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411.
D. W. Phillips 《Marine Biology》1978,49(3):237-243
When the predatory sea star Pycnopodia helianthoides was placed upstream, the sea urchin Strongylocentrotus purpuratus responded defensively by extending and opening its globiferous pedicellariae. No pedicellaria response was given in control seawater or when the sea star was downstream. The snail Tegula funebralis responded by moving up vertical surfaces when Pycnopodia helianthoides or when Pisaster ochraceus were placed upstream. When these sea stars were introduced downstream, the snail's response was not significantly different from that in control seawater. Water collected from an aquarium containing a single sea star was sufficient to trigger the response of S. purpuratus and T. funebralis; the physical presence of the sea star was not essential. This indicated that a chemical stimulus was involved, and the lack of responses when sea stars were downstream argued strongly against the possible additional involvement of visual or vibrational stimuli. S. purpuratus gave stronger pedicellaria responses to water flowing over an active Pycnopodia helianthoides than to water flowing over the same sea star when it was inactive. The significance of the ability to distinguish between actively foraging and inactive predators is discussed, and a mechanism is proposed to explain differences in the amount of stimulatory chemicals released by active and inactive sea stars. 相似文献
412.
Disappearance and dispersal of Spermophilus elegans juveniles in relation to behavior 总被引:1,自引:0,他引:1
Sharon Pfeifer 《Behavioral ecology and sociobiology》1982,10(4):237-243
Summary Patterns of disappearance and dispersal of Spermophilus elegans juveniles during the first 6-weeks postemergence were compared for 1977 and 1978 and related to quantitative and qualitative changes in social interaction involving juveniles.Juvenile disappearance (emigration or mortality) and dispersal within the study site varied between the sexes within and between years. Female disappearance and dispersal were significantly greater in 1977, and male losses in 1978 significantly exceeded male losses in 1977. Greater female loss in 1977 resulted in total male — female losses being equivalent, whereas in 1978 juvenile loss was strongly biased toward males by the end of the 6-week period.Greater female loss in 1977 was attributed primarily to increased aggression between female juveniles in that year because of larger average litter size with more females per litter. Increased disappearance of males in 1978 showed no correlation with litter size or relative increase in number of males per litter. Male young interacted with individuals of several age/sex classes, and a possible behavioral influence on male disappearance was increased aggressiveness by yearling males toward juvenile males in 1978.Behavior appeared to act as a proximate factor in juvenile disappearance and dispersal, and the observed differences between how male and female juveniles interacted in 1977 and 1978 were hypothesized to reflect the operation of different selective pressures to increase individual male or female fitness. 相似文献
413.
414.
Biological research has established that air pollution can affect the yield and quality of agricultural crops. Economic assessments of crop exposure to air pollution have focused on the yield effect. This study illustrates the implications of considering crop quality effects in addition to crop yield changes for the case of O3 impacts on soybeans. An economic model of US soybean, soybean oil, and soybean meal markets is used to simulate the impacts of increased soybean yields due to reduced O3 concentrations with and without changes in soybean quality. The simulations with quality effects are richer in their distributional implications and show larger increases in economic surplus than the simulations with yield effects only. 相似文献
415.
Integrated assessment of the impacts of agricultural drainwater in the Salinas River (California,USA) 总被引:5,自引:0,他引:5
Anderson BS Hunt JW Phillips BM Nicely PA Vlaming Vd Connor V Richard N Tjeerdema RS 《Environmental pollution (Barking, Essex : 1987)》2003,124(3):523-532
The Salinas River is the largest of the three rivers that drain into the Monterey Bay National Marine Sanctuary in central California. Large areas of this watershed are cultivated year-round in row crops and previous laboratory studies have demonstrated that acute toxicity of agricultural drainwater to Ceriodaphnia dubia is caused by the organophosphate (OP) pesticides chlorpyrifos and diazinon. In the current study, we used a combination of ecotoxicologic tools to investigate incidence of chemical contamination and toxicity in waters and sediments in the river downstream of a previously uncharacterized agricultural drainage creek system. Water column toxicity was investigated using a cladoceran C. dubia while sediment toxicity was investigated using an amphipod Hyalella azteca. Ecological impacts of drainwater were investigated using bioassessments of macroinvertebrate community structure. The results indicated that Salinas River water downstream of the agricultural drain is acutely toxic to Ceriodaphnia, and toxicity to this species was highly correlated with combined toxic units (TUs) of chlorpyrifos and diazinon. Laboratory tests were used to demonstrate that sediments in this system were acutely toxic to H. azteca, which is a resident genus. Macroinvertebrate community structure was moderately impacted downstream of the agricultural drain input. While the lowest macroinvertebrate abundances were measured at the station demonstrating the greatest water column and sediment toxicity and the highest concentrations of pesticides, macroinvertebrate metrics were more significantly correlated with bank vegetation cover than any other variable. Results of this study suggest that pesticide pollution is the likely cause of laboratory-measured toxicity in the Salinas River samples and that this factor may interact with other factors to impact the macroinvertebrate community in the system. 相似文献
416.
