Morphological disparity in the cambrian

An analysis of the range of morphology among arthropods demonstrates that disparity among living arthropods is similar to that in Cambrian arthropods. The range of morphological design resulting from the Cambrian "explosion" has been overestimated, reflecting a tendency to separate as "problematic" taxa that cannot be accommodated in the classification on the basis of the living biota. Problematic taxa are largely an artifact of an inadequate taxonomy. Special evolutionary processes may not be necessary to explain the early radiation of the metazoans.     

Trilobites and the origin of arthropods

While the question of whether the Arthropoda represent more than one phylum of animals is debatable, the jointed exoskeleton, a fundamental feature of arthropods, evolved independently in two groups that shared a worm-like common ancestor. The two major branches of Arthropoda, the primitively marine TCC and the primitively terrestrial (with one exception) Uniramia, independently arrived at arthropodization as the solution to the same problems of adaptation of the body mechanical system. New discoveries on trilobite anatomy show the unity of TCC as a group that shared a trilobite-like ancestor near the beginning of the Cambrian. With change in the constituency of Arthropoda through geologic time, the ways in which it would be categorized as a taxonomic group have also changed. The seeming isolation of the major modern arthropod groups is in large part an artifact of extinction of primitive intermediate forms such as trilobites which, in the Early Paleozoic, made the Arthropoda more diverse in basic modes of body organization than the group is at present. The appearance of fossilizable hard parts in arthropods resulted from shift in supporting function from the body cavity, primitively a hydrostatic skeleton, to the cuticle, which came to be strengthened in becoming an exoskeleton. Energetic efficiency, more than protection from predators or evolutionary size increase in itself, was probably the impetus behind the transition. On the scale provided by the general evolutionary trend toward progressive specialization of segments, TCC became arthropodized at earlier stages than did Uniramia. Among TCC, the shift may have been driven by the evolution of locomotory and feeding mechanisms that were exclusively geared to an aqueous medium.     

Evolutionary exploitation of design options by the first animals with hard skeletons

The set of viable design elements available for animals to use in building skeletons has been fully exploited. Analysis of animal skeletons in relation to the multivariate, theoretical "Skeleton Space" has shown that a large proportion of these options are used in each phylum. Here, we show that structural elements deployed in the skeletons of Burgess Shale animals (Middle Cambrian) incorporate 146 of 182 character pairs defined in this morphospace. Within 15 million years of the appearance of crown groups of phyla with substantial hard parts, at least 80 percent of skeletal design elements recognized among living and extinct marine metazoans were exploited.     

Burgess shale faunas and the cambrian explosion

Soft-bodied marine faunas from the Lower and Middle Cambrian, exemplified by the Burgess Shale of British Columbia, are a key component in understanding the major adaptive radiations at the beginning of the Phanerozoic ("Cambrian explosion"). These faunas have a widespread distribution, and many taxa have pronounced longevity. Among the components appear to be survivors of the preceding Ediacaran assemblages and a suite of bizarre forms that give unexpected insights into morphological diversification. Microevolutionary processes, however, seem adequate to account for this radiation, and the macroevolutionary patterns that set the seal on Phanerozoic life are contingent on random extinctions. They weeded out the morphological spectrum and permitted rediversification among surviving clades. Although the predictability of which clades will play in successive acts of the Phanerozoic theater is low, at least the outlines of the underlying ecological plot are already clear from the opening of the drama.     

环境质量评价中的生物指示与生物监测

通过比较生物指示与生物监测技术和仪器分析技术的分析过程及原理,结合北京市土壤中土壤脲酶与土壤重金属含量之间的相关关系的案例,及生物指示与生物监测技术在水生生态系统及大气污染研究中的应用状况,系统阐述了生物指示与生物监测技术研究的发展历程、研究前沿及发展方向.指出定量校正及不同学科与地区的科学团队的合作是生物指示与生物监测技术研究中需要克服的关键问题,并提出生物指示与生物监测技术研究的目标是整合不同学科的研究方向,为人类健康与环境安全的保护与预测提供技术支持.     

