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Payne, Willard W. (U. Michigan, Ann Arbor.) The morphology of the inflorescence of ragweeds (Ambrosia-Franseria: Compositae). Amer. Jour. Bot. 50(9): 872–880. Illus. 1963.—The ragweeds possess an inflorescence which is highly modified in relation to anemophily. Several trends from primitive to specialized character expressions may be seen in the morphology of the unisexual capitula and florets. An evolutionary scheme is presented whereby the catkinlike, acropetally maturing, staminate spike and the sessile, centrifugally developing, fruiting involucre cluster are derived from basic inflorescence types within the Compositae. Morphological evidence suggests that: (1) the taxa Ambrosia and Franseria should be combined under the older generic name Ambrosia; (2) the ragweeds and their relatives as a group appear to occupy a position intermediate between the Heliantheae and Anthemideae, as currently delimited within the Compositae.  相似文献   

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论非洲叶肢介科的分类   总被引:2,自引:2,他引:0  
沈炎彬 《古生物学报》2003,42(4):590-597
叶肢介化石生长线下缘锯齿状构造曾作为非洲叶肢介科(Afrograptidae)分类的主要特征,通过扫描图像,从比较解剖学研究入手,揭示了现生与化石叶肢介壳瓣的锯齿构造是由于分布于生长线的一排刚毛,基部关节脱落而形成的;分析了生长线刚毛的形态是属于长针形的轴刚毛,主要司触角功能;在5科18属现生叶肢介中,至少3科7属32种具有生长线刚毛,22属化石叶肢介有锯齿构造;作者认为这一构造被视为非洲叶肢介科分类的主要依据是不合适的,壳瓣的放射褶或粗瘤构造在高级分类上更重要,进而对该科的含义进行了厘定;从壳瓣具有多条放射褶这一构造特征来看,它与小叶肢介超科(Estheriellioidea)的成员在发生关系上比较密切,小叶肢介超科可提升为亚目(Estheriellidea),包括小叶肢介超科和非洲叶肢介超科,是中生代初兴起的一个类群。在白垩纪中期消失。  相似文献   

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肖蛸科蜘蛛的捕食行为   总被引:1,自引:0,他引:1  
肖蛸科蜘蛛捕食过程中的行为单元、捕食的策略以及不同种类肖蛸捕食行为的多样性及其进化。  相似文献   

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长须杵蚊Tripteroides(Rachionotomyia)longiplpisDong,ZhouetDong,1997系董学书等采自云南省西双版纳的雄蚊、蛹及幼虫描述,最近又采获一批幼虫,经饲养获雌、雄各3只,雌蚊描述如下。长须杵蚊Tripteroides...  相似文献   

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对盅口族Cyathostominea线虫分类系统的研究进行了回顾和讨论,根据各分类学家的意见,笔者提出了盅口族线虫的分类系统,该系统以Lichtenfels等人(1998)的观点为基础,其不同点在于:1)将马线虫属Caballonema Abulasze,1937和柱咽属Cylindropharynx Leiper,1911从盅口族中移出,放入柱咽族Cylindropharyngea Popova,1952;2)Scialdo-Krecek(1984)描述的Cylicodon-tophorus reineckei应归属于副杯口属Parapoteriostomum Hartwich,1986.  相似文献   

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青藏高原跳甲亚科昆虫区系研究   总被引:3,自引:0,他引:3  
讨论青藏高原(包括横断山区)的跳甲亚科昆虫区系。该区已知47属228种。1)据属级阶元的分布类型分析,以东洋属和南型属种显占优势,是区系主体,显示该区跳甲区系的热带渊源,其中高山属种赋予该区以高山区系特征;2)该区物种分化活跃,是某些多种属中国种类的分布中心和分化中心;3)联系中国跳甲亚科区系,在地理分布格局上显示西-东分布,如Hespera属的分布和西南-东北分布或西南-东北的间断分布格局,如Pentamesa和Stenoluperus属的分布。这种地理分布格局反映青藏高原的隆起给中国昆虫区系带来重要影响。  相似文献   

