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.     

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.     

The edibility of Staurastrum chaetoceras and Cosmarium abbreviatum (desmidiaceae) for Daphnia galeata/hyalina and the role of desmids in the aquatic food web

A laboratory clone of Daphnia galeata/hyalina was fed with two different planktic desmid taxa: Staurastrum chaetoceras and Cosmarium abbreviatum var. planctonicum, being about equal in cell size. Whereas Staurastrum chaetoceras was readily ingested and assimilated to a high degree, Cosmarium was hardly incorporated. This could be partly due to the presence of an extracellular mucilaginous envelope in the latter species. When decapsulated by mild sonification, Cosmarium cells were significantly better ingested but digestion was still inferior to that of Staurastrum, presumably because of the more compact cell shape of Cosmarium.From literature it appears that small-sized planktic desmid species occasionally may constitute a main food source for zooplankton, especially in eutrophic lakes. Most likely however, desmids, particularly large-sized species, play a much more important role in the food chain in the benthic compartment of shallow, oligotrophic water bodies where they serve as a food source for various macro-invertebrate taxa.     

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.     

CYTOCHALASIN B INFLUENCES DICTYOSOMAL VESICLE PRODUCTION AND MORPHOGENESIS IN THE DESMID EUASTRUM1

Cytochalasin B (CB) applied to young developing cells of the desmid Euastrum oblongum Ralfs ex Ralfs, at concentrations that do not entirely inhibit cytoplasmic streaming, retarded cell growth and caused malformations of cell shape. While the basic symmetry of the cell was maintained, only the first indentations were formed and the cell body appeared to be swollen. Electron microscopic investigations revealed that vesicle production at the dictyosomes was disturbed by cytochalasin. In contrast to untreated control cells, where vesicles with electron-dense contents (“dark vesicles”) were formed during primary wall formation, vesicles pinched off by the dictyosomes during CB treatment exhibited an “empty” appearance. These vesicles, which correspond to the “dark vesicles” in size, were accumulated around the dictyosomes without being transported to the plasma membrane and were frequently connected to the trans-cisternae of the Golgi bodies. We speculate that CB may influence the transfer of products from the endoplasmic reticulum (ER) to the dictyosomes via transition vesicles, which results in a disturbed vesicle production at the Golgi bodies. CB also causes a shift in ER and dictyosome distribution. Moreover, a cortical actin system appears to be involved in the cell shaping of Euastrum. The arrangement of microtubules around the nucleus is not affected by the drug.     

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..     

Distribution and seasonality of desmids in the Maarsseveen Lakes area

The desmid flora of mesotrophic Lake Maarsseveen I, eutrophic Lake Maarsseveen II, as well as the interconnecting broads was studied during the period 1987–1991. Seasonal perodicity of euplanktonicStaurastrum andCosmarium species in the two Maarsseveen lakes fitted the well-known general pattern of desmid abundance peaks in (late) summer time. The deviating seasonality of two euplanktonicClosterium species (C. aciculare andC. acutum var.variabile) could be related to special nutritional demands. The tychoplanktonic desmid flora encountered in the interconnecting system of peat pits and canals proved to be more diversified as the influence of nutrient-poor seepage on the habitat (appearing from conductivity, transparency and the occurrence of particular macrophyte species) was greater. The rare speciesEuastrum germanicum andHeimansia pusilla had been only incidentally recorded in The Netherlands. Hanny Kooyman-van Blokland untimely died at the age of forty, in March 1994.     

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.     

Negative Effects of P-Buffering and pH on Photosynthetic Activity of Planktonic Desmid Species

The photosynthetic activities of three planktonic desmid species (Staurastrum brachiatum, Staurodesmus cuspidatus var. curvatus, and Staurastrum chaetoceras) were compared after adaptation to medium enriched with either a 20 mM Na⁺-phosphate (P) or HEPES buffer. Incubations up to 2 d were carried out at pH 6 or 8 under normal air or air enriched with 5 % CO₂. Gross maximum photosynthetic rate (P _max) and growth rate were decreased in both S. brachiatum and Std. cuspidatus at higher pH when using the HEPES buffer and this effect was independent of CO₂ concentration, indicating that pH had an inhibitory effect on photosynthesis and growth in these species. The P-buffer at pH 8 caused a large decrease in P _max and quantum yield for charge separation in photosystem 2 (PS2), compared to HEPES-buffered algae. This effect was very large in both S. brachiatum and Std. cuspidatus, two species characteristic of soft water lakes, but also significant in S. chaetoceras, a species dominant in eutrophic, hard water lakes. The decreased P _max in P-buffer could not be related to a significant increase in cellular P content known to be responsible for inhibition in isolated chloroplasts. Experiments at pH 6 and 8 showed that two conditions, high pH and high Na⁺ concentration, both contributed to the decreased P _max and quantum yield in the desmids. Effects of a P-buffer were less pronounced by using K⁺-P buffer. The use of P-buffer at pH 8 possibly resulted in high irradiance stress in all species, indicated by damage in the PS2 core complex. In the soft water species pH 8 resulted in increased non-photochemical quenching together with a high de-epoxidation state of the xanthophyll cycle pigments.     

