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Semiaquatic bugs as predators and prey and their use in natural history teaching
JANDA, Václav
The aim of this thesis is to create an overview of scientific findings about the prey and the predators of the representatives of infraorder Gerromorpha, their feeding habits and defence strategies against predators. Gerromorphans are adapted for life on the surface of various water bodies ranging from puddles to open ocean. Majority of water striders feed on insect fallen upon water surface, hatching larvae of aquatic insect or micro-crustacean. Gerromorphans locate their prey by sight and by sensory detection of ripples at water surface caused by prey. Gathering in schools turned out to be an efficient defence strategy against predators. Some species have compound eyes with specialized ommatidia which enable them to see prey on the surface as well as predator under surface. A proposal of the use of Gerromorpha in natural history teaching is part of this thesis. Gerromorphans are convenient for teaching of natural history thanks to the possibility of observation of piercing and sucking mouthparts and various food relations such as predation, cannibalism or kleptobiotic relation. Undemanding rearing of gerromorphans enables easy realization of experiments and observations under school conditions.
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How predation risk affects the growth and development of dragonfly larvae?
PEROUTKA, Miroslav
Predation and prey responses to predators in aquatic environment are reviewed with emphasis on non-lethal effect of predators on prey life history, antipredator behavior and related mechanisms. The review focuses on dragonfly larvae and other groups of prey with complex life histories, mainly anurans. The review is complemented by laboratory experiments examining the effects of varied food availability and predation risk on a selected species of dragonfly, Sympetrum vulgatum.
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Trophic relationships between insectivorous birds and insect in Papua New Guinea
TVARDÍKOVÁ, Kateřina
The thesis describes diversity of birds along a complete altitudinal gradient and in forest fragments in lowlands of Papua New Guinea. It focuses separately on the diversity of different feeding guilds, and discusses their links to habitat and food resources. More specifically, it focuses on forest insectivorous birds, their predation pressure on arthropods, feeding specializations and preferences, and some of the ways how insectivores search for food.
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The role of species traits in predator-prey interactions and food web structure
KLEČKA, Jan
This thesis deals with the role of species traits in predator-prey interactions and food web structure. I conducted laboratory experiments with predatory aquatic insects and their prey to reveal the traits determining who eats whom in small standing waters. I also focused on the possibility of incorporating the observed dependence of predator-prey interactions on body mass into existing food web models. Further, I developed a simple simulation model to explore the consequences of body mass dependent feeding and dispersal for food web assembly. Last, I show that four common methods for sampling aquatic insects differ in their selectivity, especially on the basis of body mass of sampled insects. In conclusion, I combined laboratory experiments, field work and mathematical models to evaluate the importance of body mass and other species traits, such as foraging behaviour and microhabitat selectivity, in predator-prey interactions and explored selected food web level consequences.
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Antipredation behaviour of meercats (Suricata suricatta) in the group kept in ZOO Jihlava.
ZÍTKOVÁ, Jana
Meerkat (Suricata suricatta) is a mongoose species from South Africa. Insects are the primary food sources of their diet. Meerkat lives in groups of 2?30 individuals with a developed social structure. The group consists of a dominant pair and a different number of helpers of both sexes, which are involved in various forms of cooperation, for example care for cubs, guard service and maintaince of burrow. Meerkats are at risk of predation by mammalian predators, avian predators and snakes. One meerkat always seems to be a sentry and stands guard to keep the gang safe. When the guard senses danger they give a warning bark and the other members run for cover into their burrow. This study was done from June to September 2011 in zoo in Jihlava on a group of meerkats, which consisted of 13 individuals. There was used the method of direct observation by a scanning behaviour (behaviour sampling). Observation was specialized on sentinel behaviour. The main aim of this work was evaluate the results of observation and then compare this results with behaviour in the wild. By monitoring was demonstrably found, that dominant individuals contributed to guarding more frequently and the longest time and the juveniles contributed at least. There wasn´t set order in guarding. The most often was individually guarding or guarding in a group of 2 or 3 individuals.
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Redundant fingerling of perch (Perca fluviatilis L.) in Vír Reservoir and its impact on other trophic levels
VEJŘÍK, Lukáš
The composition and preferences of depth levels and habitats of pelagic fingerling was studied in the canyon-shaped Vír Reservoir during years 2009-2011. The perch (Perca fluviatilis) fingerling was dominant in all three years. The density of fingerling was above the mean in years 2009 and 2010. It was as many as 278 individuals in 100m3(mean is 52 individuals in 100m3). A marked fall on 1,9 individual in 100m3 was registered in 2011. Perch fingerling was mainly observed in metalimnion during the day and also at night, where concentration of oxygen was very low. The highest density of perch fingerling was observed in the middle part within longitudinal profile. A significant difference was found in food composition among the years with high density and low density of fingerling. A predation of carp (Cyprinus carpio) and bream (Abramis brama) was proved during the years with high density of fingerling.
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Ecophysiological characteristics of key members of Betaproteobacteria in freshwater bacterioplankton
KASALICKÝ, Vojtěch
This thesis primarily focuses on one segment of freshwater Betaproteobacteria, the Limnohabitans genus (including the RBT lineage). As opposed to other recent research directions, the major aim was to recover the members of the previously uncultured RBT lineage through their isolation from various freshwater habitats. However, the results presented in this thesis have also ambitions to go far beyond the taxonomic descriptions only; the dissertation intends to contribute significantly to unveiling of important ecophysiological characteristics of the studied lineage in a set of both laboratory and field research. Therefore, understanding of growth characteristics, mortality, diversity and life strategies of aquatic microbes is of highest importance regarding profound human impact on water quality and increasing need of drinking water supplies.
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