M. Kernan M. Hughes D. Hornby H. Bennion J. Hilton G. Phillips R. Thomas 《Water, Air, & Soil Pollution: Focus》2004,4(2-3):97-112
Previous attempts to identify regions of Britain vulnerable to acidification have used sensitivity maps based on the distributionof soils, geology, and land cover across Great Britain. Additionally, a systematic survey of freshwaters undertaken as partof the U.K. critical loads mapping programme provides a regional assessment of both sensitivity (critical loads) and, in tandem withdeposition data, potential impact (critical load exceedance). Both approaches, while useful for identifying regional patterns, do not enable estimates of the number of affected water bodies to be made. Recent EU legislation (e.g., The Water Framework Directive) requires member states to set water quality objectives for all water bodies. We developed a GIS-based inventory of standing water bodies in response to the need for legislation-driven assessments of the status of the U.K. lake population. This paper describes how the inventory can be used to assess the number of standing water bodies in Britain that are vulnerable to acid deposition (at current levels), building on the sensitivity mapping undertaken previously. Using this approach, approximately 31% of all standing waters in Great Britain (excluding the Shetlands and Orkney) larger than 0.02 ha are identified as `at risk' from acidification. Higher proportions are vulnerable in Scotland and Wales. Additionally, large numbers of standing waters in areas designated for environmental protection purposes are also vulnerable. 相似文献
417.
Patrick J. Phillips David A. Eckhardt Douglas A. Freehafer Gary R. Wall Hannah H. Ingleston 《Journal of the American Water Resources Association》2002,38(3):731-745
ABSTRACT: The predominant mixtures of pesticides found in New York surface waters consist of five principal components. First, herbicides commonly used on corn (atrazine, metolachlor, alachlor, cyanazine) and a herbicide degradate (deethylatrazine) were positively correlated to a corn‐herbicide component, and watersheds with the highest corn‐herbicide component scores were those in which large amounts of row crops are grown. Second, two insecticides (diazinon and carbaryl) and one herbicide (prometon) widely used in urban and residential settings were positively correlated to an urban/residential component. Watersheds with the highest urban/residential component scores were those with large amounts of urban and residential land use. A third component was related to two herbicides (EPTC and cyanazine) used on dry beans and corn, the fourth to an herbicide (simazine) and an insecticide (carbaryl) commonly used in orchards and vineyards, and the fifth to an herbicide (DCPA). Results of this study indicate that this approach can be used to: (1) identify common mixtures of pesticides in surface waters, (2) relate these mixtures to land use and pesticide applications, and (3) indicate regions where these mixtures of pesticides are commonly found. 相似文献
418.
当主流商学院开始将更多的企业社会责任(CSR)话题带入教室时,一些教育家仍认为这些机构的努力不够。他们相信,现在所需要的,是围绕可持续发展概念来确定MBA教学大纲,大纲仍然讲授基础科目,但要染上绿色。 相似文献
419.
The present report describes methods to separate, culture, and study syncytio-cytotrophoblast and mesenchymal core of the first-trimester human chorionic villus. The cultured outer layer cells (syncytio-cytotrophoblast) are multinucleated, pleomorphic, and active in the formation of human chorionic gonadotrophin (hCG). The mesenchymal core cells are more fibroblast-like in appearance, do not show multinucleation, and have less hCG in their culture media. Both cultured cell types express HLA (ABC) Class I histocompatibility antigens but not HLA (DR) Class II antigens. These and previous studies from this laboratory postulate different embryonic origins: (1) Syncytio-cytotrophoblast cultures of chorionic villus derive from differentiated trophoblast and preserve multinucleation as well as hCG hormone function. (2) Cells cultured from the chorionic villus core originate from extraembryonic mesenchyme. (3) Amniocytes (AF cells) cultured from amniotic fluid resemble the multipotential and early-stage trophoblast, retaining pleomorphism, multinucleation, and lacunae formation as well as production of hCG, progesterone, oestrogen, basement membrane glycoprotein, and Type IV collagen. These cell types cultured from the chorionic villus and amniotic fluid provide a means for in vitro study of specific embryonic cell lineages. 相似文献
420.
Allison C. Alberts Jeffrey M. Lemm Andrew M. Perry Lisa A. Morici John A. Phillips 《Behavioral ecology and sociobiology》2002,51(4):324-335
In small, insular populations, behavioral patterns that lead to increased variance in individual reproductive success can
accelerate loss of genetic variation. Over a 1-year period, we documented behavior and hormone levels in a breeding group
of adult Cuban iguanas (Cyclura
nubila) at Guantánamo Bay. Male dominance was associated with body and head size, display behavior, testosterone levels, home-range
size, and proximity to females. Based on their success in agonistic encounters, we ranked males in a linear dominance hierarchy.
During the subsequent breeding season, we conducted a removal experiment in which the five highest-ranking males were temporarily
relocated from the study site. Although we were unable to assess reproductive success directly, previously lower-ranking males
assumed control of vacated territories, won more fights, and increased their proximity to females in the absence of the dominant
males. When it results in greater mating opportunities for otherwise socially suppressed individuals, temporary alteration
of local social structure may help limit erosion of genetic variation in small, insular populations.
Electronic Publication 相似文献