16 research outputs found
Whole-mount in situ hybridization in the Rotifer Brachionus plicatilis representing a basal branch of lophotrochozoans
No full textIn order to broaden the comparative scope of evolutionary developmental biology and to refine our picture of animal macroevolution, it is necessary to establish new model organisms, especially from previously underrepresented groups, like the Lophotrochozoa. We have established the culture and protocols for molecular developmental biology in the rotifer species Brachionus plicatilis Muller (Rotifera, Monogononta). Rotifers are nonsegmented animals with enigmatic basal position within the lophotrochozoans and marked by several evolutionary novelties like the wheel organ (corona), the median eye, and the nonpaired posterior foot. The expression of Bp-Pax-6 is shown using whole-mount in situ hybridization. The inexpensive easy culture and experimental tractability of Brachionus as well as the range of interesting questions to which it holds the key make it a promising addition to the "zoo" of evo-devo model organisms
EST based phylogenomics of Syndermata questions monophyly of Eurotatoria
No full textBackground: The metazoan taxon Syndermata comprising Rotifera (in the classical sense of Monogononta+Bdelloidea+Seisonidea) and Acanthocephala has raised several hypotheses connected to the phylogeny of these animal groups and the included subtaxa. While the monophyletic origin of Syndermata and Acanthocephala is well established based on morphological and molecular data, the phylogenetic position of Syndermata within Spiralia, the monophyletic origin of Monogononta, Bdelloidea, and Seisonidea and the acanthocephalan sister group are still a matter of debate. The comparison of the alternative hypotheses suggests that testing the phylogenetic validity of Eurotatoria (Monogononta+Bdelloidea) is the key to unravel the phylogenetic relations within Syndermata. The syndermatan phylogeny in turn is a prerequisite for reconstructing the evolution of the acanthocephalan endoparasitism. Results: Here we present our results from a phylogenomic approach studying i) the phylogenetic position of Syndermata within Spiralia, ii) the monophyletic origin of monogononts and bdelloids and iii) the phylogenetic relations of the latter two taxa to acanthocephalans. For this analysis we have generated EST libraries of Pomphorhynchus laevis, Echinorhynchus truttae (Acanthocephala) and Brachionus plicatilis (Monogononta). By extending these data with database entries of B. plicatilis, Philodina roseola (Bdelloidea) and 25 additional metazoan species, we conducted phylogenetic reconstructions based on 79 ribosomal proteins using maximum likelihood and bayesian approaches. Our findings suggest that the phylogenetic position of Syndermata within Spiralia is close to Platyhelminthes, that Eurotatoria are not monophyletic and that bdelloids are more closely related to acanthocephalans than monogononts. Conclusion: Mapping morphological character evolution onto molecular phylogeny suggests the (partial or complete) reduction of the corona and the emergence of a retractable anterior end (rostrum, proboscis) before the separation of Acanthocephala. In particular, the evolution of a rostrum might have been a key event leading to the later evolution of the acanthocephalan endoparasitism, given the enormous relevance of the proboscis for anchoring of the adults to the definitive hosts' intestinal wall.Deutsche Forschungsgemeinschaft DFG [Ha 2103/4-1, SPP1174
Panorama of the Mississippi Valley : and its fortifications
No full textCovers Mississippi River, in four 60 x 16 cm. panels, from St. Louis to the Gulf of Mexico.; Includes distance list, table of "Distances navigable by steam on Mississippi River and its principal branches," and small panoramic views of St. Louis, Memphis, Vicksburg, and New Orleans
Variation und Variabilität der Unterkieferform in der Hausmaus
No full textIn this thesis, I provide a description of the shape space of wild mouse mandibles with a focus on Mus musculus. Extending the comparisons to captive mice, inbred strains and some experimental populations, I try to infer which biological processes might account for observed patterns of shape variation, including genetic and developmental aspects (variability). I obtain the following results: 1) Mahalanobis distances based on CVA of Procrustes coordinates are a good measure of the global shape difference between two populations. Combined with the use of two-dimensional projections of μCT images of mouse hemimandibles, they are sufficiently robust in the face of diverse problems with sample quality and data processing, such as limitations in sample size, sampling errors with respect to sex, age and size of the animals, orientation of the samples inside the μCT scanner, preparation of bones and landmark digitization error. 