During development of tissues, cells collectively organize to form complex patterns and morphologies. A general feature of many developing epithelia is their distinct organization into cellular compartments of different cell lineages. The interfaces between these compartments, called compartment boundaries, maintain straight and sharp morphologies. The interfaces play key roles in tissue development and pattern formation. An important model system to study the morphology of compartment boundaries during development is the wing disc of the fruit fly. Two compartment boundaries exist in the fly wing disc, the anteroposterior (AP) boundary and the dorsoventral (DV) boundary. A crucial question is how compartment boundaries are shaped and remain stable during growth. In this work, we discuss the dynamics and mechanisms of compartment boundaries in developing epithelia. We analyze the general features of interfacial phenomena in coarse- grained models of passive and active fluids. We introduce a continuum description of tissues with two cell types. This model allows us to study the propagation of interfaces due to the interplay of cell dynamics and tissue mechanics. We also use a vertex model to describe cellular compartments in growing epithelia. The vertex model accounts for cell mechanics and describes a 2D picture of tissues where the network of adherens junctions characterizes cell shapes. We use this model to study the general physical mechanisms by which compartment boundaries are shaped. We quantify the stresses in the cellular network and discuss how cell mechanics and growth influence the stress profile. With the help of the anisotropic stress profile near the interfaces we calculate the interfacial tension. We show that cell area pressure, cell proliferation rate, orientation of cell division, cell elongation created by external stress, and cell bond tension all have distinct effects on the morphology of interfaces during tissue growth. Furthermore, we investigate how much different mechanisms contribute to the effective interfacial tension. We study the mechanisms shaping the DV boundary in wing imaginal disc at different stages during the development. We analyze the images of wing discs to quantify the roughness of the DV boundary and average cell elongation in its vicinity. We quantify increased cell bond tension along the boundary and analyze the role of localized reduction in cell proliferation on the morphology of the DV boundary. We use experimentally determined values for cell bond tension, cell elongation and bias in orientation of cell division in simulations of tissue growth in order to reproduce the main features of the time-evolution of the DV boundary shape.

This dissertation examines the reconfiguration of the limits of representation in reference to the intermediary function of angels. The Modernist engagement with the figure of the angel entailed, primarily, a reconsideration of the problem of representation as well as an attempt to trace the contours of a poetics that plays itself outside the mimetic understanding of representation. My contention is that this transformation of literary referentiality was not simply a disengagement of art from reality but, rather, from the truthfalsity, reality-fiction, subject-object dichotomies. The angel, defined as the figure of passage par excellence, but also as the agency that induces the transformation of the visible in the invisible and vice versa, appears both as a model/archetype and as a guide towards the illumination of this intermediary aesthetic. Working with the joined perspectives from angelology, contemporary phenomenology, and poetics, this dissertation is an extended overview of the notion of intermediary spaces, as well as an attempt to probe the relevance of this concept for the field of literary studies. In the first case, this dissertation offers a theoretical background to the concept of intermediality, seen in its theological, phenomenological, aesthetic and ethical significances. In the second case, it presents the reader with a heuristic apparatus for approaching this problematic in the field of literary interpretation and provides examples of ways in which such an analysis can become relevant. The primary texts discussed here are all examples of attempts to redefine the notion of representation away from the truth-falsity or subject-object oppositions, as well as to create an aesthetic space with its own particularities, at the limit between visibility and invisibility, excessive presence and absence. Nicholas of Cusa’s “Preface” to The Vision of God proposes an ethics of reading defined by admiratio (the consubstantiation of immediacy and distance) under the aegis of the all-seeing icon of God. Louis Marin’s reading of the episode of the Resurrection reveals that history and narrative arise from the conjunction of the excessive absence of the empty tomb of Jesus and the excessive presence announcing the resurrection of Christ. Sohravardî’s “Recital of the Crimson Angel” is a presentation of the space-between of revelation, between cognitio matutina and cognitio vespertina. Walter Benjamin’s “Agesilaus Santander” restores the connections between the exoteric and the esoteric under the patient gaze of “Angelus Novus”. Paul Valéry’s Eupalinos, ou l’Architecte explores the aesthetic of “real appearance” in the space-between the image and the perceiving eye. Poe and Malamud’s short stories reveal the affinities between poetic language and angelophany. Elie Wiesel’s Les portes de la forêt expands the apophatic itinerary from the self to the radically other in a hermeneutical gesture which has the angel as its initial and final guide. Finally, Rafael Alberti’s Sobre los ángeles shows that the aphaeretic function of poetic language is very similar to the apophatic treatment of the world as representation; in this last sense too, the angels are indispensible guides.

