Phycologia

Published by International Phycological Society
Online ISSN: 0031-8884
Publications
Article
Hemichloris antarctica gen. et sp. nov. (Oocystaceae, Chlorococcales) is characterized by a single, articulated, pyrenoid-less, thick saucer-shaped chloroplast, which generally fills less than half of the cell periphery. Multiplication is only by autospores. The species is psychrophilic and is damaged at temperatures above 20 degree C. Hemichloris antarctica is a member of the cryptoendolithic microbial community living in porous sandstone rocks of the Antarctica cold desert. It inhabits the zone below that of cryptoendolithic lichens and survives at extremely low light intensities. In the natural habitat, morphology is somewhat different from that in culture, as chloroplasts are smaller and without articulation, and the cells develop a gelatinous sheath.
 
Percentage of collected individuals that were sexual (solid bars), asexual [stippled (dark grey) bars], or of undetermined life history either because spores did not germinate (hatched bars), or none were released (open bars) during eight periods in 1 year. Data were based on the results of carpospore cultures from Piedras Blancas (a), Cayucos (b), or Shell Beach (c). Sample sizes at each site and time are indicated.
Article
Species of the genus Mastocarpus exhibit two distinct life cycles, a sexual alternation of generations and an obligate, asexual direct life cycle that produces only female upright fronds. In the intertidal red alga, M. papillatus (Kützing) sexual fronds dominate southern populations and asexual fronds dominate northern populations along the northeast Pacific coast, a pattern of spatial separation called geographic parthenogenesis. Along the central coast of California, sexual and asexual variants occur in mixed populations, but it is not known whether they are spatially separated within the intertidal zone at a given site. We investigated reproductive phenologies and analyzed patterns of spatial distributions of sexual and asexual M. papillatus at three sites in this region. Sexual M. papillatus were aggregated lower on the shore at two sites and only reproduced during part of a year, while asexual M. papillatus occurred throughout the intertidal range at all sites and reproduced throughout the year. The distribution patterns of sexual and asexual M. papillatus are consistent with a hypothesis of shoreline topography influencing their dynamics of dispersal and colonization. Spatial and temporal partitioning may contribute to the long-term coexistence of sexual and asexual life histories in this, and other, species of Mastocarpus. The occurrence of geographic parthenogenesis at multiple spatial scales in M. papillatus provides an opportunity to gain insight into the phenomenon.
 
Article
Young and old cultures (up to 66 months) of two Chroococcidiopsis sp. strains isolated from the Negev desert, Israel, were examined by epifluorescence and electron microscopy. In old cultures, cell viability and autofluorescence were lower than in young cultures. An increase was seen with age in the polysaccharide content of the sheaths of nanocytes and nanocyte mother cells, and a decrease of phycobiliproteins was also seen. In the oldest cultures most of the cells were dead and in various stages of degeneration. Single living cells were scattered among the dead ones. No resting cells were formed in the oldest cultures, but many cell groups showed highly electron-dense sheaths and, in the cytoplasm, ribosomes and glycogen. These changes in cell structure may have a role in preventing water loss from the cell.
 
Article
Electronic cell sorting for isolation and culture of dinoflagellates and other marine eukaryotic phytoplankton was compared to the traditional method of manually picking cells using a micropipette. Trauma to electronically sorted cells was not a limiting factor, as fragile dinoflagellates, such as Karenia brevis (Dinophyceae), survived electronic cell sorting to yield viable cells. The rate of successful isolation of large-scale (> 4 litres) cultures was higher for manual picking than for electronic cell sorting (2% vs 0.5%, respectively). However, manual picking of cells is more labor intensive and time consuming. Most manually isolated cells required repicking, as the cultures were determined not to be unialgal after a single round of isolation; whereas, no cultures obtained in this study from electronic single-cell sorting required resorting. A broad flow cytometric gating logic was employed to enhance species diversity. The percentages of unique genotypes produced by manual picking or electronic cell sorting were similar (57% vs 54%, respectively), and each approach produced a variety of dinoflagellate or raphidophyte genera. Alternatively, a highly restrictive gating logic was successfully used to target K. brevis from a natural bloom sample. Direct electronic single-cell sorting was more successful than utilizing a pre-enrichment sort followed by electronic single-cell sorting. The appropriate recovery medium may enhance the rate of successful isolations. Seventy percent of isolated cells were recovered in a new medium (RE) reported here, which was optimized for axenic dinoflagellate cultures. The greatest limiting factor to the throughput of electronic cell sorting is the need for manual postsort culture maintenance and assessment of the large number of isolated cells. However, when combined with newly developed automated methods for growth screening, electronic single-cell sorting has the potential to accelerate the discovery of new algal strains.
 
