Position of the labrum in agnostid trilobites

Specimens of Peronopsis and Ptychagnostus from the House Range of western Utah provide new information on the location of the labrum (hypostoma) of agnostid trilobites. A labral position as that described here, beneath the second glabellar lobe, has two implications: (1) anomalous cephalic muscle scars described by previous workers may be interpreted as attachment areas for labral muscles; and (2) the mouth probably migrated posteriorly in agnostids. Posterior displacement of the mouth was probably one of several feeding modifications associated with a pelagic mode of life.     

Effect of Glucose and Auxins in Rooting Etiolated Stem Segments of Populus nigra

2.5 cm long stem segments of Populus nigra L. did not root when cultured in water or in auxins alone but rooted in glucose. The number of rooted segments and roots produced on them increased with rising glucose concentrations up to 0.5%, but decreased with higher concentrations. An addition of 1.0 mg/1 IAA inhibited rooting at 0.01 % glucose, was ineffective at 0.1 % and stimulative at higher concentrations of glucose which were inhibitory when used alone. The results show that the auxin effects on rooting are influenced by the nutritional status of the stem cutting of a species, and that a proper balance of the two is necessary for root development.     

Foraging activity and dietary spectrum of wood ants (Formica rufa group) and their role in nutrient fluxes in boreal forests

Abstract 1. We monitored three different‐sized wood ant (Formica aquilonia Yarrow) mounds over a 3‐year period in Finnish boreal forests dominated by Norway spruce (Picea abies Karst.), to assess the seasonal temperature dependency of ant activity. Additionally, we also monitored Norway spruce trees around the mounds for descending honeydew foragers. 2. The amount of collected honeydew and prey and its composition, as well as the carbon (C), nitrogen (N), and phosphorus (P) in honeydew and invertebrate prey was also investigated. 3. The number of warm days (average temperature above 20 °C) and the amount of precipitation differed among the years. Ant activity at the mounds (but not on the trees) was highly correlated with air temperature throughout the ant‐active season (May–September), but ant activity in spring and autumn was lower than in summer at similar temperatures. During all 3 years, honeydew played a major role in wood ant nutrition (78–92% of dry mass). Invertebrate prey was mainly Diptera (on average 26.2%), Coleoptera (12.5%), Aphidina (9.3%), and Arachnoida (8.5%). 4. The total amounts of C, N, and P input brought into the ant mounds in the form of food (both honeydew and prey) on the stand level were 12.6–39.0, 1.6–4.6 and 0.1–0.4 kg ha^?1 year^?1, respectively, which is equivalent to 2–6%, 12–33% and 27–58% of the fluxes in annual needle litterfall in typical boreal Norway spruce forests. Thus, wood ants can play a significant role in short term and local N and P cycling of boreal forest ecosystems.     

恶性疟原虫abstrakt同源基因的克隆及DEAD盒家族蛋白的序列分析

DEAD盒蛋白家族的ATP依赖性的RNA解旋酶类参与细胞内几乎所有的RNA代谢过程 ,在几乎所有生物的细胞生长发育过程中扮演着众多不可或缺的角色。在本实验中 ,通过PCR和探针杂交相结合的筛选方法 ,筛选恶性疟原虫 (Plasmodiumfalciparum)的基因组文库 ,克隆了FH1F———abstrakt同源基因的完整序列。通过搜索已经完成测序的恶性疟原虫基因组数据库 ,推测FH1F序列定位在第 5条染色体上。FH1F全长2 80 4bp,包含一个 1 1 6 1bp的完整阅读框 ,编码一个由 386个氨基酸组成的蛋白。对FH1F蛋白序列用BlastP进行搜索和分析以及用DNAStar与许多典型的DEAD盒蛋白序列进行比对分析 ,结果均提示FH1F蛋白应该是DEAD盒家族的一个Abstrakt蛋白。另一方面 ,用DNAStar对已知所有完整的DEAD盒蛋白进行详细的序列分析以及用Mega对这些序列进行系统发育研究的结果都显示 :DEAD盒家族的蛋白聚类成为若干不同的亚群 ;与DEAD盒蛋白的一般保守序列相比 ,Abstrakt,eIF 4A ,Vasa ,P6 8等不同亚群的DEAD盒蛋白在保守区具有各自不同的结构特征。本文对不同的DEAD盒蛋白的结构特征进行了总结并试图给出不同亚群分类上的结构标准 ,对Abstrakt蛋白在本应高度保守的位点上异常于其它DEAD盒蛋白的氨基酸残基的取代也进行了相关的初步分析     

