Cell biology. Bacterial spelunkers

Bacteria that are engulfed by phagocytic cells of the immune system are usually destroyed once inside the host cell but not always. Why is it that sometimes engulfed bacteria survive and thrive quite happily inside the host cell? As Mulvey and Hultgren explain in their Perspective, the answer may lie in small indentations in the host cell plasma membrane called caveolae that direct certain signal transduction pathways inside the host cell (Shin et al.). If bacteria adhere to regions of the host cell surface that is rich in caveolae, they are better able to survive once inside the cell.     

Should arthropod parasitoids and predators be subject to host range testing when used as biological control agents?

Testing of candidate biological control agents to estimate their likely field host ranges in the area of release has been part of weed biological control for several decades, with evolving techniques and goals. Similar efforts have been made less often for parasitoids and predators being introduced for arthropod biological control. Here, we review both techniques of host range testing and social objectives of such screening. We ask whether agents introduced for arthropod biological control should be subjected to host range testing before release, and if so, are methods used for estimating host ranges of herbivorous arthropods appropriate, or are different approaches needed. Current examples in which host range testing has been employed for arthropod biological control are reviewed. We conclude with recommendations concerning guiding principles about use of host range testing. We recommend modest expansion of host range testing for arthropod biological control for projects on continents. We recommend more extensive testing for projects of introduction onto islands. We note that introductions to islands could provide opportunities to gain experience in use of host range estimation for this class of organisms and to conduct post release evaluations of host ranges. We urge caution in efforts to mandate host range testing but simultaneously recommend consultation between biological control workers and insect conservationists.     

Brood parasitic cowbird nestlings use host young to procure resources

Young brood parasites that tolerate the company of host offspring challenge the existing evolutionary view of family life. In theory, all parasitic nestlings should be ruthlessly self-interested and should kill host offspring soon after hatching. Yet many species allow host young to live, even though they are rivals for host resources. Here we show that the tolerance of host nestlings by the parasitic brown-headed cowbird Molothrus ater is adaptive. Host young procure the cowbird a higher provisioning rate, so it grows more rapidly. The cowbird's unexpected altruism toward host offspring simply promotes its selfish interests in exploiting host parents.     

梨、苹果锈病转主寄主的研究

梨、苹果锈病的转主寄主是桧柏的两个不同类型。梨锈病的转主寄主树冠较稀疏,分枝角度较大,具针叶和鳞叶,在转主寄主上形成纺锤形瘿瘤,苹果锈病的转主寄主树冠较紧凑,分枝角度小,只具针叶,在转主寄主上形成球形或半球形的瘿瘤。     

Plant chemistry and the evolution of host specificity: new evidence from heliconius and passiflora

Larval growth rates of Heliconius butterflies do not closely parallel host plant choice, an indication that factors other than host plant chemistry are important in evolving host specificity. High growth rate in one species is correlated with reduction in number of palatable host species. This suggests a mechanism by which ecologically restricted species become progressively biochemically specialized.     

福建省柑桔黄龙病虫媒木虱的野生寄主及其带毒率研究

对福建省柑桔主产区的木虱野生寄主进行调查,确定福建省柑桔木虱中间寄主的品种及种类。采集在中间寄主植株生活的木虱及叶片进行PCR检测,发现九里香、金桔带毒。用饲毒20 d的木虱接种各中间寄主,1个月、半年各检测1次,确定九里香、金柑、金桔带毒,它们是柑桔黄龙病病原的寄主。其它芸香科植株未检测出病原。     

紫胶虫寄主植物研究现状与展望

归纳总结紫胶虫国内外优良寄主植物的有性繁殖技术并对寄主植物的种类、生理学、生物学和生态学的研究与进展进行了综合分析；在研究相对较少的寄主植物无性繁殖方面提出研究的思路和对策；最后展望了寄主植物今后的研究发展方向。     

蚜虫的寄主选择与取食行为

本文综述了作为植物病毒主要介体蚜虫的寄主选择和取食行为。蚜虫对寄主的选择主要为有翅蚜。有翅蚜的活动可分为4个行为阶段:停息相、迁飞相,进攻相和定居相。蚜虫的寄主选择主要在迁飞相和进攻相,并按一定的行为序列进行。决定蚜虫寄主选择行为序列执行的因素主要是食物源刺激,蚜虫在活动中若得到适当的正向刺激,就开始取食。由于大多数蚜虫吸食韧皮部,因此对蚜虫的口针导向机制进行了解释。     

搭配营造大芸的多种寄主林暨防风固沙林模式

根据实践经验和实地考察结果,提出以寄主与寄生物在生长期充分利用足够的阳光、风干、防风、固沙、提高植被覆盖率及适应现代节水技术为一体的相互独立、互不影响的搭配营造模式。模拟实验表明:①寄主树荫高度与地形条件、树的位置、树高度、树的弯度、时间及阳光照射角度有密切的关系;②主寄主菱形布置时每棵主寄主和寄生物都充分利用正常生长所需的阳光;③以高度不同的副寄主林从矮到高沿着主寄主与主风向按10°～45°布置,起减弱风速、分风及滞风的作用;④副寄主的阶梯型布置,起过滤作用;⑤副寄主的交错布置对过滤后的风起预防旋风和平衡作用。     

