Comparative Toxicity of PCBs and PBDEs Using Human Cancer Cell Lines and Zebrafish Embryos

研究了6种多氯联苯(PCBs)3,3′,4,4′-四氯联苯(PCB77)、2,3,3′,4,4′-五氯联苯(PCB105)、2,3′,4,4′,5-五氯联苯(PCB118)、3,3′,4,4′,5-五氯联苯(PCB126)、2,3,3',4,4',5-六氯联苯(PCB156)和商业型混合多氯联苯Aroclor1254,两种多溴联苯醚(PBDEs)2,2′,4,4′-四溴二苯醚(PBDE47)、十溴二苯醚(PBDE209)对人类癌细胞生长和斑马鱼脱膜与不脱膜胚胎发育的影响.8种化合物均使用0.01、0.1、1.0、10μmol·L-14个浓度进行1~6d的暴露实验.结果表明,PBDE209在最高浓度10μmol·L-1下对结肠癌细胞HCT116(暴露3d后)和RKO(暴露5d后)具有显著的生长抑制作用,所有化合物均对乳腺癌细胞没有显著影响.相比之下,化合物对受精后5~6h(5~6hpf)的斑马鱼胚胎的毒性效应显得比较明显,而各化合物对胚胎的致畸和致死效应又不相同,其毒性强弱依次为PCB126≈PCB156>PCB1254(Aroclor1254)>PBDE47>PCB77>PCB105≈PCB118≈PBDE209.其中PBDE209在未脱膜暴毒后均无致畸与致死现象,脱膜暴毒后最高浓度才表现出显著意义的致畸作用,而PBDE47在最高浓度下可产生高达80%的致畸率,这说明胚胎绒毛膜具有有效阻挡大分子物质如PBDE209进入的作用.PCBs的毒性效应与其空间结构密切相关.如PCB126和PCB105具有相同的分子式,前者在1μmol·L-1下就引起了显著的致死和致畸效应,而后者即使在10μmol·L-1下也没有显著的效应.实验结果也说明不同类型的实验对象所展示的毒性效应并不相同,化合物对体外培养的细胞和发育中的胚胎具有不同的影响.     

脱氧鬼臼毒素对斑马鱼（Danio rerio）代谢酶和抗氧化酶活性的影响（Effects of Deoxypodophyllotoxin on Activities of Metabolic Enzymes and Antioxidant Enzymes of Danio rerio）

为初步探讨脱氧鬼臼毒素(Deoxypodophyllotoxin,DOP)对鱼类的毒性效应,采用静态鱼类急性毒性试验法测定了DOP对斑马鱼(Daniorerio)代谢酶和抗氧化酶活性的影响;参照DOP的96hLC50值,设定4个浓度(0.5、1.0、2.0、4.0mg·L-1)处理斑马鱼,48h后测定斑马鱼肌肉组织腺苷三磷酸酶(ATPase)、过氧化氢酶(CAT)和超氧化物歧化酶(SOD)活性.结果表明,DOP对斑马鱼96hLC50值为3.49mg·L-1,安全浓度为0.36mg·L-1.DOP在0.5~4.0mg·L-1对斑马鱼肌肉总ATPase、Na+-K+-ATPase和Ca2+-ATPase的作用趋势均表现为:1.0和2.0mg·L-1显著激活(p<0.05,p<0.01);4.0mg·L-1显著抑制(p<0.05),抑制率分别为24.4%、12.3%和33.8%.DOP在0.5~4.0mg·L-1对斑马鱼肌肉抗氧化酶的作用趋势与对ATPase的作用趋势一致,表现为:1.0、2.0mg·L-1DOP对SOD和CAT均表现为显著激活(p<0.05,p<0.01);4.0mg·L-1DOP对SOD和CAT均表现为显著抑制(p<0.05),抑制率分别为34.1%和31.9%.以上结果表明,DOP对斑马鱼为中等毒性;斑马鱼肌肉组织ATPase、CAT和SOD可能是脱氧鬼臼毒素的作用标靶之一.     

