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

• Applicant: Dr. Kathrin Theissinger
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 548582157

It is generally thought that climate change will modify the ecological impacts of invasive species by enhancing their competitive effects on native species and by increasing the virulence of some pathogens. A highly suitable model system for investigating host-pathogen co-adaptation to climate change are freshwater crayfish and the crayfish plague disease agent, because of the existence of high- and low virulent pathogen strains originating from different host crayfish from varying climatic niches. Population trends of native crayfish species across Europe are in severe decline. The main threats they are exposed to are the increasing populations of various invasive North American crayfish species, which are vectors of the crayfish plague disease agent (Aphanomyces astaci). This oomycete pathogen is listed amongst the 100 worst invasive species worldwide. In my lab we are curating the world´s largest collection of pure A. astaci strains representative of the varying virulence observed in nature. Some A. astaci strains are adapted to rather subtropical conditions and others to milder temperatures, with respect to the natural range of their native crayfish host. Therefore, we can assume that some A. astaci strains might lose or benefit under future climate change scenarios. This strongly influences the threat they pose towards the native crayfish and accordingly impact management decisions. In addition, it has been shown that temperature stress has an effect on the crayfish immune response in general. In this research project we test the general hypothesis, that climate change has contrasted impacts on the crayfish plague disease dynamics in this host-pathogen model system, depending on the climatic origin of the A. astaci strain. In three work packages we investigate in vitro and in vivo the influence of temperature stress on A. astaci´s virulence as well as on the immune status of the crayfish. The knowledge which temperatures induce highest pathogen virulence and host immune stress is then applied for cross-infection experiments under different temperature regimes. We infect noble crayfish with A. astaci strains under temperature conditions that cause immune stress to noble crayfish but are optimal for a specific crayfish plague strain and vice versa, meaning an infection experiment under temperature conditions that are optimal for noble crayfish, but suboptimal for the respective A. astaci strain. We assess the outcome of these controlled infection experiments by recording the disease dynamics of the host, as well as pathogen load in the host and gene expression for selected target genes in host and pathogen. With the results from these experiments, we are able to assess the impact of increased temperatures on the host-pathogen dynamics in this model system under future climate change.

• DFG Programme: Research Grants