Article
Prochloron is a genus of prokaryotic algae with photosynthetic pigments like those of chlorophytes. Prochlorophytes are almost invariably found associated as symbionts with marine protochordates (didemnid ascidians), and so far none has been successfully grown in sustained culture away from in host. Based on materials collected from nature, information of various sorts (biochemical, physiological, cytological and fine-structural) has been obtained, indicating many resemblances (and probably close phylogenetic affinities) between prochlorophytes and cyanophytes. Nevertheless they are distinguished by certain unique combinations of characters. Some of the data support the symbiogenesis theory for the origin of green-plant chloroplasts. Other possibilities are briefly discussed.
 
Article
The chemical analysis of lipids of Prochloron isolated from several hosts is discussed. The object was to determine whether differences in lipid composition could be used to characterize organisms from different sources. Major lipid components are given. An analysis of fatty acid composition of individual lipids slowed a distinctive disstribution of fatty acids. While present results do not justify the use of fatty acid content in the taxonomy of Prochlon, the variations found in the lipids of cells from the same host harvested from different areas, or at different times in the same area, suggest that a study of the effects of temperature and light intensity on lipid composition would be rewarding.
 
Article
The discovery of both chlorophyll a and b in the prokaryote Prochloron Lewin, a trait otherwise unique to eukaryotic photosynthetic organisms, has stimulated speculation on the possible endosymbiont origins of the plastids of eukaryotic cells. The arrangement of DNA in Prochloron was therefore dyed in situ with the fluorochrome dye DAPI and compared with the plastid DNA of various eukaryote cells. The DNA of Prochloron is found to be clearly different in arrangement and locale from that of blue-green algae. In the great size of its nucleoids and their apparently high DNA content, Prochloron also differs from the plastids of any eukaryotes, with the possible exception of dinoflagellates. Prochloron remains an evolutionary puzzle.
 
Article
Frequencies of cell division stages in suspensions of Prochloron cells, expressed at regular intervals throughout a natural day-night cycle from several colonies of four species of host didemnid, are given. The proportion of dividing cells of Prochloron living symbiotically in colonies of a didemnid, Diplosoma virens, rises from about 4% during the night (20.00-04.00 hrs.) to about 13% in the morning (0,.00-12.00 hrs.), and then falls again in the afternoon. Similiar, though less pronounced, changes were observed among Prochloron cells in two other symbiotic didemnids, Lissoclinum patella and L. voeltzkowi.
 
Chapter
IntroductionWhat is meant by algae?Experiences of indices and indicatorsPhytoplankton and the seasonal developmentThe reaction of planktic algae to environmental changesPhytoplankton characteristics and lake typesWater-blooming and toxin-producing cyanobacteriaConclusions
 
Chapter
The study of algae is generally called ‘phycology’, from the Greek word phykos meaning ‘seaweed’. Just what algae are is difficult to define, because they belong to many different and unrelated classes including both prokaryotic and eukaryotic representatives. Broadly speaking, the algae comprise all, mainly aquatic, plants that can use light energy to fix carbon dioxide and evolve oxygen, but which are not specialized land plants like mosses, ferns, coniferous trees and flowering plants. This is a negative definition, but it serves its purpose.
 
