祁连山大野口流域青海云杉种群数量动态

种群数量动态揭示了种群的结构特征及其潜在的驱动机制，有助于预测种群未来的动态，进而为森林生态系统的保护与恢复提供理论依据。本研究基于10.2 hm²青海云杉动态监测样地数据，以种群径级结构代替年龄结构，编制静态生命表，绘制径级结构图、存活曲线、死亡率曲线、消失率曲线和4个生存分析函数曲线，分析青海云杉种群数量特征，并利用种群数量动态变化指数和时间序列模型对种群数量动态进行预测。结果表明：（1）青海云杉种群的年龄结构近似于倒"J"型，幼苗和小树储量丰富；（2）种群存活曲线趋近于Deevey-Ⅱ型，为稳定型种群，死亡率曲线和消失率曲线变化趋势基本一致，均在第2、8龄级出现高峰期；（3）生存率曲线呈下降趋势，累计死亡率曲线呈上升趋势，死亡密度曲线缓慢下降，而危险率曲线逐渐上升，该种群具有：前期减少、中期稳定、后期衰退的生长特点；（4）种群数量变化动态指数V_pi>0，表明该种群属于增长型种群，V_pi''>0且趋近于0，则表明该种群趋近于稳定型；（5）时间序列预测分析表明，在未来2、4、6、8个龄级时间后，种群呈稳定增长趋势。研究显示，祁连山大野口流域青海云杉种群为稳定增长型种群，只要未来不遭受强烈干扰，种群数量会保持逐渐增长。针对该种群幼龄个体在前期的更新过程死亡率较高情况，建议在今后的经营管理中应重点加强对第1、2龄级植株生存环境的保护和改善，提高幼苗和小树的存活率。     

Detection of protease-resistant cervid prion protein in water from a CWD-endemic area

Chronic wasting disease (CWD) is the only known transmissible spongiform encephalopathy affecting free-ranging wildlife. Although the exact mode of natural transmission remains unknown, substantial evidence suggests that prions can persist in the environment, implicating components thereof as potential prion reservoirs and transmission vehicles.^1–4 CWD-positive animals may contribute to environmental prion load via decomposing carcasses and biological materials including saliva, blood, urine and feces.^5–7 Sensitivity limitations of conventional assays hamper evaluation of environmental prion loads in soil and water. Here we show the ability of serial protein misfolding cyclic amplification (sPMCA) to amplify a 1.3 × 10⁻⁷ dilution of CWD-infected brain homogenate spiked into water samples, equivalent to approximately 5 × 10⁷ protease resistant cervid prion protein (PrP^CWD) monomers. We also detected PrP^CWD in one of two environmental water samples from a CWD endemic area collected at a time of increased water runoff from melting winter snow pack, as well as in water samples obtained concurrently from the flocculation stage of water processing by the municipal water treatment facility. Bioassays indicated that the PrP^CWD detected was below infectious levels. These data demonstrate detection of very low levels of PrP^CWD in the environment by sPMCA and suggest persistence and accumulation of prions in the environment that may promote CWD transmission.Key words: prions, chronic wasting disease, water, environment, serial protein misfolding cyclic amplification     

Freshwater crayfish invasions in South Africa: past,present and potential future

Freshwater crayfish invasions have been studied around the world, but less so in Africa, a continent devoid of native freshwater crayfish. The present study reviews historical and current information on alien freshwater crayfish species introduced into South Africa and aims to indicate which areas are at risk from invasion. As is the case elsewhere, South Africans have shown a keen interest in both farming and keeping freshwater crayfish as pets, which has resulted in Cherax cainii, Cherax destructor, Cherax quadricarinatus and Procambarus clarkii being introduced to the country. There is evidence of successful establishment in the wild for C. quadricarinatus and P. clarkii in different parts of the country. Species distribution models suggest that the eastern part of the country and parts of the Eastern and Western Cape are at higher risk of invasion. At present, illegal translocations represent the most likely pathway of crayfish spread in South Africa. A continued risk of invasion by freshwater crayfish species in South Africa is highlighted, which reinforces the need for more research, as well as for strong mitigation measures, such as stronger policing of existing regulations, management or eradication where feasible and public education.     