FLOWERING PLANTS AND ENTOMOPHAGOUS ARTHROPODS IN THE AGRICULTURAL LANDSCAPE: A PRACTISE-ORIENTED SUMMARY OF A COMPLEX RELATIONSHIP

● Most entomophagous arthropods consume nectar or pollen as alternative diets. ● The attractive of floral resource with different traits varies in a wide degree. ● Floral resource plays positive effects on not only entomophagous insects but also agricultural biodiversity, multiple ecosystem services and crop production. There is a growing demand for high-quality agricultural products and more countries have adopted landscape management by sowing flowering plants in agricultural fields as an important branch of conservation biological control. However, there has been less concern over the interactions and trade-offs between floral plants and entomophagous arthropods. This paper review progress in pollen/nectar feeding habits of entomophagous insects including parasitoids and predators which are important natural enemies of crop pests in agricultural fields. Factors that influence the preference of different guilds of natural enemies are reviewed to guide the selection of flowering plants in conservation biological control practices. Most studies find that floral resources have positive effects on both biological traits of natural enemies and their abundance and diversity, and this is believed to contribute greatly to pest control. Furthermore, the potential impacts of floral resources on crop yields are also discussed with an emphasis on a guild of entomophagous insects that provides both pest control and pollination services.     

转基因鲤的形态特征及主要经济性状研究

文章对转大麻哈鱼生长激素基因鲤的形态特征和在高寒地区的池塘的生长、生活力、抗寒、肌肉营养成分等主要经济性状进行了比较研究。结果表明,转基因鲤在生活力、抗寒、肌肉营养成分等经济性状与普通鲤经t值检验均无明显差异。而转基因鲤在体重、全长、体长、体高、头长等性状要明显大于普通鲤,主要表现在个体生长差异大,在试验鱼群体中最大个体体重比对照组群体中最大个体体重分别提高了52.5%,46.0%,76.0%,说明外源基因的导入对部分受体鱼有促生长效应,促进了转基因鲤的生长。在所测量的11种可比性状中,体长/体厚、体高/体厚,经数理统计分析与普通鲤均有显著差异,而其它9种性状,则无显著差异。     

稻鸭共作系统中主要捕食性天敌的生态位

【目的】探明稻鸭共作系统中主要捕食性天敌类群对资源的利用程度及在资源分配上的内在关系。【方法】在对稻鸭共作和常规稻作系统中主要捕食性天敌进行田间调查的基础上,研究主要捕食性天敌群落的结构和生态位,分析各类群在资源序列上分布的数量特征和资源利用状况。【结果】常规稻作区、稻鸭共作区中主要捕食性天敌的优势类群均为微蛛、园蛛、狼蛛和肖蛸科,以园蛛科的优势度指数为最高,分别为0.4999和0.6665。稻田养鸭对主要捕食性天敌类群的数量和分布格局有直接或间接的影响,使其时—空二维生态位宽度、生态位重叠度与生态位相似性比例均发生了不同程度的改变。其中微蛛、园蛛和肖蛸的生态位宽度值低于常规区,微蛛与球蛛、肖蛸与跳蛛、跳蛛与管巢蛛及管巢蛛与瓢虫的二维生态位重叠度比常规区增加了70.65%—75.57%。【结论】稻鸭共作使主要捕食性天敌在同一资源等级上的竞争加强,在时间上的同步性更为明显,尽管捕食性天敌的总个体数比常规区下降了19.56%,但天敌充分利用了时间资源序列中的较多等级,且分布更为均匀,发生时间长,可对害虫种群进行持续控制,因而控虫效果更为显著。     

Ethnoagronomy and ethnogastronomy: On indigenous typology and use of biological resources

