Approximately 100 new strains of the Pediastrum-phenotype were isolated from inland waters of India, eastern and southwestern Africa, and Germany and were studied by light and scanning electron microscopy. The 18S rRNA and ITS genes of 28 strains were sequenced and compared with 25 sequences of
Hydrodictyaceae from the GenBank database. Phylogenetic analyses confirmed the polyphyly of Pediastrum. The new species Sorastrum pediastriforme was described. This species resembled morphologically Pediastrum, however, the phylogenetic analyses revealed its affiliation within the genus Sorastrum. Furthermore, the following new combinations: Monactinus sturmii, Pseudopediastrum alternans, Pp. brevicorne, Pp. integrum, and Pp. pearsonii were established.

A 2012 microphytobenthos survey from coral reef environment at Napuka Atoll (Tuamotu Archipelago, South Pacific) focussed on diatom assemblages. Atolls are tropical carbonate, productive ecosystems, with a fast turnover, from which benthic diatom floras are poorly known. When compared to younger volcanic islands from the same area, Napuka shows a poor colonisation by benthic diatoms. Although normally rare, Achnanthales occur in the assemblages from Napuka. In the tidal zone, marine debris of sponge origin were colonized by several taxa, among others a small-celled Cocconeis here described as C. napukensis sp. nov. The new taxon has some likeness to Cocconeis subtilissima Meister and to C. vairaensis Ricard. Original drawings and type material are examined when available. A lectotypification and an emended description of Cocconeis subtilissima are proposed, along with the description of Cocconeis suzukii sp. nov. and Cocconeis meisteri sp. nov. from Meister type material. The morphological features of C. napukensis are investigated with scanning electron miscroscope (SEM) and light microscope (LM). Until now C. napukensis has not been found in the other investigated sites of Tuamotu and Society Archipelagos.
 

The type of branching is a morphological character of great significance, separating taxa within the true-branched cyanobacteria. In this paper, true-branched morphospecies of cyanobacteria belonging to genus Iphinoe Lamprinou et Pantazidou, from different and geographically isolated caves of Greece, were investigated by coupling classical approach i.e. microscopy analysis (LM, SEM, TEM, CLSM) and molecular analysis (16S rRNA gene diversity). The morphological study revealed interspecific differences which could be attributed to adaptations to local conditions: Iphinoe cf. spelaeobios from the cave 'Diktaion Andron' (Crete island) exhibit different type of branching (Y- and T-type) and smaller size compared to the type species Iphinoe spelaeobios (T-
and V-type of branching) from the caves 'Kastria' and 'Koutouki' (Peloponnese, Attica). Despite their phenotypic differences and geographical isolation molecular analysis showed identical 16S rRNA sequences which indicate that both populations belong to the same genus.

In 1911, W. & G.S. West published a detailed account of freshwater algae collected by James Murray in the vicinity of Cape Royds on Ross Island (Antarctic Continent). Out of of 84 algal taxa reported, 30 were diatoms. Although the majority of the diatoms were considered (at that time) to be cosmopolitan, eight diatom species and two varieties were described as new. While most of these new taxa are still commonly reported from Antarctic and Subantarctic localities, the exact identity of some remains uncertain. Here we document the morphology of these species from the original type material using light and scanning electron microscopy; the taxonomic identities are discussed and, where necessary, the taxonomy is updated. For several species, lectotypes are designated. In addition, two Antarctic species are described as new: Luticola pseudomurrayi Van de Vijver et Tavernier sp. nov.
and Chamaepinnularia gibsonii Van de Vijver sp. nov.