Article
Fertile and sterile specimens of the alga Chara aspera Detharding ex Willdenow (Charophyta) were collected during the period of sexual reproduction (July 1990) in an estuarine, brackish-water lake ('Darsser Bodden', salinity 8.6-8.8 parts per thousand). Turgor pressure of fertile males was 377 mosmol kg-1 and of sterile plants 304 mosmol kg-1. In the vacuolar sap of fertile and sterile plants about 30% of the osmotic pressure was due to sucrose: fertile males, 184 mol m-3; fertile females, 171 mol m-3; sterile plants, 126 mol m-3. When subjected to changing salinities C. aspera regulated turgor pressure perfectly between 8 and 0.5 parts per thousand. In higher salinities (8-18 parts per thousand) turgor was restored only incompletely. Both sucrose and ionic solutes participated in the regulation process. The pattern of ionic responses during regulation conformed to the charophyte 'brackish-water' type. This is based on shifts in the concentrations of Cl-, K+ and Na+ as previously reported in Chara canescens Desvaux et Loiseleur in Loiseleur-Deslongchamps. The role of sucrose in osmotic responses of fertile and sterile plants is discussed.
 
Article
The red alga Grateloupia doryphora (Montagne) Howe was grown in axenic culture in Provasoli's enriched seawater medium supplemented with glycerol as an organic carbon source. Carpospore seedlings showed a particular form of cell proliferation forming compact cell masses with many buds or protrusions after 12 days of growth. Histologic and histochemical techniques and studies at the electron microscope level revealed: (1) a short-term effect in which cell division was activated within 2 h in the internal cell layer of the carpospore seedling, and (2) buds derived from internal cell proliferation on the periphery. Glycerol was used to biosynthesize polymers needed for cell elongation and division as evidenced by starch accumulation and endomembrane system activity. When morphogenesis was completed, the regeneration capability remained with the internal cells that maintained their cell structure, including chloroplasts, and accumulated compounds in large vacuoles. These cells recommenced growth if c...
 
Article
Heydrichia woelkerlingii gen. et sp. nov., a new non-geniculate coralline alga from South Africa, has some affinity with Sporoltihon. Heydrichia and Sporolithon have many vegetative characters in common, but Heydrichia differs in its reproductive characters: cruciately divided tetrasporangia subtended by one or more stalk cells, and housed in sporangial complexes which are themselves within sori; dendroid spermatangial branches restricted to the floor of the gametangial conceptacles; carpogonial branches consisting of a single carpogonium on a support cell; lack of a fusion cell and carposporangia are formed across the floor of the cystocarp. The new taxon shows tetrasporangial and post-fertilization characters not described previously in the Corallinales. In order to accommodate both Heydrichia and Sporolithon within the Corallinales, we propose an emendation of the order to include all genera of red algae with calcite walls and sporangial sori. Heydrichia is an ecologically important member of the algal flora of Cape Province, South Africa, and is endophytized by many organisms including a marine ascomycete.
 
Location of the sampling stations and main surface currents in the study area. 
Examples of RAPD profiles for five individuals of each population for the OPB-17 primer. Three individuals were removed from the analysis according to the nonrepeatability of the signal: G6, G9 and J6. B, Bagaud; G, Gabini `re; J, St Jean - CF; M, Lavezzi; B1, positive control. 
Number of monomorphic (m) and polymorphic (p) sites detected within each population for each primer.
Bar plots obtained from STRUCTURE analysis for K values (number of clusters) fixed from 2 to 5. The genome of each individual is represented by a single bar. Shadings or symbols filling each bar represent the proportion of individual genome assigned by the software to one of the K clusters. The initial geographic partition of the individuals is reported above the bars (B, Bagaud; G, Gabini `re; J, St Jean - CF; M, Lavezzi). 
Article
Cystoseira amentacea var. stricta is an endemic key species in the coastal ecosystem of the northern Mediterranean basin. Because it has suffered significant population declines, it has been designated a protected species. Nothing is known about the Population genetics of Cystoseira spp. Because zygote dispersal is low among the Fucales, low genetic diversity within populations and strong differentiation among Populations were predicted. To evaluate genetic variation within and among C amentacea var. strictu populations, 54 individuals from four Populations were compared using random amplified polymorphic DNA (RAPD) markers. Data were analyzed using analysis of molecular variance (AMOVA) and Bayesian clustering of individuals into populations based on their genotypes (STRUCTURE 2.1 software). Results indicated that genetic variation is high, with most of it distributed within populations (70.93%), and with some genetic mixing among adjacent populations, a result of longer range dispersal. The Lavezzi population (Corsica) is distinct from the other three populations, suggesting isolation by distance. Although more intensive sampling is required, these preliminary results have important implications for conservation policy.
 