菲、芘、1,2,4-三氯苯对蚯蚓的急性毒性效应

测定了草甸棕壤条件下 ,菲、芘和 1,2 ,4-三氯苯单一与复合污染对蚯蚓的急性致死及亚致死效应。结果表明 ,3种化学品的浓度与蚯蚓死亡率显著相关 (α =0 .0 5 ,r菲 =0 .87,r芘 =0 .85 ,r三氯苯 =0 .95 ) ,与蚯蚓亚致死效应的相关性稍低 (α =0 .0 5 ,r菲 =0 .75 ,r芘 =0 .72 ,r三氯苯 =0 .85 )。蚯蚓个体对 3种有机物毒性的耐受程度差别较大。引起蚯蚓死亡的毒性阈值浓度菲和 1,2 ,4-三氯苯均为 2 0mg·kg-1,芘为 2 0 0 0mg·kg-1;引起蚯蚓体重增长率下降的亚急性毒性阈值浓度分别为菲 2 0mg·kg-1、1,2 ,4-三氯苯 3 0 0mg·kg-1、芘 10 0 0mg·kg-1;LC10 0 分别为菲 10 0mg·kg-1,1,2 ,4-三氯苯 3 5 0mg·kg-1。由于芘的低水溶性和低毒性 ,无法计算LC10 0 。实验还表明 ,复合污染主要表现为协同和拮抗作用     

城市污泥与稻草堆肥中多环芳烃的研究

将污泥与稻草进行翻堆、菌种 翻堆、连续通气和间歇通气 4种不同方式的堆肥 ,应用GC/MS对堆肥中的多环芳烃类化合物 (PAHs)进行分析 ,探讨堆肥产物中PAHs的含量分布模式以及不同堆肥方式对PAHs的降解效果 . 4种污泥堆肥中ΣPAHs在2 0 83—2 8 4 35mg·kg- 1之间 ,依次是菌种 翻堆 ( 2 8 4 35mg·kg- 1>翻堆 ( 7 30 3mg·kg- 1) >连续通气 ( 4 80 8mg·kg- 1) >间隙通气 ( 2 0 83mg·kg- 1) ,绝大部分化合物的含量都低于 0 2 0mg·kg- 1.堆肥前后ΣPAHs降解率在 6 5 5 %— 93 2 0 %之间 (平均为6 5 0 0 % ) ,绝大部分化合物的降解率都在 90 %以上 .通气堆肥尤其是间歇通气堆肥对污泥中PAHs的降解效果最好 .     

冬青叶兔唇花地上部分的化学成分(英文)

对冬青叶兔唇花(Lagochilus ilicifolius)地上部分的化学成分进行了分离纯化及结构鉴定.从其95%乙醇提取物中共分离得到11个化合物,包括7个环烯醚萜苷、2个长链醇、1个二萜和1个简单苯丙素类化合物.综合运用波谱数据分析和相关化学技术,这些化合物被鉴定为8-O-乙酰哈帕苷(1)、ajugoside(2)、ajujol(3)、哈帕苷(4)、京尼平苷酸(5)、玉叶金花苷酸(6)、8-deoxyshanzhiside(7)、citrusin C(8)、植醇(9)、三十一烷-12-醇(10)和二十八碳醇(11).化合物2~3、5~11均为首次从该属植物中分离得到.     

HPLC法测定多菌灵在西洋参中的残留量

本文报道了多菌灵在西洋参中残留量的HPLC检测方法.当添加水平在1.0一5.0μg·l~(-1)时,根中回收率为60一76%:添加水平在0.5一2μg·l~(-1)时,茎叶中回收率为70一80%;土壤添加2.5μg·l~(-1)时,回收率为84%.茎叶、根、土壤中残留量测定的相对标准偏差分别为2.16%.6.17%.1.24%.检测极限均为0.1μg·l~(-1)多菌灵在茎叶和土壤中的消解动态方程为C=118.42(?)和C=18.84(?)半衰期为5.87d和3.63d.     

