National Repository of Grey Literature 15 records found  1 - 10next  jump to record: Search took 0.01 seconds. 
Detection and variation of the crayfish plague pathogen in selected crayfish populations
Mojžišová, Michaela ; Petrusek, Adam (advisor) ; Buřič, Miloš (referee)
Crayfish plague is an emerging disease caused by the oomycete Aphanomyces astaci, a pathogen listed among the 100 World's Worst Invasive Alien Species. It was introduced into Europe in the second half of 19th century from North America and caused collapses of European native crayfish populations. Nowadays, A. astaci is widespread in Europe and has spread also to other parts of the world, threatening all susceptible crayfish of non-North American origin. The aims of this MSc thesis were 1) to provide information about crayfish plague outbreaks from recent years, and by using microsatellite and mtDNA markers reveal A. astaci genotypes involved; 2) to test healthy-looking indigenous crayfish for potential occurrence of chronic infections by A. astaci in Czechia. Six new crayfish plague outbreaks were confirmed from 2016 to 2018, involving at least five distinct pathogen strains. My results provide first evidence of the A. astaci genotype group D causing Astacus astacus and Austropotamobius torrentium mass mortalities in Czechia. MtDNA sequencing revealed two haplotypes of the D haplogroup, indicating two independent sources of infection presumably either from ornamental crayfish or spreading from neighbouring countries. The genotype group A was recorded in two A. astacus mortalities and genotype group...
Seasonal variation of activity and pathogen prevalence in populations of the spiny-cheek crayfish
Matasová, Klára ; Petrusek, Adam (advisor) ; Slavík, Ondřej (referee)
The most widespread of invasive crayfish in the Czech Republic is the spiny-cheek crayfish (Orconectes limosus). It is a major disease carrier of crayfish plague, caused by the pathogen Aphanomyces astaci. The infection is lethal to European native species of crayfish. Transmission of this disease is usually associated with the spread of crayfish, which is dependent on their movement. The main aim of this work was to evaluate the differences in crayfish migratory activity in the Pšovka brook among seasons, and assess the factors that may affect it, by the use of radiotelemetry and trapping. We tested the hypothesis that crayfish use brook in the period from spring to autumn and then return back into a pond to overwinter. Furthermore, we evaluated how far from the pond crayfish migrate, and whether there is any relationship between migration and the season or water temperature. The results demonstrate that the activity varies among seasons (being strongly affected by breeding season) but in most studied periods did not significantly depend on water temperature. According to our monitoring, the spiny-cheek crayfish does not spread substantially to upstream parts of the Pšovka. Seasonal migration between the pond and the brook was monitored using two-way flow-through traps installed at the mouth of...
Distribution and Ecology of the Stone Crayfish and Noble Crayfish in the Drainage Area of the Zákolanský stream
Kubínyiová, Eva ; Mourek, Jan (advisor) ; Hanel, Lubomír (referee)
This thesis is composed of two parts - research part, focused on field research of occurence and abundance of the Stone Crayfish and the Noble Crayfish in the basin of Zákolanský stream, and a pedagogical part, project Crayfish in the Czech Republic and their protection, aimed for grammar school students. The literature outline summarizes contemporary knowledge about all five species of crayfish in the Czech Republic. Our native species are the Stone Crayfish (Austropotamobius torrentium) and Noble Crayfish (Astacus astacus). The non-native are Narrow-clawed Crayfish (Astacus leptodactylus), Spiny-cheek Crayfish (Orconectes limosus) and Signal Crayfish (Pacifastacus leniusculus). Aside from the chapters concerning the particular species and their determination, the literature outline also contains general information about the life and endangerment of crayfish. I have conducted the field research from April to September 2009. I also noted and evaluated the environmental conditions of the crayfish habitats. Based on the adjusted AOPK ČR methodology, I selected eight 100-meter long brook-sections of the Europe-important locality of Zákolanský stream, with the previously confirmed occurrence of crayfish. From the eight sections, I found crayfish only in three. All the captured specimens were of the...
