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51.
Cross-infection experiments were performed to determine the influence of temperature on infection rate in the Chondrus crispus Stackhouse-Petersenia pollagaster (Petersen) Sparrow pathosystem. C. crispus thalli were collected at Pubnico Harbor, Nova Scotia, Canada in the fall of 1981 to 1984. Infective zoospores were used to inoculate healthy thalli at five different temperatures. The highest infection rate was obtained at 20°C, while significantly lower rates were obtained at temperature extremes. The parasite's life cycle, consisting of infection of healthy thalli, endobiotic development, and release of zoospores, was completed in 48 to 72 h at 15° to 20°C. 相似文献
52.
Nadine C. Chapman Benjamin P. Oldroyd William O. H. Hughes 《Behavioral ecology and sociobiology》2007,61(8):1185-1194
Which task a social insect worker engages in is influenced by the worker’s age, genotype and the colony’s needs. In the honeybee,
Apis mellifera, genotype influences both the age a worker switches tasks and its propensity of engaging in specialist tasks, such as water
collecting, which only some workers will perform. In this study, we used colonies with natural levels of genetic diversity
and manipulated colony age demography to drastically increase the stimuli for the generalist tasks of foraging and nursing,
which all workers are thought to engage in at some point in their lives. We examined the representation of worker patrilines
engaged in nursing and foraging before and after the perturbation. The representation of patrilines among foragers and nurses
differed from that of their overall colony’s population. In the case of foraging, over- and underrepresentation of some patrilines
was not simply due to differences in rates of development among patrilines. We show that replacement foragers tend to be drawn
from patrilines that were overrepresented among foragers before the perturbation, suggesting that there is a genetic component
to the tendency to engage in foraging. In contrast, the representation of patrilines in replacement nurses differed from that
in the unperturbed nursing population. Our results show that there is a genetic influence on even the generalist tasks of
foraging and nursing, and that the way patrilines in genetically diverse colonies respond to increases in task stimuli depends
upon the task. The possible significance of this genetic influence on task allocation is discussed.
Electronic supplementary material Supplementary material is available in the online version of this article at doi: and is accessible to authorized users. 相似文献
53.
Welton RG Cuthbert SJ Mclean R Hursthouse A Hughes J 《Environmental geochemistry and health》2003,25(1):139-145
For many years it has been realised that the weathering of stone is not merely determined by physical and chemical factors but also by biological agents. When the stone in question is a historic building or monument, the damage done constitutes an irretrievable loss of our heritage and history. Laboratory studies have commenced in Paisley to study the effect of photoautotrophs on the major sedimentary rock forming minerals, with a view to expanding this work to study the overall effect of these micro-organisms on heritage masonry. Tests were carried out on Albite, Calcite, Dolomite, Orthoclase, Siderite and Quartz, using axenic cultures of the following: Chlorella vulgaris, Chlorococcum tetrasporum, Scenedesmus obliquus, Oocystis marsonii, Stichococcus bacillaris. The rock chips were immersed in either water or bolds basal media and exposed to a mix of the micro-organisms listed above and then tested weekly for their pH, fortnightly for the waters chemical composition using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and visually utilising the universitys SEM facilities. Work so far has revealed biologically mediated etching of minerals, a well-defined pH profile over a period of 90 days, as well as a variety of elemental release patterns for the different minerals. 相似文献
54.
This study examined the occurrence and effects of inbreeding in the sessile, colonial hermaphrodite Celleporella hyalina. The results are discussed with regard to theoretical explanations for the prevalence of hermaphroditism in sessile clonal organisms. C. hyalina exhibited inbreeding depression at all stages, including the pre-zygotic. Outcrossing, sib and half-sib matings produced offspring but selfing did not. There was inbreeding depression in embryo production and survival. Inbred colonies showed slower growth and later maturation, with fewer reproductive zooids. The relative numbers of male and female zooids were affected by inbreeding; increased production of males is a sign of stress in C. hyalina. When mated with an outbred non-relative, inbred colonies had lower success both as males and as females in embryo production and offspring survivorship. The low survivorship of embryos fathered by inbred colonies is a clear effect of inbreeding on the F2 generation. These results indicate that C. hyalina is unlikely to inbreed in the wild, supporting the "space-limited" model of hermaphroditism for this species. This study indicates that hermaphroditism, by avoiding much of the cost of sex, can confer optimal reproductive fitness for sessile brooding animals in a space-limited habitat even in the absence of inbreeding. 相似文献
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Jonathan E. Hughes 《Journal of Environmental Economics and Management》2011,62(2):123-139
This paper provides evidence of market power in the transportation of ethanol used in reformulated gasoline and alternative transportation fuels. I estimate a reduced form model for railroad route-level prices. My identification strategy instruments for railroad entry, controls for selection and explicitly models capacity constraints. A detailed understanding of this industry is important because U.S. environmental policies seek to substantially expand ethanol use. Evidence of market power may alter the types of policies pursued by lawmakers. I find that ethanol shipment prices are lower for more competitive routes. I also find evidence that railroads price discriminate based on environmental regulation at route destinations. Monopolist prices for shipments to carbon monoxide non-attainment areas are 3% higher than shipments to other destinations. This price premium falls sharply with increased competition. This suggests a perverse result where environmental regulation increases the price of a clean input. 相似文献
59.
加速溶剂萃取-固相萃取净化-高效液相色谱法测定玉米作物中多环芳烃含量 总被引:1,自引:0,他引:1
建立了加速溶剂萃取-固相萃取净化-高效液相色谱测定玉米作物中15种多环芳烃的方法,优化了试验条件.方法线性关系良好,15种多环芳烃的检出限在0.003 8~0.079μg/kg之间,空白加标试验的相对标准偏差在3.9%~11.7%之间,基质加标回收率在69.3%~115.3%之间.实际样品的测定结果表明,该方法分离效果... 相似文献
60.
为了解可吸入颗粒物污染水平与气象因素之间的关系,从2008年9月—2010年2月采集乌鲁木齐市可吸入颗粒物样品,并对其随时间的变化特征及其与气象因素之间的相关性进行了统计分析。结果表明,采样时间内可吸入颗粒物中PM2.5和PM2.5-10的质量浓度的范围分别为38.2~468.7μg/m3和20.8~243.1μg/m3,平均浓度分别为134.2μg/m3和69.2μg/m3。可吸入颗粒物同时受几种气象因素的影响,其浓度与温度、能见度、风速呈负相关,与湿度呈正相关。 相似文献