有机化学品不同温度下(过冷)液体蒸气压预测模型的建立与评价

(过冷)液体蒸气压(PL)是评价化学品在环境中分配、迁移和归趋行为的重要参数。PL具有较强的温度依附性。发展一种能够精确预测不同环境温度下化学品PL的方法,有助于填补化学品生态风险评估的大量数据缺失。本研究收集整理了661种有机化合物在不同温度下(200~830 K)共计10 478个log PL值。在此基础上,采用偏最小二乘(PLS)回归和支持向量机(SVM)方法,构建了PL的线性和非线性预测模型。结果表明:2种模型均具有良好的拟合度、稳健性及预测能力,SVM模型的预测性能略高于PLS模型(PLS:R2adj.tra=0.912,RMSEtra=0.477,Q2ext=0.910;SVM:R2adj.tra=0.997,RMSEtra=0.092,Q2ext=0.967)。机理分析表明,温度是影响PL的主要因素,温度越高,蒸气压越大;其次,X1sol也影响PL大小,X1sol用来描述分子间的色散作用,分子间色散力越小,蒸气压越大;此外,化合物的氢键个数、极性和分子构型等因素也影响PL大小。采用Wiliams plot方法表征了PLS模型应用域。所建立的模型可用来预测烷烃、烯烃、醇、酮、羧酸、苯、酚、联苯、卤代芳香烃、含N化合物及含S化合物在不同温度下的PL数据。     

气相有机化学品与羟基自由基反应速率常数的QSAR模型

气相中有机化学品与羟基自由基(!OH)反应速率常数(k_(OH))是评价化学品大气持久性的重要参数.而化学品种类繁多,现有的k_(OH)实验数据不能满足其生态风险评估的需求.因此,需要建立一种能够快速预测有机化学品k_(OH)的方法,填补现有数据的缺失.本研究搜集整理了917种有机化合物的k_(OH)实验值,采用逐步多元线性回归法(MLR)和支持向量机法(SVM)分别构建了用于预测多种类化合物lgk_(OH)的线性和非线性定量结构-活性关系(QSAR)模型.基于MLR的预测模型具有良好的拟合度(经校正的相关系数的平方R_(adj.tr)~2=0.862、均方根误差RMSE_(tr)=0.455)、稳健性(交叉验证系数Q_(LOO)~2=0.856)和预测能力(外部验证系数Q_(ext)~2=0.850).基于SVM的预测模型也具有良好的拟合度(R_(adj.tr)~2=0.915,RMSE_(tr)=0.358)和预测能力(Q_(ext)~2=0.860).机理分析表明,最高占据分子轨道能(E_(HOMO))、卤素原子在分子中所占的百分比(X%)和分子中具有=CH—结构的数目(NdsCH)是最重要的3个描述符,解释了数据集78.3%的方差.采用Williams法表征模型的应用域.所建立的模型可用于预测烷烃、烯烃、炔烃、芳香族化合物、醇类、酮类、醚类、醛类、酸类、酯类、卤代化合物、含氮化合物、含硫化合物等室温下的k_(OH).     

外源化合物在鱼体内生物半减期的QSAR模型

生物半减期(t1/2)是评价外源化合物在鱼体内蓄积效应的重要参数。实验测定t_(1/2)的速度慢、成本高,难以满足化学品生态风险评价的需求,需要发展替代实验的模型预测方法。本研究搜集了653种化合物t1/2实测值,采用多元线性回归(MLR)和支持向量机(SVM) 2种方法,建立了鱼体logt1/2的定量构效关系(QSAR)预测模型。MLR模型的校正决定系数(R(adj)~2)为0.751,均方根误差(RMSE_(train))为0.587,去一法交叉验证系数(Q_(LOO)~2)为0.735,外部验证系数(Q_(ext)~2)为0.682,这表明模型具有较好的拟合度、稳健性和预测能力。SVM模型具有更好的拟合和预测能力(R_(adj)~2=0.839,RMSE_(train)=0.457,Q_(ext)~2=0.708)。采用Williams法对模型的应用域进行表征。所建模型可用于预测多环芳烃、多氯联苯、多溴联苯醚、有机磷农药、药物等典型化合物,以及其他烷烃、环烷烃、烯烃、醇、醚、酸、酯、酮、含卤素化合物、芳香族化合物、含硫、氮、磷化合物的在鱼体内的logt1/2值。     