La thèse, qui pose la question de la description du roman et envisage une réponse par l’interrogation d’une problématique documentaire (proposition d’un modèle théorique de représentation, base pour la conception et la réalisation d’outils de navigation raisonnée dans la fiction) conduit une réflexion sur la place de la fiction littéraire dans la construction des savoirs et, par extension, d’une culture. La réflexion et l’expérimentation se font dans le contexte scolaire du lycée d’enseignement général (définition du statut du roman dans l’utilisation qui en est faite dans les programmes et objectifs d’enseignement, analyse de la notion de lecture littéraire en lycée) et par l’analyse d’un corpus de textes : étude de La mystérieuse flamme de la Reine Loana / Umberto Eco, 2004, traduction française, Paris, Grasset et Fasquelle, 2005, doublée de l’étude d’un corpus aléatoire sur le thème de la Shoah. L’objet d’étude étant le roman, les liens entre les Sciences de l’Information et de la Communication et la sémiotique sont abordés sous un jour nouveau : construction d’une théorie sémiotique (définition, mise en place d’un langage formel, choix d’un système de représentation) adaptée à l’objet d’étude par l’explicitation des conditions de production de sens, ce qui implique une hybridation des champs (SIC et théories d’analyse littéraire). Sont développés les éléments théoriques pour un modèle de représentation de la fiction. Les définitions du roman, de la fiction littéraire narrative, de l’information, de la fictiologie (nouveau champ de recherche ouvert par l’étude) et de l'information fictiologique critique, complétées par une description du positionnement dans le champ des Sciences de l’Information et de la Communication, posent le cadre de la réflexion. Un chapitre traitant de la littérature et de la notion de mémoire permet de décrire les liens entre roman et représentation de la réalité. Pour cela, sont définies et étudiées les notions de texte, de référence et de contexte. Enfin, est explicité le titre de la thèse par la description de la faculté imaginale et de la fonction de médiation prêtées au roman. Pour clôturer cette partie d’étude, un état de l’art de la classification de la fiction est opéré par l’élaboration d’un panorama des outils proposés et utilisés, renforcé par la définition d’une recherche ouverte d’information et une étude de la notion de sens dans le traitement de la fiction. Les analyses dans le champ pratique comportent un compte-rendu d’enquêtes, menées dans le cadre de l’enseignement secondaire et de la formation des documentalistes de l’Education Nationale, sur les pratiques de lecture. L’analyse des corpus de textes permet d’interroger la problématique de la réalité visible dans le roman. Ces travaux expérimentent une ontologie fictiologique par une analyse du roman comme document et un essai de formalisation sur la littérature des camps. La proposition d’un modèle théorique à expérimenter se concrétise par l’élaboration d’un système d’organisation de connaissances info-littéraires. Une réflexion sur l’environnement technique actuel justifie les choix retenus, les propositions et solutions réfléchies. En présentant une littératie fictiologique, prolongement de la littératie médiatique, la thèse se clôture par la description d’une médiation fictiologique qui s’ancre dans une renégociation des espaces et des typologies documentaires, investiguant les pratiques participatives et collaboratives. / The dissertation, which investigates the description of the novel and considers an answer by interrogating an information problem (offering a theoretical model of representation, a basis for the conception and creation of tools for a carefully thought out navigation within fiction), carries out a reflection about the role of literary fiction in the construction of bodies of knowledge and, by extension, of a culture. These reflection and experimentation take place in the school context of the “lycee d’enseignement general” [mainstream education high school] (definition of the status of the novel in the way that it is used in education programs and objectives, analysis of the notion of literary reading in high school) and through the analysis of a body of texts: study of La Mysterieuse Flamme de la Reine Loana / Umberto Eco, 2004, French translation, Paris, Grasset et Fasquelle, 2005, combined with the study of an unpredictable collection of texts about the theme of the Shoah. Since the object of study is the novel, the links between Information and Communication Sciences and semiotics are approached in a new light: construction of a semiotic theory (definition, setting up of a formal language, choice of a representation system) made suitable to the object of study by clarifying the conditions of meaning production, which implies a hybridization of the