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181.
Effects of the bipyridylium herbicide diquat and tank-mix adjuvant Agral((R))90 were investigated on various life history traits of the freshwater pulmonate snail Lymnaea stagnalis. Trait expression was measured in simple laboratory bioassays on small size groups of snails, and under more complex, indoor microcosm conditions, on larger groups of snails. Microcosms were provided with sediment, plants, and fish, thus allowing a more complex level of intra and inter-specific interactions to develop. Treatments were performed with substances alone or in mixture, at concentrations ranging from 4.4 to 222.2mugl(-1) for diquat, and from 10 to 500mugl(-1) for Agral 90, under a fixed ratio design. Adult growth was negatively affected by diquat and its mixture with Agral 90 both at the highest concentrations (222.2 and 500mugl(-1), respectively). Fecundity expressed differently in bioassays and microcosms, but no effect of the chemicals could be observed on this trait. Progeny development was impaired by 222.2mugl(-1) diquat and its mixture with 500mugl(-1) Agral 90, as reflected by longer development time and reduced hatching rate of clutches laid by the exposed animals, as compared to the controls. Hatching data suggested that diquat bioavailability was lower in microcosms than under bioassay conditions. Consistently, chemical analysis showed that diquat disappeared more rapidly from the water in microcosms than in bioassays. Moreover, the differential expression of several life history traits under bioassays and microcosms conditions was probably also influenced by the level of intraspecific interaction, which differed among the systems. When significant, the effect of diquat was attenuated by the presence of Agral 90, indicating antagonistic interaction between the two substances. Such a deviation from additivity was partly validated statistically. 相似文献
182.
This paper provides an overview of the state of municipal solid waste (MSW) management in the capital of Cameroon, Yaoundé, and suggests some possible solutions for its improvement. The institutional, financial, and physical aspects of MSW management, as well as the livelihoods of the population, were analyzed. Our study revealed that distances and lack of infrastructure have a major impact on waste collection. Garbage bins are systematically mentioned as the primary infrastructure needed by the population in all quarters, whether it be a high or low standard community. The construction of transfer stations and the installation of garbage bins are suggested as a solution to reduce distances between households and garbage bins, thus improving waste collection vehicle accessibility. Transfer stations and garbage bins would enable the official waste collection company to expand its range of services and significantly improve waste collection rates. Several transfer stations have already been set up by non-governmental organizations (NGOs) and community-based organizations (CBOs), but they require technical, institutional and funding support. Research is needed on the quality and safety of community-made compost, as well as on soil fertility in urban and peri-urban areas. Most of the stakeholders, municipalities, the official waste collection company and households acknowledge the need for better monitoring and regulation of MSW management. The urban community of Yaoundé also needs to maintain its support of MSW management and promote the sustainability of NGOs and CBOs operating in underserved areas not yet covered by adequate infrastructures. A major opportunity for implementation of such waste policy is the heavily indebted poor countries (HIPC) program dedicated to urban planning and good governance. 相似文献
183.
Russo J Lefeuvre-Orfila L Lagadic L 《Environmental pollution (Barking, Essex : 1987)》2007,146(2):420-427
Responses of circulating hemocytes were studied in Lymnaea stagnalis exposed to 10, 30, 90, and 270 microg/L fomesafen for 24 and 504 h. Flow cytometry was used to quantify fomesafen-induced production of reactive oxygen species (ROS), phagocytic activity on Escherichia coli, and oxidative burst when hemocytes were challenged by E. coli or phorbol 12-myristate-13-acetate (PMA). Lysosomal membrane damage was assessed, using the neutral-red retention time (NRRT) assay. Exposure to fomesafen for 24 h resulted in increase in ROS levels and decreases in phagocytosis and the oxidative burst in PMA-stimulated hemocytes. After 504 h, intracellular levels of ROS returned to normal, but phagocytosis of E. coli was still inhibited and the associated oxidative burst significantly reduced. After both durations of exposure, decreases of NRRT indicated that lysosome membrane fragility increased with fomesafen concentration. Potential implications for the health and survival of the snails and consequences on populations are discussed. 相似文献
184.
185.
186.
Genetic diversity might increase the performance of social groups by improving task efficiency or disease resistance, but direct experimental tests of these hypotheses are rare. We manipulated the level of genetic diversity in colonies of the Argentine ant Linepithema humile, and then recorded the short-term task efficiency of these experimental colonies. The efficiency of low and high genetic diversity colonies did not differ significantly for any of the following tasks: exploring a new territory, foraging, moving to a new nest site, or removing corpses. The tests were powerful enough to detect large effects, but may have failed to detect small differences. Indeed, observed effect sizes were generally small, except for the time to create a trail during nest emigration. In addition, genetic diversity had no statistically significant impact on the number of workers, males and females produced by the colony, but these tests had low power. Higher genetic diversity also did not result in lower variance in task efficiency and productivity. In contrast to genetic diversity, colony size was positively correlated with the efficiency at performing most tasks and with colony productivity. Altogether, these results suggest that genetic diversity does not strongly improve short-term task efficiency in L. humile, but that worker number is a key factor determining the success of this invasive species.Communicated by L. Sundström 相似文献
187.