电子供体及受体对棕色固氮菌抗氨阻遏能力的影响

电子供体连二亚硫酸钠,甲基紫精及电子受体亚甲蓝均能强烈的抑制棕色固氮菌表达固氮活性,并引起该菌的抗氨阻遏能力减弱,适当提高氧压,能提高菌体的固氮活性近15％,但过高的氧分压反而抑制菌体的固氮活性,此外,提高氢分压能降低棕色固氮菌菌体内的还原电位,从而达到提高菌体抗氨阻遏能力的效果。     

Isolation and characterization of microsatellites in Neogobius kessleri (Perciformes,Gobiidae) and cross‐species amplification within the family Gobiidae

Fourteen polymorphic microsatellites were isolated from Neogobius kessleri, a benthic fish of Ponto‐Caspian origin which has been recently introduced into the Middle and Upper Danube River. Number of alleles and heterozygosity per locus in a sample of 32 fish individuals ranged from two to four and from 0.13 to 0.75, respectively. These primers will be useful in determining the population structure of N. kessleri. In addition, successful cross‐amplification was obtained for four related species, N. melanostomus, N. fluviatilis, N. gymnotrachelus and Proterorhinus marmoratus. These microsatellite loci may be useful for the evaluation of the origin of non‐native goby populations.     

A mRNA landscape of bovine embryos after standard and MAPK-inhibited culture conditions: a comparative analysis

Background

Genes and signalling pathways involved in pluripotency have been studied extensively in mouse and human pre-implantation embryos and embryonic stem (ES) cells. The unsuccessful attempts to generate ES cell lines from other species including cattle suggests that other genes and pathways are involved in maintaining pluripotency in these species. To investigate which genes are involved in bovine pluripotency, expression profiles were generated from morula, blastocyst, trophectoderm and inner cell mass (ICM) samples using microarray analysis. As MAPK inhibition can increase the NANOG/GATA6 ratio in the inner cell mass, additionally blastocysts were cultured in the presence of a MAPK inhibitor and changes in gene expression in the inner cell mass were analysed.

Results

Between morula and blastocyst 3,774 genes were differentially expressed and the largest differences were found in blastocyst up-regulated genes. Gene ontology (GO) analysis shows lipid metabolic process as the term most enriched with genes expressed at higher levels in blastocysts. Genes with higher expression levels in morulae were enriched in the RNA processing GO term. Of the 497 differentially expressed genes comparing ICM and TE, the expression of NANOG, SOX2 and POU5F1 was increased in the ICM confirming their evolutionary preserved role in pluripotency. Several genes implicated to be involved in differentiation or fate determination were also expressed at higher levels in the ICM. Genes expressed at higher levels in the ICM were enriched in the RNA splicing and regulation of gene expression GO term. Although NANOG expression was elevated upon MAPK inhibition, SOX2 and POU5F1 expression showed little increase. Expression of other genes in the MAPK pathway including DUSP4 and SPRY4, or influenced by MAPK inhibition such as IFNT, was down-regulated.

Conclusion

The data obtained from the microarray studies provide further insight in gene expression during bovine embryonic development. They show an expression profile in pluripotent cells that indicates a pluripotent, epiblast-like state. The inability to culture ICM cells as stem cells in the presence of an inhibitor of MAPK activity together with the reported data indicates that MAPK inhibition alone is not sufficient to maintain a pluripotent character in bovine cells.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1448-x) contains supplementary material, which is available to authorized users.     

Putting Your Money Where Your Mouth Is: Why Sustainability Reporting Based on the Triple Bottom Line Can Be Misleading

