Feeding repellence in Antarctic bryozoans

The Antarctic sea star Odontaster validus and the amphipod Cheirimedon femoratus are important predators in benthic communities. Some bryozoans are part of the diet of the asteroid and represent both potential host biosubstrata and prey for this omnivorous lysianassid amphipod. In response to such ecological pressure, bryozoans are expected to develop strategies to deter potential predators, ranging from physical to chemical mechanisms. However, the chemical ecology of Antarctic bryozoans has been scarcely studied. In this study we evaluated the presence of defenses against predation in selected species of Antarctic bryozoans. The sympatric omnivorous consumers O. validus and C. femoratus were selected to perform feeding assays with 16 ether extracts (EE) and 16 butanol extracts (BE) obtained from 16 samples that belonged to 13 different bryozoan species. Most species (9) were active (12 EE and 1 BE) in sea star bioassays. Only 1 BE displayed repellence, indicating that repellents against the sea star are mainly lipophilic. Repellence toward C. femoratus was found in all species in different extracts (10 EE and 12 BE), suggesting that defenses against the amphipod might be both lipophilic and hydrophilic. Interspecific and intraspecific variability of bioactivity was occasionally detected, suggesting possible environmental inductive responses, symbiotic associations, and/or genetic variability. Multivariate analysis revealed similarities among species in relation to bioactivities of EE and/or BE. These findings support the hypothesis that, while in some cases alternative chemical or physical mechanisms may also provide protection, repellent compounds play an important role in Antarctic bryozoans as defenses against predators.     

Development of a generalist predator,Podisus maculiventris,on glucosinolate sequestering and nonsequestering prey

Insect herbivores exhibit various strategies to counter the toxic effects of plant chemical defenses. These strategies include the detoxification, excretion, and sequestration of plant secondary metabolites. The latter strategy is often considered to provide an additional benefit in that it provides herbivores with protection against natural enemies such as predators. Profiles of sequestered chemicals are influenced by the food plants from which these chemicals are derived. We compared the effects of sequestration and nonsequestration of plant secondary metabolites in two specialist herbivores on the development of a generalist predator, Podisus maculiventris. Profiles of glucosinolates, secondary metabolites characteristic for the Brassicaceae, are known to differ considerably both inter- and intraspecifically. Throughout their immature (=nymphal) development, the predator was fed on larval stages of either sequestering (turnip sawfly, Athalia rosae) or nonsequestering (small cabbage white butterfly, Pieris rapae) prey that in turn had been feeding on plants originating from three wild cabbage (Brassica oleracea) populations that have previously been shown to differ in their glucosinolate profiles. We compared survival, development time, and adult body mass as parameters for bug performance. Our results show that sequestration of glucosinolates by A. rosae only marginally affected the development of P. maculiventris. The effects of plant population on predator performance were variable. We suggest that sequestration of glucosinolates by A. rosae functions not only as a defensive mechanism against some predators, but may also be an alternative way of harmlessly dealing with plant allelochemicals.     

Variations in stable hydrogen and oxygen isotopes in atmospheric water vapor in the marine boundary layer across a wide latitude range

The newly-developed cavity ring-down laser absorption spectroscopy analyzer with special calibration protocols has enabled the direct measurement of atmospheric vapor isotopes at high spatial and temporal resolution. This paper presents real-time hydrogen and oxygen stable isotope data for atmospheric water vapor above the sea surface, over a wide range of latitudes spanning from 38°N to 69°S. Our results showed relatively higher values of 8180 and 82H in the subtropical regions than those in the tropical and high latitude regions, and also a notable decreasing trend in the Antarctic coastal region. By combining the hydrogen and oxygen isotope data with meteoric water line and backward trajectory model analysis, we explored the kinetic fractionation caused by subsiding air masses and related saturated vapor pressure in the subtropics, and the evaporation-driven kinetic fractionation in the Antarctic region. Simultaneous observations of meteorological and marine variables were used to interpret the isotopic composition characteristics and influential factors, indicating that d-excess is negatively correlated with humidity across a wide range of latitudes and weather conditions worldwide. Coincident with previous studies, d-excess is also positively correlated with sea surface temperature and air temperature （Tair）, with greater sensitivity to Tair. Thus, atmospheric vapor isotopes measured with high accuracy and good spatial- temporal resolution could act as informative tracers for exploring the water cycle at different regional scales. Such monitoring efforts should be undertaken over a longer time period and in different regions of the world.     

