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Phenotypic plasticity and functions of morphological antipredator structures in genus Daphnia
Brož, Vojtěch ; Petrusek, Adam (advisor) ; Šorf, Michal (referee)
Predator-induced defence mechanisms are widespread among animals, plants and other organisms. One of the model taxa for research of this phenomenon is the cladoceran genus Daphnia, as its species of this genus possess many morphological, behavioural and other defence mechanisms. Among the most conspicuous examples are specialized antipredatory structures. In many species, the presence of a helmet, i.e. a head expansion that serves as a protection from various invertebrate predators, can be found. A specific case is represented by two species in which the helmet is involved in protection from planktivorous fish. Another, rather widespread defence is the formation of neckteeth, a specialized structure against predatory larvae of phantom midge (Chaoborus spp.). There are also other less frequent antipredatory structures such as a crest or a "crown of thorns". This thesis summarizes the available information on the distribution, evolution, function and mechanisms of induction of these inducible morphological defence structures.
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Host-parazite coevolution in aquatic environments
Hubová, Jana ; Petrusek, Adam (advisor) ; Votýpka, Jan (referee)
Antagonistic coevolution is a major driving force in the evolution of host and parasite. Parasites create on their host a time delay, negative frequency-dependent selection, which leads to oscillations in both genotypes of antagonists, as suggested by the Red Queen hypothesis derived for coevolution of host and parasite. The most commonly used systems for the study of host-parasite coevolution in an aquatic environment are (thanks to their features): diatom Asterionella and chytrid Zygorhizidium, aquatic snail Potamopyrgus and trematods Microphallus, water fleas Daphnia and their microparasites. Coevolution between host and parasite causes a number of phenomena, such as maintenance of genetic polymorphism, temporal oscillations of genotype frequencies, the persistence of sexual reproduction, parasite local and host adaptations. This thesis summarizes the current knowledge on the coevolution of the above-mentioned three host-parasite systems in the aquatic environment. Key words: Red Queen hypothesis, host-parasite coevolution, negative frequency-dependent selection, aquatic environments, Asterionella formosa, Potamopyrgus antipodarum, Daphnia.
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Host-parazite coevolution in aquatic environments
Hubová, Jana ; Petrusek, Adam (advisor) ; Votýpka, Jan (referee)
Antagonistic coevolution is a major driving force in the evolution of host and parasite. Parasites create on their host a time delay, negative frequency-dependent selection, which leads to oscillations in both genotypes of antagonists, as suggested by the Red Queen hypothesis derived for coevolution of host and parasite. The most commonly used systems for the study of host-parasite coevolution in an aquatic environment are (thanks to their features): diatom Asterionella and chytrid Zygorhizidium, aquatic snail Potamopyrgus and trematods Microphallus, water fleas Daphnia and their microparasites. Coevolution between host and parasite causes a number of phenomena, such as maintenance of genetic polymorphism, temporal oscillations of genotype frequencies, the persistence of sexual reproduction, parasite local and host adaptations. This thesis summarizes the current knowledge on the coevolution of the above-mentioned three host-parasite systems in the aquatic environment. Key words: Red Queen hypothesis, host-parasite coevolution, negative frequency-dependent selection, aquatic environments, Asterionella formosa, Potamopyrgus antipodarum, Daphnia.
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Impact of fish predation and littoral vegetation on the structure and behaviour of zooplankton
VESELÁ, Jana
The impact of fish predation on zooplankton assemblage was studied in the mesocosm experiment. Presented thesis focuses on the effect of size selective fish predation on species diversity, biomass and body sizes of zooplankton and the impact of fish occurrence on zooplankton behaviour with regard to diel horizontal migration. I also studied a change in some life history traits of zooplankton caused by fish with a special focus on keystone species of freshwater ecosystems Daphnia spp.
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The dynamics of sexual reproduction and ephippia production of Daphnia in reservoirs
VANÍČKOVÁ, Ivana
This thesis focused on the dynamics of the sexual reproduction of microcrustacean Daphnia (Cladocera, Anomopoda). Sex in Daphnia is induced environmentally after rounds of asexual parthenogenesis in favorable conditions. The onset of sexual reproduction and the occurrence of sexual individuals was investigated with respect to their distribution in the water column and clonal structure. The produced sexual eggs were genotyped and their density and distribution in sediment were analyzed. The impact of massive floods was investigated. The role of sexual reproduction in stable habitats and its relevance and importance for Daphnia communities is further discussed.
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The community of zooplankton in the pools in inundation area of Lužnice river
ŠEBESTA, Roman
This thesis aims to discuss generally the pools of river with a focus on the Upper Lužnice river maiinly on zooplankton communities, which ooccurs in these locations. Regular sampling of communities in different types of river pools better then identify their species and numerous changes during the year. Thesis deal with samplinng techniques and laboratory processing sampples of the zooplankton to.
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The morphological and genetic differentiation of \kur{Daphnia} in canyon-shaped reservoirs
HOROVÁ, Barbora
We analysed the pattern of spatial heterogeneity of Daphnia longispina species complex in 11 canyon-shaped reservoirs. We found for the first time that the spatial pattern is not random. Daphnia cucullata shows strong preference for upstream regions while Daphnia longispina and D. galeata x longispina are preferring the deep downstream parts of reservoirs. These not random pattern is probably driven by longitudinal and vertical ecological gradients (fish predation pressure, nutrient concentration, phytoplankton biomass etc.)
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