In the packaged food industry, Corporate Social Responsibility (CSR) is an informal requirement for which firms account through sustainability reporting. CSR behaviors are often reported and analyzed using the Triple Bottom Line (3BL) framework, which categorizes them as affecting people, planet, or profit. 3BL is useful in determining which of these categories is most elaborated upon by the firm, but has a limited scope and many documented criticisms. This paper aims to address the aforementioned insufficiencies by augmenting the 3BL framework with two important attributes of CSR practices: (1) the presence of change in core firm behavior of the firm itself or of others in the supply chain, and (2) whether the behavior qualifies as being outside of the firm’s normal business practice or is something that they might have done anyway. We qualitatively analyze CSR behaviors described in sustainability reports and interviews from major players in the packaged food industry and categorize them using these attributes as a supplement to 3BL. This enables us to separate the behaviors from their framing and analyze them more critically. Our results demonstrate how the visible CSR efforts of a firm can be misleading at first glance. Using only 3BL, we find that the CSR focus of firms in this industry is people. We then discover that the codes focusing on people (as opposed to planet or profit) require the least amount of real structural change from a firm or its supply chain partners, and thus arguably, the least amount of effort. We also find that behaviors that focus on planet require the most effort within the firm itself, but for behaviors involving supply chain partners, effort is required for behaviors in all three categories. Finally, we find that CSR behavior that is related to planet tends to go beyond normal business practice.     

Preliminary evaluation of non-native rainbow trout (Oncorhynchus mykiss) impact on the Cederberg ghost frog (Heleophryne depressa) in South Africa’s Cape Fold Ecoregion

We evaluated the impact of non-native rainbow trout Oncorhynchus mykiss on a population of endemic Cedarberg ghost frog Heleophryne depressa in the upper Krom River (Olifants-Doring River Catchment, Cape Fold Ecoregion). We compared H. depressa abundance (using kick-sampling and underwater video analysis) and environmental conditions between sites above and below a waterfall that marks the upper distribution limit of O. mykiss. Heleophryne depressa abundance was significantly greater above the waterfall than that below it, and, because there was no significant difference in measured environmental variables, O. mykiss presence is identified as the most likely explanation for the observed decrease in H. depressa abundance.     

Distribution and conservation of mobile elements in the genus Drosophila

Essentially nothing is known of the origin, mode of transmission, and evolution of mobile elements within the genus Drosophila. To better understand the evolutionary history of these mobile elements, we examined the distribution and conservation of homologues to the P, I, gypsy, copia, and F elements in 34 Drosophila species from three subgenera. Probes specific for each element were prepared from D. melanogaster and hybridized to genomic DNA. Filters were washed under conditions of increasing stringency to estimate the similarity between D. melanogaster sequences and their homologues in other species. The I element homologues show the most limited distribution of all elements tested, being restricted to the melanogaster species group. The P elements are found in many members of the subgenus Sophophora but, with the notable exception of D. nasuta, are not found in the other two subgenera. Copia-, gypsy-, and F-element homologues are widespread in the genus, but their similarity to the D. melanogaster probe differs markedly between species. The distribution of copia and P elements and the conservation of the gypsy and P elements is inconsistent with a model that postulates a single ancient origin for each type of element followed by mating-dependent transmission. The data can be explained by horizontal transmission of mobile elements between reproductively isolated species.      

Temporal and spatial fluctuations of heavy metals in Opa Reservoir,Ile-Ife,Nigeria

The Opa Reservoir, established for water supply to the Obafemi Awolowo University community, over the years has received direct linkage to township drains as a result of the widening and dredging of its river channels. The current study aimed at documenting monthly heavy metal loads at its riverine, transition and lacustrine zones in 2012–2013. Most of the heavy metals, analysed using an atomic absorption spectrophotometer, occurred within wide ranges, with coefficients of variation ranging from 60% to 300%, although the differences in heavy metal loads between the different zones were statistically insignificant at both the surface and bottom levels. The overall order of dominance of the metals was Ni > Cu > Fe > Zn > Cd = Cr > Pb, with nickel concentration being very high throughout. Heavy metal total mean concentration was higher during the rainy season (1.889 mg l?1) than the dry season (1.503 mg l?1) irrespective of sampling sites, having highly significant seasonal differences (p < 0.001) in Ni, Cd, Fe and Cu concentrations. The mean concentrations of Zn (0.074 mg l?1), Fe (0.176 mg l?1), Cu (0.507 mg l?1) and Pb (0.004 mg l?1) were within the WHO acceptable limit. However, the recorded levels of toxic elements Cd (0.031 mg l?1) and Ni (0.905 mg l?1) pose potential health risk to water consumers.