Article
Abstract: Digital in-line holographic (DIH) microscopy was used to track motility in several related species of the marine dinoflagellate Alexandrium in response to temperature after acclimation at selected temperatures. Numerical reconstruction of DIH holograms yielded high-contrast three-dimensional images of the trajectories of many motile cells swimming simultaneously throughout the sample volume. Swimming speed and trajectory were determined for clonal isolates of A. ostenfeldii, A. minutum and A. tamarense within the temperature range from 8 to 24°C. The strains of these species revealed differences in temperature optima for growth and tolerance that were a function of both acclimation responses and genetic factors reflecting the origin of the isolates. The fastest swimming speeds were recorded at 24°C for cells of A. minutum. Acclimated strains of all three species swam significantly slower at lower temperatures, although fastest swimming speeds did not always occur at temperature optima for growth. Aged cells from stationary phase cultures swam more slowly than cells in exponential growth phase. Doublets from a rapidly dividing culture swam faster than singlets from the same culture, confirming the propulsive advantage of paired cells. Holographic microscopy is a powerful tool for the acquisition of detailed observations of swimming behaviour of microalgal cells in the form of three-dimensional trajectories over the appropriate temporal (sub-second) and spatial (micrometer) scales. no NOT AVAILABLE THROUGH VL; AVAILABLE IN PRINT
 
Factorial ANOVAs for the effects of herbivore exclusion and sampling period (season) on length of Padina boergesenii. 1 
Factorial ANOVAs for the effects of herbivore exclusion and sampling period (season) on width of Padina boergesenii. 1 
Article
Many coral reef benthic algae exhibit morphological plasticity enabling them to persist in diverse habitats under different environmental pressures. Morphological plasticity has been previously observed in the brown alga Padina jamaicensis, which displays a foliose morphology under low grazing pressure and a turf morphology in habitats with medium to high herbivory levels. To determine whether a different species of Padina, P. boergesenii, exhibits morphological plasticity regulated by herbivory, we excluded macroherbivores from experimental plots containing P. boergesenii thalli on a rocky reef off Santa Marta in the Colombian Caribbean. The experiment used exclusion cages to test for effects of herbivores and was carried out in two contrasting oceanographic seasons: upwelling (low water temperature and high water transparency) and rainy (higher temperature and low water transparency). The morphology of P. boergesenii was significantly affected by herbivory but only during the upwelling season. Padina boergesenii rapidly changed from a turf morphology to a fan-shaped form and increased in size when protected from herbivores in full cages in a period of less than a week. Thalli exposed to macroherbivores in open plots did not shift to a foliose morphology, and neither did thalli investigated during the rainy season, independent of herbivore treatment. Our results show that herbivory plays an important role in controlling the morphology and may affect life history processes of the alga P. boergesenii but suggest that plant response to herbivory may be a seasonal process. This suggests that there are important climatic (e.g. trade winds inducing upwelling) and oceanographic factors (e.g. water temperature) limiting algal abundance and that these factors may mediate morphological plasticity of algae. Therefore, reductions of grazing are not enough to promote morphological plasticity during the rainy season.
 
Article
The red alga Lenormandia prolifera (C. AG.) J. AG. (Rhodomelaceae: Amansia group) contains the red pigment floridorubin in addition to R-phycoerythrin. The pigments of species of the Amansia group previously reported as containing only floridorubin should thus be reinvestigated. Since two other genera of the Amansia group contain floridorubin, the pigments of the remaining members should be examined.
 