The present work summarizes the current diversity, distribution and autecology of desmids found within the Czech Republic; the focus is on the occurrence and autecology of rare taxa. Data are based on the author's extensive sampling from 2003-2009, during work for both his master's degree, and currently, his Ph.D. dissertation. Over 1 400 samples were collected, from various types of wetland habitats ranging from eutrophic fishponds, diverse bogs and fens, to ephemeral pools and various aerophytic habitats. Altogether, 526 taxa of desmids (401 species) belonging to 27 genera were found, 80 of them newly described in the Czech Republic. In the present work, 169 rare or otherwise noteworthy taxa, belonging to the following genera: Mesotaenium (1), Netrium (1), Roya (2), Tortitaenia (1), Gonatozygon (2), Closterium (14), Haplotaenium (2), Pleurotaenium (3), Docidium (1), Actinotaenium (6), Euastrum (9), Micrasterias (7), Cosmarium (78), Xanthidium (7), Staurodesmus (4), Staurastrum (25), Cosmocladium (2), Sphaerozosma (2), Hyalotheca (1) and Desmidium (1) are depicted by line drawings and briefly discussed with regard to their ecology, taxonomy or distribution within the Czech Republic or Central Europe. In addition, SEM images are provided for 45 taxa, and, finally, a comprehensive table is included with indicative notations concerning all taxa found.

The Island of Majorca (Spain) is characterized by a Mediterranean climate and a karstic geology that favors the formation of numerous springs and spring-fed streams on the island's Northwester zone. Water and epilithic diatom samples were collected from two springs and four spring-fed streams, located at altitudes ranging from 0 to 756 m a.s.l., in different seasons between 2005 and 2008. Water chemistry in these systems is characterized by high concentrations of dissolved calcium and pH values ranging from 6.6 to 8.4. A total of 111 diatom taxa belonging to 40 genera were found and the most abundant taxa were illustrated with LM and SEM. The diatom communities of the studied sites were dominated by species such as Achnanthidium minutissimum, A. pyrenaicum, Amphora pediculus, Cymbella vulgata, Diploneis separanda, Encyonopsis minuta, Gomphonema lateripunctatum and Navicula cryptotenella, reflecting the calcareous geological nature of Majorca Island. In the framework of the study 22 diatom taxa, which are new for Balearic Islands were recorded, such as Achnanthidium straubianum, Amphora indistincta, Cymbella lange-bertalotii, Encyonopsis subminuta, Karayevia kolbei, Navicula aff. margalithii, N. reichardtiana and N. subalpina. In addition, a new freshwater diatom species belonging to the genus Cymbopleura, C. margalefii was found in the Torrente of Deià. Cymbopleura margalefii is described as a new species based on LM and SEM observations, and compared with similar taxa. A checklist of the 309 diatom taxa recorded so far from the Balearic Islands is also presented.

Three new araphid diatom species, Pseudostaurosira decipiens E. Morales, G. Chávez et Ector, P. sajamaensis E. Morales et Ector and Staurosira kjotsunarum E. Morales, Novais et Ector are described from a single sample taken from the Desaguadero River in the Bolivian Altiplano. These species clearly belong in their respective genera as evidenced by their morphological features studied using light (LM) and scanning electron microscopy (SEM). Pseudostaurosira decipiens is unique in its genus because of the combination of lanceolate-shaped valves with central area, well-developed spines lacking ligulae, siliceous deposits on outer and inner areolar openings similar to flaps, and the inner rounded structure of the apical pore fields. Pseudostaurosira
sajamaensis is different from other species of Pseudostaurosira due to its elliptic to lanceolate valves bearing a wide central sternum, spines with developed ligulae and bilobed flaps, robust volae and reduced or absent apical pore fields. Staurosira kjotsunarum is unique within Staurosira in having elevated costae on both external and internal views, narrowly spatulate spines that hold onto areolae of neighboring valves along a chain, and striae composed of round poroids underneath the apical pore fields on the valve mantle. The three species are compared with morphologically similar taxa and a brief analysis of the richness found in the studied sample in the context of previous publications on diatoms from the Andes and contiguous regions is presented.

In the present paper, the morphology and taxonomy of seven desmid taxa collected in various European habitats is discussed, mainly on the basis of scanning electron microscopic observations of cell wall sculpturing. Four taxa (Actinotaenium riethii, Closterium pseudocostatum, Cosmarium discrepans and C. hostensiense) are newly described and the name of one taxon (Cosmarium lenzenwegeri) is recombined. In addition, the morphology of Cosmarium cataractarum and C. cinctutum is described in greater detail, confirming their status as independent species.