部分城市污泥中氯苯类化合物的初步研究

应用GC/MS对我国 1 1个城市污泥中的 5种氯苯化合物 (CBs)进行了研究 .结果表明 ,各城市污泥中CBs的总含量 (ΣCBs)在 0 0 1 0— 6 91 7mg·kg- 1之间 ,绝大部分低于 1 0mg·kg- 1,依次是兰州 >北京 >香港大埔 >无锡 >香港元朗 >广州 >佛山>香港沙田 >西安 >珠海 >深圳 .各城市污泥的CBs都是以个别或少数化合物为主 ,显示出不同的分布特征 ,主要是 1 2 4 三氯苯和六氯苯 ,其它化合物含量普遍较低 .各种CBs化合物的最高含量主要分布于兰州污泥和无锡污泥中 .城市污泥中CBs的含量与污水来源、污水处理方式、污泥类型和CBs化合物的理化性质有关 .     

Representation of the world's biophysical conditions by the global protected area network

Protected areas (PAs) are often implemented without consideration of already existing PAs, which is likely to cause an overrepresentation of certain biophysical conditions. We assessed the representativeness of the current PA network with regard to the world's biophysical conditions to highlight which conditions are underprotected and where these conditions are located. We overlaid terrestrial and marine PAs with information on biophysical conditions (e.g., temperature, precipitation, and elevation) and then quantified the percentage of area covered by the PA network. For 1 variable at a time in the terrestrial realm, high temperature, low precipitation, and medium and very high elevation were underrepresented. For the marine realm, low and medium sea surface temperature (SST), medium and high sea surface salinity (SSS), and the deep sea were underrepresented. Overall, protection was evenly distributed for elevation across the terrestrial realm and SST across the marine realm. For 2 variables at a time, cold and very dry terrestrial environments had mostly low protection, which was also the case for low SST and low and medium SSS across most depths for marine environments. Low protection occurred mostly in the Sahara and the Arabian Peninsula for the terrestrial realm and along the Tropic of Capricorn and toward the poles for the marine realm. Although biodiversity measures are of prime importance for the design of PA networks, highlighting biophysical gaps in current PAs adds a frequently overlooked perspective. These gaps may weaken the potential of PAs to conserve biodiversity. Thus, our results may provide useful insights for researchers, practitioners, and policy makers to establish a more comprehensive global PA network.     

Quantitative composition of the defensive secretion ofBledius species (Coleoptera: Staphylinidae: Oxytelinae) is adapted to naturally occurring predators

Summary The adaptation of defensive secretions to their target organisms was examined for the abdominal gland secretions ofBledius furcatus, B. spectabilis andB. arenarius. Therefore the target organisms of the secretion of theseBledius species (i.e. their predators) had to be identified. At the collection sites examined these were the earwigLabidura riparia, the antCataglyphis bicolor, the flyLispe candicans, different carabids of the generaPogonus, Dichirotrichus, Dyschirius, Bembidion andCalathus and the wading birdsHaematopus ostralegus andCalidris alba. The secretion of the abdominal glands contains the toxin ptoluquinone dissolved in either-dodecalactone and 1-undecene (B. furcatus andB. spectabilis) or in octanoic acid and octyloctanoate (B. arenarius). The ratio of these solvents is species-specific. Application experiments using some of the natural insect predators (L. riparia, C. bicolor, Pogonus, Di. gustavii, Dyschirius) revealed that these solvent ratios provided a more effective deterrent than other possible ratios. Thus by combining the solvents in certain ratios, the capability of cuticular penetration and therefore the effectiveness of the defensive secretions are adapted to their natural targets.     

