Influence of feeding procedure on biomarkers in caged rainbow trout (Oncorhynchus mykiss) used in environmental monitoring

Biomarkers in feral fish can be a useful tool for environmental monitoring of aquatic ecosystems. Drawbacks, however, are that suitable fish species are not always available and that natural variations can bias the results. An alternative strategy is to use farmed fish placed in cages. There is, however, still a risk that factors other than pollution level could have an impact on the biomarkers and the observed responses in the fish. The present study evaluates the effects of feeding procedure on biomarkers in caged fish. Two feeding rations (2% and 8% weekly feeding) have been examined for a large number of biomarkers in caged rainbow trout (Oncorhynchus mykiss). Significant effects of feeding rations were found on hepatic ethoxyresorufin-O-deethylase (EROD) and catalase activity, PAH metabolites in bile, plasma ion concentrations and the presence of immature red blood cells. The influence on EROD activity and PAH metabolites seems to be caused by elevated uptake of pollutants when feeding ratios are higher. The effects on other biochemical and physiological variables are more likely caused by stress due to insufficient feeding. According to these results, valid comparison of fish groups in environmental monitoring requires standardized feeding levels.     

Three lessons conservation science can learn from the COVID-19 pandemic

Article impact statement: COVID-19 has demonstrated the need to optimize research activity, convey the gravity of loss, and reevaluate merit in conservation science.     

We're all in this together…except for you: The effects of workload,performance feedback,and racial distance on helping behavior in teams

We draw from social categorization theory and the actor–observer hypothesis to extend previous research regarding receiving high levels of help from team members. Specifically, we explore how a team member's performance feedback on how they handled a disproportionately heavy share of the team's workload and how their racial distance from the rest of their teammates affect the amount of helping that person receives from their teammates. Results from a laboratory study in which 79 teams worked on a computerized, decision‐making task demonstrated a three‐way interaction between workload, performance feedback, and the racial distance between the feedback recipient and the rest of their teammates. Racially distant negative feedback recipients who had a disproportionately heavy share of their team's workload received less help from teammates than their racially similar counterparts. Copyright © 2012 John Wiley & Sons, Ltd.     

红树林呼吸根上生物固氮作用的初步观测研究

在热带海洋环境中,红树林是具有较高生产力的生态系[1,2].通常认为,红树林湿地区域可为毗连的沿岸水域和相关的生物群落生境提供有机物和无机物[3～5].尽管在红树林区域中具有很高的生产率,但红树林的树木一般是生长在营养比较贫瘠的热带地区.     

Intracellular cyanobiont Richelia intracellularis: ultrastructure and immuno-localisation of phycoerythrin,nitrogenase, Rubisco and glutamine synthetase

In marine tropical or subtropical plankton the filamentous, heterocyst-forming cyanobacterium Richelia intracellularis forms a symbiosis with the diatom Rhizosolenia clevei. An ultrastructural analysis of the apex of Rhizosolenia clevei showed that the cytoplasm in that particular part of the cell was present only where the cyanobiont was located. The cyanobiont was, however, always outside the host cytoplasm. Vegetative cells as well as the heterocysts of the cyanobiont were devoid of gas vesicles and cyanophycin granules, while carboxysomes and large glycogen granules were common. The cyanobacterial cell wall apparently remained intact in both vegetative and heterocyst cells. In green excitation light the heterocysts and vegetative cells emitted a bright yellow fluorescence, indicating that both cell types possessed high concentrations of the pigment phycoerythrin (PE) commonly associated with photosystem (PS) II. The presence of this pigment in both cell types was verified by immunogold localisation. Using the same technique, the nitrogenase (dinitrogenase reductase) enzyme was shown to be exclusively present in the heterocysts, while Rubisco was localised primarily to the carboxy-somes, which were only detected in vegetative cells. Using an antiserum against the ammonia assimilating enzyme glutamine synthetase (GS), we could demonstrate very low levels of this enzyme, indicating repression of GS in the cyanobiont.     

