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The crayfish plague pathogen Aphanomyces astaci in its introduced ranges: vectors, introduction pathways, genetic variation and host-pathogen interactions
Mrugała, Agata ; Petrusek, Adam (advisor) ; Füreder, Leopold (referee) ; Vralstad, Trude (referee)
- ABSTRACT - The crayfish plague pathogen, Aphanomyces astaci, is responsible for substantial declines and local extinctions of native European crayfish populations. As a consequence, the pathogen is now listed among 100 world's worst invasive alien species. The spread of A. astaci is greatly facilitated by its natural hosts, North American crayfish, that thanks to a long co-evolutionary history with the crayfish plague pathogen evolved efficient defence mechanisms. In contrast, European, Australian and Asian crayfish species are highly susceptible to this disease agent. However, progress of A. astaci infection in native European crayfish was observed to differ between distinct pathogen strains, indicating variability in their virulence. Indeed, we demonstrated a relationship between patterns in crayfish immune response and A. astaci virulence in an experimental infection involving the European noble crayfish and three differently virulent crayfish plague strains. The European continent is currently inhabited by at least eight North American crayfish species. The carrier status was confirmed in six of them, including also Orconectes cf. virilis occurring in the Netherlands and the UK. In this country, we detected Aphanomyces astaci presence in some populations of the non-indigenous crayfish species as well...
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Embryonic and postembryonic development of marbled crayfish in different temperatures
FOJT, Martin
The aim of this bachelor thesis was to characterise the life cycle by parthenogenetic reproduction of marbled crayfishProcambarus fallax f. virginalis and to focus on the effects of its life cycle at different temperatures. The theoretical part of this thesis is focused on the reproductive biology of crayfish, with emphasis on embryonic and postembryonic development of marbled crayfish. It also acquaints us with the reproduction of indigenous crayfish and introduced crayfish species occurring in the territory of the Czech Republic. The practical part acquaints us with the conditions that need to be adhered during the experiment, changes in embryo development and assessing embryo development at different temperatures. Our experiment confirmed that the postembryonic stages of marbled crayfish were able to survive at low temperature (10 °C). Individuals were able to undergo the first postembryonic stadium at the lower temperature, but they developed slowly. Individuals develop without problems at 15 °C. The duration of postembryonic development was a little bit longer than in warmer temperature. There were expectations that the highest survival rate would be at higher temperatures, but our experiment showed that our predictions were false. Temperature of 20 °C was shown as the lowest survival rate, but we suspect that this poor result wasn't caused by the effect of water temperature, but rather by other physical-chemical water parameters which were not controlled. The highest survival rate of embryos in our experiment was at 15 °C. This thesis deals with the prediction of survival rates of marbled crayfish in the Czech Republic as written in the scientific literature and the obtained results refer to the ability in hatched individuals of marbled crayfish to tolerate the natural conditions of low temperatures in the Czech Republic.
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