Democracy versus development: New urban debates

The politics of development includes subtexts of choice, as underpinned by community consensus (or lack of it), against the larger backdrop of a liberal democracy, with its intricate power structures that influence the choice of concepts and often lead to complicity rather than consent. A dilemma exists between the understanding of field-level practitioners and that of academics, whose understandings of progress differ. Progress can (and often does) imply long-term change across generations whereas development is often more a matter of crisis management and delivering tangible results to end-users. This makes it a bone of contention across political systems, irrespective of local or global dynamics. Development can emerge as a tool to be wielded for power and further political mileage at the expense of progress. Progress cannot be studied as a counterpoint to development as the sense of history is often missing in development interventions. Development tends to be piecemeal as its very logic often stems from the rationale of power. This is not to suggest, however, that development is only about politics; it is definitely more than the politics of everyday life and involves all of civil society that requires its critical and immediate attention. In this sense, it has become a priority for politicians with an underlying agenda designed to out-manouevre dissent and all statements of protest.     

A framework to measure the wildness of managed large vertebrate populations

As landscapes continue to fall under human influence through habitat loss and fragmentation, fencing is increasingly being used to mitigate anthropogenic threats and enhance the commercial value of wildlife. Subsequent intensification of management potentially erodes wildness by disembodying populations from landscape-level processes, thereby disconnecting species from natural selection. Tools are needed to measure the degree to which populations of large vertebrate species in formally protected and privately owned wildlife areas are self-sustaining and free to adapt. We devised a framework to measure such wildness based on 6 attributes relating to the evolutionary and ecological dynamics of vertebrates (space, disease and parasite resistance, exposure to predation, exposure to limitations and fluctuations of food and water supply, and reproduction). For each attribute, we set empirical, species-specific thresholds between 5 wildness states based on quantifiable management interventions. We analysed data from 205 private wildlife properties with management objectives spanning ecotourism to consumptive utilization to test the framework on 6 herbivore species representing a range of conservation statuses and commercial values. Wildness scores among species differed significantly, and the proportion of populations identified as wild ranged from 12% to 84%, which indicates the tool detected site-scale differences both among populations of different species and populations of the same species under different management regimes. By quantifying wildness, this framework provides practitioners with standardized measurement units that link biodiversity with the sustainable use of wildlife. Applications include informing species management plans at local scales; standardizing the inclusion of managed populations in red-list assessments; and providing a platform for certification and regulation of wildlife-based economies. Applying this framework may help embed wildness as a normative value in policy and mitigate the shifting baseline of what it means to truly conserve a species.     

Achieving Open Access to Conservation Science

Conservation science is a crisis discipline in which the results of scientific enquiry must be made available quickly to those implementing management. We assessed the extent to which scientific research published since the year 2000 in 20 conservation science journals is publicly available. Of the 19,207 papers published, 1,667 (8.68%) are freely downloadable from an official repository. Moreover, only 938 papers (4.88%) meet the standard definition of open access in which material can be freely reused providing attribution to the authors is given. This compares poorly with a comparable set of 20 evolutionary biology journals, where 31.93% of papers are freely downloadable and 7.49% are open access. Seventeen of the 20 conservation journals offer an open access option, but fewer than 5% of the papers are available through open access. The cost of accessing the full body of conservation science runs into tens of thousands of dollars per year for institutional subscribers, and many conservation practitioners cannot access pay‐per‐view science through their workplace. However, important initiatives such as Research4Life are making science available to organizations in developing countries. We urge authors of conservation science to pay for open access on a per‐article basis or to choose publication in open access journals, taking care to ensure the license allows reuse for any purpose providing attribution is given. Currently, it would cost $51 million to make all conservation science published since 2000 freely available by paying the open access fees currently levied to authors. Publishers of conservation journals might consider more cost effective models for open access and conservation‐oriented organizations running journals could consider a broader range of options for open access to nonmembers such as sponsorship of open access via membership fees. Obtención de Acceso Abierto a la Ciencia de la Conservación     