This paper describes and illustrates Aulacoseira brasiliensis Tremarin, Torgan et T. Ludwig sp. nov. under light and electron microscopy and compares their ultrastructure with similar species obtained from Hustedt's collection samples. The new species is characterized by forming short chains linked by ovate-attenuate spines, rounded areolae occluded by vola, undeveloped ringleist and sessile rimoportulae arranged in two circumferential alternate rows. The spines shape, rimoportulae disposition, valve surface and mantle areolation pattern are very particular. The ultrastructural features of the frustules of A. brasiliensis are compared with those of A. muzzanensis, A. agassizii var. agassizzi and A. agassizii var. malayensis, particularly with respect to the areolation pattern, position, number and shape of rimoportulae. A. brasiliensis was found in lotic and lentic environments of tropical and subtropical regions from Brazil.

A taxonomical study of 15 Rhoicosphenia species based on light and scanning electron microscope was performed. The genus Rhoicosphenia is characterized by frustule heterovalvy, with a fully developed raphe on the concave valve (referred also as R valve) and reduced raphe on the convex valve (referred as D-valve). One of the most frequently reported species, R. abbreviata, is characterized by narrow, linear valves with low stria density. In contrast, Rhoicosphenia macedonica has broadly clavate valves with a high stria density. According to valve shape R. macedonica is similar to the widely distributed marine species R. marina, but the latter has broader valves (8.5-11 μm wide) and a lower stria density. Both, R. tenuis and R. baicalensis have similar valve sizes and shapes, but the latter is characterized by a lower stria density on the D-valve. Rhoicosphenia baltica is a brackish water species with protracted and subcapitate base poles, narrower valves and lower stria density compared with R. marina. The main distinctive features of R. flexa are the absence of a raphe branch on the head pole of the convex D-valve, and coarsely punctate striae. R. genuflexa has isopolar, linear valves. Four other species have
different combinations of characters (valve size, shape and stria density) compared to above mentioned species, and their formal descriptions are provided. Rhoicosphenia lacustris sp. nov. is characterized by larger and broadly clavate valves, densely spaced striae and elongated areolae. Rhoicosphenia affinis sp. nov. has broadly lanceolate valves with attenuated and slightly protracted head pole with a higher stria density compared to R. abbreviata. Rhoicosphenia adriatica sp. nov. is a brackish water species having narrow, linear valves, with a high stria density. Finally, R. omblaensis sp. nov. has a characteristic central area, which appears as a narrow hyaline area around the central pores.

An edaphic, filamentous, nonheterocytous cyanobacterium was collected from the Etosha Pan, Namibia. Based on multilocus sequencing of the 16S rRNA gene, beta and alpha subunits (cpcBA-IGS) of the phycocyanin operon and morphological and ecological features, we describe the new species Phormidium etoshii (Oscillatoriales). The taxon was differentiated from the phylogenetically closest taxa in morphological features and ecology.

Olifantiella Riaux-Gobin et Compère (Bacillariophyta, Biraphidineae), a monospecific diatom genus from coral reef environments in Réunion Island (Western Indian Ocean), was collected from Rodrigues Island (easterly island of the Mascarene archipelago) in 2007. Several taxa with the external characteristics of Olifantiella were observed in shallow lagoon sediments. The external opening connected to the internal process is easily identified in each taxon. The processes are on the same or opposite side of the frustule, depending on the taxon. Several taxa are present: 1) Olifantiella cf. mascarenica Riaux-Gobin et Compère, 2) O. rodriguensis sp. nov., with an elongate shape and a double buciniportula, 3) O. gorandiana sp. nov., with a naviculoid shape and a complex
buciniportula composed of two flattened tubes, that do not protrude, flanked by two small satellites, and 4) O. pilosella sp. nov., O. paucistriata sp. nov. and O. pseudobiremis sp. nov., which are only described from external views. The scarcity and minute size of the taxa necessitated the use of scanning electron microscopy (SEM) to examine and distinguish them accurately. Some LM observations were made when possible. During previous tropical marine surveys, the genus Olifantiella may have been overlooked or misidentified, due to its small size, fragile frustules, and often naviculoid shape. We discuss the morphological diversity of the genus, e.g. the frustule and buciniportula shape and structure, and propose a formal emended description of the genus Olifantiella.

