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Selected aspects of biology of the invasive species \kur{Pectinatella magnifica}
JEŽKOVÁ, Eva
Pectinatella magnifica, invazní organismus, statoblast, rozmnožování, laboratorní kultivace SUMMARY Pectinatella magnifica is an invasive organism transfered to Czech republic from the USA with the international boat transport. Here it poses a lot of potencial threats toour native species, as well as to submerged technical constructions. It is a species of freshwater Bryozoan that is able to create colonies of considerable sizes. On the surface of a gelatinuous matrix there are small living indiviuals called the zooids. These can reproduce both sexually and asexually, which gives them a huge competitive potential. The dormant asexual spores, e.g. statoblasts, are extremely resistant towards various natural conditions and have characteristics enabling them to spread to substantial distances. This thesis aimed to identify and describe several life aspects of Pectinatella magnifica, especially reproduction and spreading strategy. I monitored the organism in the nature, as well as in a number of laboratory experiments. I was able to succesfully transfer the colonies of Pectinatella from the ponds into a special aquarium system. Under the laboratory conditions, 80 % of statoblasts germinated within five to eight days, depending on the water temperature. Then the zooids emerged and survived for around eight weeks, enabling me to observe different development and behaviour. Obtained photo and viceodocumentation shows details of a sexual reproduction of zooids, proving that it occurs even in our environment. The most prefered natural conditions seem to be the flooded mezotrophic sand quarries and protected and recreational ponds with a low fishing stock (without a massive algeae presence, fluctuating oxygen levels, etc.) The results do not suggest that Pectinatella magnifica is currently a significant competitor to our native Bryozoan species.
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The selected aspects of nesting biology of Great Crested Grebe (Podiceps cristatus) in relation to environmental conditions
JEŽKOVÁ, Eva
The aim of the thesis was the appraisal of Great Crested Grebe (Podiceps cristatus) nesting biology aspects in relation to environmental conditions. The research took 6 months from the 2nd of April to the 2nd of October in 2013 and was realised in the Naděje fishpond system on the ponds Víra, Láska, Skutek, Dobrá Vůle, Rod and Naděje. This fishpond system is situated in CHKO Třeboňsko nearby villages Frahelž and Klec and it consists of total of 15 ponds which are used for intensive fish farming, partly for breeding of Wild Ducks for hunting purposes. The counting of birds, active searching of nests and measuring parameters of nests and eggs were carried out during the work. The nests were found on ponds Naděje, Skutek and Láska. In 2013 18 nests were measured altogether. On the fishpond Naděje 8 nests were situated, on the fishpond Láska 4 nests and on the fishpond Skutek 6 nests altogether. 13 nests of the total were found on a free water surface and 5 nests were situated in the vegetations of the Great Reedmace (Typha latifolia) at a maximum distance of 1 m from the free water surface. In 2013 64 eggs were measured altogether. On the fishpond Naděje parameters of 33 eggs were obtained, on the fishpond Láska 17 eggs and on the fishpond Skutek 14 eggs were found altogether.
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The characteristics of Great Crest Grebe (Podiceps cristatus) population in select pond system
JEŽKOVÁ, Eva
The aim of the thesis was the characterictic of breeding population of the Great Crested Grebe on a chosen fishpond system. The research was realised from the 28th of March to the 14th of October in 2011 on the Naděje fishpond systém, specifically on the ponds Víra, Skutek, Láska, Naděje, Dobrá Vůle and Rod. This fishpond system of 15 ponds is situated to the east of the village Frahelž and it´s a part of CHKO Třeboňsko. The data were obtained by regular counting and active searching of nests and measuring their parameters. In 2011 the Great Crested Grebe (Podiceps cristatus) preferred ponds Víra, Skutek and Láska. There were found 70 nests altogether. On the fishpond Víra were measured 36 nests altogether, on the fishpond Skutek 30 nests and on the fishpond Láska 4 nests. In 2011 57 % of nests were found in the vegetation of lesser reedmace (Typha angustifolia) on the fishponds Víra and Láska and 43% of nests in the vegetations of the great reedmace (Typha latifolia). On a free surface just 2 nests were found. In 2011 235 eggs were found altogether. On the fishpond Víra 112 eggs were found, on the fishpond Skutek 105 eggs and on the fishpond Láska 15 eggs. The parameters of size were measured on 182 eggs altogether.
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