Indigenous systems of recognition and classification of plants and arthropods are based on local criteria of relationship and contrast. Both inherent intellectual interest and utility considerations play a part in the choice of distinguishing features emphasized. In distinguishing among non-cultivated plants informants display awareness of life habits and morphological features that have little direct bearing on agronomic properties. In discriminating among harmless arthropods, physiological/behavioral attributes are emphasized. When the tasks include cultivated plants and harmful arthropods, functional criteria tend to dominate with respect to plant discrimination while negative human-directed effects are emphasized with respect to arthropods. Focusing on rice varieties, the discrimination criteria used are significantly gastronomic. One implication is that there is a need to broaden our perspective on farmers to admit a view of them as consumers rather than just as producers and to take their gastronomic preferences into account in breeding cultivars that have improved agronomic and market performance. In terms of integrated pest management, there is a need for taking stock of indigenous knowledge before any attempt to supplant it with “scientific” information is initiated. In sum, more serious attention needs to be paid to “ethnoagronomy” and “ethnogastronomy” — cognized models in the spheres of production and consumption — in order to design and promote agricultural recommendations that have a better chance of passing through the preattentive filters and being deliberately considered by farmers for their possible merits.     

Hyperphoretic dispersal of a pyxidiophora anamorph

It has been suggested that Thaxteriola species and other minute, nonmycelial fungi associated with arthropods have phylogenetic relationships with the Laboulbeniales. However, direct development of the thallus of Thaxteriola from an ascospore of Pyxidiophora has now been discovered. Thaxteriola is specialized for dispersal by mites carried on pine bark beetles; other fungi dispersed by arthropods in this symbiotic assemblage rely primarily on arthropod specializations.     

浅析家禽饲养环境与禽病防控

养禽业的飞速发展,使得规模养殖、养殖小区、大型集约化养殖越来越普及,养殖队伍不断壮大。在饲养管理实践中,为获得更高的经济效益,人为地改变了家禽的生长和生活环境,使整个"宿主-病原-环境"生态系统发生了变化。对于养禽场而言,饲养的关键是禽病防治的群体防控。然而疾病的发生与环境之间存在着密切的关系。如空气、车辆、用具、人员以及动物与动物之间的疾病传播等。因此,全面认识环境因素与疾病之间的相互关系是非常重要的。     

Acoel flatworms: earliest extant bilaterian Metazoans, not members of Platyhelminthes

Because of their simple organization the Acoela have been considered to be either primitive bilaterians or descendants of coelomates through secondary loss of derived features. Sequence data of 18S ribosomal DNA genes from non-fast evolving species of acoels and other metazoans reveal that this group does not belong to the Platyhelminthes but represents the extant members of the earliest divergent Bilateria, an interpretation that is supported by recent studies on the embryonic cleavage pattern and nervous system of acoels. This study has implications for understanding the evolution of major body plans, and for perceptions of the Cambrian evolutionary explosion.     

农商经济解析——以安徽太和县为例

安徽省太和县农商经济的发展有20~30年的历史,现在已经具有相当的规模,拥有农商30万~40万人,其中一些产业已形成集群,在全国同行业中具有重要的地位。太和县利用第三产业带动一、二产业的发展,在县域经济的发展中独具特色,被称为农村经济发展的“第三条道路”。对太和县经济发展的现状、农商经济的形成和所具有的特征进行逐一的分析,旨在讨论农商经济存在的可行性和对于中国其他县域经济发展的借鉴意义。     

Bats limit insects in a neotropical agroforestry system

Exclosure experiments have demonstrated the effects of bird predation on arthropods. In a Mexican coffee plantation, we excluded foliage-gleaning bird and bat predators from coffee plants. Effects of bats and birds were additive. In the dry season, birds reduced arthropods in coffee plants by 30%; birds and bats together reduced arthropods by 46%. In the wet season, bats reduced arthropods by 84%, whereas birds reduced them by only 58%. We conclude that previous "bird" exclosure experiments may have systematically underestimated the effects of bats.     