fields (Information and Communication Sciences and literary analysis). The theoretical elements for a representation model of fiction are developed. Definitions of the novel, of literary narrative fiction, of information, of fictiology (a new field of research opened up by the study) and of critical fictiological information, complemented by a description of positioning of this research in the field of Information and Communication Sciences, frame the reflection. A chapter tackling literature and the notion of memory allows for a delineation of the links between novel and representation of reality. For this purpose, the notions of text, reference, and context are defined. Finally, the title of the dissertation is explained through the description of the imaginal faculty, and of the mediation function attributed to the novel. To close this part of the study, drafting a panorama of the proposed and employed tools helps operate a state of the art of fiction classification, reinforced by the definition of an open information research and a study of the notion of meaning in the handling of fiction. Analyses in the practical field include a report of investigations on reading practices conducted in the contexts of secondary education and of the training of ‘Education Nationale’ information librarians. Analyzing bodies of texts allows the problem of visible reality in the novel to be interrogated. This research tests out a fictiologic ontology by examining the novel as document and by attempting a formalization of the camps literature. The proposition of a theoretical model to be experimented is concretized by the development of a system of organization of information and literary knowledge. A reflection on the current technical environment justifies the choices considered, the propositions and solutions offered. By presenting a fictiological information literaty, an extension of media information literaty, the dissertation ends with the description of fictiological mediation anchored into a renegotiation of information spaces and typologies, investigating participatory and collaborative practices.

During development of tissues, cells collectively organize to form complex patterns and morphologies. A general feature of many developing epithelia is their distinct organization into cellular compartments of different cell lineages. The interfaces between these compartments, called compartment boundaries, maintain straight and sharp morphologies. The interfaces play key roles in tissue development and pattern formation. An important model system to study the morphology of compartment boundaries during development is the wing disc of the fruit fly. Two compartment boundaries exist in the fly wing disc, the anteroposterior (AP) boundary and the dorsoventral (DV) boundary. A crucial question is how compartment boundaries are shaped and remain stable during growth. In this work, we discuss the dynamics and mechanisms of compartment boundaries in developing epithelia. We analyze the general features of interfacial phenomena in coarse- grained models of passive and active fluids. We introduce a continuum description of tissues with two cell types. This model allows us to study the propagation of interfaces due to the interplay of cell dynamics and tissue mechanics. We also use a vertex model to describe cellular compartments in growing epithelia. The vertex model accounts for cell mechanics and describes a 2D picture of tissues where the network of adherens junctions characterizes cell shapes. We use this model to study the general physical mechanisms by which compartment boundaries are shaped. We quantify the stresses in the cellular network and discuss how cell mechanics and growth influence the stress profile. With the help of the anisotropic stress profile near the interfaces we calculate the interfacial tension. We show that cell area pressure, cell proliferation rate, orientation of cell division, cell elongation created by external stress, and cell bond tension all have distinct effects on the morphology of interfaces during tissue growth. Furthermore, we investigate how much different mechanisms contribute to the effective interfacial tension. We study the mechanisms shaping the DV boundary in wing imaginal disc at different stages during the development. We analyze the images of wing discs to quantify the roughness of the DV boundary and average cell elongation in its vicinity. We quantify increased cell bond tension along the boundary and analyze the role of localized reduction in cell proliferation on the morphology of the DV boundary. We use experimentally determined values for cell bond tension, cell elongation and bias in orientation of cell division in simulations of tissue growth in order to reproduce the main features of the time-evolution of the DV boundary shape.