The analysis of the type material of Pinnularia divergentissima (Grunow in Van Heurck) Cleve revealed the presence of two distinct Pinnularia taxa in the same slide. Comparison with the original drawing of P. divergentissima by Grunow showed that recent taxonomic treatments of P. divergentissima are not in accordance with the original diagnosis. Both species in the type material are morphologically characterized and the correct identity of P. divergentissima is established whereas the second taxon is described as P. pseudodivergentissima sp. nov. Additionally, the type material of P. fottii J.Bílý et Marvan and P. martinii Krasske is likewise analysed and both taxa are separated from P. divergentissima. Finally, the morphological analysis of a fifth taxon from the sub-Antarctic Region resulted in the description of a new taxon, P. lindanedbalovae Van de Vijver et Moravcová sp. nov.

The identity of a small-celled diatom Naviculadicta pseudofallacia Witkowski, Metzeltin et Lange-Bertalot, originally described from Bear Island, southernmost island of the Norwegian archipelago Svalbard, is reconsidered. Observations of marine samples from the Kerguelen archipelago (Southern Ocean, Indian Ocean sector) revealed that this species also occurs in the Subantarctic region. The original classification within Naviculadicta was erroneous since this species is a monoraphid taxon and belongs to the Achnanthales. Its morphological features justify creating a new genus Scalariella Riaux-Gobin, which is distinguished from other achnanthoid genera by a peculiar raphe system, the stria structure of the sternum valve (each stria composed of a depressed macroareola), and the presence of a lateral solid area in the raphe valve, splitting each stria into two areolae. Based on light and electron microscopy, N. pseudofallacia is renamed Scalariella pseudofallacia (Witkowski, Metzeltin et Lange-Bertalot) Riaux-Gobin et Witkowski comb. nov. The genus also includes a second and rare species, observed in the Kerguelen material, S. oblongella Riaux-Gobin, Witkowski et Ruppel, which is described and illustrated, but which needs complementary observations. The morphology of Scalariella is compared to that of some genera split from the genus Achnanthes Bory. The biogeography of Scalariella pseudofallacia, a marine taxon probably misidentified in the past due to its small size, is reconsidered with respect to its affinity for subpolar, cold water habitats, in both hemispheres.

For decades, the diatom genus Haslea has been known to comprise both "colorless" species and one species containing a blue pigment, the latter being known as H. ostrearia. Recently, a new blue diatom named H. karadagensis has been isolated from the Black Sea. The mating compatibility of the two species has been tested, and their reproductive isolation confirmed. We provide a detailed description of the heterothallic sexual reproduction process in this new species. Cells from clones which are sexually compatible arrange gametangial pairs. Each gametangium in the pair produces two gametes, which to a large extent are morphologically and behaviorally isogamous. No mucilage or mucilage structures are observed. Zygotes and auxospores have no contact with parental frustules, and their orientation is rather irregular though they tend to lie parallel to each other. Evaluation of the position of cardinal points in the life cycle of the species, and the rate of cell size decrease in culture are presented. In the breeding system of this species both homo- and heterothallic ways of reproduction are realized. The latter is basic and predominant. Among the 36 clones investigated, 16 were sexually compatible with the other 20. Homothallic behavior was extremely rare; only one clone displayed a homothallic mode of reproduction.

Diversity and ecology of desmids (Zygnematophyceae) were studied within eight peat bog sites in the Jeseníky Mts during the years 2006-2009. Altogether, 51 taxa were found in the course of our investigation. A detailed study of spatial distribution of desmids in relation to environmental characteristics was performed. The composition of desmid communities was influenced especially by water table elevation and pH. Among all chemical substances measured and statistically tested, Mg, Ca and Pb concentrations appeared to have a considerable effect. Several remarkable desmid taxa were found and discussed in terms of their occurrence and broad morphological variability.

