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Thesis (Ph. D.)--University of Kansas, 1966. / Bibliography: leaves 51-57.

A common alga of oligotrophic slightly acidic fresh water habitats, Synura sphagnicola, has never been suspected for a presence of cryptic diversity. The publicly available SSU rDNA sequences showed very slight genetic differences between the S. sphagnicola isolates. However, I suspected that if any cryptic lineages exist, the sequencing of ITS region will show the differences between them. A total of 37 S. sphagnicola sequences (36 from Europe and 1 from Korea) were analyzed in this thesis. The ITS rDNA sequencing clearly recognized the presence of two distinct cryptic species, referred here as lineage SP1 and SP2. The morphological analysis of 14 cultivated strains (6 belonging to the lineage SP1 and 8 to the lineage SP2) validated the genetic distinction. The statistical analyses showed that 4 morphological aspects (length of a scale, width of a scale, length of a spine, length of a rim) were found to have significant differences in length of measured factors between species. The most visible difference is in the length of a spine that is connected to the scale. The analysis of published S. sphagnicola scales showed that the two lineages can be morphologically distinguished also in natural conditions. According to the morphological analyses, the lineage SP2 (species with a longer spine)...

The resting resistant stage has several important roles for phytoplankton microorganisms. It protects them from hostile conditions, allows them to spread to new locations and is often part of their life cycle. Chrysophytes form large populations for only a short part of the year, and therefore the formation of a resting stage is key for them to re-establish a vegetative population the following year. Chrysophyte resting stages are called stomatocysts, which are silicified and have a unique species-specific morphology. They can be form after both sexual and asexual reproduction. This is an understudied area. Most described stomatocysts are not assigned to species and much is not known about the triggers of encystation and excystation. It is thought that a combination of external (temperature, light, nutrients) and internal (cell age and cell concentration) factors are involved. So far, only sexual encystation in Dinobryon cyindricum and Synura petersenii has been studied in detail. My diploma thesis is based on laboratory experiments with Ochromonas tuberculata, Synura uvella and two strains of Synura petersenii. The aim of the study was to investigating whether external conditions such as temperature and lack of nitrogen or phosphorus have the effect on asexual encystation and whether it is...