Biodegradation of low aqueous concentration pentachlorophenol (PCP) contaminated groundwater 总被引:4,自引:0,他引:4
Bioremedial treatment to remove low level organic contamination to regulatory standards has met with limited success. In this study source water from a contaminated surficial aquifer at a former wood treatment facility was used to evaluate the potential for indigenous microorganisms to degrade low level (< 1.0 mg) pentachlorophenol (PCP) to a regulatory drinking water standard of 0.001 mg/L. PCP degradation was evaluated in series of batch reactors in a two phase study to (a) determine the rate and extent of PCP removal and (b) evaluate the impact of nutrient amendment (N and P) on removal rate. All reactors with the exception of the abiotic control demonstrated PCP removal to a level < 0.002 mg/L within a maximum period of 32 d with and without nutrient amendment. A regression analysis of reactive phosphate (ortho-P) concentration versus removal rate produced an R2 of 0.94 (p = 0.006) indicating a significant correlation between the level of available phosphate and PCP degradation rate. Selective bacterial enumeration (for PCP degrading bacteria) revealed PCP-degrading bacteria increased in abundance prior to and in conjunction with the degradation phase to a density of between 10(3) to 10(4) CFU/ml. Isolates were also analyzed for total fatty acids using Fatty Acid Methyl Ester (FAME) methodology and the results indicated that PCP degrading bacteria were present in the aquifer and consisted of predominately fluorescent, oxidase positive Pseudomonas species. Overall, data indicate that autochthonous microbes are capable of removing low level PCP (< 1.0 mg/L) to approach if not reach the regulatory standard of 0.001 mg/L with the addition of oxygen, with or without nutrient amendment. Results of this research can be applied to full-scale implementation of in-situ or ex-situ bioremediation of groundwater at former wood treatment facilities. 相似文献
188.
Pascal?Laurent Jean-Claude?Braekman Désiré?Daloze Jacques?M.?PasteelsEmail author 《Chemoecology》2003,13(3):109-111
Summary. 22-Acetyl-20-hydroxyecdysone was identified
as a major component in the secretion of elytral and pronotal
glands of Chrysolina carnifex, at an estimated concentration
of 1.5 x 10-1 M. This unexpected high concentration
of an ecdysteroid in an exocrine secretion of an insect is
discussed in terms of its potential defensive function, and in
the light of steroid production in similar glands of closely
related leaf beetles. 相似文献
189.
Laurence Faivre Thierry Rousseau Nicole Laurent Philippe Gosset Damien Sanlaville Christel Thauvin-Robinet Véronica Cusin Stéphanie Lionnais Patrick Callier Philippe Khau Van Kien Frédéric Huet Catherine Turleau Paul Sagot Francine Mugneret 《黑龙江环境通报》2004,24(5):393-395
Overgrowth is rarely associated with chromosomal imbalances. Here, we report on a male foetus presenting with overgrowth and additional material on the short arm of one of the chromosome 15 in 12% of lymphocytes and 50% of amniotic cells. Parents' karyotypes were normal, indicating a de novo origin for this unbalanced rearrangement. Complementary studies using cytogenetic and FISH studies showed that this additional material resulted in a 15q25-qter trisomy and confirmed the presence of three copies of the insulin-like growth factor 1 receptor (IGF1R) gene, included in the trisomic region. Autopsy performed after termination of pregnancy revealed isolated overgrowth and absence of visceral malformations. The possible mechanisms and origins for the formation of this mosaic pure trisomy are complex. The present observation emphasises the hypothesis that the overgrowth phenotype, frequently reported in patients with trisomy including the 15q26 region, might be causally related to a dosage effect of the IGF1R gene, as well as the importance of chromosome analysis in patients with overgrowth. It also confirms that the overgrowth is of prenatal onset in those observations. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
190.
Dental microwear in relation to changes in the direction of mastication during the evolution of Myodonta (Rodentia,Mammalia) 总被引:2,自引:1,他引:1
Observations of dental microwear are used to analyse the correlation between changes in molar tooth crown morphology and the
direction of masticatory movement during the evolution of Myodonta (Rodentia, Mammalia). The studied sample includes 36 specimens
representing both superfamilies of Myodonta (Muroidea and Dipodoidea) spanning 16 dipodoid and 9 muroid species. Microscopic
scratches on occlusal surfaces resulting from contact between opposite teeth during mastication are analysed. Using these
features, we determine the direction of masticatory movements. Microwear patterns display diverse orientations among Dipodoidea:
oblique in Sicistinae, Euchoreutinae and Zapodinae, propalinal in Dipodinae and intermediary in Allactaginae. Similarly, Muroidea
exhibit the following orientations: oblique in Cricetinae and propalinal in Arvicolinae, Cricetomyinae, Gerbillinae and Murinae.
These various chewing types illustrate different evolutionary grades within the superfamilies. Acquisition of the antero-posterior
masticatory movement in Dipodoidea is related to flattening of the molar occlusal surface. However, in some muroid subfamilies,
this direction of mastication is associated with low-crowned and cuspidate molars (Cricetomyinae, Murinae). 相似文献