA variability was compared within and between populations of P. gunnii using restriction fragment length polymorphisms. Genetic variability was found to be high among P. gunnii in Hamilton compared to those in Tasmania (higher diversity index, nucleotide sequence divergence, and greater number of haplotypes), despite the known decline and subdivision of the Hamilton population. Restriction fragment length polymorphisms distinguished animals from the east and the west of Hamilton and from the north and south of Tasmania. Nucleotide sequence divergence was substantial (2.2–2.5%) between Hamilton and Tasmania. Implications are that captive breeding and reintroduction should be designed to genetically represent the structure within Hamilton in order to minimize inbreeding and that the introduction of Tasmanian P. gunnii would not benefit the Hamilton population. It is concluded that mitochondrial DNA markers clearly can provide useful information about the history and current status of endangered marsupial populations, to the benefit of conservation management. 相似文献
68.
69.
Rajkumar T Guesgen HW Robinson S Fisher GW 《Journal of the Air & Waste Management Association (1995)》2000,50(1):3-20
The problem of making quantitative assessments of the risks associated with human exposure to toxic contaminants in the environment is a pressing one. This study demonstrates the capability of a new computational technique involving the use of fuzzy logic and neural networks to produce realistic risk assessments. The systematic analysis of human exposure involves the use of measurements and models, the results of which are sometimes used in regulatory decisions or in the drafting of legislation. Because of limited scientific understanding, however, interpretation of models often involves substantial uncertainty. Extensive measurement programs can be very expensive. The high complexity and inherent heterogeneity of exposure analysis is still a major challenge. The approach to this challenge tested here is to use a new model incorporating sophisticated artificial intelligence algorithms. Exposure assessment often requires that a number of factors be evaluated, including exposure concentrations, intake rates, exposure times, and frequencies. These factors are incorporated into a system that can "learn" the relevant relationships based on a known data set. The results can then be applied to new data sets and thus be applied widely without the need for extensive measurements. In this analysis, an example is developed for human health risk through inhalation exposure to benzene from vehicular emissions in the cities of Auckland and Christchurch, New Zealand. Risk factors considered were inhaled contaminant concentration, age, body weight, and activity patterns of humans. Three major variables affecting the inhaled contaminant concentration were emissions (mainly from motor vehicles), meteorology (wind speed, temperature, and atmospheric stability), and site factors (hilly, flat, etc.). The results are preliminary and used principally to demonstrate the technique, but they are very encouraging. 相似文献
70.
The age at which worker honey bees begin foraging varies under different colony conditions. Previous studies have shown that
juvenile hormone (JH) mediates this behavioral plasticity, and that worker-worker interactions influence both JH titers and
age at first foraging. These results also indicated that the age at first foraging is delayed in the presence of foragers,
suggesting that colony age demography directly influences temporal division of labor. We tested this hypothesis by determining
whether behavioral or physiological development can be accelerated, delayed, or reversed by altering colony age structure.
In three out of three trials, earlier onset of foraging was induced in colonies depleted of foragers compared to colonies
depleted of an equal number of bees across all age classes. In two out of three trials, delayed onset of foraging was induced
in colonies in which foragers were confined compared to colonies with free-flying foragers. Finally, in three out of three
trials, both endocrine and exocrine changes associated with reversion from foraging to brood care were induced in colonies
composed of all old bees and devoid of brood; JH titers decreased and hypopharyngeal glands regenerated. These results demonstrate
that plasticity in age-related division of labor in honey bee colonies is at least partially controlled by social factors.
The implications of these results are discussed for the recently developed ‘‘activator-inhibitor” model for honey bee behavioral
development.
Received: 8 November 1995/Accepted after revision: 10 May 1996 相似文献