Hosts and transmission of the crayfish plague pathogen Aphanomyces astaci
Svoboda, Jiří
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...
Detection and variation of the crayfish plague pathogen in selected crayfish populations
Mojžišová, Michaela ; Petrusek, Adam (advisor) ; Buřič, Miloš (referee)
Crayfish plague is an emerging disease caused by the oomycete Aphanomyces astaci, a pathogen listed among the 100 World's Worst Invasive Alien Species. It was introduced into Europe in the second half of 19th century from North America and caused collapses of European native crayfish populations. Nowadays, A. astaci is widespread in Europe and has spread also to other parts of the world, threatening all susceptible crayfish of non-North American origin. The aims of this MSc thesis were 1) to provide information about crayfish plague outbreaks from recent years, and by using microsatellite and mtDNA markers reveal A. astaci genotypes involved; 2) to test healthy-looking indigenous crayfish for potential occurrence of chronic infections by A. astaci in Czechia. Six new crayfish plague outbreaks were confirmed from 2016 to 2018, involving at least five distinct pathogen strains. My results provide first evidence of the A. astaci genotype group D causing Astacus astacus and Austropotamobius torrentium mass mortalities in Czechia. MtDNA sequencing revealed two haplotypes of the D haplogroup, indicating two independent sources of infection presumably either from ornamental crayfish or spreading from neighbouring countries. The genotype group A was recorded in two A. astacus mortalities and genotype group...
Rak mexický {Cambarellus patzcuarensis} - přehledová studie
TOMAN, Jan
Indigenous crayfish are increasingly threatened by their non-indigenous counterparts, which species are often more tolerant and adaptable. In case of North American species, they are also chronic carries of crayfish plague, a disease mostly lethal to crayfish of non-North American origin. In this bachelor thesis entitled "Mexican dwarf crayfish (Cambarellus patzcuarensis) - an overview", there is a summary containing available information about the Mexican dwarf crayfish, while main, so far unknown biological features of this species, are defined. Nowadays, this crayfish is one of the most bred and sold crayfish within the pet trade. However, its introductions can lead to unwanted alterations in newly occupied ecosystems. This overview of the available information on the Mexican dwarf crayfish and the definition of so far insufficiently known aspects of its biology can serve as a valuable basis for follow-up studies.
Raci v měnících se biotických a abiotických podmínkách
VESELÝ, Lukáš
Abiotic and biotic factors directly or indirectly influence physiology, behaviour, ecology and the distribution of organisms. This thesis provides unique results in terms of the ability of crayfish to cope with a series of these abiotic and biotic factors. Successful overwintering is key factor facilitating establishment and spread of non-indigenous species. We provide experimental evidence of substantial resistance of three out of four warm water crayfish species to the low water temperatures tested in our study. To sum up, red swamp crayfish together with yabby demonstrated high survival in experimental conditions and exhibited feeding activity even during the coldest part of the experiment. Marbled crayfish suffered high mortality, but a single specimen of survived. Redclaw is expected not to pose a risk for the European temperate zone in the near future. Drought is an important factor for freshwater organisms determining their success in a given ecosystem. One of the strategies how to survive drought are an elevated desiccation capacity and burrowing ability. We evaluated the ability of three European native and five non-native crayfish to survive and burrow in a humid sandy-clayey substrate under a simulated one-week drought. Survival of non-native species was substantially higher, being absolute in the red swamp crayfish and yabby. Red swamp crayfish and marbled crayfish constructed bigger and deeper burrows than yabby and spiny-cheek crayfish. Three native species (noble crayfish, narrow-clawed crayfish and stone crayfish) suffered extensive mortalities. The native species and signal crayfish exhibited no ability to burrow under drought conditions. Marbled crayfish are a successful invader, capable of colonization new habitats. It is also established in the wild of Ukraine and pet-traded in Eastern Europe. If released, it might pose a risk to populations of native crayfish that also inhabit saline ecosystems of the Black, Azov and Caspian Sea. We conducted the first study on salinity tolerance in marbled crayfish. In summary, marbled crayfish are probably unable to invade saline ecosystems due to its low