自然条件下昆虫染螨类群的初步调查

通过对我国13个省(区、市)自然条件下昆虫染螨情况的野外调查,结果表明,染螨昆虫有13目、50科。并报道了部分昆虫染螨率、染螨部位及其主要螨类类群(蜱螨亚纲3目、16科),还讨论了寄生螨对寄主及其体位的选择偏好性等现象。     

甘肃省斑痣盘菌科真菌

甘肃省针、阔叶树生斑痣盘菌科真菌５属１８种。其中寄主新记录４种,国内分布新记录７种。     

Species coextinctions and the biodiversity crisis

To assess the coextinction of species (the loss of a species upon the loss of another), we present a probabilistic model, scaled with empirical data. The model examines the relationship between coextinction levels (proportion of species extinct) of affiliates and their hosts across a wide range of coevolved interspecific systems: pollinating Ficus wasps and Ficus, parasites and their hosts, butterflies and their larval host plants, and ant butterflies and their host ants. Applying a nomographic method based on mean host specificity (number of host species per affiliate species), we estimate that 6300 affiliate species are "coendangered" with host species currently listed as endangered. Current extinction estimates need to be recalibrated by taking species coextinctions into account.     

管花肉苁蓉幼苗发育解剖学研究

采用光学显微镜和透射电镜方法,研究管花肉苁蓉吸器侵入寄主根和幼苗分化建成过程的形态学。结果表明:1)管花肉苁蓉吸器接触柽柳根表皮层后,吸器顶端分化出侵入细胞。在侵入细胞引领下,吸器呈楔形结构依次侵入柽柳根皮层、中柱和木质部。在吸器侵入寄主根过程中,与寄主根皮层细胞接触的吸器细胞壁呈现增厚反应,与吸器顶端邻近的多层寄主皮层细胞被机械挤压而变形,乃至被破坏。2)在吸器侵入木质部后,与寄主根表皮连接的管花肉苁蓉芽端薄壁组织恢复分生能力,分化出芽端生长点;生长点分化鳞叶原基,鳞叶原基长大为鳞叶幼叶,在鳞叶幼叶的叶腋内分化出生长点,发育成肉苁蓉幼苗。结果显示,管花肉苁蓉吸器侵入寄主根是一个主动过程,并有机械力的参与。吸器侵入寄主根和芽端生长分别呈现单极生长方式。     

Some aspects of intracellular parasitism

In intracellular parasitism the host cell is a true and hospitable host. The parasite does not have to break in the door. It has subtle ways of inducing the host to open the door and welcome it in. One of the exciting fields in the future of parasitology is to find out what these ways are and why they are sometimes so highly specific that the cell that invites one parasite in will not open the door to another closely related species. Once inside, the parasite not only exploits nutrients already available in the cell, and the cell's energy-yielding system, but it further induces the cell to assist actively in its nutrition. Like a bandit who has cajoled his way in, the parasite now forces his host to prepare a banquet for him. Finally it may destroy its host cell, as in most of the associations I have described herein, or it may stimulate its host cell to abnormal increase in size or to have an altered metabolism with the formation of new products. Or it may even contribute some positive benefit to the host cell or to the multicellular organism of which the cell is a part, so that the two kinds of organisms then live together in a state of mutualism or symbiosis (26).     

食物对樟蚕幼虫生长发育的影响

樟蚕幼虫取食不同食物,对其食量、龄期、死亡率等均有明显影响。试验结果表明:樟蚕的主要寄主植物是樟树、枫香和枫杨。樟蚕幼虫取食乌桕叶后中毒死亡,取食漆树叶、喜树叶和毛冬青叶均不能化蛹、原报道该几种植物是樟蚕寄主不确。而榕树和豆梨则是首次发现的新寄主。     

Virulence and local adaptation of a horizontally transmitted parasite

Parasites are thought to maximize the number of successfully transmitted offspring by trading off propagule production against host survival. In a horizontally transmitted microparasitic disease in Daphnia, a planktonic crustacean, increasing geographic distance between host and parasite origin was found to be correlated with a decrease in spore production and virulence. This finding indicates local adaptation of the parasite, but contradicts the hypothesis that long-standing coevolved parasites are less virulent than novel parasites. Virulence can be explained as the consequence of balancing the positive genetic correlation between host mortality and strain-specific spore production.     

植物病原真菌致病分子机理的研究进展

综述了植物病原真菌致病分子机理的研究进展,围绕植物病原真菌粘附寄主表面、侵染结构的形成、侵入寄主、在寄主内定殖与扩展四个侵入寄主的主要步骤,进行分子解析的阐明,有助于更好的评估病原真菌致病性的影响,并对今后的工作进行了展望.     

西安地区烟粉虱寄主植物及其危害程度调查

调查记录了西安地区烟粉虱的寄主植物，经鉴定达24科53种（变种），茄科、葫芦科、豆科、十字花科和菊科的种类较多，其中包括蔬菜、果树、花卉园林植物、经济植物和杂草等，并根据寄主植物上烟粉虱的数量将烟粉虱的危害程度划分成4个不同的等级。     

斜纹夜蛾寄主植物名录

在田间调查和查阅国内外文献的基础上,整理出斜纹夜蛾寄主植物名录。该虫寄主涉及到蕨类植物、裸子植物、双子叶植物、单子叶植物,共计109科389种(包括变种)。