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Green coenobial algae of the family Hydrodictyaceae, their phenotypic plasticity and use in ecology and paleoecology
Zavadilová, Kateřina ; Neustupa, Jiří (advisor) ; Knotek, Petr (referee)
Algae of the family Hydrodictyaceae attract our attention because of their unusual appearance. They belong to the order Sphaeropleales in the class Chlorophyceae. This family includes the coenobial algae, traditionally classified into the genus Pediastrum, which has recently been split into multiple genera based on the phylogenetic analyses. They are typically found in eutrophicated rivers, lakes and ponds. They form characteristic oval-shaped coenobia that may resemble tiny stars in their appearance. Their shape and size may be influenced by environmental factors such as pH or nutrients. Geometric morphometrics can also be helpful in detecting morphological variation or in refining the phylogenetic tree. The outer layer of the cell wall contains the polymer algaenan. Since algaenan is acid resistent, the cell wall remnants are preserved in the sediment. These cell wall remnants are found mainly in Tertiary freshwater sediments and their occurrence serves mainly as an indicator of eutrophicated conditions, for example in the context of anthropogenic eutrophication of lakes. The cell wall remnants could also be used for palaeolimnologic reconstruction. The thesis presented studies regarding their ekology, morphology, and associated phenotypic plasticity, and studies regarding their palaeobiological...
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Life cycle of Haematococcus pluvialis (Chlorophyceae) species complex
Vávrová, Karolína ; Němcová, Yvonne (advisor) ; Nedbalová, Linda (referee)
Freshwater green algae within species complex Haematococcus pluvialis are best natural producers of secondary carotenoid astaxanthin famous for its strong antioxidant activity. Despite worldwide distribution, great biotechnological potential and extensive literature dealing with different approaches to the cultivation of these organisms, there still remains surprising gaps in knowledge of their complex life cycle and behaviour. First uncertainty concerns asexual cell division of zoospores, hypothetically limited to five cell doublings (Lee & Ding 1994). No such genetic limitation was observed in this thesis, number of cell divisions is thus influenced mainly by cultivation conditions. There is still considerable uncertainty regarding to the asexual reproduction, as well. Ambiguity might be caused by scarce observation of the whole process of gametogenesis and conjugation of gametes. Published studies differed in some particular points. Unfortunately, we did not succeed in induction of gametogenesis despite broad scale of tested cultivation conditions applied to two different species within the H. pluvialis complex, namely H. pluvialis and H. rubicundus. This failure might be caused by heterothalism of the studied strains. Haematococcus pluvialis inhabits mainly ephemeral pools. Its ability to...
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