Apoptosis-induced proliferation (AiP) is a compensatory mechanism to maintain tissue size and morphology following unexpected cell loss during normal development, and may also be a contributing factor to cancer growth and drug resistance. In apoptotic cells, caspase-initiated signaling cascades lead to the downstream production of mitogenic factors and the proliferation of neighboring surviving cells. In epithelial Drosophila tissues, the Caspase-9 homolog Dronc drives AiP via activation of Jun N-terminal kinase (JNK); however, the specific mechanisms of JNK activation remain unknown. Using a model of sustained AiP that produces a hyperplastic phenotype in Drosophila eye and head tissue, I have found that caspase-induced activation of JNK during AiP depends on extracellular reactive oxygen species (ROS) generated by the NADPH oxidase Duox. I found these ROS are produced early in the death-regeneration process by undifferentiated epithelial cells that have initiated the apoptotic cascade. I also found that reduction of these ROS by mis-expression of extracellular catalases was sufficient to reduce the frequency of overgrowth associated with our model of AiP. I further observed that extracellular ROS attract and activate Drosophila macrophages (hemocytes), which may in turn trigger JNK activity in epithelial cells by signaling through the TNF receptor Grindelwald. We propose that signaling back and forth between epithelial cells and hemocytes by extracellular ROS and Grindelwald drives compensatory proliferation within the epithelium, and that in cases of persistent signaling, such as in our sustained model of AiP, hemocytes play a tumor promoting role, driving overgrowth.

In den Jahren 2005 bis 2010 erfolgte im Rahmen der Erarbeitung der vorliegenden Dissertationsschrift eine ökologische Untersuchung der Chironomidenfauna in der Talsperre Saidenbach (Sachsen, Erzgebirge). Drei Arten mit hoher Abundanz konnten bei der umfassenden Artenanalyse im Jahr 2005 ermittelt werden: Procladius crassinervis, P. choreus und Chironomus anthracinus. Zusätzlich wurde die Art C. plumosus aufgrund ihrer engen Verwandtschaft zu C. anthracinus in die Untersuchung einbezogen. Die Arbeit ist auf vier Schwerpunkte fokussiert, wobei die Larven und Puppen der vier Arten analysiert wurden. (1) Die Erarbeitung einer zuverlässigen Methode zur Unterscheidung der Larven der beiden eng verwandten Procladius-Arten basierend auf morphologischen Kriterien (Imaginalscheiden-entwicklung, Kopfkapselgröße und Körperlänge) sowie die Tiefenverteilung der Puppen waren eine Vorbedingung für weiterführende Analysen des Lebenszyklus (LZ) dieser beiden Arten. (2) Die Untersuchung des LZ war der zweite Schwerpunkt. Der LZ wurde stark von abiotischen Faktoren wie Temperatur, Sauerstoff und Biovolumen des Phytoplanktons kontrolliert. (3) Die raum-zeitlichen Verteilungsmuster der vier Arten wurden zunächst bezüglich großräumiger Unterschiede über einen Tiefengradienten innerhalb eines Transektes analysiert. Hierbei zeigte sich bei allen vier Arten eine zeitliche Änderung im jeweiligen Hauptverbreitungsgebiet. Die jungen Larven von C. anthracinus, C. plumosus und P. choreus wanderten im Verlauf ihrer Entwicklung bis zur Verpuppung in flachere Bereiche, P. crassinervis wanderte in tiefere Bereiche. Die Analyse der Verteilungsunterschiede der Larven zwischen zwei verschieden stark eutrophierten Buchten ergab höhere Dichten der beiden Chironomus-Arten in der Bucht mit dem größeren Zulauf und der höheren Phytoplanktonkonzentration im Vergleich mit den anderen Arten. Eine Analyse des kleinräumigen Verteilungsmusters fokussierte auf der Frage, ob die Larven gleichmäßig verteilt oder aggregiert auftraten. Die Untersuchung des vertikalen Verteilungsmusters erforschte das Schwimmverhalten der Larven. (4) Der letzte Aspekt war eine experimentelle Untersuchung, die am Beispiel von C. anthracinus durchgeführt wurde mit dem