枯草芽孢杆菌对土臭素和2-甲基异冰片的降解动力学特性

土臭素(geosmin,GSM)和2-甲基异冰片(2-methylisoborneol,2-MIB)是2种普遍存在于养殖水体中的土腥异味化合物,微生物降解是去除这两种物质的有效途径.本文研究了枯草芽孢杆菌(Bacillus subtilis)降解GSM和2-MIB的动力学特性.结果表明,枯草芽孢杆菌对GSM(1 000~2 000 ng·L-1)和2-MIB(1 000~2 000 ng·L-1)具有较好的降解性能,降解率均达90%以上;枯草芽孢杆菌对这些异味化合物的降解符合伪一级反应动力学,其生物降解速率常数(K)范围为0.14~0.41,降解速率不随GSM和MIB初始浓度的变化而变化;枯草芽孢杆菌对GSM降解的最大比生长速率umax为0.311,Monod常数KS为1.73,而在降解MIB过程中枯草芽孢杆菌的生长不符合Monod方程(R2=0.781).     

Heteropteran chemical repellents identified in the citrus odor of a seabird (crested auklet: Aethia cristatella): evolutionary convergence in chemical ecology

The exogenous application of chemical repellents is widespread in birds, but endogenous production is exceedingly rare. We herein report a new class of avian defensive compounds isolated from the feathers and volatile odor of the crested auklet (Aethia cristatella). Mass spectra indicate that n-hexanal, n-octanal, n-decanal, Z-4-decenal and a 12-carbon unsaturated aldehyde comprise the auklet odorant. Octanal and hexanal are also secreted in the repugnant metasternal gland emissions of heteropteran insects and are known to be potent invertebrate repellents. We suggest that the auklet odorant functions as an ectoparasite repellent and a signal of mate quality. This would represent a rare and direct link between vigor, quality and parasite resistance, one of several putative bases for mate selection. This is the first report of defensive compounds produced by a seabird or colonial bird and one of the few examples of chemical defense in a polar or subpolar marine vertebrate.     

Feeding responses to selected alkaloids by gypsy moth larvae, Lymantria dispar (L.)

Deterrent compounds are important in influencing the food selection of many phytophagous insects. Plants containing deterrents, such as alkaloids, are generally unfavored and typically avoided by many polyphagous lepidopteran species, including the gypsy moth Lymantria dispar (L.) (Lepidoptera: Lymantriidae). We tested the deterrent effects of eight alkaloids using two-choice feeding bioassays. Each alkaloid was applied at biologically relevant concentrations to glass fiber disks and leaf disks from red oak trees (Quercus rubra) (L.), a plant species highly favored by these larvae. All eight alkaloids tested on glass fiber disks were deterrent to varying degrees. When these alkaloids were applied to leaf disks, only seven were still deterrent. Of these seven, five were less deterrent on leaf disks compared with glass fiber disks, indicating that their potency was dramatically reduced when they were applied to leaf disks. The reduction in deterrency may be attributed to the phagostimulatory effect of red oak leaves in suppressing the negative deterrent effect of these alkaloids, suggesting that individual alkaloids may confer context-dependent deterrent effects in plants in which they occur. This study provides novel insights into the feeding behavioral responses of insect larvae, such as L. dispar, to selected deterrent alkaloids when applied to natural vs artificial substrates and has the potential to suggest deterrent alkaloids as possible candidates for agricultural use.     

基于可疑筛查技术研究有机磷阻燃剂V6转化规律

运用Orbitrap高分辨质谱仪,评估了人体肝微粒体(HLM)代谢V6的转化规律.除5种已被报道过的O-脱烷基、氧化性去磷酸化和氧化脱氯产物外,首次发现了6种新型产物.基于其MS/MS质谱图,该6种代谢产物被鉴定为醛基和羧基产物.其中,5种代谢物生成量随孵育时间呈线性增加趋势,具有累积性.此外,推导的代谢途径表明,脱烷基化和羟基化代谢物进一步转化为次级代谢物,即醛和羧基代谢物.     