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.     

Wisconsin desmids. III. Desmid community composition and distribution in relation to lake type and water chemistry

This investigation summarizes quantitative data on the generic composition of the euplankton and aufwuchs desmid communities of 61 Wisconsin lakes, and analyzes the information with respect to 1) the role of the various genera in terms of frequency, density, and relative importance, 2) the suitability of various lake types for harboring desmid communities, and 3) the relationships between chemical parameters and desmid distribution. The generaStaurastrum, Cosmarium, andClosterium are of wide occurrence, appear to play major roles in the communities of all lake types, and are the most tolerant of varying chemical conditions. Most euplankton genera are of importance only in acid bogs, but aufwuchs genera generally are more widely distributed. Both the euplankton and the aufwuchs communities appear to be composed of 1–4 desmid assemblages, each with a differing range of importance values. Based on biological criteria, acid bogs appear to be the most suitable lake type for harboring desmid communities and calcareous spring ponds the least suitable type. High generic diversity of desmids appears to be correlated with low conductivity, calcium and alkalinity levels, pH values of 5.1–7.0, and the presence of free CO₂. The evidence attending various hypotheses concerning water chemistry and desmid distribution appears contradictory, and further studies are needed to help clarify the situation.     

Desmidiacee della torbiera del Vedes (Trento)

Abstract

Desmids of the peat-bog of Vedes (Trento, North-Italy). A list of 27 Desmids s.l. (Desmidiaceae, Closteriaceae and Mesotaeniaceae) observed in some samples coming from the peat-bog of Vedes (Trento, North-Italy) is reported. This is a high moor bog situated at an altitude of 1496 m and rich in Sphagnum species (Sphagnum medium, S. fuscum, S. robustum, S. laricinum, etc.). The most interesting Desmids found are: Actinotaenium cucurbita, A. crassiusculum, Bambusina brebissonii, Penium polymorphum, Tetmemorus brebissonii, T. laevis, Closterium intermedium, Cosmarium amoenum, Euastrum insigne, Netrium digitus and Staurastrum erostellum, the last one being a very rare species found for the first time in Italy; thirteen entities are new for the algal flora of Trentino-Alto Adige.     

Diversity and ecology of desmids of peat bogs in the Jizerské hory Mts

The present study focuses on diversity and ecological preferences of desmids in peat bogs in the Jizerské hory Mts (Czech Republic). Altogether 76 desmid algae taxa have been recorded at 18 sites of the study area during our investigation in 2003–2006. Taxa Actinotaenium crassiusculum (De Bary) Teiling, Hyalotheca dissiliens var. tatrica Racib., Staurastrum avicula var. subarcuatum (Wolle) West & G. S. West, S. borgeanum Schmidle, S. simonyi var. semicirculare Coesel, Staurodesmus extensus var. isthmosus (Heimerl) Coesel, S. extensus var. vulgaris (Eichler & Racib.) Croasdale and S. spencerianus (Mask.) Teiling are new for the Czech Republic. In addition, several rare and remarkable taxa were also encountered. The species richness was relatively high in comparison to similar localities in the Czech Republic. Desmid distribution was influenced by pH and conductivity. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

New and interesting desmids (Zygnematales, Chlorophyceae) collected from Brazil and Argentina

The morphology and taxonomy of nine desmid taxa belonging to the three genera Closterium, Euastrum and Cosmarium are studied based on freshwater algal collections from Brazil and Argentina. They represent five new varieties (Closterium cynthia De Notaris var. minutum Kanetsuna var. nov., Euastrum attenuatum Wolle var. saitoi Kanetsuna var. nov., Cosmarium laticollum Delponte var. minutum Kanetsuna var. nov., Cosmarium pseudovariolatum Grönblad var. major Kanetsuna var. nov. and Cosmarium taxichondrum Lundell var. yamagishii Kanetsuna var. nov.), two new forms (Euastrum hypochondrum Nordstedt var. hypochondrum f. divergens Kanetsuna f. nov. and Euastrum insulare (Wittrock) Roy var. silesiacum (Gronblad) Krieger f. brasiliense Kanetsuna f. nov.) and one new status (Cosmarium pseudovariolatum Gronblad var. incrassatum (Scott et Gronblad) Kanetsuna f. elonga‐tum (Scott et Gronblad) Kanetsuna stat. nov.). In addition, a new combination (Cosmarium pseudovariolatum Gronblad var. incrassatum (Scott et Gronblad) Kanetsuna comb, nov.) is proposed.     

