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  • crystal structure
  • evolution
  • nitrogen
  • porous silicon
  • 2000-2004  (256)
  • 1980-1984  (82)
  • 1
    Publication Date: 2015-05-08
    Description: The Tenasserim lutung Trachypithecus barbei was previously known from museum specimens and field observations only. We discovered a zoo specimen and present the first confirmed evidence for the continued existence of the species since 1967. We describe the cranial pelage and coloration characteristics of this species which were previously unknown. We present first molecular evidence for recognizing T. barbei as a distinct species and for assessing its phylogenetic affinities relative to other members of the genus Trachypithecus. We document the taxonomic history of T. barbei and present a distribution map based on a compilation of all known locality records.
    Keywords: Trachypithecus barbei ; taxonomy ; systematics ; evolution ; genetics
    Repository Name: National Museum of Natural History, Netherlands
    Type: Article / Letter to the editor
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  • 2
    Publication Date: 2015-05-08
    Description: Investigations of amphipod embryonic development have a long tradition. However, many aspects of amphipod embryology are still controversial. These concern, among others, the nature of the cleavage, the origin of the germ disc, and the mode of gastrulation. On the other hand, amphipods show the same characteristic type of invariant cell division pattern in the germ band as other malacostracans. Since amphipods seem to undergo a stereotyped pattern of early cleavage they are highly interesting for our understanding of the evolution of arthropod development. In this paper, we describe the cleavage pattern of the amphipod crustacean Orchestia cavimana from the zygote to gastrulation and the formation of the germ disc using direct observation, scanning electron microscopy, histology, video recording, and lineage tracing with a vital dye. The early development follows the mode of a total, radial, unequal cleavage with a determinate stereotyped pattern. A small transient blastocoel is formed. The 8-cell stage is characterised by 4 micromeres and 4 macromeres. One quadrant is smaller than the others. There are two kinds of eggs that show a mirror handed image. The 16-cell stage is the last regular stage after which the blastomeres divide highly asynchronously. The germ disc is formed by the descendants of the macromeres and some micromere derivatives. The other micromeres constitute the extra-embryonic region. Migration of macromere descendants is involved in germ disc formation accompanied by the extrusion of the yolk. During this process some vitellophages are formed. The gastrulation sensu stricto is initiated by the micromere derivatives of the smallest quadrant at the anterior of the forming germ disc. A true blastopore occurs which involves an invagination and the immigration of cells. Our data help to correct erroneous interpretations of former students of amphipod development. We can show that many chaiacters of amphipod embryonic development are apomorphic supporting amphipod monophyly. With the present investigation we contribute to a complete understanding of the embryonic cell lineage of amphipods from the egg to segment formation and organogenesis.
    Keywords: cell lineage ; cell migration ; Arthropoda ; phylogeny ; evolution
    Repository Name: National Museum of Natural History, Netherlands
    Type: Article / Letter to the editor
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  • 3
    Publication Date: 2024-02-12
    Description: Sandmischkulturen unterschiedlichen Alters sowie einige Ausgangstorfe der kultivierten Moorböden wurden auf den Gehalt und die Verteilung an organisch gebundenem Stickstoff in verschiedenen N-Fraktionen untersucht. Mit zunehmendem Alter der Sandmischkulturen steigt der Humifizierungsgrad und der Gesamtstickstoffgehalt der organischen Substanz. Parallel dazu steigt in Relation zum Gesamt-Stickstoff der Anteil des insgesamt nicht-hydrolysierbaren, vorwiegend heterozyklisch organisch gebundenen Stickstoffs stärker an, und entsprechend stärker verringert sich der Anteil des insgesamt hydrolysierbaren Stickstoffs. Im Zuge dieser Umstrukturierung der organischen Substanz nähert sich die Verteilung des organisch gebundenen Stickstoffs auf die einzelnen N-Fraktionen auch in Moorkulturböden dem Muster, wie es an isolierten Huminsäuren aus Podsolen oder Schwarzerden bekannt ist. Auch der absolute Gehalt an Aminosäure-N pro g organischer Substanz nimmt mit zunehmendem Alter der Sandmischkulturen zu, eine typische Veränderung am Verteilungsmuster der einzelnen Aminosäuren zueinander ist jedoch nicht zu erkennen. Bei den Aminozuckern tritt dagegen eine charakteristische Veränderung ein. Während die Relation von Glukosamin zu Galaktosamin im sauren Hochmoortorf etwa 1 ist, liegt diese Relation in der Fehnkultur bei 2,5.