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The secondary gill of the pulmonate limpet Siphonaria capensisis located in the dorsal portion of the mantle cavity. Eachlamella of the gill is triangular in shape and bears ciliarytufts which have a density of about 400/mm2. The free ends ofsome of the cilia are enlarged biconcave discs. Each gill lamellais covered by a single layer of cuboidal (4x4 µm) epitheliumon each side, separated by a central haemocoelic space. Ciliatedand mucus secreting cells are interspersed amongst the epithelialcells. The haemocoelic space is spanned at intervals by trabeculaecontaining longitudinal and transverse muscle fibres. (Received 29 August 1986;  相似文献   

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Abstract— The recently published phylogeny of Braconidae by Quicke and van Achterberg is reassessed. Character-state definitions and character polarities are evaluated, and more rigorous methods are suggested. Our results indicate that there are many more parsimonious solutions to their data set, the consensus of which differs substantially from their results. Based on our reassessment, little can be said about the relationships among braconid subfamilies. Consensus trees show the cyclostomes as a largely unresolved basal grade. The two other major lineages which have been proposed, the helconoids and microgastroids, are somewhat better resolved, but not consistently so. Relationships among the helconoids vary considerably depending on the parameters used for parsimony analysis.  相似文献   

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External features of the puparium, larvae and egg of the Queensland fruit fly, Dacus (Bactrocera) tryoni (Froggatt) were studied by scanning electron microscopy and significant morphological characters are described and illustrated. Cephalopharyngeal skeletons are described from examination by light microscopy.  相似文献   

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During the early development of Pecten maximus, the prototrochof the trochophore becomes the rim of the velum of the veliger.The prototroch consists of a tract of randomly-distributed cilia,but in the veliger an ordered pattern of ciliation with somecompound cilia develops. The thin epithelium connecting thevelum to the body of the larva bears no cilia, nor does theupper surface of the velum (except for an apical tuft); themuch thicker epithelium of the velum rim, however, is profuselyciliated. The cilia are arranged in five bands or rings eachextending round the rim of the velum. The ring closest to theupper (i.e. ventral) surface of the velum is the inner preoralring of single cilia. Below this are two rings of much longercilia grouped to form blade-shaped cirri, which each consistof 2 or 3 rows of 10-15 cilia. The cilia substructures indicatethat the direction of active beat of the cirrus is along theaxis of the rows. This beating generates the main swimming current.The energy demands of beating are reflected in the numerouslarge mitochondria in the cells bearing the cirri. Nerve processesin the velum may control beating. Below the cirri are an adoraltract of shorter cilia and then a ring of postoral cilia. Thevelum anatomy is that of a typical bivalve veliger, but somefeatures distinguish Pecten maximus from other bivalves. Theonfiguration of the bands of cilia and the orientation of theirbeating suggest that the veliger captures food particles bythe ‘opposed band’ method. This configuration islikely to be homologous with those of other spiralian larvae. *Present address: School of Biological Scrences, PortsmouthPolytechnic, King Henry I Street, Portsmouth, PO1 2DY, U.K. (Received 30 September 1988; accepted 1 December 1988)  相似文献   

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Shell variation within a single population of Litlorina rudis(Maton), collected near the Biological Station at Trondheim,Norway, was studied. The variation of the shell features studied, which includedthe shape of the basal part of the outer lip, and the relativeheight of the spire, width of the shell and of the aperture,were found to be at least partially related to shell height.Furthermore, the shell shape in the population investigated,besides varying with age, also varies due to shell damage. Nosignificant differences were found between the shapes of theshells of males and females. The shell characteristics of different populations of L. rudisalso vary greatly, one of the causes being differences in theenvironmental conditions. When studying this variation betweendifferent populations, however, it must be emphasized that onlyundamaged shells of individuals of about the same age shouldbe compared, in order to obviate the effects of the variabilitydue to age differences and shell damage within each individualpopulation. *Contribution from Trondhjem Biological Station no. 199 (Received 18 February 1980;  相似文献   

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