2) Phenotypic plasticity as a reaction to environmental differences affects mandible shape by a smaller amount than the average distance between samples of wild-caught populations, suggesting that the shape differences between wild populations mostly have a genetic basis. 3) Various types of selection may have acted on shape. Four populations of mice from summer-dry regions cluster closely together, indicating that stabilizing selection may have conserved their shape. A M. m. domesticus sample from a site in Spain where the mice live in sympatry with a population of M. spretus is highly divergent from other M. musculus. This could represent a case of character displacement. Two populations of M. m. domesticus representing rather recent events of colonization on the subantarctic Kerguelen islands have diverged from other M. musculus in partially similar directions, which could represent an adaptation to the cold climate on these islands. 4) Inbred mouse strains are more divergent from wild mice and from each other than different species in nature, suggesting that nonadditive mechanisms of inheritance, especially epistasis, are important determinants of shape. This idea is supported by the finding that F1 of outcrosses between inbred strains look more similar to wild mice than their parentals, i. e. their phenotype is not just intermediate, and there is some complementation of changes from the wildtype, but no complete reversal. 5) Wild-derived outbred populations kept in the laboratory diverge from wild mice over the course of a few generations, albeit less so than inbred mice. They are, however, not more divergent from each other than wild populations. This finding may point toward the existence of some epigenetically inherited mechanism of shape change which is somehow induced under laboratory conditions. 6) The Kerguelen mice, inbred strains, and wild-derived outbred populations (“derided populations”) do not diverge from wild mice in random directions. This pattern needs to be analyzed from a trait-based perspective. Geometric morphometrics alone is not suitable to dissect overall variation into individual traits. Simple alternative methods based on interlandmark distances (ILMDs) help to quantify the similarity between directions of shape change and to dissect shape changes with respect to the mandibular subregions involved. 7) Using a purpose-designed manual protocol, 20 groups of covarying ILMDs are identified, which can themselves be grouped into 5 “major traits”. These can largely be assumed to represent tradeoffs of tissue mass allocation during growth and to some degree functional coupling between parts of the mandible. 8) The 5 major traits explain large proportions of variation in several contexts: divergence of the derived populations from wild mice, variation within outbred and inbred populations (for the latter, i.e. developmental instability), “epistatic deviations” of outcross F1 from the interparental mean, and postnatal longitudinal ontogenetic shape change. This variety of contexts indicates that a large part of the genetically/developmentally generated variation is expressed via a limited number of types of shape changes. At the same time, the 5 traits are less important for the explanation of differences between populations and species. 9) Taking together the evidence for epistatic genetic architecture of shape and the results on the specific contexts in which the corresponding shape changes are observed, I hypothesize that epistatic shape variance may relate to developmental instability and provides the major part of phenotypic variance in wild populations. Stabilizing selection is unable to control this variation. Evolutionary divergence, however, happens predominantly along axes of additive variance, which provide a lower part of phenotypic variance within populations under this model, potentially due to the action of stabilizing selection.Zusammenfassung...................3 Summary.................................6 Introduction........................... 8 Material and Methods ........... 11 Results Chapter 1.................. 17 Results Chapter 2..................21 Results Chapter 3..................26 Results Chapter 4..................28 Results Chapter 5..................31 Results Chapter 6..................36 Discussion part 1...................39 Results Chapter 7..................50 Results Chapter 8..................59 Discussion part 2...................79 Supplements..........................94 Literature..............................11
Panorama of the Mississippi Valley : and its fortifications /
No full textCovers Mississippi River, in four 60 x 16 cm. panels, from St. Louis to the Gulf of Mexico.Includes distance list, table of "Distances navigable by steam on Mississippi River and its principal branches," and small panoramic views of St. Louis, Memphis, Vicksburg, and New Orleans.LC Civil War maps (2nd ed.) 42.
