Alkaline phosphatase activity in two planktonic desmid species and the possible role of an extracellular envelope

1. Cosmarium abbreviatum var. planctonicum , a desmid from oligo‐mesotrophic lakes, had a higher maximum alkaline phosphatase activity (APA) and affinity constant under both continuous and pulsed inorganic phosphorus (P_i) limitation than Staurastrum chaetoceras , a desmid predominantly encountered in eutrophic lakes.
2. APA of both species increased when measured in starved cells subjected to pulsed P_i conditions when compared to continuous P_i limitation.
3. The portion of extracellular relative to cellular APA was higher in S. chaetoceras than in C. abbreviatum , indicating that S. chaetoceras secreted the enzymes more readily into its environment.
4. The difference in APA could explain the dominance of C. abbreviatum during competition between these two species under conditions of continuous organic P (P_o) limitation, but not the outcome under a pulsed P_o shortage. The dominance of S. chaetoceras in the latter experiment can, however, be explained by species‐specific P_i‐uptake characteristics.
5. After a saturating pulse of P_i, no increase in P_i in the extracellular mucus layer of C. abbreviatum was found and it was therefore concluded that the mucilage sheath does not store P. However, the sheath could have a main function as an accumulation site of cellular APA, providing the cell with P_i.     

Indonesian desmids

Summary There are described 526 desmid taxa found in 49 freshwater algal collections from Kalimantan (Borneo), Java, Bali and Sumatra, including 152 new taxa in the genera Closterium, Pleurotaenium, Euastrum, Micrasterias, Cosmarium, Arthrodesmus, Xanthidium, Staurastrum, Onychonema, Bambusina, and Desmidium.     

New and interesting cases of conjugating desmids from Lapland

A number of desmid samples collected in Lapland appeared to be remarkably rich in zygospores. The spore morphology of Euastrum sinuosum Lenorm. ex Arch., Cosmarium tumidum Lund., C. isthmochondrum Nordst., Staurastrum dilatatum Ehr. ex Ralfs, Actinotaenium wollei (W. & G. S. West) Teil. ex Růž. & Pouz. and A. didymocarpum (Lund.) comb, nov., either when hitherto unknown or requiring a critical discussion is extensively treated. A new species, Cosmarium taxillus (with zygospores) is described.
Repeatedly recorded incidences of a disturbed zygospore development and the grey to black pigmentation of the mesosporium are discussed in connection with the possible effect of habitat factors.     

Taxonomic and biogeographical notes on Malagassy desmids (Chlorophyta, Desmidiaceae)

At least 40 % of the desmid taxa encountered during a short stay in Madagascar appeared to be characterized by a non-cosmopolitan distribution. The majority of those taxa have only been reported from Africa or from both Africa and tropical Asia, suggesting dispersal biogeography as underlying model of present day composition of the Malagassy desmid flora. A number of species are taxonomically and biogeographically discussed. Two species are described as new to science: Cosmarium madagascariense sp. nov., and Micrasterias madagascariensis sp. nov.     

Remarkable desmids (Desmidiaceae, Charophyta) from Sardinia, Italy

A number of benthic microfauna samples collected in Sardinia in the 1970s, and screened for the occurrence of microalgae in the 1990s, revealed some remarkable desmid species. Most of these species could not be found in a series of samples collected in 2006. Eleven desmid taxa are discussed in detail, two of which are described as new to science; Cosmarium majaeforme sp. nov. and Xanthidium sardiniense sp. nov. The specific composition of the Sardinian desmid flora is discussed both in relation to the prevailing environmental conditions and to its geographic position close to the African continent.     

Desmids (Chlorophyta, Desmidiaceae) from Thale Noi (Thailand)

The desmid flora of laguna Thale Noi, a large freshwater lake in the south-eastern part of Thailand, appeared to be characterized by a high portion of non-cosmopolitan taxa. Next to a series of pantropical species, quite a lot of Indo-Malaysian/North Australian flora elements were encountered. A number of species are taxonomically discussed. As new to science are described: Euastrum siamense sp. nov., Cosmarium javanicum var. williamsonii var. nov. and Cosmarium siamense sp. nov.     