Bioassay-directed fractionation of organic compounds associated with airborne particulate matter; An interseasonal study

Bioassay-directed fractionation based upon a modification of a published technique is applied to the study of three seasonal composites of dichloromethane extracts of inhalable particulate matter collected in Newarks, New Jersey The “profiles” of mass distribution and Salmonella TA98 mutagenic activity vs polarity are similar for the three seasons. Only at the second and especially the third fractionation levels are significant differents seen with a slight shift toward more polar compounds during summer. In all three seasons, polar neutral compounds make the greatest contribution toward mutagenic activity. Hydroxynitropolyciclic aromatic hydrocarbons are difficult to analyse by GC/MS) (El and negative chemical ionization), but HPLC/UV appears to be useful. A number of techniques are emplited in the analysis of specific compounds and classes of compounds. Subsequent acetone extraction of filters yields highly polar mutagens where the acidic fractions account for most of the mutagenic activity. These compounds show significantly enhanced mutagenic activity with TA100 relative to TA98 suggesting the presence of highly polar, acidic substances that are strong alkylating agents. The compound 2-acetoxyl-1-nitronaphthalene, found in fresh diesel particalates, is shown to hydrolyse during fractionation, thus introducing a note of caution into the use of such procedures.     

Orange/lemon-scented beetles: opposite enantiomers of limonene as major constituents in the defensive secretion of related carabids

The major constituent in the pygidial gland defensive fluid of the carabid beetle Ardistomis schaumii is (R)-(+)-limonene, whereas that of Semiardistomis puncticollis is (S)-(−)-limonene. This was an unanticipated result, since it is not very common to find the opposite enantiomers of the same compound among the secondary metabolites of related species. Moreover, the glandular liquid of A. schaumii contains 1,8-cineole, and that of S. puncticollis has β-pinene, β-phellandrene, sabinene, and p-cymene. Of about 500 carabid species that have been chemically investigated, this is the first report of the presence of such complex mixtures of monoterpenes in their defensive secretions.     

Large and small particle size screening of organic compounds in urban air

A gas chromatographic (GC)-mass spectrometric (MS) study of the large (> 7.2 μm) and small (< 0.5 μm) particle fractions of aerosols collected in Barcelona (Catalonia, Spain) has allowed the identification of the major sources of airborne organic matter in urban environments. The extracts have been column chromatography separated in three fractions encompassing aliphatic hydrocarbons, aromatic hydrocarbons+semi-polar compounds, and polar products. The whole analytical procedure has allowed the identification of 186 molecular species that have been grouped according to their precursors. The study has also afforded the characterization of organic source-particle size associations as well as the effects of seasonality on the occurrence of the compounds identified.     

不同粒径黄河沉积物中可提取腐殖质的含量分布及光谱特性

测定了黄河表层沉积物3种粒径组分（Ⅰ：100～300 μm;Ⅱ: 63～100 μm;Ⅲ: <63 μm）中总有机碳和可提取腐殖质的含量,分析了可提取腐殖质的紫外-可见吸收光谱、红外光谱和三维荧光光谱特征,探讨了不同粒径组分沉积物中可提取腐殖质含量分布及其化学组成特性.结果表明,沉积物有机质主要为粘土矿物吸附的天然腐殖质成分,总有机碳中可提取腐殖质的比例随沉积物有机质与矿物质相互作用的增强而降低,顺序为Ⅰ>Ⅱ>Ⅲ.3种粒径组分沉积物中可提取腐殖质的紫外-可见吸收光谱相似但相对峰强不同;红外光谱主要有5个吸收峰,各吸收峰面积百分含量的计算结果表明酚、醇及羧酸类官能团为主要的活性官能团,占可提取腐殖质组成的75%以上;三维荧光光谱主要有3个荧光峰,除了典型的类腐殖质荧光峰（峰A和峰C）外,还有源于小分子类蛋白或酚类物质的荧光峰（峰T′）.比较3种粒径组分沉积物中可提取腐殖质的紫外-可见、红外及三维荧光光谱的特征参数,发现Ⅰ、Ⅱ组分沉积物中可提取腐殖质的芳香度高,脂肪族和芳香族含量高于Ⅲ组分,而Ⅲ组分沉积物可提取腐殖质中酚、醇及羧酸类活性基团含量相对较高.     

Extraction and quantification of "condensed tannins" as a measure of plant anti-herbivore defence? Revisiting an old problem

Contents of phenolic compounds in leaf extracts often serve as a measure of plant anti-herbivore defence. This method suffers from the multifunctionality of phenolics and from problems with their colorimetric quantification. Here we present further evidence for the pertinence of these problems. Contents of condensed tannins (CCT) were spectrophotometrically quantified in leaf extracts of 11 closely related mimosoid species, and Spodoptera littoralis caterpillars were reared on artificial diet containing these extracts. The relationship of CCT with caterpillar growth differed considerably among plant species, since both positive and negative correlations were detected. There was, however, a negative correlation of CCT with fungal spore germination, indicating a role of these compounds in resistance to fungi. Detailed knowledge on the structure and biological function of defensive compounds and on the overall composition of leaves is required to estimate a plant's defensive efficacy against a particular group of enemies.     