Article
Nine species of unicellular marine algae were cultured in a synthetic medium in which the sulfate concentration was varied. Final growth in response to sulfate concentration was determined for each species. Sulfate concentrations in the range of 1/100 to 1/200 of that found in natural sea water were sufficient to satisfy the sulfur requirements of seven of the species. Two of the species had somewhat higher requirements, perhaps attributable to additional demands for the accumulation of extracellular sulfated polysaccharides. In the range of limiting concentrations, final growth was proportional to sulfate concentration in most instances. Rapid bleaching of the cells occurred after the sulfate in the medium had become exhausted. A sulfate concentration of 0.2–0.4 g/l, employed in experiments with radioactive sulfur, allowed a high level of incorporation of radioactivity into the algal cells.
 
Article
The distribution and frequency of shell-boring green and blue-green algae in the intertidal at Goa, India were studied. The green alga Gomontia sp. and the blue green algae Hyella caespitosa Bornet et Flahault, H. gigas Lucas et Golubic, Mastigocoleus testarum Lagerheim, Pletonema terebrans Bornet et Flahault, and Phormidium sp. were found in the shells of Placuna placenta, Crassostrea cucullata, Perna viridis and Turritella turritella, Plectonema terebrans occurred most frequently in all shells, and Phormidium sp. occurred least frequently. The presence of chlorophyll b in green algae and its absence in the blue-green algae were used to estimate the contribution of these two groups of algae in shells. Using the ratio of chlorophyll, dry weight and particulate organic carbon (POC) values in cultures of the green alga Gomontia sp. and the blue-green alga Plectonema terebrans, in biomass and POC contribution of these two types of microalgae in shells were calculated.
 
Article
The tribe Amansieae, including the genus Lenormandia, is characterized by the presence of the pigment floridorubin. Two species of Lenormandia do not contain floridorubin and their morphological characteristics are distinct. L. coronata Lindauer et Setchell is transferred to the Chondrieae as Cladhymenia coronata (Lindauer et Setchell) Saenger. L. allanii Lindauer shows an affinity to both Sonderella linearis (Harvey) Schmitz and the Sarcomenieae, and is transferred to the new genus Lembergia, as Lembergia allanii (Lindauer) Saenger.
 
Article
Epulo multipedes gen. et sp. nov. is described for a coralline red alga growing parasitically on Jania collected from eastern Australia. Epulo is a monospecific genus with vegetative filaments that invade host cells and totally disrupt them, a phenomenon not seen before in the Corallinaceae. The new genus comprises two phases: an unconsolidated vegetative portion that is endophytic within the host tissue, and reproductive conceptacles formed at the surface of the host. Vegetative cells are uninucleate and form haustoria within host cells. Reproductive conceptacles are formed when outgrowths of the parasite consolidate at the surface. Tetrasporangial conceptacles are multiporate, with zonate tetrasporangia. Sexual conceptacles are uniporate. Epulo is included in the tribe Austrolithoideae and has affinities with Austrolithon, but differs in being parasitic, having uninucleate rather than multinucleate cells, and having conceptacles formed externally on the host.
 
Article
Sinkoraena gen. nov. is proposed for the Japanese and Korean species currently known as Grateloupia okamurae Yamada and the southeastern Australian G. tasmanica Womersley et Lewis. Characters distinguishing the new genus from Grateloupia are the cartilaginous texture, densely proliferous frond faces and margins, thick cortex, predominantly stellate inner cortical cells, reproductive structures (carpogonial and auxiliary-cell ampullae, cystocarps, spermatangia, and tetrasporangia) borne primarily in lateral proliferations, and bushy auxiliary-cell ampullae similar to those of the genus Polyopes. Polyopes, the probable closest relative, differs from Sinkoraena in lacking stellate inner cortical cells and proliferous frond surfaces, and in forming tetrasporangia in nemathecial sori. Sinkoraena okamurae (Yamada) comb. nov. is distinguished from S. tasmanica (Womersley et Lewis) comb. nov. by its wider frond (to 40 mm vs 8 mm) and confinement of its cystocarps and spermatangia to lateral proliferations, as opposed to non-thickened regions of both proliferations and upper main axes.
 
