Projects

On November 9, 2023  Kathrin Theissinger was awarded to join the Heisenberg Programme of the German Research Foundation DFG with her research project entitled;

“Molecules, species and environment: key factors shaping interactions of freshwater crayfish and their invasive disease crayfish plague”

In this research project, we want to further infer the molecular mechanisms of pathogen virulence and host resistance shaping host-pathogen coevolution, for developing a multi-omics rescue plan for the conservation of European freshwater crayfish and the functioning of freshwater ecosystems in Europe. We use our collection of live crayfish plague strains of varying virulence for in vitro approaches and controlled infection experiments. Coupled with multi-omic methods we then characterize the pathogen toxins and host immune genes, encoding particularly immune related effector molecules such as antimicrobial peptides, to infer pathogen virulence and host resistance mechanisms under host-pathogen coevolution in freshwater crayfish. Furthermore, we test in vitro and in vivo the influence of temperature stress on the virulence of the crayfish plague disease agent and the immune status of the crayfish, for developing sustainable management strategies in the context of ongoing climate change. Finally, we use transgenerational immune priming of female crayfish to test whether epigenetic mechanisms can transfer an increased disease resistance to the offspring. The longer-term vision is to develop an oral vaccine in form of customized feed for crayfish that makes them more tolerant against the crayfish plague. The breeding of crayfish plague tolerant crayfish will enable conservation initiatives to restock native crayfish in waterbodies inhabited by invasive crayfish carrying the crayfish plague, which will be a milestone for sustainable disease control and conservation of this threatened species.

Find out more: 

Link to CrayTGIP

Link to ClimpHIT

The European pond turtle Emys orbicularis is a small freshwater turtle native to Central Europe. It relies on both aquatic and terrestrial environments for ensuring its physiological and reproductive needs. As an ectotherm, its activity is highly dependent on the ambient temperature making this species directly impacted by climate change. Additionally, global changes, including climate and human activities, have been dramatically impacting its habitats and natural populations. Nowadays, the European pond turtle is considered as the reptile that has suffered the most dramatic decline in Europe. The species is of conservation concern and benefits from conservation initiatives, including reintroductions. The success of reintroduction depends on both intrinsic (individual quality, population genetics) and extrinsic (environmental conditions, habitat quality, food resource availability) factors. The monitoring of Emys orbicularis behavior and ecology in the wild through traditional capture-mark-recapture methods is challenging mainly due to its cryptic, discrete, and mostly aquatic lifestyle and nocturnal nesting behavior. Furthermore, the polygamous mating strategy of E. orbicularis makes it difficult to assess the actual drivers of a populations‘ genetic structure. A good understanding of the turtles‘ behavior, habitat use and reproductive strategies (including nesting site selection and mating selection) is the basis for effective land management and conservation initiatives as well as for assessing their capacity to adapt to global and climatic changes. In this project we aim to expand this knowledge by incorporating data from advanced biologgers and genomic pedigree analysis.

Project members:       DR. KATHRIN THEISSINGER     DR. JEAN-YVES GEORGES     STEFANIE KNELL

Climate change impacts on host-pathogen co-adaptation between freshwater crayfish and the invasive crayfish plague disease agent

Climate change could have contrasting effects on the range expansion of invasive non-native crayfish in Europe and consequently on the crayfish plague disease agent (Aphanomyces astaci). Several genetically distinct strains of A. astaci are nowadays present in Europe, each originally associated with different North American crayfish hosts, which vary widely in their virulence. Pathogen virulence is shaped by natural selection and can shift in response to environmental change, including rising temperatures. Some strains appear better suited to warmer, subtropical conditions, while others perform well in cooler environments, which is most likely due to the geographical origin of their original host as a consequence of host-pathogen coevolution. As climate conditions shift, certain A. astaci strains may become more or less successful, altering the level of threat they pose to native European crayfish and influencing management strategies. On the host side, temperature also affects crayfish physiology more broadly. Warmer water can reduce survival and disrupt metabolic processes, suggesting that heat stress may impair components of the innate immune system. Despite this, controlled studies examining how temperature affects immune function in the noble crayfish (Astacus astacus), an ecologically important native species and one of high value in European aquaculture, are still lacking.

