The paper is dedicated for 100^th death anniversary of the famous Hungarian diatomologist József Pantocsek (1846-1916). Previous morphological studies showed that the description of the Cyclotella genus was too general and according to new morphological criteria new genera were established based on both recent and fossil taxa (e.g. Discostella, Handmannia, Puncticulata, Tertiarius). Furthermore, previous molecular biological investigations proved that the Cyclotella genus was not monophyletic. Integrating the above mentioned knowledge the former Cyclotella genus has been split into 4 genera (Cyclotella s.s., Discostella, Tertiarius and Lindavia). Based on the position of rimoportula Lindavia genus was formed for involving the species of both the Cyclotella ocellata and C. bodanica lineages. Our morphological and molecular (genetic distance and phylogenetic analyses of rbcL and 18S rDNA sequences) investigations suggested that "Lindavia/Cyclotella ocellata group" could be raised from the Lindavia as a separate genus. Its distinctive morphological features are the followings: striae unequal in length, central area without areolae. We describe the new genus Pantocsekiella gen. nov. and we transferred several Lindavia taxa into it. We also provide an amended diagnosis for the genus Lindavia.

Phytoplankton research in a number of shallow lakes in southern Patagonia revealed the occurrence of three noteworthy Cosmarium species. One of them, Cosmarium decussare Brook et Williamson, found only once before in Antarctica, is remarkable for its highly asymmetric cell morphology. The other two species, Cosmarium chapuense and Cosmarium mickeyoides, striking by an unusual cell shape, are described as new to science. Ecological and biogeographical characteristics are discussed.

Diatom assemblages in carbonate spring habitats at low elevations, with low discharge, and affected by direct human impacts were studied only recently and in some geographic areas. We describe and characterize the ecology of a new Navicula species from springs with these characteristics within the basin of the River Adige in the south-eastern Alps and Alpine foothills (Province of Verona, Italy). Navicula veronensis sp. nov. is in the group of species around N. cincta but has distinct outline, size, central area, and proximal raphe endings. The availability of data on the distribution of the new species in streams of the Island of Cyprus allowed to quantitatively compare the ecological preferences, niche position, and niche breadth of Navicula veronensis sp. nov. with those of allied species. The new species was found to be characteristic of medium-high conductivity freshwaters, rich in sulphates and chloride, often nitrate enriched and affected by marked discharge fluctuations and seasonal desiccation. Niche position however differed only slightly from those of morphologically-similar species, with the exception of Navicula dealpina that was found to be characteristic of oligotrophic, calcium-bicarbonate rich environments with medium(-low) conductivity. Canonical Correspondence Analysis clearly showed that the most influential environmental variables determining the diatom assemblages of low-elevation carbonate springs affected by anthropogenic disturbance were nitrate enrichment, spring morphology alteration (in particular for water abstraction), and low discharge.

Two new species of the diatom genus Cymatopleura, Cymatopleura aquastudia and Cymatopleura xinjiangiana, that have torsion about the apical axis of the valves, are reported from Xinjiang Region, China, using light and scanning electron microscopy. The valves of Cymatopleura aquastudia sp. nov. exhibit torsion about the apical axis, are heteropolar, and are slightly constricted at the margin in the middle of the valves. These characters differentiate it from morphologically similar taxa in the genus, e.g. C. solea (Brébisson) W. Smith and C. spiralis Behning in Rauschenbach et Behning. The valves of Cymatopleura xinjiangiana sp. nov. also exhibit torsion about the apical axis, but are small and have curved ridges at both ends and rounded apices that are protracted at the wider ends. These features distinguish C. xinjiangiana from C. cochlea Brun and C. elliptica f. spiralis Boyer. These two new taxa help to demonstrate the unique nature of the freshwater diatom flora from Xinjiang Region, China.

The revision of the serie Desmodesmus, based on light microscopy, TEM, SEM and ITS2r DNA, allowed us to distinguish among the taxa Desmodesmus communis var. communis, var. polisicus, D. curvatocornis, D. rectangularis comb. nov., D. pseudocommunis n. sp. var. texanus n. var. and f. verrucosus n. f., D. protuberans, D. protuberans var. communoides var. nov., D. pseudoprotuberans n. sp., D. schmidtii n. sp. Keys were given for light microscopy, electron microscopy and ITS2r DNA.