Micro-evolutionary divergence patterns of mandible shapes in wild house mouse (<it>Mus musculus</it>) populations
No full textAbstract Background Insights into the micro-evolutionary patterns of morphological traits require an assessment of the natural variation of the trait within and between populations and closely related species. The mouse mandible is a particularly suitable morphological trait for such an analysis, since it has long been used as a model to study the quantitative genetics of shape. In addition, many distinct populations, sub-species and closely related species are known for the house mouse. However, morphological comparisons among wild caught animals require an assessment in how far environmental and technical factors could interfere with the shape change measurements. Results Using geometric morphometrics, we have surveyed mandible shapes in 15 natural populations of the genus Mus, with a focus on the subspecies Mus musculus domesticus. In parallel we have carefully assessed possibly confounding technical and biological factors. We find that there are distinct differences on average between populations, subspecies and species, but these differences are smaller than differences between individuals within populations. Populations from summer-dry regions, although more ancestral, are less distinct from each other than are populations from the more recently colonized northern areas. Populations with especially distinct shapes occur in an area of sympatry of M. m. domesticus and M. spretus and on recently colonized sub-antarctic islands. We have also studied a number of inbred strains to assess in how far their mandible shapes resemble those from the wild. We find that they fall indeed into the shape space of natural variation between individuals in populations. Conclusions Although mandible shapes in natural populations can be influenced by environmental variables, these influences are insufficient to explain the average extent of shape differences between populations, such that evolutionary processes must be invoked to explain this level of diversity. We discuss that adaptive evolution may contribute to shape changes between populations, in particular in newly colonized areas. A comparison between inbred strains and wild mice suggests that the laboratory environment has no major systematic effect on the mandible shape and that such strains can be used as representatives of the natural shape differences between individuals.</p
Gradgrinding the Social Sciences: The Politics of Metrics of Political Science
No full textCopyright @ 2009 The AuthorThis article employs an interpretive approach, and in the light of contributions to this symposium by Butler and McAllister, and McLean et al., holds that metrics of research ‘quality’ are socially constructed and hence are as ‘subjective’ as peer review. Thus it rejects the use of stand-alone metrics as an ‘objective’ basis to inform funding allocations. Rather, the optimum method of ‘quality’ assessment is a panel-based exercise with expert judgement informed by a range of discipline-sensitive metrics and peer review of publications. The article maintains that the politics of metrics of political science conceals interests about the foundations of social scientific knowledge, and so the dispute over metrics and peer review is a metaphor for the conflicting epistemological preferences of UK political scientists. It is also argued that metrics-led assessment subjects political science to ‘Gradgrinding’ on two fronts: that political science departments amount to less than the sum of their parts, and the audit culture strips the discipline of its humanism
On the Use of Literary Texts in the DaF Lesson with the Example of Heinrich Boell’s Short Story “Die Blasse Anna” with a Focus on Writing on a B2 Level
No full textFor the promotion and optimization of teaching foreign languages, new methods and strategies are always considered that include literary texts. The aim of the present paper is to provide arguments for the use of literature in the classroom. Learning target areas and selection criteria for the use of literary texts in the classroom are presented. A short story by German author Heinrich Boell named “Die blasse Anna” will be taken as an example to demonstrate the usability of literary texts in language learning.</jats:p
A comparative assessment of mandible shape in a consomic strain panel of the house mouse (<it>Mus musculus</it>) - implications for epistasis and evolvability of quantitative traits
No full textAbstract Background Expectations of repeatedly finding associations between given genes and phenotypes have been borne out by studies of parallel evolution, especially for traits involving absence or presence of characters. However, it has rarely been asked whether the genetic basis of quantitative trait variation is conserved at the intra- or even at the interspecific level. This question is especially relevant for shape, where the high dimensionality of variation seems to require a highly complex genetic architecture involving many genes. Results We analyse here the genetic effects of chromosome substitution strains carrying M. m. musculus chromosomes in a largely M. m. domesticus background on mandible shape and compare them to the results of previously published QTL mapping data between M. m. domesticus strains. We find that the distribution of genetic effects and effect sizes across the genome is consistent between the studies, while the specific shape changes associated with the chromosomes are different. We find also that the sum of the effects from the different M. m. musculus chromosomes is very different from the shape of the strain from which they were derived, as well as all known wild type shapes. Conclusions Our results suggest that the relative chromosome-wide effect sizes are comparable between the long separated subspecies M. m. domesticus and M. m. musculus, hinting at a relative stability of genes involved in this complex trait. However, the absolute effect sizes and the effect directions may be allele-dependent, or are context dependent, i.e. epistatic interactions appear to play an important role in controlling shape.</p
Die Darstellung des Luftkriegs bei Hans Erich Nossack, Heinrich Boell, Alexander Kluge und Dieter Forte
No full textW.G. Sebald claimed that German writers of the post-war time have remained silent when it came to writing about the air-raids over Germany, the bombing of the German cities and the suffering of the people living there. There are several more or less known works adressing the topic Luftkrieg. For this project, Sebald's work is used as a point of departure. Four different German literary works concerning the Luftkrieg will be examined: Hans Erich Nossack's Der Untergang, Heinrich Böll's Der Engel schwieg, Alexander Kluge's Der Luftangriff auf Halberstadt am 8. April 1945 and Dieter Forte's Der Junge mit den blutigen Schuhen. This work aims for two goals: 1. Pointing out how the different texts are approaching the topic Luftkrieg and the linguistic features the authors use to describe the air-raids. The focus is on the depiction of the people living in the German cities. 2. Comparing the results and finding differences and similarities among the four works. The project produces the following results: Every author has his individual way to deal with the topic Luftkrieg what makes a generalization difficult. But although the texts have different authors and originate from different periods of time in or after World War Two, they have several things in common. It can be noticed that the silence Sebald adressed exists indeed, every author has to deal with the trauma the Luftkrieg caused in his very own way. There recurring motives in most of the texts, such as hunger, resignation and the appearance of nature