芦苇抑藻化感物质的分离及其抑制蛋白核小球藻效果研究

采用乙醇提取、溶剂萃取法从芦苇中分离出2组能抑制蛋白核小球藻生长的化感物质. 该2组化感物质对蛋白核小球藻的半效应浓度(EC₅₀)分别为0.68mg/L和2.65mg/L. 将前者用碱性氧化铝层析柱分离得到一组抑藻活性更强的化感物质和一组能够促进蛋白核小球藻生长的化感物质: 前者对蛋白核小球藻的EC₅₀为0.50mg/L, 是目前报道的抑藻能力最强的化感物质; 后者在浓度为0.63mg/L时能显著促进蛋白核小球藻的生长. 芦苇化感物质可以用来控制淡水中有害藻类.     

Biogeochemical cycles of selenium in Antarctic water

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Fatty acids and algal lipids as precursors of chlorination by-products

Six common algal fatty acids (FAs) with different numbers of double bonds, lipophilic fractions and proteins extracted from the diatom Navicula pelliculosa and algal cells were chlorinated to evaluate their potential in generating disinfection by-products (DBPs). The result showed that the more double bonds in the FAs, the higher the amounts of chloroform and dichloroacetic acid (DCAA) produced, but such a pattern was not observed for trichloroacetic acid (TCAA). Based on the previously reported composition of fatty acids in algal lipids, the DBP generation potentials of algal lipids were calculated. These predicted values were much lower than those measured in the chlorinated algal lipophilic fraction, suggesting unknown lipophilic fraction(s) served as potent DBPs precursors. Another calculation attempted to predict DBP production in algal cells based on algal lipid and protein composition, given quantified measured DBP production per unit algal lipid and proteins. The analysis showed that the observed DBP production was similar to that predicted (< 35% difference), suggesting that algal biochemical compositions may serve as a bioindicator for preliminary estimation of chloroform, DCAA and TCAA formation upon chlorinating algae.     

南极菲尔德斯半岛近岸海洋生物体有机锡污染状况

在南极地区已发现丁基锡污染,但有关苯基锡污染及有机锡在食物链中的传递等相关研究尚未见报道.为此,自2014年12月—2015年1月从南极菲尔德斯半岛周边采集了20种海洋生物共32个混合样品(即由多个同种生物个体混合而成),经甲醇/醋酸提取、四乙基硼化钠衍生和弗洛里硅土柱净化等过程处理后,采用气相色谱-质谱联用仪(GC-MS)对样品中一丁基锡(MBT)、二丁基锡(DBT)、三丁基锡(TBT)、二苯基锡(DPhT)和三苯基锡(TPhT)进行测定,并讨论了不同有机锡化合物在食物链中的传递特征.结果表明:海藻、无脊椎动物、鱼类、海豹、鸟类中有机锡含量分别为n.d.~19.5、8.6~11.0、10.8、4.2~12.9、21.6~27.0 ng·g~(-1)(以Sn计,若未注明均以干重计),生物样品中TBT、DBT、TPhT、DPhT均有检出,而MBT均未检出;大型海藻对TBT、DBT有一定富集能力,且TBT一定程度上表现出随营养级生物放大效应;TBT和TPhT在食物链顶端含量最高,同时发现高营养级的生物具有排出部分有机锡的能力.     

Repeated exposure to cat urine induces complex behavioral,hormonal, and c-fos mRNA responses in Norway rats (<Emphasis Type="Italic">Rattus norvegicus</Emphasis>)

Prey species show specific adaptations that allow recognition, avoidance, and defense against predators. This study was undertaken to investigate the processing of a chronic, life-threatening stimulus to Norway rats (Rattus norvegicus). One hundred forty-four Norway rats were tested by repeated presentation of cat urine for 1 h at different days in a defensive withdrawal apparatus. Rats exposed to urine for short periods showed significantly larger defensive behavioral and medial hypothalamic c-fos messenger RNA (mRNA) responses than other groups. These defensive responses habituated shortly after the presentation of cat urine. Serum levels of adrenocorticotropic hormone and corticosterone increased significantly when animals were repeatedly exposed to cat urine. However, the hormonal responses took longer to habituate than the behavioral and molecular responses did. We conclude that the behavioral and c-fos mRNA responses are “primed” for habituation to repeated exposures to cat urine, while the hormonal responses show “resistance.” The results support our hypothesis that the strongest anti-predator responses at three levels would occur during short-term exposure to cat urine and that these responses would subsequently disappear on prolonged exposure. This study assists understanding the way in which the different levels of defensive responses are integrated and react during chronic stress.     

