Stefan Fischer

Stefan Fischer
University of Tuebingen | EKU Tübingen · Centre of Applied Geosciences

PhD

About

28
Publications
6,123
Reads
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304
Citations
Additional affiliations
November 2014 - June 2020
University of Tuebingen
Position
  • Professor (Assistant)
June 2013 - October 2014
Dalhousie University
Position
  • PostDoc Position

Publications

Publications (28)
Article
In permafrost peatlands, up to 20% of total organic carbon (OC) is bound to reactive iron (Fe) minerals in the active layer overlying intact permafrost, potentially protecting OC from microbial degradation and transformation into greenhouse gases (GHG) such as CO2 and CH4. During the summer, shifts in runoff and soil moisture influence redox condit...
Preprint
In permafrost peatlands, up to 20% of total organic carbon (OC) is bound to reactive iron (Fe) minerals in the active layer overlying intact permafrost, potentially protecting OC from microbial degradation and transformation into greenhouse gases (GHG) such as CO2 and CH4. During the summer, shifts in runoff and soil moisture influence redox condit...
Article
In freshwater wetlands, redox interfaces characterized by circumneutral pH, steep gradients in O2, and a continual supply of Fe(II) form ecological niches favorable to microaerophilic iron(II) oxidizing bacteria (FeOB) and the formation of flocs; associations of (a)biotic mineral phases, microorganisms, and (microbially-derived) organic matter. On...
Data
Video S1. Animation of the rotated segmented 3D reconstruction of the terebra of Habrobracon hebetor.
Data
Video S2. Animation of the rotated segmented 3D reconstruction of the proximal region of the terebra of Habrobracon hebetor (cf. Fig. 3), highlighting the 1st and 2nd valvulae, the ligaments, and the duct of the venom gland.
Article
Full-text available
The Braconidae are a megadiverse and ecologically highly important group of insects. The vast majority of braconid wasps are parasitoids of other insects, usually attacking the egg or larval stages of their hosts. The ovipositor plays a crucial role in the assessment of the potential host and precise egg laying. We used light- and electron-microsco...
Article
Full-text available
Using two-dimensional top-down view microscopy, researchers have recently described chondrocytes as being spatially arranged in distinct patterns such as strings, double strings, and small and large clusters. Because of the seeming association of these changes with tissue degeneration, they have been proposed as an image-based biomarker for early o...
Article
Stemmata of strepsipteran insects represent the smallest arthropod eyes known, having photoreceptors which form fused rhabdoms measuring an average size of 1.69 × 1.21 × 1.04 μm and each occupying a volume of only 0.97–1.16 μm³. The morphology of the stemmata of the extremely miniaturized first instar larva of Stylops ovinae (Strepsiptera, Stylopid...
Preprint
Full-text available
A hallmark in snails’ anatomy is the conspicuous crossing of the pleurovisceral nerve cords present in all but the most derived gastropod clades. This feature is called streptoneury and hitherto near-universally believed to derive from the process of torsion which is, ontogenetically, visible by a 180° rotation of the visceral sac relative to the c...
Article
Little morphological information is available about subretinal pigment shields in insect compound eyes, especially ultrastructural information. The latter is however needed in order to detect possible smallest projections that emanate from pigment‐granule‐bearing cells and pass through the basal matrix (BM), but that are not visible in light microg...
Article
Pigment granules, found in different cell types of the retina in insect compound eyes, fulfill important functions. They isolate the individual ommatidia from stray light, regulate the angular sensitivity and restrict the light that reaches the photoreceptor according to ambient light intensities. Descriptions of pigment cells within the retina are...
Article
Existing information on insect compound eyes is mainly limited to two-dimensional information derived from histological or ultrathin sections. These allow a basic description of eye morphology, but are limited in z-axis resolution because of the section thickness or intervals between sections, so that accurate volumetric information cannot be gener...
Article
Full-text available
Solar cells with increased short‐circuit current density and energy conversion efficiency can be realized by integrating moth eye textures in the design of perovskite and amorphous silicon thin film solar cells. Broadband light incoupling in solar cells can be achieved by using hexagonally arranged arrays of nipples or domes with parabolically shap...
Article
Most studies dealing with the limits to miniaturization in insect brains have until now relied on information based on data collected in two dimensions: either histological sections imaged by light microscopy, or electron micrographs of single ultrathin sections imaged by transmission electron microscopy (TEM). To test the validity of transferring...
Article
Due to their small size, diminutive parasitic wasps are outstanding subjects for investigating aspects of body miniaturization. Information on minute compound eyes is still scarce, and we therefore investigated eye morphology in one of the smallest known Hymenopteran species Megaphragma mymaripenne (body size 0.2 mm) relative to Anaphes flavipes (b...
Article
The Acanthopteroctetidae are one of the first-originated family-group lineages within "tongue moths" (Lepidoptera-Glossata). The purpose of this study is to provide a comprehensive account (based on whole mount preparations, serial sections, and Scanning electron microscopy) of the cephalic structure of an adult exemplar of the family, to supplemen...
Article
Superposition and apposition compound eyes are commonly associated with moths and butterflies, respectively. However, recently intermediate eye designs, combining features of both apposition and superposition eyes were found in tiny insects. Here, we examine the eyes of 12 species of moth, ranging from 1.88 to 6.03 mm body size, by scanning and tra...
Article
In spite of the numerous studies on insect compound eyes within the last 100 years, the number of investigations specifically dealing with the eyes of species of small body size is near to negligible. Based on theoretical optical examinations it had been predicted that an unlimited reduction in the size of a compound eye, especially if the latter w...
Article
Full-text available
The two lemon-shaped compound eyes of the moth Cameraria ohridella measure in dorsal–ventral direction 263.0 μm in male and 238.9 μm in female individuals. In anterior–posterior direction no significant differences were found between the sexes, eye length being about 194.6 μm. The eyes of males consist of ca. 417 hexagonal facets, while those of fe...
Article
With a body length of only 2 mm, the nepticulid Stigmella microtheriella (Stainton, 1854) is one of the smallest moths known to date. We investigated the optical design of its lemon-shaped compound eyes, which measure 83.60 μm in anterior-posterior and 119.77 μm in dorso-ventral direction. The eyes consist of about 123 facets, each of the latter ju...
Article
Nipples on the surface of moth eye facets exhibit almost perfect broadband anti-reflection properties. We have studied the facet surface micro-protuberances, known as corneal nipples, of the chestnut leafminer moth Cameraria ohridella by atomic force microscopy, and simulated the optics of the nipple arrays by three-dimensional electromagnetic simu...
Article
Full-text available
With a body length of only 0.3-0.4 mm, the parasitoid wasp Trichogramma evanescens (Westwood) is one of the smallest insects known. Yet, despite its diminutive size, it possesses compound eyes that are of oval shapes, measuring across their long axes in dorsoventral direction 63.39 and 71.11 μm in males and females, respectively. The corresponding...
Article
Full-text available
In the framework of several field excursions to the Balearic Island of Ibiza (Western Mediterranean Sea) conducted every spring and autumn between 1998 and 2007, extensive studies were carried out on the structure, diversity and ecology of the coastal ichthyofauna. The ichthyofaunistic observations were made in the months of March, April, September...

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Projects

Project (1)
Project
investigate morphological adaptations with respect to spatial and functional constraints in photoreceptors and visual neuropiles of miniaturized insects Methods: SEM, TEM, ssTEM, 3D reconstruction