survival, reduced growth and inhibited reproduction. Nevertheless, it showed an ability to withstand the highest salinity for an extended period of time, opening a possibility for its spread to other freshwaters via this corridor. Also, a short generation time might lead to local adaptations to saline environments in the future. Yabby demonstrated an ability to withstand simulated low winter temperatures, opening the question of its potential establishment in the region of Central Europe. To successfully do so, yabby would have to deal with present strains (A, B, and E) of Aphanomyces astaci, a causative agent of crayfish plague, a devastating disease to all crayfish not originating from North America. Our comparative study revealed the ability to survive (strain A) or delay the effects (strains B and E) of crayfish plague compared to native noble crayfish. Our result, highlights a high potential for its establishment in temperate Europe. As a prominent invader, it may cause negative impacts on entire ecosystems and contribute to the spread of crayfish plague in Europe. Nowadays, organisms face multiple global drivers influencing the strength of links in food webs. Altogether, we found that predator identity, prey density, and temperature all affect trophic and non-trophic interaction strengths. Effects of prey density were always independent of temperature and predator identity in trophic as well as non-trophic interaction strength. On the other hand, the magnitude of responses in trophic as well as non-trophic interaction strengths varied strongly across predator pairs and temperatures. Based on the current evidence, we could not find strong support for a general mechanism underlying the dependence of interaction strengths on species traits and environmental conditions. Therefore, other studies are need it.
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...
Hosts and transmission of the crayfish plague pathogen Aphanomyces astaci
Svoboda, Jiří
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...
Prediction of invasive marbled crayfish (Procambarus fallax f. virginalis) global spread
Nováková, Pavla ; Patoka, Jiří (advisor) ; Antonín, Antonín (referee)
Biological invasions are currently a global problem. They often cause a loss of biodiversity and severely disrupt the balance of entire ecosystems. One of the most dangerous among the many species of crayfish known to be invasive is the marbled crayfish or Marmorkrebs (Procambarus fallax f. virginalis Martin et al., 2010). The marbled crayfish is a major ornamental crayfish species. It is a known vector of infectious crayfish plague, which is lethal for crayfish species of non-North American origin. Marbled crayfish is also very tolerant to different water temperatures. The most important feature making it an especially dangerous invasive species, is the way of its reproduction. Marbled crayfish reproduces via apomictic parthenogenesis. Therefore, only females are able to reproduce and males of this taxon has not been recorded. This crayfish is characterised by a very quick maturation and extremely rapid growth. Even though some established populations of this taxon in the wild have already been recorded, and probability of the establishment in selected regions was evaluated, no predictions for expansion on a global scale have been conducted. The program CLIMATCH was used in this thesis to match the climate conditions between the source area (distribution of established populations of marbled crayfish in the wild) and target areas (all continents excluding Antarctica) based on temperatures during the coldest and warmest quarters of the year. The results showed that marbled crayfish can probably survive and reproduce in even colder regions of the temperate zone. The presented findings additionally indicate that temperate zones contain slightly higher potentially suitable regions than in the case of tropics. There are temperature conditions most suitable for the survival and reproduction of the marbled crayfish within Europe in comparison of the rest of the world; and the least favourable temperature conditions are within Australia. The marbled crayfish introduction and ability to survive and reproduce in the wild is a potential threat to native biota and entire ecosystems on all continents assessed. Therefore, it is strongly recommended that the breeding of and the pet trade with this crayfish should be regulated by policymakers and wildlife managers by improvement of legislative restrictions (such as in the EU) and intensive future education of general public. It is obvious that the monitoring of invasive crayfish species might be continuous. Nevertheless, the most important step is to make producers and hobbyists aware of the risks related with marbled crayfish.

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