Ziel, den Proximatfaktor für die beobachtete Wanderung der Larven zu ermitteln, der letztendlich die Temperatur war. Puppen bevorzugten im Experiment wärmere Temperaturen und junge Larven kühlere Temperaturen. Die fünfjährige Untersuchung der Chironomiden in der Talsperre Saidenbach beschreibt insgesamt die komplexe Verhaltensreaktion der Chironomiden, die einen wesentlichen Teil der benthischen Lebensgemeinschaft darstellen, bezüglich der Lebenszyklusmuster (Voltinismus, Verpuppung), der Abundanzänderungen (inner- und zwischenjährlich) sowie der groß- und kleinräumigen Verteilung unter der Einwirkung der wichtigsten Umweltfaktoren. / In the context of the present dissertation an ecological study was performed about chironomids in Saidenbach Reservoir in the Saxony Ore Mountains, Germany during the five years from 2005 to 2010. A preliminary overall species analysis in 2005 showed that three species were most abundant: Procladius crassinervis, P. choreus and Chironomus anthracinus. Additionally, the species C. plumosus was examined because of its close relationship to C. anthracinus. The study is focussed on four subjects, whereby larvae and pupae of the four species were analysed. (1) The elaboration of a reliable method to distinguish the larvae of the two closely related species P. crassinervis and P. choreus on the basis of morphological criteria (imaginal disc development, larval head capsule size and body length) as well as the depth distribution of their pupae was a precondition to the profound analysis of their life cycles. (2) The investigation of the life cycle pattern of the four species was the second focus. The life cycle of the four species was found to be strongly influenced by abiotic conditions such as temperature, oxygen and biovolume of the phytoplankton. (3) The spatial and temporal distribution pattern of the four species was analysed in view of large scale differences over a depth gradient in one transect. Here, in all four species a shift in the mainly settled lake bottom area occurred. The young larvae of C. anthracinus, C. plumosus and P. choreus migrated during maturing and pupation towards shallower areas; P. crassinervis migrated to deeper areas. The distribution differences between two different bays showed that the two Chironomus species had higher densities in the bay with the higher inflow which resulted in a higher phytoplankton standing stock compared to the other species. A small scale distribution pattern analysis focussed on finding out whether the larvae were aggregated or randomly distributed. The vertical distribution analysis examined the swimming behaviour of the larvae. (4) The last aspect was an experimental setup exemplarily driven with C. anthracinus which showed that the migration was stimulated by the proximate factor temperature as pupae preferred warmer temperatures and young larvae colder temperatures. Altogether, the five year study about chironomids in Saidenbach Reservoir pointed out the complex reaction in the behaviour of an important part of the benthic community concerning the life cycle pattern (voltinism, pupation pattern), the changing in abundances (inter-annual and intra-annual) and the large scale and small scale distribution pattern under the rule of the most important environmental factors.

In den Jahren 2005 bis 2010 erfolgte im Rahmen der Erarbeitung der vorliegenden Dissertationsschrift eine ökologische Untersuchung der Chironomidenfauna in der Talsperre Saidenbach (Sachsen, Erzgebirge). Drei Arten mit hoher Abundanz konnten bei der umfassenden Artenanalyse im Jahr 2005 ermittelt werden: Procladius crassinervis, P. choreus und Chironomus anthracinus. Zusätzlich wurde die Art C. plumosus aufgrund ihrer engen Verwandtschaft zu C. anthracinus in die Untersuchung einbezogen. Die Arbeit ist auf vier Schwerpunkte fokussiert, wobei die Larven und Puppen der vier Arten analysiert wurden. (1) Die Erarbeitung