The benthic diatoms collected during our recent research in athalassic habitats exemplify a high morphological variability within Chamaepinnularia krookiformis Lange-Bertalot et Krammer. The species has already been known from freshwater ecosystems as well as from brackish waters in different regions of Europe. This variability has been also confirmed by the analysis of the literature. However, this is the first time that the morphological variability of the species has been addressed. In order to revise C. krookiformis and describe a new species, which has been distinguished on the basis of our material, we compared it with the type material of Pinnularia krookiformis Krammer 1992 from the periodic saline pool in Nordrhein-Westfalen (Germany). This study deals with a morphological analysis based on a large populations of C. krookiformis from Pełczyska (Central Poland). Selected morphological features were analysed, i.e.: valve length and width, number of striae in 10 µm, apices width, constrictions width, apices/constrictions width ratio, central-area length, and valve/central area length ratio. The results of light (LM) and scanning (SEM) microscopy, supported by multidimensional scaling (MDS), allowed for the distinction of three different morphotypes. Two of them match Krammer concept of Pinnularia krookiformis from 1992, while the third, occurring in our samples in three sampling sites, is clearly different. Thus, we described a new species Chamaepinnularia plinskii sp. nov., by the following major features: the valves are linear, symmetric, with rounded, capitate apices, the axial area is narrow, expanding to a wide central area forming a fascia, distal raphe endings are hooked to the same side of the valve and striae slightly radiate in the middle and in the rounded apices, becoming parallel in constrictions, 20-26 in 10 µm. This species occurs in inland waters with a wide range of chloride concentration, from 1000 to 3500 mg.l^-1.

Specimens of a very small diatom were found in a dead oxbow of Tisza River (Hungary), in Eula River (Germany) and Parroy Pond (France). After SEM studies we identified all of them as Eolimna archibaldii J.C. Taylor et Lange-Bert., which is currently regarded as endemic species to South Africa. Furthermore, the results of Principal Components Analysis of morphometric characters clearly demonstrated an overlap between the type material and European populations. Therefore this diatom cannot be considered endemic to South Africa. Moreover, E. archibaldii and a very similar species, E. becaresii are transferred to the genus Sellaphora. Our results confirm the benefit of SEM for verifying the identity of small-sized diatoms, especially for routine monitoring, and allow more precise ecological assessment.

In this paper we describe Navicula nielsfogedii sp. nov., a commonly occurring diatom through central and southern Africa and distributed from the sub-tropical zones of South Africa to tropical central Africa. We have examined the material of the most closely related species described from Africa, Navicula feuerbornii f. africana Foged and suggest that this species may be conspecific with Navicula heimansioides Lange-Bertalot and to have no link to the taxon N. feuerbornii Hustedt sensu Simonsen. With reference to Navicula feuerbornii f. africana we also discuss the changes over time in diatom species concepts, what we have dubbed 'species concept drift', and the consequences this holds for accurately identifying diatom taxa. As the newly described species is widely distributed and common in some samples from tropical and subtropical Africa we conclude that it may be a useful additional indicator organism for water quality monitoring in the region.

Most studies on springs assumed stability, and reduced seasonal changes in the biota. We focused on two macroalgae (the rhodophyte Hildenbrandia rivularis and the chrysophyte Hydrurus foetidus) to unveil their seasonal-development patterns in springs. H. rivularis cover remained virtually constant throughout the year, although seasonal fluctuations in ecophysiological parameters were detected. The most important determinant of seasonal changes in H. rivularis was shown to be the complex interplay between solar radiation (day length) and shading. Negative cross-correlation between Chl-a and shading was found to be significant but with a time lag. H. foetidus seasonal changes were evident both at the macroscopic level and in ecophysiological parameters. Interestingly, it occurred throughout the year in the spring whilst it completely disappeared in summer in a nearby glacial stream. Unexpectedly, variability of ecophysiological parameters (coefficients of variation) was shown to be 15-20% higher in H. rivularis than in H. foetidus.

