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Ecology of the Dice snake (Natrix tessellata) in the Chrudimka River
Pešanová, Věra ; Rehák, Ivan (advisor) ; Moravec, Jiří (referee)
The dice snake, Natrix tassellata, is legally declared a critically endangered species in the Czech Republic. The history of the herpetologically and conservationally remarkable population on the Chrudimka River is short and fragmented in literary records - first records from the middle reaches of the Chrudimka are from the 1970s and from the lower reaches, they're only from the1990s. Until now, there was no detailed population data, only observations that tended to include mostly single specimens. This thesis therefore focuses on the size, composition and dispersal of the Chrudimka population, on obtaining relevant morphological, ecological, ethological and genetic data, and on identification of important landscape features and threatening factors as a basis for the conservation of the local population. Results from the field data collected in 2019-2021 indicate a viable population with annual reproduction. Based on estimates using a capture-recapture method, the population of the lower reaches of the river in the Pardubice region numbers 220-440 adults. The hibernation site used by the majority of the population is located in the Nemošická stráň PP, with the main hunting grounds located downstream of the weir on the Nemošice river and in the nearby oxbow lake. A smaller part of the population...
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Dental stem cells during development of vertebrate dentitions
Pešanová, Věra ; Soukup, Vladimír (advisor) ; Hovořáková, Mária (referee)
Vertebrate dentition is a dynamic structure, which continuously renews its elements, the teeth. Continuous tooth renewal is enabled thanks to the presence of epithelial and mesenchymal dental stem cells. Epithelial stem cells are located in the dental lamina, which, together with the adjacent mesenchyme, takes part in regulation of the stem cells through a complicated signalling network. This network is responsible for the positioning, correct amount, inactivity, proliferation and differention of the stem cells. Vertebrate dentitions are morphologically diverse. However, their development is, to a certain extent, controlled by shared evolutionarily conserved mollecular mechanisms. For example, epithelial stem cells of all vertebrate groups examined so far express the transcription factor Sox2 and are shown to be regulated by signalling pathways, such as Wnt/β-catenin, Shh, Fgf and Bmp. Due to the rich diversity in dental lamina morphologies, the locations of presumptive stem cells correspondingly differ among vertebrates. This thesis summarizes current knowledge on dental stem cells in each lineage to identify shared and derived aspects of vertebrate dentitions.
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