    Description: Sand-mixed cultivated soils of different age and the original peat Substrates were analysed for their nitrogen content and for their distribution of organically bound nitrogen in different nitrogen fractions. With increasing age of sand-mixed cultivated bogs the degree of humification and the total nitrogen content of the organic matter increase as well in these soils. Corresponding with these changes the relative amounts of non hydrolysable , heterocyclically bound nitrogen increase more than the relative amounts of total hydrolysable nitrogen. In the course of this structural change of the organic matter the distribution pattern of organically bound nitrogen in different nitrogen fractions of the sand-mixed cultivated soils becomes simular to that which is known from isolated humic acids of podsolic soils or chernozems. The absolute amount of amino-acid-ni trogen per g organic matter increases with the age of sand-mixed cultivated soils too. A typical change in the distribution pattern of the different amino acids was not observed. On the other side a typical change in the distribution pattern of amino sugars takes place. Whereas the ratio of glucosamine to galacto samine in the original high moor peat is near 1, the corresponding ratio in the older sand-mixed cultivated soil is about 2,5.
    Description: research
    Description: DFG, SUB Göttingen, DGMT
    Keywords: ddc:553.21 ; Moor ; Torf ; peat ; peatland ; Bodenkunde ; Stickstoff ; nitrogen
    Language: German
    Type: doc-type:article
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  • 4
    Publication Date: 2024-01-12
    Description: Investigations of amphipod embryonic development have a long tradition. However, many aspects of amphipod embryology are still controversial. These concern, among others, the nature of the cleavage, the origin of the germ disc, and the mode of gastrulation. On the other hand, amphipods show the same characteristic type of invariant cell division pattern in the germ band as other malacostracans. Since amphipods seem to undergo a stereotyped pattern of early cleavage they are highly interesting for our understanding of the evolution of arthropod development. In this paper, we describe the cleavage pattern of the amphipod crustacean Orchestia cavimana from the zygote to gastrulation and the formation of the germ disc using direct observation, scanning electron microscopy, histology, video recording, and lineage tracing with a vital dye. The early development follows the mode of a total, radial, unequal cleavage with a determinate stereotyped pattern. A small transient blastocoel is formed. The 8-cell stage is characterised by 4 micromeres and 4 macromeres. One quadrant is smaller than the others. There are two kinds of eggs that show a mirror handed image. The 16-cell stage is the last regular stage after which the blastomeres divide highly asynchronously. The germ disc is formed by the descendants of the macromeres and some micromere derivatives. The other micromeres constitute the extra-embryonic region. Migration of macromere descendants is involved in germ disc formation accompanied by the extrusion of the yolk. During this process some vitellophages are formed. The gastrulation sensu stricto is initiated by the micromere derivatives of the smallest quadrant at the anterior of the forming germ disc. A true blastopore occurs which involves an invagination and the immigration of cells. Our data help to correct erroneous interpretations of former students of amphipod development. We can show that many chaiacters of amphipod embryonic development are apomorphic supporting amphipod monophyly. With the present investigation we contribute to a complete understanding of the embryonic cell lineage of amphipods from the egg to segment formation and organogenesis.
    Keywords: cell lineage ; cell migration ; Arthropoda ; phylogeny ; evolution
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 5
    Publication Date: 2024-01-12
    Description: The Tenasserim lutung Trachypithecus barbei was previously known from museum specimens and field observations only. We discovered a zoo specimen and present the first confirmed evidence for the continued existence of the species since 1967. We describe the cranial pelage and coloration characteristics of this species which were previously unknown. We present first molecular evidence for recognizing T. barbei as a distinct species and for assessing its phylogenetic affinities relative to other members of the genus Trachypithecus. We document the taxonomic history of T. barbei and present a distribution map based on a compilation of all known locality records.