Lake Ohrid is the oldest existing lake in Europe and it is known for its high diversity with around 200 endemic or relict diatom species recognized. In order to understand this phenomenon, a large project on deep drilling was performed and a core with maximum sediment depth of 569 m which spans > 1.2 million years was recovered. Two new species of Cyclotella were discovered in the core samples, which are described here as Cyclotella cavitata sp. nov. and Cyclotella sollevata sp. nov. The species have been studied with light and scanning electron microscopes, their morphological features and their relevance to other members of the genus Cyclotella are discussed. Cyclotella cavitata sp. nov. is characterized by round to elliptical shape; elliptic and tangentially undulate central area with one to three papillae on the elevated side. Central fultoportulae are absent while marginal fultoportulae internally are located on slightly depressed costae, with short tube openings with two satellite pores surrounded by cowlings. Satellite pores are situated circumferentially. Internally the rimoportula is situated in the marginal area with a sessile labium. Cyclotella sollevata sp. nov. is characterized by round valves with convex or concave central area which is uneven, colliculate, with papillae and granules. Central fultoportulae are present with variable number (9-21), internally with short tube openings with two satellite pores, which are surrounded by cowlings; Internally marginal fultoportulae are located on depressed costae and have short tube openings with two satellite pores situated circumferentially, surrounded by cowlings. The rimoportulae are located in the marginal area with a sessile labium variably orientated. Cyclotella sollevata and Cyclotella cavitata have been observed only in the fossil sediments of Lake Ohrid. Comments on the position of rimoportula, used as synapomorphic character to separate Lindavia from Cyclotella sensu lato are provided.

Psammothidium germainii is a widespread freshwater monoraphid diatom species in the Antarctic Region. Detailed analysis of the populations in the different parts of the Antarctic Region revealed the presence of several species that were lumped under the name 'P. germainii'. The type material of both Achnanthes germainii and Achnanthes ninckei has been investigated to allow a better morphological delimitation of both taxa and to better characterize the new taxa. Two new taxa are proposed: Psammothidium rostrogermainii sp. nov., typical for its rostrate apices and its rather distantly spaced stria pattern, and Psammothidium germainioides sp. nov., formerly identified in Antarctica as Achnanthes ninckei. Both new taxa are illustrated using light and scanning electron micrographs and are compared with similar taxa worldwide. Additionally, two populations of Psammothidium germainii lacking a raphe on the raphevalve are illustrated and discussed.

The taxonomic separation of the related heterocytous cyanobacterial genera Wollea and Anabaena is unclear according to traditional taxonomic features, as modern polyphasic approach has not yet been applied to compare them. However, comparison of the type species of these genera and their polyphasic analyses enable the separation of both generic entities. Definitions of their diacritical characters follow from the combination of their phylogenetic and morphological criteria. The concepts of Anabaena sensu stricto (particularly without planktic types with gas vesicles in cells - Dolichospermum) and Wollea, derived from their types are proposed in the article and their review is presented in the table. A new species from saltworks in southern Thailand, W. salina, is described.

The aim of this study was a combined and multifaceted characterization (morphological, molecular, lipid, pigment, and ecological data) of a Lemanea (freshwater red alga) population from the south-eastern Alps, exploring its adaptive strategies to the montane habitat, (turbulent, very-cold glacial stream with extremely low-conductivity). Although the thalli were small (only up to 1 cm), the morphology was within the current circumscription of Lemanea fluviatilis. The molecular data placed this population within a clade of specimens identified as L. fluviatilis and L. fucina. This L. fluviatilis population was determined to possess lipid classes, especially phosphatidylcholine and monogalactosyldiacylglycerol with high unsaturation index (UI) and long acyl chains, which are typical adaptations for maintaining adequate membrane fluidity and consequently all the metabolic processes associated to the plasma membrane. The carotenoids profile revealed that, besides α /β-carotene, there are significant amounts of zeaxanthin and lutein. This study further demonstrated that red algae are a rich source of important food web w-3 fatty acids and may play an important role in the diets of grazers. L. fluviatilis is reported from one of the highest elevations (2,170 m a.s.l.) known for the genus Lemanea and this species. This study confirms the presence of L. fluviatilis in a cold, unpolluted, turbulent stream and this type of stream may be its preferred habitat.

Two new species of the genus Mastogloia are described. Mastogloia sawensis sp. nov. and M. vestigiostriata sp. nov. were encountered as epiphytes on Chara sp. which covers the sediment of Sawa Lake, an isolated saline water body in southern Iraq. Mastogloia sawensis belongs to the section Lanceolatae and is closely similar to M. lanceolata but differs in raphe curvature, areolae shape and arrangement, and the presence of rounded pores at the junction of the partecta. Mastogloia vestigiostriata resembles under light microscopy to M. lyra and M. braunii but shows differences in several features including valve mantle structures, H-shaped lateral hyaline area, siliceous flanges and partectal formation. This study gives morphological details on the ultrastructure of the new species and provides a detailed comparison with all related taxa.