A new benthic freshwater diatom species belonging to the genus Pinnularia Ehrenb. has been recorded in the Água Forte stream surrounding the Aljustrel mining area in southern Portugal. Pinnularia aljustrelica Luís, Almeida et Ector sp. nov. is described as a new species based on light and scanning electron microscopy observations and on its particular habitat in an acidic environment due to acid mine drainage, high metal concentrations (As, Cd, Cu, Fe, Mn, Pb and Zn) and high sulphate and conductivity. The taxa most similar to P. aljustrelica are P. acidophila Hofmann et Krammer, P. acoricola Hustedt and P. acoricola var. lanceolata Hustedt, so type materials of these taxa were studied for comparative purposes. Although, the ecology of the three similar taxa is also quite similar, the new species has a combination of particular morphological characteristics studied under LM and SEM that separates it from the rest. Pinnularia aljustrelica has a general shape relatively similar to P. acidophila and P. acoricola, but the valve outline is not as linear as in P. acidophila and not as oval as in P. acoricola.

Phylogenetic analyses of SSU rDNA sequences of 130 Spirogyra strains have revealed that these strains were subdivided into eight clades. Approximately 60% of the assessed strains (clades A-D) contain a 1506 group I intron, whereas strains without introns form individual clades (E-H). The Spirogyra intron shared the common insertion site of the Zygnematalean intron (position 1506 relative to the Escherichia coli small-subunit rRNA). Phylogenetic analyses of the Spirogyra group I intron showed the monophyletic origin within the Zygnematophyceae. Therefore, we assume the secondary loss of the intron in clades E-H is caused by the high evolutionary rate of Spirogyra and its long evolutionary history. The Spirogyra intron belongs to the IC group I introns and shares many common features with the intron of other Zygnematophyceae (the typical domain structure (P1-P9), the base composition, the highly conserved regions the U preceding the 5' splice site and the G to which it pairs, and the G preceding the 3' splice site are typical for IC group I intron). Spirogyra group I introns exhibit features of early desmids (optional P2 domain) as well as of later diverging desmids (variation from the typical L5b-GAAA tetraloop). The P2 domain shows an additional optional P2 sub-domain in clade B. Surprisingly, the mutation rate of the Spirogyra SSU rRNA exceeds the rate of the intron by far. Evolutionary rates differ significantly within the Spirogyra SSU rRNA accessions, but not within the respective group I intron sequences.

As part of a study on the diatom flora of the Gokyo Valley, Everest National Park, Nepal, eleven species of Cymbopleura (Bacillariophyta), including two new species, Cymbopleura gokyoensis Jüttner et Van de Vijver sp. nov. and Cymbopleura emoda Jüttner et Van de Vijver sp. nov., were investigated using light and electron microscopy. Some taxa could not be identified with certainty using the currently available literature due to small differences in valve dimensions, raphe structure and striation patterns. It remains unclear whether they represent new species or whether the original descriptions should be emended to include the populations from Nepal.

The morphology and mode of reproduction in Ettiella tetraspora Hindák 1988, a green coenobial alga described from the Czech Republic and Finland, were studied from the plankton of the water reservoir Förmitzspeicher in NE Bavaria, Germany. The morphology of cells and coenobia of the species in this population was in agreement with published data for the species, but its reproduction was not of the Oocystis - type as it has been declared in the relevant literature. The protoplast of mother cells does not divide simultaneously into 4 autospores as in many coccal green algae, but always in two autospores. The first division of the mother cell is perpendicular to the longitudinal axis of the cell and two walled daughter cells arise. Subsequently, the newly formed daughter cells divide again, but this time perpendicular to the new formed cell cross wall. Ultimately, in a new coenobium all four daughter cells are arranged in parallel. Daughter cells remain inside a slightly enlarged mother cell wall (well visible only near the cross wall) and are released by its gelatinisation. Such subsequent production of four autospores from the mother cell represents a special type of multiplication in the green coccal algae known also in some other species [e.g. Tetrastrum komarekii Hindák 1977, Willea irregularis (Wille) Schmidle 1900, Makinoella tosaensis Okada 1949].

A new morphotype of the genus Pseudanabaena (Cyanoprokaryota, Oscillatoriales) was identified from bloom samples of Aphanizomenon flos-aquae Ralfs ex Bornet et Flahault taken from large central North American water bodies, Lake Winnipeg (LWPG) and Lake of the Woods (LOW), which drains into Lake
Winnipeg (Fig. 1) and a strain of this morphotype was isolated from LOW in the fall of 2009. Here we describe the morphology and basic ecology, cytology and phylogenetic position of this new chromatic adaptive and colony forming planktonic species and propose a new species Pseudanabaena rutilus-viridis Kling et al. Preliminary research has indicated that it has the ability to produce the toxin microcystin and further research is under way to assess its ability to produce taste-odour and other toxins and nitrogen-fixing capacity.