einer zuverlässigen Methode zur Unterscheidung der Larven der beiden eng verwandten Procladius-Arten basierend auf morphologischen Kriterien (Imaginalscheiden-entwicklung, Kopfkapselgröße und Körperlänge) sowie die Tiefenverteilung der Puppen waren eine Vorbedingung für weiterführende Analysen des Lebenszyklus (LZ) dieser beiden Arten. (2) Die Untersuchung des LZ war der zweite Schwerpunkt. Der LZ wurde stark von abiotischen Faktoren wie Temperatur, Sauerstoff und Biovolumen des Phytoplanktons kontrolliert. (3) Die raum-zeitlichen Verteilungsmuster der vier Arten wurden zunächst bezüglich großräumiger Unterschiede über einen Tiefengradienten innerhalb eines Transektes analysiert. Hierbei zeigte sich bei allen vier Arten eine zeitliche Änderung im jeweiligen Hauptverbreitungsgebiet. Die jungen Larven von C. anthracinus, C. plumosus und P. choreus wanderten im Verlauf ihrer Entwicklung bis zur Verpuppung in flachere Bereiche, P. crassinervis wanderte in tiefere Bereiche. Die Analyse der Verteilungsunterschiede der Larven zwischen zwei verschieden stark eutrophierten Buchten ergab höhere Dichten der beiden Chironomus-Arten in der Bucht mit dem größeren Zulauf und der höheren Phytoplanktonkonzentration im Vergleich mit den anderen Arten. Eine Analyse des kleinräumigen Verteilungsmusters fokussierte auf der Frage, ob die Larven gleichmäßig verteilt oder aggregiert auftraten. Die Untersuchung des vertikalen Verteilungsmusters erforschte das Schwimmverhalten der Larven. (4) Der letzte Aspekt war eine experimentelle Untersuchung, die am Beispiel von C. anthracinus durchgeführt wurde mit dem Ziel, den Proximatfaktor für die beobachtete Wanderung der Larven zu ermitteln, der letztendlich die Temperatur war. Puppen bevorzugten im Experiment wärmere Temperaturen und junge Larven kühlere Temperaturen. Die fünfjährige Untersuchung der Chironomiden in der Talsperre Saidenbach beschreibt insgesamt die komplexe Verhaltensreaktion der Chironomiden, die einen wesentlichen Teil der benthischen Lebensgemeinschaft darstellen, bezüglich der Lebenszyklusmuster (Voltinismus, Verpuppung), der Abundanzänderungen (inner- und zwischenjährlich) sowie der groß- und kleinräumigen Verteilung unter der Einwirkung der wichtigsten Umweltfaktoren.:1. GENERAL INTRODUCTION 2. MORPHOLOGICAL DIFFERENTIATION OF TWO PROCLADIUS AND TWO CHIRONOMUS SPECIES IN THE MESOTROPHIC SAIDENBACH RESERVOIR 2.1 Introduction 2.2 Material and methods 2.2.1 Sampling of larvae 2.2.2 Species identification 2.2.3 Differentiation of the Procladius species by means of head capsule size and depth distribution 2.2.4 Other morphological criteria 2.2.5 Development of imaginal discs 2.3. Results 2.3.1 Procladius crassinervis and P. choreus 2.3.2 Chironomus anthracinus and C. plumosus 2.4. Discussion 2.4.1 Method discussion 2.4.2 Head capsule width 2.4.3 Larval growth 3. FIVE - YEAR LIFE CYCLE PATTERN OF TWO PROCLADIUS AND TWO CHIRONOMUS SPECIES IN THE MESOTROPHIC SAIDENBACH RESERVOIR 3.1 Introduction 3.2 Material and methods 3.2.1 Study area 3.2.2 Sampling of chironomid larvae 3.2.3 Sampling of chironomid pupae 3.2.4 Mortality 3.2.5 Abiotic conditions and phytoplankton 3.3 Results 3.3.1 Abiotic conditions and phytoplankton 3.3.1.1 Temperature 3.3.1.2 Oxygen 3.3.1.3 Phytoplankton 3.3.2 Life cycle analysis 3.3.2.1 Composition of instars 3.3.2.2 Procladius crassinervis 3.3.2.3 Procladius choreus 3.3.2.4 Chironomus anthracinus 3.3.2.5 Chironomus plumosus 3.3.2.6 Tanytarsini 3.3.2.7 Other species 3.3.3 Influence of abiotic conditions on pupation and life cycle 3.3.3.1 Procladius crassinervis 3.3.3.2 Procladius choreus 3.3.3.3 Chironomus anthracinus 3.3.3.4 Chironomus plumosus 3.3.3.5 Tanytarsini 3.3.4 Mortality of larvae during pupation 3.4 Discussion 3.4.1 Method discussion 3.4.2 Life cycle 3.4.3 Influence of controlling factors 3.4.4 Larval mortality and chironomid pupae as prey 4. SMALL AND LARGE SCALE DISTRIBUTION ASPECTS AND MIGRATION