Article
The Solieriaceae, has the largest number of genera (16-18) of any family in the carrageenophyte order Gigartinales. One of these genera, Meristotheca, consists of three or four species of foliose, erect to prostrate plants sporadically recorded from the tropics of both hemispheres. The hot-water-soluble polysaccharides from Australian representatives of the type species, M. papulosa, and M. procumbens from Lord Howe Island have been characterized by compositional assays, linkage analysis, and Fourier transform infrared and C-13-nuclear magnetic resonance spectroscopy. The results show that polysaccharides from both species are similar, being predominantly composed of 4-linked 3,6-anhydro-alpha-D-galactopyranose 2-sulphate alternating with 3-linked beta-D-galactopyranose 4-sulphate, as is typical of iota-carrageenan. Small proportions of the 3-linked units occur as the pyruvated residue 4,6-O-(1-carboxyethylidene)-beta-D-galactopyranose, and other minor variations from idealized iota-carrageenan were also detected. The polysaccharides from representatives of Meristotheca are comparable to those of other solieriacean algae analysed to date, but the minor structural variations suggest a closer chemotaxonomic affinity with noneucheumoid genera of the Solieriaceae, such as Sarconema, Solieria, and Tikvahiella, than to the eucheumoid genera Eucheuma, Kappaphycus and Betaphycus (tribe Eucheumatoideae) from which most kappa- and iota-carrageenans are commercially extracted.
 
Article
Phycologia, vol. 34, nr. 2, 135-144 Scrippsiella hangoei (Schiller) comb. nov. is one of the most abundant species during the winter-season in the northern Baltic Sea. It has formed blooms under the ice on several occasions with cell concentrations reaching 24 x 10 61-1. The species is described by light and scanning electron microscopy and shown to be identifcal to Peridinium gracile Lindemann 1924. nom. illeg. The plate formula is pp. vap or X,4',3(4)a,7",6c,7s,5". Op, 2"". In the northern Baltic it forms organic cysts, and an extension of the generic boundary of Scrippsiella is discussed, to include species with non-calcareous cysts.
 
Article
Typescript. Thesis (M.S.)--University of Rhode Island, 1984. Includes bibliographical references (leaves 52-63).
 
Article
Species- and genus-level taxonomy of desmids depends largely on shape and detail of the cell wall and chloroplast morphology. The depth of most desmid semicells, relative to the focal depth of conventional light microscopes, means that morphological characteristics are usually illustrated by drawings, made from material that is mounted in water to allow reorientation of specimens to different aspects of shape and pattern. Though a productive approach for two centuries, this has the disadvantages that features not initially detected or thought irrelevant are not recorded, drawing quality is variable, and individual specimens are rarely retained for further study. We describe methods for making permanent preparations of desmid cell walls and using these to produce extended depth of focus summary images and three-dimensional (3-D) reconstructions. Together with World-Wide Web dissemination of image stacks, these advances make it practical to make a desirable change from typification via drawings to typification via single or multiple preserved specimens. They will also facilitate standardization of taxon concepts and identification.
 
Article
A simple method has been developed for better quantification of the dimethylsulphoniopropionate (DMSP) content in macroalgae as examplified in Acrosiphonia arcta (Dillwyn) J. Agardh, Desmarestia anceps Montagne, Enteromorpha bulbosa (Suhr) Montagne, Gigartina skottsbergii Bory, Halopitys incurvus (Hudson) Batters, Himantothallus grandifolius (A. et E.S. Gepp) Zinova, Iridaea cordata (Turner) Bory, Palmaria decipiens (Reinsch) Ricker, Polysiphonia urceolata (Lightfoot) Greville, Polysiphonia pacifica Hollenberg, Polysiphonia paniculata Montagne, and Ulva lactuca Linnaeus collected from different geographic regions. Four different methods for pretreatment of the algal samples were tested to improve breaking up cells and tissue. Oven-drying prior to preparation for gas-chromatographic analysis gave up to 682-fold higher DMSP concentrations compared to fresh material - the standard method. This points to an underestimation of many DMSP values published previously. Only Polysiphonia paniculata exhibited higher DMSP concentrations after analysis of fresh material.
 