Analysis of mono- to deca-brominated diphenyl ethers in chickens at the part per billion level

Polybrominated diphenyl ethers (PBDEs) are flame retardants which have been found to be increasing in the environment. Because of structural similarities to the polychlorinated biphenyls and concerns that PBDEs may be widespread, we have investigated their presence in a food source, namely chickens. A GC-MS method was developed to analyze mono- through deca-BDEs in chicken fat samples. The method utilized GC pressure programming and selected ion monitoring to quantitate PBDEs at the low part per billion level. Four 13C-labeled surrogates were used to determine recoveries; recoveries averaged from 76% to 114%. Thirteen chickens from the Southern US and a composite sample of chickens from North Dakota were analyzed by this method. The total concentrations of PBDEs on a whole weight basis ranged from 1.7 ppb in North Dakota chickens to 39.4 ppb in a chicken from Arkansas. On a lipid weight basis, these levels were lower than those generally found in fish and fish-eating mammals. The PBDE pattern was also different from other samples reported; penta-BDEs rather than tetra-BDEs were the most prominent congeners.     

Thermal degradation of polychlorinated alkanes

Thermal degradation products of two polychlorinated alkanes (PCA) containing 59 % and 70 % chlorine, respectively, and also a commercial chlorinated paraffin (CP) containing 70 % chlorine were determined by gas chromatography and mass spectrometry. Thermolyses were performed in both inert atmosphere and air at different temperatures and times. Aliphatic and aromatic hydrocarbons and minor amounts of chlorinated substances were identified products of the medium chlorinated PCA. The highly chlorinated PCA and the commercial CP in addition gave products such as polychlorinated benzenes, toluenes, biphenyls and naphthalenes.     

Synthesis of halogenated diphenyl ethers and dibenzofurans - A discussion of specific isomers available

Synthetic routes for the preparation of halogenated diphenyl ethers and dibenzofurans are reviewed, and isomers reported in the literature are listed. In addition, the routes preferred for the synthesis of specific chlorinated isomers - especially from the point of view of an unambiguous structural assignment - are discussed in detail. The route recommended for chlorinated diphenyl ethers is the coupling of biaryliodonium salts with phenols, and for chlorinated dibenzofurans the palladium acetate-promoted cyclization of diphenyl ethers. Chlorinated isomers of diphenyl ethers and dibenzofurans which are available via these routes are listed. Furthermore, the synthesis of a new octachlorodiphenyliodonium salt and its coupling with three different chlorophenols are described, and the cyclization of an octachlorodiphenyl ether to octachlorodibenzofuran is shown.     

雄性波罗的海灰海豹(Halichoerus grypus)骨组织的矿物密度

本文利用非侵入计算层析X射线摄影法(pQCT)研究了雄性波罗的海灰海豹(4～23岁龄)骨组织的矿物密度(mg/cm3).资料按照收集的年份分组.A组1850～1955年,有机氯(OCs)大量引入之前的时期;B组1965～1985年,OC污染十分严重的时期;C组1986～1997年,OCs浓度逐渐减小的时期.测量结果的复现性良好,变异系数(CV)为0.1%～2.1%.1986～1997年收集的标本中桡骨小梁的矿物密度比1965～1985年收集的标本的明显要高(p＜0.05).1986～1997年收集的标本中,下颌骨的皮层骨矿物密度明显地低于1850～1955年收集的标本(p＜0.05).这些结果表明小梁和皮层骨在一段时间内的不同响应.在OC污染非常严重的时期(1965～1985年),小梁骨矿物密度最低,而在1985～1997年收集的标本中,皮层骨密度最低,该时段是一个OC污染程度相当低的时期.有关这些效应背后的机制目前尚不知道.但是,可以假定这里涉及到OCs.由于目前缺乏有关研究个体中OCs残留水平的资料,因此不可能评估OCs在这方面的影响.