昆虫寄主标记信息素

综述了昆虫寄主标记信息素的研究进展。昆虫寄主标记信息素是指由昆虫产生的用来标记寄主上有同种个体存在的化学物质。昆虫寄主标记信息素的主要生态学功能是调节昆虫的产卵行为,通过阻止自身或同种其它个体对已标记寄主的产卵选择,或减少产卵量来减少后代之间对寄主资源的竞争。寄主标记信息素也会给释放着带来不利的影响,如信息盗用和盗寄生现象等。昆虫寄主标记信息素也调节昆虫近缘种之间对共同寄主资源的竞争。近缘种昆虫对相互寄主标记信息素识别能力的差异反映了不同昆虫对同一寄主资源竞争能力的强弱。寄主标记信息素产生和贮存的部位一般与外分泌腺、消化系统或生殖系统相联系,杜氏腺、毒腺、前胸腺、腹腺、下唇腺、后产卵管、卵巢、中肠和后肠等是产生或贮存寄主标记信息素的常见部位。产生的寄主标记信息素一般在成虫产卵时由产卵器、口器或排泄口释放到寄主体内或体表。卵寄生蜂的寄主标记信息素一般标记在寄主的体表,雌成蜂用触角检测;其它寄生蜂的寄主标记信息素常产在寄主体内,用产卵器检测;植食性昆虫的寄主标记信息素只产在寄主表面,用触角或产卵器检测。昆虫的产卵器、口器、触角或跗节上着生有感受寄主标记信息素的化感器,可以检测到标记在寄主体内或体表的寄主标记信息素。昆虫寄主标记信息素的完全定性涉及活性化合物的分离、鉴定、合成以及行为测定等,已有几种昆虫的寄主标记信息素成分得到了分离鉴定。     

多寄主型寄生性天敌昆虫的寄主适应性及其影响因素

寄生性天敌昆虫对不同寄主资源的适应能力是其存活和繁殖的必要条件,它们的寄主选择行为则是其重要的适应结果。多寄主型寄生性天敌昆虫虽然对某种特定寄主资源的利用效率可能不如单寄主型寄生蜂,但却有利于拓展更宽的寄主范围,因此对环境的适应能力更强,更容易在自然界维持其种群的生存。统计结果也表明多寄主型天敌的生物防治效果往往比专食性天敌更高。有时生物防治成功的关键可能并不在于所利用的天敌种类的不同,而在于天敌的不同生物型或地理宗。总结了多寄主型寄生性天敌昆虫的寄主适应能力及其影响因素。寄生性天敌昆虫不仅因地理隔离产生种群分化,也可能因寄生不同的寄主产生种群内的分化,从而更加适应寄主的生活特性和栖境条件。寄主种类、寄主发育阶段、寄主大小、寄主营养、寄主免疫反应、寄主逃避反应、其它天敌的竞争、寄主共生或共栖生物的存在、寄主植物、天敌自身的学习能力及其共生微生物等多种因素对寄生性天敌昆虫的寄主适应性可产生影响。展望了多寄主型寄生性天敌昆虫对新寄主资源的拓展利用能力和适应性在生产上的可能应用前景和途径,以期为明确天敌与寄主间的互作关系,人工驯化寄生性天敌昆虫增强对靶标害虫的控制作用,合理利用天敌提高生物防治效率提供新的思路和理论支持。     

拟寄生蜂搜索产卵过程中对寄主的竞争

综述拟寄生蜂搜索产卵过程中对寄主竞争的最新研究进展.这类竞争具有四种方式,即标记寄主、杀卵和杀幼、守护寄主和捕食寄主.（1）标记寄主常涉及寄主标记信息素,这是由雌蜂在产卵前、产卵时或产卵后分泌的化学物质.寄主标记信息素常介导拟寄生蜂对已寄生和健康寄主的辨别、减少过寄生和多寄生、减轻种内和种间竞争压力.（2）雌蜂遇到已寄生寄主时,很多种类杀死前一雌蜂遗留的卵和幼虫,再产下自己的卵.雌蜂使用三种方法杀卵和杀幼,即产卵器穿刺、取食和使用有毒物质.通过杀卵和杀幼,产卵雌蜂清除了前一雌蜂遗留的后代,主动改善了寄主品质,从而有利于自身后代的生存.（3）守护寄主在肿腿蜂科、缘腹细蜂科、金小蜂科、缨小蜂科和茧蜂科中均有报道,守护者驱逐入侵者以保护后代及健康寄主.（4）捕食寄主不仅减少了健康寄主数量,且直接导致已寄生寄主中拟寄生蜂卵和幼虫的死亡.雌蜂一般在体内成熟卵量较少时捕食寄主.讨论了研究拟寄生蜂搜索产卵过程中竞争寄主的理论意义和实际应用价值.     