In search of monophyletic taxa in the family Desmidiaceae (Zygnematophyceae, Viridiplantae): the genus Cosmarium

Nuclear-encoded small subunit (SSU) rDNA, 1506 group I introns, and chloroplast rbcL genes were sequenced from 97 strains representing the largest desmid genus Cosmarium (45 spp.), its putative relatives Actinotaenium (5 spp.), Xanthidium (4 spp.), Euastrum (9 spp.), Staurodesmus (13 spp.), and other Desmidiaceae (Zygnematophyceae, Streptophyta) and used to assess phylogenetic relationships in the family. Analyses of single genes and of a concatenated data set (3260 nt) established 10 well-supported clades in the family with Cosmarium species distributed in six clades and one nonsupported assemblage. Most of the clades contained representatives of at least two genera highlighting the polyphyletic nature of the genera Cosmarium, Euastrum, Staurodesmus, and Actinotaenium. To enhance resolution between clades, we extended the data set by sequencing the slowly evolving chloroplast-encoded large subunit (LSU) rRNA gene from 40 taxa. Phylogenetic analyses of a concatenated data set (5509 nt) suggested a sister relationship between two clades that consisted mainly of Cosmarium species and included C. undulatum, the type species of the genus. We describe molecular signatures in the SSU rRNA for two clades and conclude that more studies involving new isolates, additional molecular markers, and reanalyses of morphological traits are necessary before the taxonomic revision of the genus Cosmarium can be attempted.     

SPECIES PHYLOGENY OF COSMARIUM AND STAURASTRUM (DESMIDIACEAE) BASED ON RBC L SEQUENCES

Cosmarium and Staurastrum are the two most diverse genera of placoderm desmids (Family Desmidiaceae), with approximately 1100 and 800 species, respectively. Phylogenetic analysis of relationships of species has been extremely difficult. In a monograph of North American placoderm desmids, Prescott et al. described early phylogenetic work that concluded Staurastrum to be polyphyletic and certainly polymorphic. Likewise, Cosmarium has also been viewed as polyphyletic, and a number of workers have proposed splitting these genera. The classical view of West and West grouped species within each genus into two divisions and 6–8 sections based on wall features and semicell shape. We sequenced rbc L from 18 species of Cosmarium (2 divisions, 7 sections) and 12 species of Staurastrum (2 divisions and 7 sections) and performed a phylogenetic analysis (parsimony, maximum likelihood, bootstrap) using other placoderm desmids and Zygnematales as outgroups. The results exhibit little support for the monophyly of sections or divisions of the two genera. Furthermore, although there is support for the monophyly of clades within each genus, there is also support for a separate clade containing species from both genera.     

The pH-related morphological variations of two acidophilic species of Desmidiales (Viridiplantae) isolated from a lowland peat bog,Czech Republic

Morphological variation related to pH was investigated in two acidophilic desmid species (Euastrum binale var. gutwinskii and Staurastrum hirsutum) utilizing geometric morphometric methods. Clones isolated from acidic habitats were cultured using a range of pH values from 3.5 to 6.5. The plasticity of ensuing populations was quantified and illustrated by the general Procrustes superimposition of landmarks placed along the outline of cells and subsequent statistical analyses of shape data. In both species, there was a significant effect of pH on the morphology of cells. In Staurastrum hirsutum, the pH-related morphological change was accompanied by a decrease in the size of cells cultured at a higher pH. However, in Euastrum binale, cell size did not differ in relation to pH, but cell shape was characterized by a deepening of the incisions between cell lobes at higher pH. In both species, cell complexity based on surface-to-volume ratio was positively correlated with increasing pH. We conclude that by manipulating their surface-to-volume ratios, these desmid species can respond to pH variations in their environment.     

Rare and new desmids (Desmidiaceae, Chlorophyta) from Japan

A number of rare or unknown desmid species were revealed in samples collected from a range of aquatic habitats in Japan. In the present paper we describe one new species of the family Desmidiaceae, Staurastrum tsukubicum sp. nov. and report the presence in Japan of two species, Staurastrum levanderi Grönbl. and Cos-marium dilatatum Lütkem. in Järnefelt et Grönblad, previously found only in Europe. One taxon, Euastrum englerii Schmidle var. madagascariense Bourr. et Manguin, is renamed as Euastrum biverrucosum nom. nov. et stat. nov. The morphology of these taxa was studied using light and scanning electron microscopy and their taxonomic affinities are discussed.     

