| Popis: |
The crayfish plague pathogen, the oomycete Aphanomyces astaci, has been decimating populations of European crayfish species for more than 150 years, and is therefore considered one of the 100 worst world's invasive species. A. astaci is highly specialised for a parasitic life, but it can be isolated from moribund crayfish and grown on synthetic media, as it is the case also for several other oomycetes (chapter 7). The life of A. astaci includes three basic forms: mycelium in host's tissues, and the infective units occurring in water, zoospores and cysts. All North American crayfish species tested so far have shown some resistance to A. astaci, i.e., they could carry the infection for long, serving as vectors of the pathogen. Massive sporulation from infected North American crayfish starts when the host is moulting, stressed, or dying (chapter 4). However, I could show in my experiments that some sporulation occurs even from apparently healthy and non-moulting American crayfish hosting A. astaci, so infected North American crayfish must be considered a permanent source of the infection (chapter 4). Five genotype groups of A. astaci have already been distinguished. Strains from a particular genotype group probably share the same original host crayfish species of North American origin. Nevertheless, they can... |