Article
A new phototrophic species of freshwater dinoflagellates, Peridinium euryceps sp. nov., is described from Lake Erken, Sweden. It is a large and extremely flattened dinoflagellate with a characteristic shape and a tabulation that differs from known species of the same genus. Peridinium euryceps appears during winter underneath the ice, encysts at ice melt, and then remains dormant as cysts during summer. This new species has morphological and ecological similarities with Peridinium baicalense, a species endemic to Lake Baikal, Russia. The autoecology of P. euryceps is discussed, as well as the ecology of cryophilic and cold-stenothermic dinoflagellates in general. It is argued that these species have special adaptations for survival underneath the ice, such as a flattened shape and mixotrophic feeding.
 
Article
In enriched sea-water cultures inoculated with a mixture of algae and other organisms, concentrations of GeO2 above 1.5 mg/l specifically suppressed the growth of diatoms. In experiments with 14 pure cultures of diatoms (10 species), 1 mg GeO2/l sufficed to reduce the growth rates significantly; 10 mg GeO2/l was even more inhibitory to growth, and in a few cases killed the cells. Phaeodactylum tricornutum, the most weakly silicified diatom, was the least sensitive to GeO2 inhibition. In experiments with four selected marine species, an appropriate increase in the SiO2 concentration of the medium reversed the inhibitory action of GeO2 on growth. A similar effect of SiO2 was observed in growth experiments with the fresh-water diatom Navicula pelliculosa. (A non-silicified green fiagellate responded quite differently, its growth being unaffected by relatively high concentrations of GeO2.) At these low concentrations, GeO2 presumably had no effect on respiratory metabolism, since, even in concentrations of GeO2 as high as 400 mg/l, oxygen uptake of N. pelliculosa was unimpaired. All of these experimental results are consistent with the hypothesis that GeO2 is a specific inhibitor of silicate utilization.
 
Article
This report details a reliable and efficient RNA extraction protocol for the symbiotic dinoflagellate Symbiodinium microadriaticum Freudenthal (Gymnodiniales, Dinophyceae). The method typically gives yields of 500 mu g total RNA from 0.4 g wet weight of algae, and, in comparison to current protocols, it is technically simple and less time consuming. This method isolates high-quality, intact RNA from in vine cultured as well as host-isolated cells, as demonstrated by spectrophotometry, gel electrophoresis, and northern analysis. The total RNA obtained was suitable for reverse transcription and PCR amplification of Symbiodinium cDNAs. We have successfully applied our method to isolate total RNA from a different dinoflagellate, Amphidinium carterae Hulburt (Gymnodiniales, Dinophyceae), found in symbiotic association with marine invertebrates.
 
Article
Metapeyssonnelia , a new genus of the Peyssonneliaceae (Rhodophyta), is described. This encrusting orbicular alga is completely calcified by aragonite. Small unicellular rhizoids are present. The centre of the thallus shows a Peyssonnelia -like structure that metamorphes towards the margins of older thalli: in these metamorphosed parts, an inferior perithallus is generated downwards. Each hypothallic cell gives rise to only one coxal cell, even in the metamorphosed parts: this characteristic distinguishes the structure of Metapeyssonnelia from that of Polystrata . The type species is M. feldmannii nov. sp., collected at Port-Cros island (Mediterranean, France).
 