New and interesting desmids (Zygnematales, Chlorophyceae) collected from Asia

Many desmid taxa were found in collections from Asia (Japan, Cambodia, Malaysia and Thailand). The following 21 new taxa and two new combinations belonging to five genera (Closterium, Euastrum, Cosmarium, Xanthidium and Staurastrum) and a rare species of Xanthidium, are reported. These include Closterium nasutum Nordstedt var. kazukoae Kanetsuna var. nov., Closterium nematodes Joshua var. nematodes f. kriegeri Kanetsuna f. nov., Euastrum binale (Turpin) Ehrenberg ex Ralfs var. protuberans Kanetsuna var. nov., Euastrum borgeanum Scott et Prescott var. cambodiense Kanetsuna var. nov., Euastrum dubium Nägeli var. protuberans Kanetsuna var. nov., Euastrum fissum W. et G. S. West var. yasukoae Kanetsuna var. nov., Euastrum gemmatum Brébisson var. tenuius Krieger f. porosum (Förster) Kanetsuna comb. nov., Euastrum pseudojenneri Scott et Prescott var. glabrum Kanetsuna var. nov., Cosmarium denticulatum Borge var. multispinum (Hirano) Kanetsuna comb. nov., Cosmarium furcatospermum W. et G. S. West var. fallax Kanetsuna var. nov., Cosmarium pileatum Borge var. cambodiense Kanetsuna var. nov., Cosmarium retusiforme (Wille) Gutwinski var. incrassatum Gutwinski f. retusum Kanetsuna f. nov., Cosmarium trapezoideum Kanetsuna sp. nov., Cosmarium zonatum Lundell var. zonatum f. majus Kanetsuna f. nov., Xanthidium cristatum Brébisson var. delpontei Roy et Bisset f. mizoroensis Kanetsuna f. nov., Xanthidium fasciculatum Ehrenberg ex Ralfs var. siamense Kanetsuna var. nov., Xanthidium pseudofreemanii Kanetsuna sp. nov., Xanthidium subtrilobum W. et G. S. West var. inornatum Skuja f. depressum Kanetsuna f. nov., Xanthidium subtrilobum W. et G. S. West var. inornatum Skuja f. singulare Kanetsuna f. nov., Staurastrum boergesenii Raciborski var. verrucosum Kanetsuna var. nov., Staurastrum dickiei Ralfs var. polypyrenoideum Kanetsuna var. nov., Staurastrum neglectum G. S. West var. fuseense Kanetsuna var. nov., Staurastrum trissacanthum Scott et Prescott var. dissacanthum Scott et Prescott f. longispinum Kanetsuna f. nov., and a rare interesting form, Xanthidium superbum Elfving var. centricornis Prowse.     

Seasonal periodicity of planktonic desmids in oligotrophic lake Grane Langsø, Denmark

60 desmids were identified from plankton samples collected during 20 years, bimonthly, or monthly in 5 of the years. Only 5 desmids were perennial, performing cell divisions in a frozen lake at PAR at only 5 cal cm ^–2 day ^–1, below ice-cover. The greatest number of desmids per 100 ml lake water was found in September; it never exceeded 150. Owing to a concentration of free CO₂ of only 0.02 mM l^–1 and a HCO _inf3 ^sup– concentration of 0.002 mM l^–1 the densities of desmid cells were often smaller than 1 cell per 100 ml lake water. A density of 1 cell per 1 ml was attained only by Staurastrum longipes, a desmid showing temporal variation. The relation of the compound phytoplankton quotient to two components of the CO₂-system is discussed. Three new taxa are described: Staurastrum brachiatum Ralfs var. bicorne n. var., Staurastrum thomassonii n.sp. and Xanthidium antilopaeum Kütz. f. bimaculatum n.f..     

A multilocus phylogeny of the desmid genus Micrasterias (Streptophyta): evidence for the accelerated rate of morphological evolution in protists

Micrasterias, the name of which is derived from the Greek for 'little star', comprises possibly the most spectacularly shaped desmids (Desmidiales, Streptophyta). Presently, the genus Micrasterias includes about 60 traditional species, the majority of which were described in the early 19th century. We used a comprehensive multigene dataset (including SSU rDNA, psaA, and coxIII loci) of 34 Micrasterias taxa to assess the relationships between individual morphological species. The resulting phylogeny was used to assess the patterns characterizing the morphological evolution of this genus. The phylogenetic analysis led to the recognition of eight well-resolved lineages that could be characterized by selected morphological features. Apart from the members of Micrasterias, three species belonged to different traditional desmid genera (Cosmarium, Staurodesmus, and Triploceras) and were inferred to be nested within the genus. Morphological comparisons of these species with their relatives revealed an accelerated rate of morphological evolution. Mapping morphological diversification of the genus on the phylogenetic tree revealed profound differences in the phylogenetic signal of selected phenotypic features. Whereas the branching pattern of the cells clearly correlated with the phylogeny, cell complexity possibly reflected rather their adaptive morphological responses to environmental conditions. Finally, ancestral reconstruction of distribution patterns indicated potential origin of the genus in North America, with additional speciation events occurring in the Indo-Malaysian region.     