    Keywords: Trachypithecus barbei ; taxonomy ; systematics ; evolution ; genetics
    Repository Name: National Museum of Natural History, Netherlands
    Type: info:eu-repo/semantics/article
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of ornithology 141 (2000), S. 263-274 
    ISSN: 1439-0361
    Keywords: Systematics ; evolution ; anagenesis ; genealogy ; reference system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Description / Table of Contents: Zusammenfassung Verglichen mit anderen Tiergruppen, scheint die artliche Bestandsaufnahme der rezenten Vögel nahezu abgeschlossen zu sein. Doch ist das System der Vögel weiterhin umstritten und mit vielen Neuerungen konfrontiert. Die Gründe dafür liegen hauptsächlich in neuen, vor allem molekularbiologischen Methoden und in den unerwartet reichen Fossilfunden der jüngsten Zeit. Als Beispiele werden Altgaumenvögel, Kranichvögel, Ibisse, Flamingos, Mausvögel, Hopfe und Sperlingsvögel kurz behandelt. Die hier erzielten Fortschritte lassen die Befürchtung Stresemanns, die Großsystematik der Vögel sei mit den vorhandenen Methoden phylogenetisch nicht interpretierbar, zunächst als unbergründet erscheinen. Doch erwachsen einer solchen Interpretation andere Hindernisse, deren Bedeutung bisher zu wenig beachtet wurde, nämlich Parallelentwicklungen, die viel verbreiteter sind als gemeinhin angenommen. Ihre Häufigkeit lässt sich sogar mit evolutionsbiologischen Argumenten begründen. Es ist deshalb nicht zu erwarten, dass die Diskussionen um das „richtige“ System bald verstummen. Um dennoch die Eindeutigkeit der Information in nicht-systematischen Veröffentlichungen zu wahren, wird empfohlen ein etabliertes Referenzsystem auf Zeit zu wählen.
    Notes: Summary Unlike in most animal classes the inventory of extant species of the class Aves seems to be almost complete. Nevertheless avian systematics is challenged by many novelties and seems far from being settled. This is caused mainly by the application of novel methods of molecular analysis to phylogenetic problems and by the unexpectedly rich fossil record collected within the last 10–20 years. Examples from the Palaeognathae, Gruiformes, Threskiornithidae, Phoenicopteridae, Coliiformes, Upupiformes and Passeriformes are briefly treated. The progress in the field seems to disprove Stresemann's pessimistic view that the phylogeny of higher categories (orders) cannot be reconstructed by the available methods. However, phylogenetic interpretations are impeded by obstacles not considered by Stresemann and highly underestimated in most cases, namely by multiple independent developments leading to identical features. Frequent parallel developments are to be expected for theoretical evolutionary reasons. The diagnosis of such homoplasies can be extremely difficult or even impossible. Therefore we cannot expect the discussion about the “best” system of birds to end in the near future. Considering this dynamic situation in systematics, it is recommended to maintain unambiguousness of information in not strictly systematic publications by refering to a well established system as a temporally limited reference.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Acta biotheoretica 48 (2000), S. 137-147 
    ISSN: 1572-8358
    Keywords: Sex ; sexual selection ; mate selection ; evolution ; ploidy ; assortative mating ; recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Using computer simulations I studied the simultaneous effect of variable environments, mutation rates, ploidy, number of loci subject to evolution and random and assortative mating on various reproductive systems. The simulations showed that mutants for sex and recombination are evolutionarily stable, displacing alleles for monosexuality in diploid populations mating assortatively under variable selection pressure. Assortative mating reduced excessive allelic variance induced by recombination and sex, especially among diploids. Results suggest a novel adaptive value for sex and recombination. They show that the adaptive value of diploidy and that of the segregation of sexes is different to that of sex and recombination. The results suggest that the emergence of sex had to be preceded by the emergence of diploid monosexual organisms and provide an explanation for the emergence and maintenance of sex among diploids and for the scarcity of sex among haploid organisms.