棉花型和黄瓜型棉蚜(Aphis gossypii Glover)的寄主适应性及转移通道

采用寄主转接建立生命表的方法研究了棉花型和黄瓜型棉蚜对不同寄主植物的适应性,以及两寄主型棉蚜是否可通过中间桥梁寄主实现寄主互换的问题。结果表明,两寄主型棉蚜直接互换寄主后,其存活和繁殖力显著下降,表现为棉花型和黄瓜型棉蚜的净增殖率比在原寄主上分别下降980倍和12倍,平均世代寿命缩短5～12d。两寄主型棉蚜均能利用木槿植物,并且适应性没有显著差异。但是两寄主型棉蚜均不能在车前草和大叶黄杨上存活和繁殖后代。西葫芦作物对棉蚜在木槿、棉花和黄瓜寄主上的相互转移起到了重要的桥梁寄主作用。冬寄主木槿上棉蚜可通过甜瓜或西葫芦转移到黄瓜寄主上,棉花和黄瓜上棉蚜也可通西葫芦作物分别转移到黄瓜和棉花作物上,从而形成棉蚜在不同寄主植物间的相互转移通道,造成为害和病毒病的扩张。     

寄生蜂对寄主生长发育的调控

寄生蜂在产卵时,常将一些特殊因子注射进寄主体内,从而对寄主的生长发育产生一定的调控作用.本文综述这几年的研究进展,着重从寄生蜂与寄主发育同步性的调控、寄生蜂对寄主代谢的调控及寄生蜂对寄主激素的调控三个方面概述了寄生蜂对寄主生长发育的调控.     

斑痣悬茧蜂的寄主辨别能力及其影响因素

为评价斑痣悬茧蜂Meteorus pulchricornis (Wesmael)的寄主辨别能力及其影响因素, 采用双选试验（斜纹夜蛾2龄寄主幼虫, 健康∶被寄生=5∶5）, 观察了寄生经历（无寄生经历、 有1次寄生经历、 有1次过寄生经历）和寄主被首次寄生后的间隔时间（1 - 7 d）对斑痣悬茧蜂在健康寄主和被寄生寄主之间的选择; 为探究斑痣悬茧蜂是否能够辨别寄主斑块质量, 观察了斑痣悬茧蜂连续3次访问不同质量寄主斑块（被寄生寄主∶健康寄主分别为 2∶8, 5∶5和 8∶2）时的产卵刺扎次数。对选择频次进行的分析表明, 寄主被首次寄生后的间隔时间和寄生蜂的寄生经历均对过寄生发生有显著影响(P<0.05), 过寄生概率随寄主首次被寄生后的间隔时间延长而降低; 有寄生经历的寄生蜂发生过寄生的概率低于无寄生经历的寄生蜂。用Cox比例风险模型对寄主辨别时间进行的分析表明, 发生过寄生的风险随寄主被初次寄生后间隔时间的延长而减小, 也因寄生蜂具有过寄生经历而减小。斑痣悬茧蜂在连续3次访问不同质量寄主斑块中, 产卵刺扎次数随寄主斑块的质量提高而显著增多。据此推论, 斑痣悬茧蜂不仅能够辨别被寄生寄主, 而且能够辨别含有被寄生寄主的寄主斑块。     

青藏高原北部革螨的数量和寄主关系

根据在青藏高原北部采得的革螨资料,利用聚类分析方法,对革螨进行了分类。给出了革螨与寄主种数的关系方程。其与寄主关系,５５．４％为单寄主;东北血革螨是多种寄主的优势螨种。     