OF TWO PROCLADIUS AND TWO CHIRONOMUS SPECIES IN THE MESOTROPHIC SAIDENBACH RESERVOIR 4.1 Introduction 4.2 Study area 4.3 Material and methods 4.3.1 Sampling of chironomid pupae 4.3.2 Sampling of chironomid larvae 4.3.3 Large scale distribution 4.3.3.1 Depth gradient of the larval abundance 4.3.3.2 Distribution between different lake areas 4.3.4 Small scale distribution - patchiness 4.3.5 Vertical distribution 4.3.5.1 Residence depth in the sediment 4.3.5.2 Larvae in the water column 4.4 Results 4.4.1 Large scale distribution 4.4.1.1 Depth gradient of the larval abundance 4.4.1.2 Distribution between different lake areas 4.4.2 Small scale distribution - patchiness 4.4.3 Vertical distribution 4.4.3.1 Residence depth in the sediment 4.4.3.2 Larvae in the water column 4.5 Discussion 4.5.1 Large scale distribution 4.5.1.1 Depth gradient of the larval abundance 4.5.1.2 Distribution between different lake areas 4.5.2 Small scale distribution - patchiness 4.5.3 Vertical distribution 4.5.3.1 Residence depth in the sediment 4.5.3.2 Larvae in the water column 5. INVESTIGATIONS ON THE PREFERENCE TEMPERATURE OF C. ANTHRACINUS FROM THE MESOTROPHIC SAIDENBACH RESERVOIR 5.1 Introduction 5.2 Material and methods 5.2.1 Influence of temperature on the timing of pupation 5.2.2 Preference temperature 5.2.3 Locomotory activity of larvae 5.3 Results 5.3.1 Migratory activity of C. anthracinus in the field 5.3.2 Influence of temperature on the timing of pupation 5.3.3 Preference temperature 5.3.4 Locomotory activity of larvae 5.4 Discussion 5.4.1 Influence of temperature on the timing of pupation 5.4.2 Preference temperature 5.4.3 Agitation activity of larvae 6. OVERALL SUMMARY AND FUTURE PROSPECTS 7. REFERENCES EIDESSTATTLICHE ERKLÄRUNG DANKSAGUNG / In the context of the present dissertation an ecological study was performed about chironomids in Saidenbach Reservoir in the Saxony Ore Mountains, Germany during the five years from 2005 to 2010. A preliminary overall species analysis in 2005 showed that three species were most abundant: Procladius crassinervis, P. choreus and Chironomus anthracinus. Additionally, the species C. plumosus was examined because of its close relationship to C. anthracinus. The study is focussed on four subjects, whereby larvae and pupae of the four species were analysed. (1) The elaboration of a reliable method to distinguish the larvae of the two closely related species P. crassinervis and P. choreus on the basis of morphological criteria (imaginal disc development, larval head capsule size and body length) as well as the depth distribution of their pupae was a precondition to the profound analysis of their life cycles. (2) The investigation of the life cycle pattern of the four species was the second focus. The life cycle of the four species was found to be strongly influenced by abiotic conditions such as temperature, oxygen and biovolume of the phytoplankton. (3) The spatial and temporal distribution pattern of the four species was analysed in view of large scale differences over a depth gradient in one transect. Here, in all four species a shift in the mainly settled lake bottom area occurred. The young larvae of C. anthracinus, C. plumosus and P. choreus migrated during maturing and pupation towards shallower areas; P. crassinervis migrated to deeper areas. The distribution differences between two different bays showed that the two Chironomus species had higher densities in the bay with the higher inflow which resulted in a higher phytoplankton standing stock compared to the other species. A small scale distribution pattern analysis focussed on finding out whether the larvae were aggregated or randomly distributed. The vertical distribution analysis examined the swimming behaviour of the larvae. (4) The last aspect was an experimental setup exemplarily driven with C. anthracinus which showed that the migration was stimulated by the proximate factor