A species new to science, Germainiella clandestina, was discovered during experiments performed in an artificial freshwater channel. This species is described based on valve morphology typical for the genus Germainiella Lange-Bertalot et Metzeltin. The major features conforming to Germainiella are the valve face as well as a part of the mantle covered by a conopeum and the presence of very small apertures corresponding to a subconopeum canal system close to the raphe fissure. These characters clearly differentiate this taxon from the two more related genera, namely Fallacia Stickle et Mann and Pseudofallacia occulta (Krasske) Y. Liu, J.P. Kociolek et Q.X. Wang. Moreover, two chloroplasts could be observed for the first time in Germainiella, providing an additional feature to separate Germainiella and both genera cited above. Some information is given on its ecology.

As first observed on a group of taxa related to Cocconeis peltoides Hustedt, several other Cocconeis Ehrenberg (Bacillariophyta) taxa possess a row of minute marginal pores on the external side of their sternum valve (SV) connected to small and simple internal portules, or processes. These processes are often located in continuity with the striae, but can also be slightly shifted or distant from the distal areola of the striae. The row of pores is often, but not always, externally separated from the stria by a crista marginalis. Within Cocconeis, and possibly all raphid diatoms, these processes seem unique and restricted to a few taxa. A list is presented of the taxa pertaining (or close) to Cocconeis that are actually known to share these micro-structures. In addition, the morphological variability of the processes is described in detail and a morphological comparison of the taxa is provided. The characteristic features of taxa showing a row of SV processes permit the tentative definition of several morphological groups. It is difficult to prove the taxonomic affiliation of these taxa and demonstrate or refute that these processes are ancestral characters. Some of these taxa are rare and restricted to low latitudes (e.g., tropical taxa) while others are frequent and ubiquitous.

This paper provides information on the origin and the etymology of the names of genera of Cyanophyta/Cyanobacteria in current use and on the way new names are formed under the provisions of the International Code of Botanical Nomenclature and the International Code of Nomenclature of Prokaryotes. Special emphasis is placed on the differences between the two Codes that should be taken into account when creating new names compatible both with the botanical and with the bacteriological nomenclature system, to support the ongoing efforts to harmonize the nomenclature of the Cyanophyta/Cyanobacteria under the two Codes.

We frequently utilized the first edition of this book for educational purposes, because  it provides an excellent summarization of the most important characteristics of freshwater microalgae of the temperate zone (Wehr & Sheath 2003). Thus, we welcome new edition and we expect that it will become the basic guide for phycologists during the next decade.
New edition is a result of fruitful cooperation of a large author collective, mostly composed of top specialists in phycology. It is worthy to buy second edition containing updated references, illustrations, methods and approaches. Moreover, an alteration of species concepts, which is a result of expanding molecular and phylogenetic research during the last decade, is projected there. Some chapters have been added or enlarged (Harmful algal blooms, Habitats of freshwater algae), others were reorganized. Colour images and colorized drawings replaced or replenished black–and–white drawings or photos. Although the quality of colour images varied between chapters, there are mostly high quality microphotographs. Particularly Chapter 10, dealing with Photosynthetic  Euglenophytes, contains excellent images which are enough instructive to help beginners with identification of this hyperactive organisms. Colour images of living diatoms in Chapter 16 show overlooked cytology of this algal groups, which makes of this book an exception, because their study is almost exclusively based on dead frustules. Another well illustrated chapters are Chrysophyceae, Synurophyte Algae, Dinoflagellates, Cryptomonads. Finally, a myriad of new electron microscopy (both scanning and transmission)  images of good quality have been added to several chapters.

A small Cyclotella species (Thalassiosiraceae) from a subalpine lake Schliersee (Bavaria, Germany) is described. The species has characteristic valve morphology different from this of the other similar taxa. It differs from them especially with the presence of radially arranged ghost structures in the valve central part and with the presence and low number of transversal trabeculae inside the alveolus - maximally 6 in 1 μm. The valve morphology and ultrastructure of this taxon is described and its new name, Cyclotella hinziae, is proposed. Its valve morphology is compared and discussed with this of other similar taxa.