甜菜夜蛾不同龄期幼虫被斑痣悬茧蜂寄生的风险分析

寄生蜂的寄主识别期是构建最优接受寄主模型的重要参数之一。本研究观察了斑痣悬茧蜂(Meteorus pulchricornis)对甜菜夜蛾(Spodoptera exigua)不同龄期幼虫的识别期,并首次用生存分析方法估计寄主被寄生的风险以及寄生经历对寄主识别期的影响。结果表明:在2.5h观察期内,除1龄寄主幼虫外,其他各龄(2~5龄)幼虫均被寄生;对首次寄主识别期的Cox回归模型拟合分析表明,与2龄寄主幼虫(参照虫龄)相比,3~5龄寄主幼虫被寄生的累计风险比率显著高于2龄寄主幼虫(2·6~4·0倍),而对再次寄主识别期的分析未发现3~5龄寄主幼虫与2龄幼虫之间存在显著差异。根据对首次与再次寄主识别期进行的生存曲线比较表明,对2~4龄幼虫的再次寄主识别期显著短于首次寄主识别期;说明寄生经历显著提高了寄生蜂的寄主识别期。由此推测,较高龄期甜菜夜蛾幼虫被无寄生经验斑痣悬茧蜂寄生的风险高于低龄幼虫。     

云杉矮槲寄生内寄生系统的解剖学研究

采用石蜡切片和显微观察的方法,以被云杉矮槲寄生侵染的青海云杉枝条为材料,从解剖学水平观察云杉矮槲寄生的内寄生系统。结果表明:云杉矮槲寄生的内寄生系统由分布在寄主皮层内的皮层根和镶嵌在寄主木质部中的吸根组成。皮层根可以沿着寄主枝条,通过挤压寄主皮层细胞的方式扩展,并穿透寄主表皮层形成云杉矮槲寄生的寄生芽;在靠近或接触寄主次生韧皮部时形成吸根,吸根顶端细胞定向穿透寄主韧皮部和形成层,侵染木质部,并沿木射线方向生长。当云杉矮槲寄生侵入寄主以及皮层根向外生长时,寄主表皮层发生加厚现象。随着云杉矮槲寄生侵染部位的寄主皮层细胞数增多,引起枝条膨大。研究认为,云杉矮槲寄生可以进行系统侵染,反映了云杉矮槲寄生与其寄主在组织水平上的相互作用。     

鱼类三代虫的寄主特异性分析

分析了迄今为止世界范围三代虫的寄主情况。三代虫具有很强的寄主特异性,并且在种、属及科等水平上的特异性均有较明显差异;分析同一种寄主上所寄生的三代虫种类之间的关系,显示大部分寄主只寄生一种三代虫,体现出了三代虫很强的寄主特异性。     

A Unique Protease Cleavage Site Predicted in the Spike Protein of the Novel Pneumonia Coronavirus (2019-nCoV) Potentially Related to Viral Transmissibility

正Dear Editor,In December 2019, a novel human coronavirus caused an epidemic of severe pneumonia(Coronavirus Disease 2019,COVID-19) in Wuhan, Hubei, China(Wu et al. 2020; Zhu et al. 2020). So far, this virus has spread to all areas of China and even to other countries. The epidemic has caused 67,102 confirmed infections with 1526 fatal cases     

Curcuminoids as inhibitors of thioredoxin reductase: A receptor based pharmacophore study with distance mapping of the active site

Curcumin is the yellow pigment of turmeric that interacts irreversibly forming an adduct with thioredoxin reductase (TrxR), an enzyme responsible for redox control of cell and defence against oxidative stress. Docking at both the active sites of TrxR was performed to compare the potency of three naturally occurring curcuminoids, namely curcumin, demethoxy curcumin and bis-demethoxy curcumin. Results show that active sites of TrxR occur at the junction of E and F chains. Volume and area of both cavities is predicted. It has been concluded by distance mapping of the most active conformations that Se atom of catalytic residue SeCYS498, is at a distance of 3.56 from C13 of demethoxy curcumin at the E chain active site, whereas C13 carbon atom forms adduct with Se atom of SeCys 498. We report that at least one methoxy group in curcuminoids is necessary for interation with catalytic residues of thioredoxin. Pharmacophore of both active sites of the TrxR receptor for curcumin and demethoxy curcumin molecules has been drawn and proposed for design and synthesis of most probable potent antiproliferative synthetic drugs.     

Comparative morphology of the carpel in the Liliaceae: Hewardieae, Petrosavieae, and Tricyrteae

The young pistils in the melanthioid tribes, Hewardieae, Petrosavieae and Tricyrteae, are uniformly tricarpellate and syncarpous. They lack raphide idioblasts. All are multiovulate, with bitegmic ovules. The Petrosavieae are marked by the presence of septal glands and incomplete syncarpy. Tepals and stamens adhere to the ovary in the Hewardieae and the Petrosavieae but not in the Tricyrteae. Two vascular bundles occur in the stamens of the Hewartlieae and Tricyrtis latifolia. Ventral bundles in the upper part of the ovary of the Hewardieae are continuous with compound septal bundles and placental bundles in the lower part. Putative ventral bundles occur in the alternate position in the Tricyrteae and putative placental bundles in the opposite. position in the Petrosavieae. The dichtomously branched stigma in each carpel of the Tricyrteae is supplied by a bifurcated dorsal bundle.     

