- Studium der Biologie, Heinrich-Heine-Universität Düsseldorf
- Promotion zum Dr. rer.nat., Heinrich-Heine-Universität Düsseldorf
- Wissenschaftliche Mitarbeiterin HHU Düsseldorf und WWU Münster
- Wiedereinstiegsstipendium HHU Düsseldorf
- Akademische Rätin/Oberrätin WWU Münster
- Differentielle Hämoglobininduktion bei Daphnia magna
- Akklimation und Thermotoleranz bei Daphnia
1. Molecular physiology of Daphnia haemoglobin
Haemoglobin (Hb), the extracellular respiratory protein in the haemolymph of Daphnia, is a multi-subunit, multi-domain macromolecule with a molecular weight of approximately 500 kDa in D. magna. In this species, at least four Hb genes (dhb1 - dhb4) encode for at least seven different Hb subunit types (DHbA - DHbG) with molecular weights between 36 and 41 kDa. In response to changes of environmental factors as oxygen concentration or temperature, the Hb concentration in the haemolymph varies (up to 19fold). Additionally, the subunit composition of the macromolecules varies with concomitant changes of Hb oxygen affinity (up to 5fold). At present, we focus on the relationships between Hb genes and Hb subunits and on the Hb macromolecule structure in haemoglobin-poor ("pale") and haemoglobin-rich ("red") D. magna. Molecular biological methods (e.g. Southern blot analysis, quantitative RT-PCR), proteinbiochemical methods (e.g. 2-D gel electrophoresis and MALDI mass spectroscopy; chromatofocussing) and other techniques (e.g. in situ hybridization, computer modelling of macromolecule structure based on transmission electron micrographs ) are applied (partly in collaboration) to reveal the molecular reasons for the Hb subunit heterogeneity, to analyze composition and structure of the macromolecules and to relate structure to molecular function
2. Mechanisms, phenotypic plasticity and genotypic determination of thermal tolerance in Daphnia and Chaoborus larvae: consequences for fitness and biotic interactions (Project within the AQUASHIFT Priority program)
Global warming may have far-reaching effects on aquatic ecosystems through direct or indirect effects on the physiological systems of its members. The genus Daphnia plays a central role in the ecology of almost all standing freshwater, and Chaoborus larvae are prominent invertebrate predators of Daphnia. For a mechanistic understanding of thermal effects in Daphnia and in Chaoborus larvae, field data analysis, physiological and ecological experiments, biochemical and genetical investigations and retrospective studies will be brought together: investigation of the seasonal changes of phenotypic acclimatization and/or of population structure (clonal structure) and clone-specific thermal tolerance will allow to evaluate future ecological consequences of global warming. Both, mechanisms and degrees of thermal tolerance as well as traits related to physiological fitness will be analyzed and linked to environmental conditions.
Answers to the following questions will be sought: What are the physiological and biochemical mechanisms causing differences in thermal tolerance? Which part of these mechanisms is genetically fixed (adaptation) and which is phenotypically plastic (acclimatization)? Which part is species- or clone-specific and which are characteristics common to all? What are the costs of an improved or the benefits of a reduced thermal performance and vice versa? Are there any seasonal changes concerning thermal tolerance and fitness due to phenotypic plasticity or due to the clonal structure of Daphnia populations? How near to the edges of their thermal tolerance ranges do species and clones live during the seasons? The necessary data base for a general view on Daphnia will come from a comparison of differently thermally adapted, yet closely related clones and species.