Sexual Predators,Energy Development,and Conservation in Greater Yellowstone

Abstract: In the United States, as elsewhere, a growing debate pits national energy policy and homeland security against biological conservation. In rural communities the extraction of fossil fuels is often encouraged because of the employment opportunities it offers, although the concomitant itinerant workforce is often associated with increased wildlife poaching. We explored possible positive and negative factors associated with energy extraction in the Greater Yellowstone Ecosystem (GYE), an area known for its national parks, intact biological diversity, and some of the New World's longest terrestrial migrations. Specifically, we asked whether counties with different economies—recreation (ski), agrarian (ranching or farming), and energy extractive (petroleum)—differed in healthcare (gauged by the abundance of hospital beds) and in the frequency of sexual predators. The absolute and relative frequency of registered sex offenders grew approximately two to three times faster in areas reliant on energy extraction. Healthcare among counties did not differ. The strong conflation of community dishevel, as reflected by in‐migrant sexual predators, and ecological decay in Greater Yellowstone is consistent with patterns seen in similar systems from Ecuador to northern Canada, where social and environmental disarray exist around energy boomtowns. In our case, that groups (albeit with different aims) mobilized campaigns to help maintain the quality of rural livelihoods by protecting open space is a positive sign that conservation can matter, especially in the face of rampant and poorly executed energy extraction projects. Our findings further suggest that the public and industry need stronger regulatory action to instill greater vigilance when and where social factors and land conversion impact biological systems.     

Comparison of the insecticidal effects of water extracted and intact aromatic plants onAcanthoscelides obtectus,a bruchid beetle pest of kidney beans

Summary Acanthoscelides obtectus (Say) is one of the most damaging pests of kidney beans,Phaseolus vulgaris L. worldwide. However, aromatic plants from the families Lamiaceae, Lauraceae, Myrtaceae and Poaceae can protect kidney beans by direct or delayed insecticidal effect, through increased adult mortality and inhibition of beetle reproduction (both oviposition and adult emergence). The efficiency of hydrodistillated and intact plants fromThymus vulgaris andT. serpyllum, Mentha piperata, Rosmarinus officinalis, Satureia hortensis, Eucalyptus globulus, Laurus nobilis, Origanum vulgare, andCymbopogon nardus was compared. For both extracts,Origanum vulgare had the best effect. The insecticidal effect was induced by more than the essential oils because no significant difference was noticed between distilled and intact plants extract. Inhibition of reproduction was particularly important. These results suggest that lipidic as well as non lipidic, allelochemicals, such as phenolics, or non-protein amino-acids, or flavonoids may be involved in the toxicity of aromatic plants to this beetle.     

Rapid,recurring, structured survey versus bioblitz for generating biodiversity data and analysis with a multispecies abundance model

A bioblitz inexpensively and quickly generates biodiversity data, but bioblitzes are often conducted with haphazard, unreplicated sampling. Results tend to be taxonomically, geographically, or temporally biased, lack metadata, and consist of lists of observed taxa that do not enable further analyses or correction for imperfect detection. A rapid, recurring, structured survey (RRSS) uses a structured sampling design and temporal and spatial replication to survey randomly selected sites on a conservation property. We participated in a loosely structured bioblitz and a subsequent RRSS at Big Canoe Creek Nature Preserve in Springville (St. Clair County), Alabama (USA) to compare observed richness derived from the 2 survey approaches. The RRSS data structure enabled us to fit models that accounted for imperfect detection to estimate abundances, occupancy probabilities, and habitat associations. The loosely structured bioblitz data could not be used in such models. We present a new integrated multispecies abundance model that we applied to avian RRSS data. Our model extension enables estimation for the community, employs data augmentation to estimate the number of undetected species, and incorporates covariates. The RRSS generated a more comprehensive and less biased list of observed taxonomic richness than the loosely structured bioblitz (e.g., 73 vs. 45 bird species and 104 vs. 63 insect families from the RRSS vs. loosely structured bioblitz, respectively). Models fit to the RRSS data identified seasonal patterns in avian community composition and allowed for estimation of habitat–occupancy relationships for insect taxa. The RRSS protocol has potential for broad transferability as a standardized, quick, and inexpensive way to inventory biodiversity and estimate ecological parameters while providing an outreach opportunity.     

