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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. |