A new freshwater diatom species belonging to the genus Achnanthidium Kütz. has been found in several French rivers namely those of the Languedoc-Roussillon and Rhin-Meuse regions. Achnanthidium delmontii sp. nov. is described based on light and scanning electron microscopy observations. This species belongs to the group of Achnanthidium taxa with terminal raphe fissures curved to the same side of the valve and it is compared to the most related species: Achnanthidium pfisteri Lange-Bertalot, Achnanthidium pyrenaicum (Husdedt) Kobayasi, Achnanthidium temniskovae Ivanov et Ector and Achnanthidium zhakovschikovii Potapova. The assessment of its ecology was made through physicochemical analysis carried out on sites which are part of water quality monitoring networks. Some comments are made on the rapid expansion of Achnanthidium delmontii sp. nov.

Coccoid green algae generally are difficult to classify because of their depauperate morphology, and for this reason many of them have a complicated taxonomic history. In the present study we use analyses of molecular sequence data to demonstrate the close relationship of two green coccoid taxa that have undergone multiple taxonomic transfers in the past, and argue for the recognition of a distinct lineage. We resurrect the genus Chromochloris to accommodate C. zofingiensis (= Muriella zofingiensis) and we provide data regarding the lineage's phylogenetic relationships to other chlorophyte genera, especially Bracteacoccus, Chlorella, Muriella, Mychonastes, and Pseudomuriella. In addition, we synonymize B. cinnabarinus and Bracteacoccus minutus with
C. zofingiensis, and clarify the identity of three UTEX strains heretofore listed as Bracteacoccus.

A new small Discostella (Bacillariophyceae), D. tatrica Procházková, Houk et Nedbalová sp. nov., from lakes of the High Tatra mountains (Slovakia/Poland, Europe) is described here on the basis of light and electron microscopy. This species is reminiscent of D. guslyakowyi Genkal, Bondarenko et Popovskaya and D. stelligeroides (Hustedt) Houk et Klee. However, it differs from D. guslyakowyi in having alveolae in the central parts, and from D. stelligeroides in the possibility of having an incomplete stellate pattern in its convex central parts and possessing an alveolus in its concave central parts. The valve morphology and ultrastructure is documented here in light and electron microscope images, and it is discussed, as well as its ecology, with these of other similar Discostella taxa.

In 2006 the desmid flora of Lake Nabugabo and some adjacent peat bogs was studied. All in total some 108 taxa were identified. Fourteen taxa, most of them being only known from the African continent, are discussed in detail. Six taxa are newly described: Euastrum gemmatum var. quadrituberosum, Micrasterias stuhlmannii var. nabugabonum, Cosmarium nabugabonum, Xanthidium thomassonii, Staurodesmus eckertii var. africanus and Staurastrum capitulum var. foersteri. The morphological variation found in Staurastrum longicolle is discussed in the light of possible speciation of desmids in a limnetic environment.

Sexual behaviour, pattern of auxosporulation, and breeding system of the araphid diatom Tabularia fasciculata were studied using 64 clones derived from two natural populations from the Canadian Atlantic seashore and the Black Sea. Both inter- and intraclonal reproductions were observed. Heterothallic reproduction was morphologically and behaviourally heterogamous. The heterothallic nature of sexual reproduction in this species allowed the determination of sex ratio in the population, which was 1:1 male:female. A novel type of active movement of gametes designated as male was described and pathways traced and recorded. A few male clones could reproduce intraclonally, but this was not abundant compared to interclonal reproduction. The advantages and inferred significance of each mode of reproduction are discussed. In the semi-natural population of T. fasciculata, two size classes were detected among sexualized individuals, and they gave rise to two size groups of initial cells. Sexual compatibility of all derived clones was independent of cell size class. In cultures, the apical length of initial cells was also strongly correlated to the size of parental gametangia. Cell sizes corresponding to cardinal points in the life cycle were established. Interbreeding of clones derived from the Canadian Atlantic and the Black Sea suggests a pan-Atlantic reproductive compatibility of populations of diatoms conforming to current morphological delineation of T. fasciculata.