Compliance with and ecosystem function of biodiversity offsets in North American and European freshwaters

Land-use change via human development is a major driver of biodiversity loss. To reduce these impacts, billions of dollars are spent on biodiversity offsets. However, studies evaluating offset project effectiveness that examine components such as the overall compliance and function of projects remain rare. We reviewed 577 offsetting projects in freshwater ecosystems that included the metrics project size, type of aquatic system (e.g., wetland and creek), offsetting measure (e.g., enhancement, restoration, and creation), and an assessment of the projects’ compliance and functional success. Project information was obtained from scientific and government databases and gray literature. Despite considerable investment in offsetting projects, crucial problems persisted. Although compliance and function were related to each other, a high level of compliance did not guarantee a high degree of function. However, large projects relative to area had better function than small projects. Function improved when projects targeted productivity or specific ecosystem features and when multiple complementary management targets were in place. Restorative measures were more likely to achieve targets than creating entirely new ecosystems. Altogether the relationships we found highlight specific ecological processes that may help improve offsetting outcomes.     

Some polyphagous Homoptera gain protection from their natural enemies by feeding on the toxic plantsSpartium junceum andErythrina corallodendrum (Leguminosae)

Summary Interactions were studied among alkaloid-containing legumes (Erythrina corallodendrum andSpartium junceum) and non-toxic plants (Citrus sinensis, Cucurbita moschata andEuphorbia tirucalli), several polyphagous homopterans,Aphis craccivora (Aphididae),Icerya purchasi, I. aegyptiaca (Margarodidae),Lepidosaphes ulmi (Diaspididae) andPlanococcus citri (Pseudococcidae), and some major natural enemies of these homopterans. Significant reductions in survival due to negative effects of alkaloid containing as compared with non-alkaloidal plants were recorded for the predatorsRodolia cardinalis andChilocorus bipustulatus, but not forCryptolaemus montrouzieri (Coleoptera: Coccinellidae),Chrysoperla carnea (Neuroptera: Chrysopidae) andSympherobius sanctus (Neuroptera: Sympherobiidae). The development time of the larvae or pupae ofR. cardinalis, C. carnea andS. sanctus was longer on the toxic plants than on the non-toxic ones. The percentage of parasitism ofA. craccivora collected from the non-alkaloidal plantsVicia palaestina andMelilotus albus was much higher than that onS. junceum. The parasitoid complexes ofA. craccivora differed between both plant groups. The nutritive value of honeydew ofI. purchasi andA. craccivora, as expressed by the life span ofEncyrtus infelix (Hymenoptera: Encyrtidae) adults, was also investigated. Life spans were significantly longer when the wasps fed on honeydew produced on non-alkaloidal plants (C. sinensis andPittosporum tobira) than on alkaloid containing plants whenI. purchasi — but notA. craccivora — was the producer. It is suggested that the chemical defense ofE. corallodendrum andS. junceum is exploited by polyphagous phytophages to reduce predation. In nature, population growth and density of four of the investigated homopterans are conspicuously high when they developed on the alkaloid containing plant species, and very low on non-alkaloid plants. The efficiency of their natural enemies may be reduced by sequestration of alkaloids (or other toxic plant compounds) or their transfer into excreted honeydew. Therefore it is assumed that a generalist phytophagous homopteran may be protected from its natural enemies, although at different rates of efficiency, if it can safely sequester the host allelochemical when it develops on toxic species within its host range.