The genus Eunotia Ehrenb. (Bacillariophyta) in the Cheremsky Nature Reserve, Ukrainian Polissya, and refined terminology relevant to the raphe system morphology

Abstract. Numerous species of Eunotia Ehrenb., widely distributed in the world flora, prefer acidic, dystrophic or oligotrophic freshwater habitats with low conductivity and usually occur in epiphytic or epilithic hydrotopes. In Ukraine, only 32 species and eight varieties of Eunotia were known until this study. For the first time, 9 more species have been recorded mainly from the Cheremsky Nature Reserve, located in Ukrainian Polissya. New findings include 2 species widely distributed in the world flora on most continents and 7 rare species known from several locations, among them E.genuflexa, E.jarensis and E.ruzickae, which are probably European endemics as they have not been reported from other continents. For the present time in the Cheremsky Nature Reserve, the 20 species recorded here, the highest species richness of Eunotia in Ukraine, bring the total number of Eunotia in Ukraine to 41 species, which comprises only 7% of Eunotia species in the world flora. This is indirect evidence of insufficient investigation of the wetlands in Ukraine where Eunotia usually is represented with high species richness. Several definitions are suggested to describe morphological features that are peculiar to the diatom frustule particular to the Eunotia species. The genus Eunotia possesses a mirror-symmetric, mantle-offset, brevisslit raphe system, which may or may not have terminal raphe fissures. Morphological analysis provided in this study revealed the absence of terminal raphe fissures for many species of Eunotia. Instead, the distal ends of the raphe slits finish on the outer valve surface by funnel holes, sometimes pore-like ones, connected with the helictoglossae. However, in the literature those distal ends of the raphe slits were described erroneously as terminal raphe fissures. For the first time different types of raphe system are grounded. Two species Eunotiaimplicata Nörpel-Schempp et al. in Alles et al. and Eunotiaincisa W. Smith ex Gregory were lectotypified.