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  • 8
    ISSN: 1570-7458
    Keywords: EPG ; stylectomy ; phloem amino acids ; nitrogen ; aphid-plant interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of nitrogen deficiency in hydroponically grown barley seedlings (Hordeum vulgare L.) on the development and reproduction of the aphid Rhopalosiphum padi (L.) (Hemiptera: Aphididae) were investigated. Plant growth was significantly reduced in seedlings grown without nitrogen. Aphid intrinsic rate of increase (r m) was also significantly lower on these plants compared with that on plants grown with 8 mol m−3 nitrogen. Phloem sap was collected from seedling stems by aphid stylectomy and amino acids quantified by HPLC. There was a significant reduction in the concentration of non-essential amino acids as a group, but not of essential amino acids. Electrical penetration graphs (EPG) indicated that aphids reached the phloem more quickly and fed for longer on plants grown with nitrogen. This is the first reported study in which this combination of techniques has been used to understand the interactions of an aphid and plant under different environmental conditions.
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Entomologia experimentalis et applicata 97 (2000), S. 237-249 
    ISSN: 1570-7458
    Keywords: herbivores ; predators ; parasitoids ; mutualism ; induced defence ; behaviour ; ecology ; evolution ; sensory physiology ; plant fitness ; pathogens
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Herbivorous and carnivorous arthropods use plant volatiles when foraging for food. In response to herbivory, plants emit a blend that may be quantitatively and qualitatively different from the blend emitted when intact. This induced volatile blend alters the interactions of the plant with its environment. We review recent developments regarding the induction mechanism as well as the ecological consequences in a multitrophic and evolutionary context. It has been well established that carnivores (predators and parasitoids) are attracted by the volatiles induced by their herbivorous victims. This concerns an active plant response. In the case of attraction of predators, this is likely to result in a fitness benefit to the plant, because through consumption a predator removes the herbivores from the plant. However, the benefit to the plant is less clear when parasitoids are attracted, because parasitisation does usually not result in an instantaneous or in a complete termination of consumption by the herbivore. Recently, empirical evidence has been obtained that shows that the plant's response can increase plant fitness, in terms of seed production, due to a reduced consumption rate of parasitized herbivores. However, apart from a benefit from attracting carnivores, the induced volatiles can have a serious cost because there is an increasing number of studies that show that herbivores can be attracted. However, this does not necessarily result in settlement of the herbivores on the emitting plant. The presence of cues from herbivores and/or carnivores that indicate that the plant is a competitor- and/or enemy-dense space, may lead to an avoidance response. Thus, the benefit of emission of induced volatiles is likely to depend on the prevailing faunal composition. Whether plants can adjust their response and influence the emission of the induced volatiles, taking the prevalent environmental conditions into account, is an interesting question that needs to be addressed. The induced volatiles may also affect interactions of the emitting plant with its neighbours, e.g., through altered competitive ability or by the neighbour exploiting the emitted information. Major questions to be addressed in this research field comprise mechanistic aspects, such as the identification of the minimally effective blend of volatiles that explains the attraction of carnivores to herbivore-infested plants, and evolutionary aspects such as the fitness consequences of induced volatiles. The elucidation of mechanistic aspects is important for addressing ecological and evolutionary questions. For instance, an important tool to address ecological and evolutionary aspects would be to have plant pairs that differ in only a single trait. Such plants are likely to become available in the near future as a result of mechanistic studies on signal-transduction pathways and an increased interest in molecular genetics.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Acta biotheoretica 30 (1981), S. 79-102 
    ISSN: 1572-8358
    Keywords: evolution ; modifier theory ; dominance evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The problem of modifier evolution was examined with regard to the idea that modifier evolution can be considered as a result of selection for adaptation speed in populations far from equilibrium. This kind of selection was called ‘feedback selection’ in order to emphasize the difference to theories which consider modifier evolution near the equilibrium. The basic principles of this kind of selection are derived for asexual populations and the problem of dominance is discussed in the light of this concept. In general the results support the view, that the genetic properties of a character are selected along with the character itself.
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