New species of Uroglena and Ochromonas (Chromulinales, Chrysophyceae) from Estonia

• During the spring of 2003 ninety-five water bodies in southeastern Estonia were surveyed for chrysophytes. The sampling was carried out as the ice broke up, when, within two weeks, the water temperature rose from 3 degrees C to 13 degrees C. Large lakes to small pools of different water chemistry were investigated. The plankton collected was studied alive within a few hours after sampling. Preparations for scanning electron microscopy (SEM) were made from fresh samples and later also from material preserved in Lugol's solution. About 95% of the water bodies contained chrysophytes. Species belonging to the genera Chrysosphaerella, Dinobryon, Mallonionas, Synura, Ochromonas, Paraphysomonas, Spiniferomonas, Uroglena and Uroglenopsis were recorded. The genus Uroglena was frequent and recorded in 30% of the localities studied. Mass development of different Uroglena species was found in several waterbodies. Many populations had developed stomatocysts (statospores, cysts) of different morphology, and, using LM, smooth stomatocysts and stomatocysts with long spines could be recognised. However, using SEM, it was shown that also the smooth stomatocysts had short spines. Four new species of Uroglena were found and are described here. Uroglena estonica and U. spinosa had long spines while U. kukkii and U. pikamae had very short spines. In addition, mass development of stomatocysts of an Ochromonas was recorded in two lakes. This species had similarities with Ochromonas stellaris, but differed in stomatocyst ornamentation, and is also described as a new species, O. magnifica.

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NATURVETENSKAP  -- Biologi -- Ekologi (hsv//swe)

NATURAL SCIENCES  -- Biological Sciences -- Ecology (hsv//eng)

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