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The influence of global warming on the interaction between freshwater native crayfish species and Aphanomyces astaci (Schikora, 1906), the causative agent of crayfish plague

Crayfish, as keystone species of freshwater ecosystems, are endangered by climate change and multiple anthropogenic influences. Among them, invasive crayfish species act as carriers of pathogen Aphanomyces astaci (Schikora, 1906). The aim of this study was to investigate potential in vivo effects of increased water temperature on virulence of A. astaci and physiological condition of two native species of crayfish: the narrow-clawed crayfish (Astacus leptodactylus Eschscholtz, 1823) and the stone crayfish (Austropotamobius torrentium (Schrank, 1803)). We used newly developed noninvasive method of molecular detection of pathogen from the crayfish cuticle which enabled us to select only non-infected individuals for the experiments, as well as to identify the cause of death of each individual. Experiments were performed at two water temperatures: 18 °C (control temperature) and 22 °C (elevated temperature – simulation of global warming). The crayfish were infected with 500 A. astaci zoospores / mL (PsI genotype) and the mortality rate was monitored for four weeks. In both species, A. astaci virulence was lower at higher temperature (22 °C). Simultaneously, higher temperature caused more stress for A. torrentium, which exhibited higher mortality rate in comparison to A. leptodactylus. In conclusion, global warming could decrease A. astaci (PsI genotype) virulence, but it could also have negative impacts on fitness of protected and endangered native species such as A. torrentium. Future research should examine the virulence of other A. astaci strains in relation to changes in water temperature as well as the potential of A. astaci PsI genotype to adapt to elevated temperature.

crayfish, crayfish plague, global warming, Aphanomyces astaci

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