engleski

Predicting the effects of climate change on pathogen-host balance in freshwater ecosystems: a case study of indigenous European crayfish and crayfish plague

Anthropogenically induced climate change has multiple negative effects on ecosystems. Many freshwater organisms are especially vulnerable to climate change-related habitat alterations since animals have limited possibilities to migrate to areas with more favourable conditions. Thus, crayfish as keystone species and ecosystem engineers of many freshwater ecosystems could be negatively affected. Furthermore, it has been shown for multiple pathogen-host pairs that elevated water temperature caused by climate change favours spreading of pathogens. The aim of this study was to investigate whether a 4 °C increase in water temperature (from 18 to 22 °C) will also increase the virulence of Aphanomyces astaci (Schikora, 1906), the causative agent of crayfish plague. Transmission of crayfish plague by invasive crayfish species is one of the main drivers of native European crayfish populations declines. We used a highly virulent A. astaci strain B (PsI genotype, transmitted by the most successful invasive crayfish) and two indigenous crayfish species: the stone crayfish Austropotamobius torrentium (Schrank, 1803) and the narrow-clawed crayfish Astacus leptodactylus Eschscholtz, 1823. In their natural habitat in Croatia, the selected species are either in direct contact (A. leptodactylus) or in the close proximity (A. torrentium) to invasive crayfish and the presence of A. astaci was already detected in some populations. Before the experiment, we have tested all animals for A. astaci presence, using a non-invasive PCR method. Only A. astaci-free animals were included into the experiment. After acclimatization, we have infected the crayfish with 500 zoospores per mL at water temperature of 18⁰C (control conditions) and 22⁰C (increased water temperature - simulation of climate change). After four weeks the results have shown that the mortality of both crayfish species was significantly lower at increased water temperature (22⁰C). This suggests that the increase of water temperatures caused by climate change will probably not result in the increased spread of A. astaci strain B in stone crayfish and narrow-clawed crayfish populations. Results will be discussed in adaptation and evolutionary perspective as well as in the context of A. astaci strains that have different water temperature preference. In conclusion, this study presents the first experimental data on the balance between A. astaci and indigenous crayfish in the context of climate change. As such, it can serve as a starting point for new research in this area and the development of adjusted conservation programs.

climate change, indigenous crayfish, Aphanomyces astaci

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