Potential influence of overwintering benthic algae on water quality

Overwintering benthic algae not only directly impact drinking water safety, but also affect the algae recruitment in warm spring seasons. Thus, understanding the characteristics of overwintering benthic algae can provide scientific references for formulating preventative strategies of reasonable water resource. However, they have received less attention. In this study, the spatiotemporal variation of benthic algae and their harmful secondary metabolites were studied from autumn to summer in Qingcaosha Reservoir. Benthic algae (picophytobenthos accounting for 55.42%) had a high biomass during overwintering, and the groups of overwintering benthic algae included pico-Cyanobacteria, pico-Cryptomonas, pico-Chlorophyta, pico-Diatoms, Cyanobacteria, Chlorophyta, Cryptomonas and Diatoms, which were consistent with the planktonic algae species in warm seasons. In oligotrophic or mesotrophic water bodies, micronutrients of iron and manganese were key nutrient factors influencing the biomass of benthic algae. Furthermore, picophytobenthos were important potential contributors of harmful secondary metabolites. The content of microcystins, anatoxin-a, geosmin and 2-methylisoborneol in sediment were 15.75 µg/kg·FW, 48.16 µg/kg·FW, 3.91 ng/kg·FW, and 11.76 ng/kg·FW during winter, which had potential to be released into water bodies to impact water quality. These findings indicate that water quality monitoring programs need to consider sediment in winter as a potential source of toxins and preventative measures to prevent excessive proliferation of algae should be implemented in winter.     

Stimulation of gaseous phosphine production from Antarctic seabird guanos and ornithogenic soils

Matrix-bound phosphine (MBP) is a general term used to indicate non-gaseous reduced phosphorus compounds that are transformed into phosphine gas upon reaction with bases or acids. Antarctic seabird guanos and ornithogenic soils were used as materials to compare the different digestion methods for transforming matrix-bound phosphine into phosphine gas. The results demonstrated that more phosphine gas in most of Antarctic environmental materials was formed of matrix-bound phosphine by caustic digestion than by acidic digestion. The comparative study on different digestion methods also revealed that the fraction of MBP converted to gaseous phosphine during the digestion depended on the temperature. The optimal digestion temperature was close to 70℃ and the optimal digestion time was about 20 min. Acidic conditions were more favorable for the release of matrix-bound phosphine compared to the central[u1] conditions. The proper additional water dilution can increase the production and emission of phosphine from the Antarctic penguin guanos.     

Evaluation of soil washing process with carboxymethyl-β-cyclodextrin and carboxymethyl chitosan for recovery of PAHs/heavy metals/fluorine from metallurgic plant site

Polycyclic aromatic hydrocarbons(PAHs)/heavy metals/fluorine(F) mixed-contaminated sites caused by abandoned metallurgic plants are receiving wide attention. To address the associated environmental problems,this study was initiated to investigate the feasibility of using carboxymethyl-β-cyclodextrin(CMCD) and carboxymethyl chitosan(CMC) solution to enhance ex situ soil washing for extracting mixed contaminants. Further,Tenax extraction method was combined with a first-three-compartment model to evaluate the environmental risk of residual PAHs in washed soil. In addition,the redistribution of heavy metals/F after decontamination was also estimated using a sequential extraction procedure. Three successive washing cycles using50 g/L CMCD and 5 g/L CMC solution were effective to remove 94.3% of total PAHs,93.2% of Pb,85.8% of Cd,93.4% of Cr,83.2% of Ni and 97.3% of F simultaneously. After the 3rd washing,the residual PAHs mainly existed as very slowly desorbing fractions,which were in the form of well-aged,well-sequestered compounds; while the remaining Pb,Cd,Cr,Ni and F mainly existed as Fe–Mn oxide and residual fractions,which were always present in stable mineral forms or bound to non-labile soil fractions. Therefore,this combined cleanup strategy proved to be effective and environmentally friendly.