Four species of Achnanthes sensu stricto have been observed in several subaerial habitats/localities in Macedonia. The morphological features of all recorded species have been described based on light and scanning electron microscope observations. Two species posses similar morphological features as already described species and were identified as A. coarctata (Brébisson ex W. Smith) Grunow and A. sinaensis (Hustedt) stat. nov. Two species have unique set of characters that separate them from the known species and are described in this study as A. pseudocoarctata Levkov et Tofilovska sp. nov. and A. prominula Levkov et Tofilovska sp. nov. All recorded species were compared with the type populations including A. coarctata, A. coarctata var. sinaensis Hustedt, and A. intermedia Kützing. Observations of the syntype populations of A. coarctata give precise frame of the morphological variability of the species. Achnanthes pseudocoarctata appears similar to A. coarctata, but can be easily differentiated by the morphological and ultrastructural features of the rapheless valve. Achnanthes coarctata var. sinaensis has distinct morphological characters that make clear separation from A. coarctata, and therefore we propose a new status of this taxon with raising its rank to a species level. Achnanthes prominula appears similar to A. intermedia, but from latter can be easily separated by the position of the rapheless sternum. From other species with lanceolate or elliptic-lanceolate valves, A. prominula can be differentiated by the valve shape, position of the rapheless sternum, central area, stria and areola density.

During a survey of the freshwater aquatic and limno-terrestrial diatom flora of the Maritime Antarctic Region, five taxa belonging to the genus Stauroneis that could not be identified were observed. Based on detailed LM and SEM observations, these five taxa have been described as new taxa: Stauroneis australobtusa sp. nov., S. acidojarensis sp. nov., S. delicata sp. nov., S. jamesrossensis sp. nov. and S. reichardtiopsis sp. nov. Comments are made on their taxonomic position and separation from other species in this genus. Brief notes on the ecology and distribution of the five taxa are added. A compiled list of all Stauroneis taxa present in the (sub-)Antarctic region is included in this paper and their Biogeography based on the compiled data is discussed.

During a survey of the freshwater aquatic and limno-terrestrial diatom flora of the Maritime Antarctic Region, six taxa belonging to the genus Muelleria that could not be identified were observed. Based on detailed LM and SEM observations, these six taxa have been described as new taxa: Muelleria desseiniana
sp. nov., M. levkoviana sp. nov., M. nogae sp. nov., M. spauldingiana sp. nov., M. subsabbei sp. nov. and M. undulatoides sp. nov. Comments are made on their taxonomic position and how they can be distinguished from other species in this genus. Brief notes on the ecology and distribution of the six taxa are added. A compiled list of all Muelleria taxa described worldwide is included in this paper.

Genkalia digitulus (Hustedt) Lange-Bert. et Kulikovskiy (≡ Navicula digitulus Hustedt) is recorded from several lakes in the northern Europe and from high altitude lakes all over Europe. Wide distribution and characteristic autecology of this species allow its use as a bioindicator of pH changes and reliable marker of environmental reconstruction. A comparison of specimens found in lakes from the Carpathian and Balkan Mountains with the type material of Genkalia digitulus (Hustedt) Lange-Bert. et Kulikovskiy resulted in description of a new species - G. boreoalpina Wojtal, C.E. Wetzel, Ector, Ognjanova-Rumenova et Buczkó. Genkalia boreoalpina is characterised by valve outline, size and parallel striae throughout most of the valve. The separation was based on light and scanning electron microscopy. Genkalia boreoalpina was the most common diatom of the genus from high mountain lakes of slightly acidic waters with a very low mineral content. The third species, Navicula subprocera Hustedt, was found in the Lake Câlcescu (Parâng Mountains) in alkaline waters and in a mountain fen in Herzegovina. The nomenclatorial combination to Genkalia was made for this species. Previously published data suggest there is a much larger diversity of species in the genus Genkalia and the cosmopolitan distribution of this group is mostly presented at the genus level.
 

Desertifilum is a filamentous cyanobacterium of crusts and biofilms, recently described from the extreme hot and dry Thar Desert in north-western India. A new species was isolated from a warm spring near Lake Bogoria, Kenya and was characterised by light and electron microscopy and phylogenetically using the 16S rRNA gene, beta and alpha subunits including intergenic spacer (cpcBA-IGS) and 16S-23S internal transcribed spacer (ITS). The aquatic habitat of the new material from Kenya revealed a wider distribution of members of this genus. The new taxon was found to be closest to Desertifilum tharense (Oscillatoriales). The separation of the new species described here as D. fontinale sp. nov., using conventional and molecular traits, was based on differences in phenotypic features, 16S-23S ITS sequence and habitat.

Staurosira longwanensis sp. nov. is described from Sihailongwan maar lake, northeast China. The morphology of this new species is documented with light and scanning electron micrographs and discussed in comparison with several small species of Fragilariaceae. Staurosira longwanensis belongs in the genus
Staurosira since it shares many features with taxa currently ascribed to it such as the position and characteristics of the spines, the characteristics of the areolae and apical pore fields. Apart from the type locality, S. longwanensis also occurs in another volcanic lake in northeast China, with circumneutral and oligotrophic water. Diatom analysis of the long sedimentary record retrieved from Lake Sihailongwan indicates that S. longwanensis has been present at low relative abundances in this lake at least since the Late Pleistocene. 
 

