Gaponova L. The centrohelid heliozoans (Centrohelea Cavalier-Smith, 1993) of Kyiv and the Chernigiv regions of Polissya.

The thesis is devoted to investigation on taxonomic structure, morphology, distributions and autecology of centrohelid heliozoans in Kyiv and Chernigiv regions of Ukrainian Polissya. In the investigated region the centrohelids are presented by 3 families, 6 genera and 14 species, from which 2 genus and 8 species are new for the fauna of Ukraine and 3 genera and 10 species are new for the fauna of Ukrainian Polissya. The morphological peculiarities of the registered species are specified, the descriptions of the found genera and species as for differential species diagnoses are given. On the base of the SEM data the redescription of Acanthocystis penardi is given. Based on the SEM data a correspondence of the cyst external cover in Ch. aculeata and P. pallida to periplast of their vegetative individuals were established. . It is revealed that the majority of centrohelid species are not dated for any types of water reservoirs except the acidophilous species which live preferably in bogs. On the character of seasonal dynamics the centrohelid species divide on two groups: first characterized by two peaks of quantity (in spring and autumn) and second characterized by one peak (in summer). In the investigated region the centrohelids which were in an active condition were not recorded in winter. During the winter period centrohelids were registered only at stage of the cyst.