Some New Taxa of Desmidiaceae from the Hengduan Mountains Region of China

Fifteen new taxa of the Desmidiaceae are described and illustrated from the Hengduan Mountains region of China. They are Euastrum gemmatum f. denticulatum, Cosmarium asphaerosporum var. subcapitum, C. dovrense var. fontanum, C. foveolatum, C. sichuanense, C. subdanicum var. granulatum, C. subsuperbum, C. tibeticum var. papilliferum, C. venustum var. arcuatum, C. yunnanense, Staurastrum elaticeps var. eximium, S. longiradiatum f. basispinulosum, S. pseudosebaldi var. compactum f.reductum, S. sebaldi var. ornatum f. spiniferum,S. sonthalium f. spiniferum.     

Some rare desmids (Zygnematophyceae) from Central Europe

The morphology and taxonomy of eight rare desmids (Zygnematophyceae) from Central Europe are studied, i.e. six taxa from Slovakia [Tortitaenia bahusiensis (Nordstedt et Lütkemüller) Coesel, Closterium limneticum Lemmermann var. fallax R??i?ka, Euastrum sublobatum de Brébisson in Ralfs, morpha, Cosmarium simplicius (W. et G.S. West) Grönblad, Pachyphorium canadense (Irénée-Marie) G. H. Tomaszewicz et Hindák, stat. et comb. nova, Staurastrum bloklandiae Coesel et Joosten], one species from Poland (Spirotaenia bacillaris Lütkemüller) and Austria (Cosmarium geminatum Lundell). All desmids taxa are new records for the country of their origin.     

Desmids (Chlorophyta,Zygnematophyceae) from the Girutiskis mire complex reserve (East Lithuania)

The desmid flora of the Girutiskis mire complex reserve in Lithuania, a Natura 2000 territory and a potential Ramsar site, was investigated for the first time. Despite being a relatively small area with homogenous ecological conditions and a narrow range of pH-values, some pattern in the distribution of desmid species was observed. The lowest number of species was observed in the highly acidic lakes that were surrounded by sub-shrub bogs, and the highest number in less acidic lakes that were surrounded by trembling bogs. A total of 78 desmid taxa were found of which 16 were first records for Lithuania. Almost half of the taxa were uniquely found at one site, and only 10% were classified as frequent. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

黑龙江扎龙国家级自然保护区鼓藻类植物中国新记录

于2011年5月(春季)、7月(夏季)和10月(秋季),先后3次对黑龙江扎龙国家级自然保护区进行鼓藻类植物调查,并对采集到的57份标本进行鉴定。结果发现,有6个分类单位为鼓藻类植物中国新记录,隶属于5个属,分别为:微小胶球鼓藻(Cosmocladium pusillum Hilse),中凹鼓藻(Cosmarium medioretusum Coesel),近前膨胀鼓藻锥形变种(Cosmarium subprotumidum var.pyramidale Coesel),双孢辐射鼓藻美国变种[Actinotaenium diplosporum var.americanum(West et West)Teiling],双臂角星鼓藻优美变种[Staurastrum bibrachiatum var.elegans(West et West)Prescott],冠毛多棘鼓藻钩状变种波兰变型(Xanthidium cristatumvar.uncinatumf.polonicumGutwingski)。     

INTERSPECIFIC HYBRIDITY IN THE DESMID GENUS PLEUROTAENIUM1

Three desmid taxa, isolated from different parts of Australia, conform to the morphological taxa Pleurotaenium ehrenbergii, P. mamillatum, and P. coronatum. Use of successful zygospore formation between cells of mixed populations as an indication of ability to share a common gene pool shows that all 3 taxa are at least closely related and probably are members of the same biological species. Tentatively, we suggest synonymy of these taxa and urge the adoption of sexual criterion in delimiting desmid species.     

Protoplasts of Cosmarium as a Potential Protein Source

Cosmarium turpinii, a fast-growing desmid alga, transforms into protoplasts in 4 h when incubated in a mineral medium + 0.4 M mannitol + 0.5% Cellulysin.     

Desmids of the Staurastrum tetracerum-group from a eutrophic lake in mid-wales

Seven desmids have been found in the phytoplankton of a markedly eutrophic lake in mid Wales. All have grown well in laboratory cultures and so an opportunity has been provided to explore the taxonomy and morphological variability of four species, Staurastrum tetracerum, S. irregulare, S. bibrachiatum and S. pseudotetracerum, previously described inadequately. Suggestions for nomenclatural changes are made for S. irregulare and the very variable S. bibrachiatum, which is recorded from the British Isles for the first time. Reasons for the occurrence of the seven desmid species in the eutrophic lake plankton are discussed.