temperature as pupae preferred warmer temperatures and young larvae colder temperatures. Altogether, the five year study about chironomids in Saidenbach Reservoir pointed out the complex reaction in the behaviour of an important part of the benthic community concerning the life cycle pattern (voltinism, pupation pattern), the changing in abundances (inter-annual and intra-annual) and the large scale and small scale distribution pattern under the rule of the most important environmental factors.:1. GENERAL INTRODUCTION 2. MORPHOLOGICAL DIFFERENTIATION OF TWO PROCLADIUS AND TWO CHIRONOMUS SPECIES IN THE MESOTROPHIC SAIDENBACH RESERVOIR 2.1 Introduction 2.2 Material and methods 2.2.1 Sampling of larvae 2.2.2 Species identification 2.2.3 Differentiation of the Procladius species by means of head capsule size and depth distribution 2.2.4 Other morphological criteria 2.2.5 Development of imaginal discs 2.3. Results 2.3.1 Procladius crassinervis and P. choreus 2.3.2 Chironomus anthracinus and C. plumosus 2.4. Discussion 2.4.1 Method discussion 2.4.2 Head capsule width 2.4.3 Larval growth 3. FIVE - YEAR LIFE CYCLE PATTERN OF TWO PROCLADIUS AND TWO CHIRONOMUS SPECIES IN THE MESOTROPHIC SAIDENBACH RESERVOIR 3.1 Introduction 3.2 Material and methods 3.2.1 Study area 3.2.2 Sampling of chironomid larvae 3.2.3 Sampling of chironomid pupae 3.2.4 Mortality 3.2.5 Abiotic conditions and phytoplankton 3.3 Results 3.3.1 Abiotic conditions and phytoplankton 3.3.1.1 Temperature 3.3.1.2 Oxygen 3.3.1.3 Phytoplankton 3.3.2 Life cycle analysis 3.3.2.1 Composition of instars 3.3.2.2 Procladius crassinervis 3.3.2.3 Procladius choreus 3.3.2.4 Chironomus anthracinus 3.3.2.5 Chironomus plumosus 3.3.2.6 Tanytarsini 3.3.2.7 Other species 3.3.3 Influence of abiotic conditions on pupation and life cycle 3.3.3.1 Procladius crassinervis 3.3.3.2 Procladius choreus 3.3.3.3 Chironomus anthracinus 3.3.3.4 Chironomus plumosus 3.3.3.5 Tanytarsini 3.3.4 Mortality of larvae during pupation 3.4 Discussion 3.4.1 Method discussion 3.4.2 Life cycle 3.4.3 Influence of controlling factors 3.4.4 Larval mortality and chironomid pupae as prey 4. SMALL AND LARGE SCALE DISTRIBUTION ASPECTS AND MIGRATION OF TWO PROCLADIUS AND TWO CHIRONOMUS SPECIES IN THE MESOTROPHIC SAIDENBACH RESERVOIR 4.1 Introduction 4.2 Study area 4.3 Material and methods 4.3.1 Sampling of chironomid pupae 4.3.2 Sampling of chironomid larvae 4.3.3 Large scale distribution 4.3.3.1 Depth gradient of the larval abundance 4.3.3.2 Distribution between different lake areas 4.3.4 Small scale distribution - patchiness 4.3.5 Vertical distribution 4.3.5.1 Residence depth in the sediment 4.3.5.2 Larvae in the water column 4.4 Results 4.4.1 Large scale distribution 4.4.1.1 Depth gradient of the larval abundance 4.4.1.2 Distribution between different lake areas 4.4.2 Small scale distribution - patchiness 4.4.3 Vertical distribution 4.4.3.1 Residence depth in the sediment 4.4.3.2 Larvae in the water column 4.5 Discussion 4.5.1 Large scale distribution 4.5.1.1 Depth gradient of the larval abundance 4.5.1.2 Distribution between different lake areas 4.5.2 Small scale distribution - patchiness 4.5.3 Vertical distribution 4.5.3.1 Residence depth in the sediment 4.5.3.2 Larvae in the water column 5. INVESTIGATIONS ON THE PREFERENCE TEMPERATURE OF C. ANTHRACINUS FROM THE MESOTROPHIC SAIDENBACH RESERVOIR 5.1 Introduction 5.2 Material and methods 5.2.1 Influence of temperature on the timing of pupation 5.2.2 Preference temperature 5.2.3 Locomotory activity of larvae 5.3 Results 5.3.1 Migratory activity of C. anthracinus in the field 5.3.2 Influence of temperature on the timing of pupation 5.3.3 Preference temperature 5.3.4 Locomotory activity of larvae 5.4 Discussion 5.4.1 Influence of temperature on the timing of pupation 5.4.2 Preference temperature 5.4.3 Agitation activity of larvae 6. OVERALL SUMMARY AND FUTURE PROSPECTS 7. REFERENCES EIDESSTATTLICHE ERKLÄRUNG DANKSAGUNG