Maximizing information in systematic revisions: a combined molecular and morphological analysis of a cryptic green pitviper complex (Trimeresurus stejnegeri)

Although the integration of DNA information in taxonomy has been invaluable, logistical problems relating to sampling can seriously limit its applicability. Here we describe the analysis of a morphologically cryptic species complex, in which we maximize the information present by using both a DNA phylogeny and a multivariate morphometric approach. The green pitviper Trimeresurus stejnegeri s.l. is widespread in Asia, with a number of described subspecies (some of which are considered full species by some workers) and two new species that have recently been described from Thailand. The phylogeny indicates three clades, which can also be discerned in the principal component analyses of morphological variation. Combining molecular and morphological information permits evaluation of the taxonomic position of populations not represented in the phylogeny − in particular, the subspecies T. s. chenbihui and T. s. yunnanensis . We discuss nomenclatural issues raised by this analysis, although these cannot be fully resolved until the holotypes of these subspecies can be examined. Finally, we apply a molecular clock calibrated in New World pitvipers, and discuss some of the palaeoclimatic changes that might have impacted upon diversification in this group.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society, 2004, 82 , 219–235.     

Linking above- and belowground responses to global change at community and ecosystem scales

Cryptic belowground organisms are difficult to observe and their responses to global changes are not well understood. Nevertheless, there is reason to believe that interactions among above- and belowground communities may mediate ecosystem responses to global change. We used grassland mesocosms to manipulate the abundance of one important group of soil organisms, arbuscular mycorrhizal (AM) fungi, and to study community and ecosystem responses to CO₂ and N enrichment. Responses of plants, AM fungi, phospholipid fatty acids and community-level physiological profiles were measured after two growing seasons. Ecosystem responses were examined by measuring net primary production (NPP), evapotranspiration, total soil organic matter (SOM), and extractable mineral N. Structural equation modeling was used to examine the causal relationships among treatments and response variables. We found that while CO₂ and N tended to directly impact ecosystem functions (evapotranspiration and NPP, respectively), AM fungi indirectly impacted ecosystem functions by influencing the community composition of plants and other root fungi, soil fungi and soil bacteria. We found that the mycotrophic status of the dominant plant species in the mesocosms determined whether the presence of AM fungi increased or decreased NPP. Mycotrophic grasses dominated the mesocosm communities during the first growing season, and the mycorrhizal treatments had the highest NPP. In contrast, nonmycotrophic forbs were dominant during the second growing season and the mycorrhizal treatments had the lowest NPP. The composition of the plant community strongly influenced soil N, and the community composition of soil organisms strongly influenced SOM accumulation in the mesocosms. These results show how linkages between above- and belowground communities can determine ecosystem responses to global change.     

A Temperature-Sensitive Mutation Affecting Synthesis of Outer Arm Dyneins in Tetrahymena thermophila

ABSTRACT. We have characterized a novel, temperature-sensitive mutation affecting motility in Tetrahymena thermophila . Mutants grew and divided normally at the restrictive temperature (38°C), but became nonmotile. Scanning electron microscopic analysis indicated that nonmotile mutants contained the normal number of cilia and that the cilia were of normal length. Transmission electron microscopic analysis indicated that axonemes isolated from nonmotile mutants lacked outer dynein arms, so the mutation was named oad I ( outer arm defficient ). Motile mutants shifted to 38° C under conditions that prevent cell growth and division (starvation) remained motile suggesting that once assembled into axonemes at the permissive temperature (28° C) the outer arm dyneins remain functional at 38° C. Starved, deciliated mutants regenerated a full complement of functional cilia at 38° C, indicating that the mechanism that incorporates the outer arm dynein into developing axonemes is not affected by the oad I mutation. Starved, nonmotile mutants regained motility when shifted back to 28° C, but not when incubated with cycloheximide. We interpret these results to rule out the hypothesis that the oad I mutation affects the site on the microtubules to which the outer arm dyneins bind. Axonemes isolated from mutants grown for one generation at 38° C had a mean of 6.0 outer arm dyneins, and axonemes isolated from mutants grown for two generations at 38° C had a mean of 3.2 outer arm dyneins. Taken together, these results indicate that the oad I mutation affects the synthesis of outer arm dyneins in Tetrahymena .