Selection with two alleles and complete dominance

For a plant selection model with frequency-independent viabilities, fertilities and selfing rates, it is shown that apart from global fixation, for certain parameter combinations a protected polymorphism and facultative fixation (either allele may become fixed according to initial frequencies) may both occur. Facultative fixation requires different selling rates for the dominant and recessive type. Protection of the polymorphism requires resource allocation for male and female function. In this connection the problem of purely genetically caused population extinction is discussed.
For general frequency dependence and regular segregation, the chances for establishment of a completely recessive gene are compared to those of a completely dominant gene. It is proven that the process of establishment of the recessive gene, despite a fitness advantage, may be considerably endangered by drift effects if random mating prevails. The recessive gene may reach the same effectivity in establishment as a dominant gene, only if the recessive homozygote mates exclusively with its own type during the period of establishment.     

Composition and diversity of bird communities in Swedish farmland–forest mosaic landscapes

CapsuleThe amount of forest (at local and landscape scales) and occurrence of residual habitats at the local scale are shown to be the major factors influencing bird community composition in farmland–forest landscapes in central Sweden.

Aims To investigate the importance of local habitat and landscape structure for breeding birds in farmland–forest landscapes in central Sweden.

Methods Breeding birds were censused at 292 points. A detailed habitat mapping was made within 300 m of the points. Within a 300–600 m radius only two major habitats (forests and arable fields) were identified.

Results Cluster analyses of bird communities identified three site types that also differed in habitat composition: (i) partially forested sites in forested landscapes; (ii) heterogeneous sites with residual habitats in mosaic landscapes; and (iii) field-dominated farmland sites in open landscapes. A total of 19 of 25 farmland bird species (restricted to farmland or using both farmland and forest) had the highest abundance in farmland sites with mosaics of forest and farmland, while only six farmland species had the highest abundance in field-dominated sites. The bird community changed from being dominated by farmland species to being dominated by forest species (common in forest landscapes without farmland) at small proportions (10–20%) of forest at the local scale. A major difference in habitat composition between heterogeneous and field-dominated sites was the occurrence of different residual habitats (e.g. shrubby areas and seminatural grasslands). These habitats seemed to influence bird community composition more than land-use, despite covering <10% of the area. Seminatural grasslands were important for bird community composition and species-richness, but grazing seemed to be less important. Among different land-use types, cereal crops were the least preferred fields. Set-asides with tall vegetation and short rotation coppices were positively associated with species-richness of farmland birds.

Conclusion In general, the composition of the landscape was important for bird community composition, although amount and distribution of forests, occurrence of residual habitats and land-use of fields at the local scale had the strongest influence on bird community composition. The possible implications of these patterns for managing farmland–forest landscapes are discussed.     

Chemical constituents from the fruits of Rhus typhina L. and their chemotaxonomic significance

This work describes the isolation and characterization of twenty-nine compounds from the fruits of Rhus typhina L., including eleven flavonoids (1–11), eleven phenols (12–22), two pentacyclic triterpenes (23–24), two organic acids (25–26), one lumichrome (27), one courmarin (28) and one pyrimidine (29) on the basis of their spectroscopic data. Compounds apigenin (1), daidzein (4), orobol (5), 3′, 5, 5′, 7-tetrahydroxyflavanone (6), naringenin (7), butein (8), (-)-catechin (9), quercetin-3-O-α-L-(3″-O-galloyl)-rhamnoside (11), 2-hydroxybenzoic acid (13), 4-hydroxybenzaldehyde (14), vanillin (15), methyl 3,4-dihydroxybenzoate (16), 3,5-dihydroxybenzamide (18), tyrosol (19), caffeic acid (20), 3-(2,4,6-trihydroxyphenyl)-1-(4-hydroxyphenyl)-propan-1-one (21), phlorizin (22), friedelin (23), oleanolic acid (24), 4,4-dimethyl-heptanedioic acid (25), anthranilic acid (26), lumichrome (27), scoparone (28) and uracil (29) have not been recorded before in this plant. This is the first report on the occurrence of compounds 4–7, 9, 11, 13–14, 16, 18–21, 25–29 from the genus Rhus. Moreover, the chemotaxonomic significance of these isolated compounds was also summarized.