Evidence for monophyly and arthropod affinity of cambrian giant predators

The Chinese Early Cambrian Chengjiang fauna includes three different anomalocaridids, a globally spread, extinct marine group including the largest known Cambrian animals. Anomalocaridids were active predators, and their presence implies that a complex ecosystem appeared abruptly in the earliest Phanerozoic. Complete specimens display several sets of characters shared only with some other exclusively Cambrian forms. This evidence indicates that anomalocaridids, Opabinia, and Kerygmachela form a monophyletic clade. Certain features indicate arthropod affinities of the lade, and for this group an unnamed (sub)phylum-level taxon within an arthropod (super)phylum is proposed.     

晋枣品种变异研究

对晋枣的12个无性系的16个性状进行了调查研究,根据其中4个数量性状,进行了聚类分析,将12个无性系分为3类,其中G2与其他无性系有明显差异.同时,利用POD同工酶技术,根据酶谱类型也将12个无性系分为3类.综合两种方法研究结果表明,晋枣品种内部存在一定程度的变异,同时可以确定G2是一个变异单株或同名异物品种.     

Lower Cambrian vendobionts from China and early diploblast evolution

Ediacaran assemblages immediately predate the Cambrian explosion of metazoans and should have played a crucial role in this radiation. Their wider relationships, however, have remained refractory and difficult to integrate with early metazoan phylogeny. Here, we describe a frondlike fossil, Stromatoveris (S. psygmoglena sp. nov.), from the Lower Cambrian Chengjiang Lagerst?tte (Yunnan, China) that is strikingly similar to Ediacaran vendobionts. The exquisite preservation reveals closely spaced branches, probably ciliated, that appear to represent precursors of the diagnostic comb rows of ctenophores. Therefore, this finding has important implications for the early evolution of this phylum and related diploblasts, some of which independently evolved a frondose habit.     

小麦全蚀病为害新特点及其治理对策研究

经４年研究证明,进入９０年代以来,山东省小麦全蚀病有两个新的为害特点,其一是全蚀病发生区有所扩大,已遍及全省１７个市地,发病县区占全省农业县区的８５％,病情仍然严重;其二是病地由以往的全蚀病单一为害,发展为近年来的以全蚀病为主、多种根腐性病害同田甚至同株侵染为害。其形成原因主要包括长期推行小麦、玉米一年两熟制,偏施氮肥,缺少有机肥和磷、钾肥,以及普遍种植感病品种等。经试验、示范,提出“三改一治”的农业生态综合治理对策,推广应用效果显著,平均防效为８５．８％。     

A Cambrian peak in morphological variation within trilobite species

Morphological variation within species is a raw material subject to natural selection. However, temporal change in morphological diversity has usually been studied in terms of variation among rather than within species. The distribution of polymorphic traits in cladistic character-taxon matrices reveals that the frequency and extent of morphological variation in 982 trilobite species are greatest early in the evolution of the group: Stratigraphically old and/or phylogenetically basal taxa are significantly more variable than younger and/or more derived taxa. Through its influence on evolutionary tempo, high intraspecific variation may have played a major role in the pronounced Cambrian diversification of trilobites.     

昆虫滞育的研究进展

昆虫是世界上数量最多、分布最广的节肢动物,作为自然界中长期生存的生物,其具有高度的适应能力,滞育就是其适应能力的表现之一。昆虫滞育期间维持极低的代谢速率,无明显的形态学变化。这一表面看来似乎静止的状态有其复杂的生理学及生物化学基础,昆虫的滞育一直为人们所关注。从20世纪10年代初开始,学者们对引起滞育的环境因素、滞育的生理生化、内分泌学、滞育激素的分离纯化等进行了大量研究。笔者对已有的研究成果进行了综述,以期为今后昆虫滞育的研究提供参考。