Project aim: In this project, we analyze in vitro and in vivo the temperature-dependent host-pathogen interactions within the model system of freshwater crayfish (A. astacus) and the invasive crayfish plague agent (A. astaci) under future climate scenarios. The results will advance our knowledge regarding the interface between host-pathogen coevolution and key ecological processes in the face of global environmental change.

Project members:    DR. KATHRIN THEISSINGER      DR. JEAN-YVES GEORGES     ISABELL KUHN                                                                              DR. LENA BONASSIN      DR. LJUDEVIT LUKA BOŠTJANČIĆ

A novel vaccination strategy for the endangered european Noble crayfish Freshwater crayfish are ecosystem engineers with a big influence on biological diversity and functioning ecosystems. Unfortunately, populations of native crayfish are declining in all of Europe. The biggest threat to european crayfish are the rising populations of invasive north-american crayfish that are transmitters for the crayfish plague  Aphanomyces astaci. That Oomycet in ranked under the 100 worst invasive species world-wide and caused the extinction of whole populations of freshwater crayfish in Europe with massive effects on ecosystems. Therefore it is of great ecological significance to research how native crayfish species can resist the crayfish plague.

Project aims: For a long time it was assumed that invertebrates lack an immune memory. For crustaceans though, first proof for an immune memory was provided through immune priming experiments. The underlaying mechanism behind that phenomena is most likely connected to epigenetic processes, which are changes on the level of gene expression. Maternal transgenerational immune priming (mTGIP) is such an epigenetic mechanism. The females brace there offspring against germs that they themselves had come in contact with. This mTGIP triggers the expression of certain immune respones gene which leads to a similar immune defence then the one of the mother. Our aim is therefore to develop and test a vaccination for female novel crayfish (Astacus astacus), that will protect there offspring from the crayfish plague through mTGIP.

For centuries, the crayfish plague has caused great ecological damage in Germany and Europe. Regardless, a treatment to produce native crayfish with stronger immune systems was not tested so far. The availability of plague resistant stocking crayfish would significantly improve the long-term success of management strategies. Therefore the proposed vaccination method can be regarded as highly innovative and ecologically relevant. A positive result would be a milestone for the management of freshwater crayfish, that would greatly improve the success of restocking measures.

To reach our goals we plan to do our experiment in three consecutive work packages:

1. Vaccination of the females before mating:
   The female crayfish are injected subcutaneously of raw hyphae extract from A. astaci to intensify their immune answer without actually infecting them (the hyphae are the non-infectious stage of A. astaci). To identify the best time and dose the crayfish will be grouped in three vaccination groups: They will receive a vaccination either four weeks (Group 1) or eight weeks (Group 2) before mating. Some females will get vaccinated on both times (Group3), receiving twice the amount of vaccine. A fourth group of female breeding animals remains unvaccinated as a control. To assess the immune status of the female crayfish we take sublethal hemolymph samples for qPCR of immune genes at different time points before and after vaccination as well as before mating.
    

2. Mating under mTGIP
   We use the vaccinated females for controlled mating in indoor ponds containing multiple males. After mating, the eggs of every female will be incubated in separate incubation baskets where the larvae can hatch and develop into juveniles. The immune status will be assessed using qPCR of immune genes during the development of the eggs and the offspring. The F1 generation will be raised until their first summer, separated by vaccination groups. At this point the juveniles should have reached an average size of 4 cm. This is adequate for the following controlled infection experiments to test if TGIP is sufficient.
    

3. Infection experiment to proof mTGIP
   We use the F1 generation of noble crayfish for controlled infection experiments to verify the efficiency of the mTGIP approach. Therefore we conduct a controlled infection experiment on every vaccination group with 10 treated and 10 control animal from each group. We monitor the treated individuals for disease symptoms. After the infection experiment, the immune status of all crayfish will be examined with qPCR. The surviving F1-groups can be used for restocking measures.