Anabaenopsis elenkinii Miller forms bloom in the alkaline shallow lakes of the Brazilian Pantanal. The A. elenkinii CCIBT1059 strain was isolated from one of these alkaline lakes and the experiments were made in growth chamber during 30 days, under modified medium BG-11 (3 % NaNO3), temperature 25 ºC, photoperiod 12-12 light-dark cycle and irradiance of 80-100 μmol photons m-2 s-1 at three different pH values: 7.0, 9.5 and 10.5. In relation to growth rate and cell yield the higher values were observed at pH 10.5. Morphologically, the longest trichomes were found at pH 7 (maximum 45 cells) in comparison with pH 9.5 (maximum 32 cells) and pH 10.5 (maximum 23 cells). The occurrence of heterocytes was observed in all treatments, but akinetes were never formed. The morphometric variability within each treatment between exponential and stationary growth was clearly higher than the variability among different treatments in most cases. Our results indicate that A. elenkinii is typical of alkaline systems and also that in lower pH values the growth limitation can occur in terms of number of cells and biomass. This study represents the first experimental evidence of the effects of pH on growth rate, cell yield and morphometric variability of A. elenkinii.

The Atlantic rainforest is considered one of the most important hotspots of biodiversity on Earth. This great diversity results from the variation of climatic conditions (rainy, warm and cold in high mountains), what generates a unique series of rain forest ecosystems quite distinct from each other. Unfortunately, due to the human impact over the centuries, today there are just fragments of preserved native rainforest. During the investigation
about the cyanobacterial flora from the Atlantic rainforest, a special Chamaesiphon morphotype was found on a rock in streaming water. Chamaesiphon stratosus sp. nova is close to C. britannicus (Fritsch) Komárek et Anagn., C. geitleri Luther and C. fuscus (Rostaf.) Hansg ., and differs from them mainly because of the cells disposition in one layer and exocytes liberation in a sheath at the upper part of cells. These two features belong to different subgenera of Chamaesiphon (Godlewskia and Chamaesiphonopsis). Thus, the Brazilian material displays features of both subgenera and puts in evidence the fragility of these characteristics at subgenus level. Therefore, a discussion about the taxonomy of these subgenera and a proposal for including Chamaesiphonopsis as a synonym of the Godlewskia were done.

Venezuelan Table Mountains (tepuis) are among world's most unique ecological systems and have been shown to have high incidence of endemics. The top of Roraima, the highest Venezuelan tepui, represents an isolated enclave of species without any contact with the surrounding landscape. Daily precipitation enables algae and cyanobacteria to cover the otherwise bare substrate surfaces on the summit in form of a black biofilm. In the present study, 139 samples collected over 4 years from various biotopes (vertical and horizontal moist rock walls, small rock pools, peat bogs, and small streams and waterfalls) were collected and examined for algal diversity and species composition. A very diverse algal flora was recognized in the habitats of the top of Mt. Roraima; 96 Bacillariophyceae, 44 Cyanobacteria including two species new to science, 37 Desmidiales, 5 Zygnematales, 6 Chlorophyta, 1 Klebsormidiales, 1 Rhodophyta, 1 Dinophyta, and 1 Euglenophyta were identified. Crucial part of the total biomass consisted of Cyanobacteria; other significantly represented groups were Zygnematales and Desmidiales. Investigated biotope types were demonstrated to have different composition of algal communities.

This paper deals with the characterization of a filamentous cyanobacterial strain, isolated from the microbial mats developing on the thermal muds of Ischia Thermal District (Naples, Italy).
The survey was carried out by a polyphasic approach that includes morphological, ultrastructural, biochemical, and genetic analyses. For the molecular analyses the 16S rDNA gene and the rbcL gene were considered. All results showed that this filamentous cyanobacterium belongs to the order Oscillatoriales, family Pseudanabaenaceae. Moreover, the phylogenetic reconstruction suggests that strain ITD-01 might represent the first described entity belonging to a new cyanobacterial genus, whose name might be Protolyngbya.