Cymbella (Encyonema) grossestriata var. recta was studied based on analysis of the type material from Argentina and newly collected material from southern Brazil. In light microscopy the taxon presents dorsiventral valves, asymmetric and expanded central area, striae slightly radiate at the ends, becoming strongly radiate, and sigmoid in the center of valve. In scanning electron microscopy it is possible to observe features that are similar to the Navicula genus, such as slit-like areolae, accessory rib in the primary side, which is wider (expanded) at the center and valves with a marked virgae. Beyond these features the presence of two chloroplasts per cell definitively excludes the taxon from the Cymbellales group and allows us to transfer it to the genus Seminavis. Seminavis recta comb. et stat. nov. was found associated to Spartina and Scirpus species and living in the sediment of salt marshes in oligo to mesohaline zones, in a wide range of temperature and pH. This species is rare, and has been reported only to South America until now.

A study was made of the type material of Achnanthidium exiguum (Grunow) Czarnecki. This often encountered and apparently ubiquitous species was originally described as Stauroneis exilis by Kützing from the island of Trinidad and later re-named as Achnanthes exigua by Grunow. The type material for this taxon (Kützing sample 397), housed in the Van Heurck collection at the National Botanic Garden of Belgium, Meise was investigated and the ultrastructure of this taxon was documented using both LM and SEM observations. A new Antarctic taxon, formerly identified as A. exigua, was described as a new species, Achnanthidium australexiguum sp. nov. The position of both taxa within the genus Achnanthidium is briefly discussed.

A large study on Gomphonema Ehrenberg species from Macedonia recently has been started. In this article two species are presented having unique set of characters than already known species and therefore are described as new species. The comparison was made using type material of G. brebissonii Kützing and G. gautieri (Van Heurck) Lange-Bertalot et Metzel tin. Gomphonema scardicum sp. nov. resembles G. montanum (Schumann) Grunow and G. brebissonii Kützing with respect to the valve outline and size. Main differential characters of G. scardicum are the cuneate shape of the headpole and less pronounced constriction near the head pole. Similarly, G. gautieriforme sp. nov. differs from G. gautieri with respect to the valve outline and the shape of the head pole. The valves of G. gautieriforme are almost rhombic in outline and gradually narrowing towards the footpole. The head pole of G. gautieriforme is rounded and cuneate opposite to truncate and apiculate in G. gautieri.

The type material of Achnanthidium lanceolatum (transferred in 1999 to the genus Planothidium) is investigated to reveal the identity of several Planothidium populations from the Antarctic Region. The morphology and the ultrastructure was analysed using light and scanning electron microscopy. The results of this analysis revealed the presence of two so far undescribed Planothidium species in the investigated Antarctic material. Both species are described as new to science: P. rostrolanceolatum Van de Vijver, Kopalová et Zidarova sp. nov. and P. subantarcticum Van de Vijver et C.E.Wetzel sp. nov. The new species can be differentiated based on differences in valve outline and the shape and size of the central area. Planothidium lanceolatum is formally lectotypified. Notes on the ecology and distribution of the new Antarctic species are added.

Phylogenetic position, morphology and ultrastructure were investigated for biotechnologically remarkable strain Chlorella vulgaris IFR C-111, utilized in various commercial applications. Molecular phylogenetic analyses based on the SSU and ITS rDNA data revealed that the strain IFR C-111 forms a distinct lineage within the Parachlorella-clade in Chlorellaceae. We describe this organism as a new genus and species, Planktochlorella nurekis. Vegetative cells of this newly recognized species are spherical, possessing a single pot-shaped chloroplast with starch-covered pyrenoid. Asexually it reproduces by the formation of 2-16(-32) autospores. Cell wall is composed of two layers, the outer layer containing extended microfibrillar material. The fuzzy cell wall structure improves the buoyancy resulting in low sedimentation rate of P. nurekis. To resolve the phylogenetic position of Planktochlorella and its relationship to the closely related genera, nucleotide saturation present in the ITS rDNA data was reduced by four different approaches. The resulting topologies pointed to the poor phylogenetic signal in generally utilized SSU and ITS rDNA data and the need of sequencing other molecular markers.