|
|
Teplotní adaptace trávicích enzymů želvušek žijících v trvale chladném prostředí
JOZIĆ, Nikola
This thesis presents a literature review of the phylum Tardigrada, exploring the impact of cold temperatures on living organisms in general and focusing on adaptations of organisms to cold and freezing, particularly in terms of enzymatic adaptations. The experimental part of this work involves comparing the enzymatic activity of the -glucosidase enzyme in tardigrades from Arctic glacier (Svalbard) and soil tardigrades from a temperate climate (Czech Republic) at different temperatures. The results showed higher enzymatic activity in tardigrades from a temperate climate at all measured temperatures, suggesting that the enzymes of glacier dwelling tardigrades are not cold adapted.
|
|
|
The relationships among functional traits of tardigrades (Tardigrada), their diet, and environmental conditions
TŮMOVÁ, Michala
In this thesis, I explore several ways how to use functional traits to study the tardigrade role in the soil food web. The goal of the thesis was to show that it is possible to study tardigrade ecology even without species identification. Trophic classification of tardigrades, as well as morphometric traits of each individual, were used as functional traits. First, I confirmed the existence of different trophic groups, testing the whole spectrum of potential diet in three tardigrade species from different trophic groups. I showed that tardigrades differed not only in the scope of ingested items but also in survival and fecundity under different types of diet. Secondly, I compared trophic group composition with species composition in natural tardigrade communities. The results showed that species, as well as trophic group composition, responded to the same environmental drivers. Trophic group composition enabled easier interpretation of the tardigrade role in the soil food web, while species composition illustrated also species-specific preferences that were not connected to their feeding habits such as preferences for different levels of soil moisture. Finally, I have used morphometric traits measured in each individual separately which allowed me for evaluation of inter-specific as well as intra-specific variation. As a result, buccal tube length was selected as a predictor of tardigrade feeding preferences among nematode, rotifer, and tardigrade prey. In summary, the thesis documented that functional traits provide a tool for the prediction of tardigrade feeding behaviour and detection of changes in the role of tardigrades along environmental gradients without the need of species identification.
|
|
|
Storage cells and their role in tardigrade physiology.
Czerneková, Michaela ; Svoboda, Petr (advisor) ; Delagoutte, Emmanuelle (referee) ; Weyda, František (referee)
STORAGE CELLS AND THEIR ROLE IN TARDIGRADE PHYSIOLOGY Abstract Tardigrades possess remarkable tolerance to numerous stress conditions (e.g. almost complete desiccation, exposure to very low sub-zero temperature, heat stress and even exposure to space in low Earth orbit). Indeed, they are among the most radiation-resistant multi-cellular organisms. The body cavity of tardigrades is filled with the storage cells (SC). Their role in anhydrobiosis has been discussed. The main objectives of this work were to analyse (i) the occurrence of mitosis in SC, (ii) the factors constraining anhydrobiotic survival, and (iii) the general ultrastructure of SC and their ultrastructure concerning the stress conditions. Our model species, R. cf. coronifer is one of the most extensively studied tardigrades concerning anhydrobiosis. Comprehensive histochemical techniques were used in combination with SEM, TEM, and confocal microscopy. First, mitotic divisions of tardigrade SC occur with a higher frequency in juveniles than in adults and correlate with animal growth. Mitosis is more frequent in moulting tardigrades, but the overall mitotic index is low. Furthermore, tardigrades of R. cf. coronifer can survive the maximum of 6 repeated desiccation cycles with significantly declining survival rate with repeated desiccations and...
|
|
|
Historical record of the fairyshrimp Branchinecta gaini in the James Ross archipelago, and its phylogeography
Pokorný, Matěj ; Sacherová, Veronika (advisor) ; Janko, Karel (referee)
The Fairy shrimp Branchinecta gaini Daday, 1910 is the largest freshwater invertebrate in Antarctica and the top-level consumer of local freshwater food webs. Ecological demands of B. gaini that are accompanied by 'ruderal' life strategy together with its spatial distribution that exceeds to Patagonia indicate that it had survived last glacial period in South America and expanded to Antarctica shortly after this epoch endeed. On James Ross Island that is the most extreme environment where B. gaini occurs today was this fairy shrimp considered extinct until year 2008. Its disappearance was based on paleolimnological analysis of several lake sediment cores according to which it inhabited this island between years 4200 to approximately 1500 before present when it died out because of changes in lake catchments caused by harsh neoglacial conditions. Paleolimnological analysis of Monolith Lake presented in this study has shown that this assumption was wrong and B. gaini has lived on James Ross Island throughout neoglacial period up to recent time. Phylogeographic analysis of 16S rDNA of specimens from Patagonia, South Orkneys, South Shetlands and James Ross Island revealed that its high morphological diversity is not supported by this gene and that all examined populations of B. gaini is one species with very few...
|
|
| |
guest ::