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.     

Diversity of desmids in three Thai peat swamps

Three peat swamps situated in the southern part of Thailand were investigated for their desmid flora in relation to a number of physical and chemical habitat parameters. Altogether, 99 species were encountered belonging to 22 genera. 30 species are new records for the Thai desmid flora. Laempagarung peat swamp showed the highest diversity (45 species), followed by Maikhao peat swamp (32 species) and Jud peat swamp (25 species). Despite its relatively low species richness, Jud swamp appeared to house a number of rare taxa, e.g., Micrasterias subdenticulata var. ornata, M. suboblonga var. tecta and M. tetraptera var. siamensis which can be considered Indo-Malaysian endemics. Differences in composition of the desmid flora between the three peat swamps are discussed in relation to environmental conditions. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Desmids in mountain lakes of the subpolar Urals

The species composition of desmids was studied in eight mountain lakes of the Kozhim and Malyi Patok River basins in the “Yugyd Va” National Park (subpolar Urals, Russia). A total of 98 desmid taxa representing 13 genera belonging to 4 families were identified. Geographical and ecological analyses showed that the desmid flora is typical, with a predominance of cosmopolitan species, planktic-benthic forms, acidophilic and pH indifferent species, and halophobic to salinity indifferent species. The investigated lakes can be classified as pristine and in good ecological condition on the basis of their hydrochemical and algal biodiversity characteristics. Presented at the International Symposium Biology and Taxonomy of Green Algae V, Smolenice, June 26–29, 2007, Slovakia.     

Confocal pH Topography in Plant Cells — Acidic Layers in the Peripheral Cytoplasm and the Apoplast

The distribution of intracellular pH was studied in cultured cells of Gossypium hirsutum by con-focal pH topography using the fluorescent probe car-boxy SNARF1 and a ratio imaging procedure. The resulting pH maps can visualize pH differences with an accuracy of 0.1 unit in the investigated range between 7.5 and 5.6. They reveal the following characteristic features of the Gossypium cells: – the pH of the cytoplasmic core regions ranges from near 7.4 in younger to near 6.0 in older cells; – vacuoles show the expected acidity with pH < 5.6; – the cell wall/apoplastic region is acidic with a pH near 5.6 or below, especially in young, growing cells; – interestingly, acidic areas appear also at the periphery of the cytoplasm, i.e. beneath the plasma membrane. They remain stable in the presence of 5/μmol/I of the protonophore CCCP. Acidic layers of peripheral cytoplasm were also detected in protoplasts of Penicillium cyclopium, i.e. eukaryotic cells of simpler structure, which served as a reference object. This ronfirms earlier findings obtained with classical fluorescence microscopy and another fluoroprobe (fluorescein diacetate). Though additional experimental support is needed, low pH regions at the cytoplasm/plasma membrane interface should be considered a real contribution to the pH control of plant and fungal cells, facilitating e.g. the maintenance of cytosolic pH in acidic environments.     

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.     

SIMILARITIES IN THE ASEXUAL REPRODUCTION OF THE OCEANIC DINOFLAGELLATES, PYROCYSTIS FUSIFORMIS, PYROCYSTIS LUNULA, AND PYROCYSTIS NOCTILUCA1

Three cultured species of Pyrocystis (Dinoccoccales) reproduced asexually by forming 2 (or 1) aplanospores or zoospores inside the parent cell wall. In all 3 species these small reproductive cells, although they may not resemble the parent cells, swell up rapidly (～ 10 min) to the approximate size and shape of the parent cell. These swollen cells become new vegetative cells. The above asexual process is the only way by which cells numbers increase in our cultures. Pyrocystis lunula was propagated at the lunula stage of the life cycle. The nonmotile crescent-shaped cells produced reproductive cells that were Gymnodinium-shaped and had, in some cases, a trailing flagellum. With P. fusiformis and P. noctiluca, the reproductive cells were not flagellated. With P. fusiformis, these bodies had a pronounced equatorial constriction like a girdle, while in P. noctiluca the “girdle” was an inconspicuous feature if present. With P. noctiluca and P. fusiformis on a 12:12 ld cycle, reproductive cells were formed early in the dark period and they swelled up at the beginning of the light period. Reproduction of P. lunula was not well phased in our experiments, with reproductive cells developing at the end of the light period and the end of the dark period.