Specificity of FM 1-43 for the symbiotic interface between host cell and resident algae. Symbiodinium in the crude gastrodermal cell extract from Zoanthus robustus stained with FM 1-43 (30 mM) using epifluorescence microscopy. Scale bar 5 20 mm. Fig. 3. Symbiodinium in the crude gastrodermal cell extract from Zoanthus robustus examined under bright-field microscopy. cn 5 cnidoblast. Scale bar 5 20 mm. Fig. 4. Autofluorescent inclusion bodies in Symbiodinium. Symbiodinium in the crude gastrodermal cell extract from Zoanthus robustus were examined using epifluorescence microscopy in the absence of FM 1-43. Inclusion bodies (arrowed) are evident only with extended exposure time. cn 5 cnidoblast. Scale bar 5 20 mm. Fig. 5. Cultured Symbiodinium stained with high concentration of FM 1-43 (50 mM). The degree of staining to the exterior of the alga is much reduced in comparison with their symbiotic counterparts, with the exception of small punctate regions (arrowed). Scale bar 5 20 mm. Fig. 6. Isolated Zoanthus robustus gastrodermal cells examined under TEM: thy 5 thylakoid membranes, s 5 starch grain, gc 5 gastrodermal cell cytoplasm, n 5 nucleus, pm 5 host cell plasma membrane. Scale bar 1 mm. Fig. 7. Gastrodermal cell containing three endosymbionts stained with 6CFDA examined under epifluorescent microscopy (insert: brightfield of same field of view). Scale bars 5 10 mm.  
Article
The zoanthid Zoanthus robustus was used as a model organism to develop procedures for isolating pure symbiosomes and symbiosome membranes. The symbiosome is comprised of a zooxanthella (Symbiodinium sp.) cell that divides rarely and is separated from the host gastrodermal cytoplasm by a symbiosome multimembrane complex. Devising a method to isolate membranes at the interface between the symbiotic partners is a critical first step in characterising the molecular components involved in the metabolic trafficking necessary to sustain an effective symbiosis. After zoanthid gastrodermal cells were extracted, symbiosomes were released by mechanical disruption, recovered by centrifugation, and then purified using discontinuous sucrose gradient centrifugation. The material forming the membrane complex around symbiosomes proved highly resistant to disruption. Methods used to dissociate this interface from symbionts included (1) Triton X-100 detergent solubilisation, (2) osmotic shock with mechanical disruption, and (3) vigorous mechanical disruptions, where powerful shearing forces were used, combined with a series of sucrose density gradient centrifugation steps. The lipophilic styryl fluorochrome FM 1-43, at a concentration of 30 µM, selectively labelled the symbiosome membrane complex, both for isolated symbiosomes and those in hospite. Other cell membranes, including plasma membranes, endoplasmic reticulum, tonoplast, and organelle membranes, were not visibly labelled at this concentration. The selective labelling of the symbiosome membrane complex remained stable even after long exposure times (3 h). At 30 µM concentration, FM 1-43 also labelled symbiosome membrane fragments isolated using methods (1), (2) and (3). Method (3) proved to be the most effective in producing a fraction enriched in FM-143-labelled membrane material, which we call a symbiosome membrane complex. Transmission electron microscopy, together with confocal and conventional epifluorescence microscopy of the FM 1-43-stained preparations, was used to validate the purity of symbiosome preparations and to infer the complexity of the symbiosome membrane complex. This membrane complex has regions where the membranes contributed by the alga are appressed, and punctate regions whose function remains unclear.
 
Article
Article
Phaeosomes, extracellular cyanobacterial symbionts of the genus Synechococcus Nageli, of some species of tropical marine dinoflagellates were investigated for the presence of nitrogenase, phycoerythrin (PE) and ribulose 1,5-bisphosphate carboxylase/oxygenase (RUBISCO). The dinoflagellates Ornithocercus magnificus Stein, and O. steinii Schiitt were collected in the Caribbean Sea, and transmission electron microscopy revealed that, in addition to phaeosomes, bacterial consorts were also present between the upper and the lower girdle list of the cingular groove. The bacteria were uniform in size, ranging between 0.2 and 0.3 μm approximately. Immunogold labelling techniques indicated that the cyanobacterial phaeosomes contained high amounts of the photosystem II associated pigment PE. The CO2-fixing enzyme RUBISCO was mainly located in carboxysomes. Those examined for nitrogenase were collected at both day and night, but nitrogenase was not detected. Ornithocercus spp. are non-photosynthetic organism...
 
Article
Neochloris oleoabundans was described as a freshwater unicellular green microalga; however, some literature suggested that it was an edaphic and halotolerant alga. Neochloris oleoabundans was studied so far for its high lipid content, especially under nitrogen starvation, for possible industrial applications. Information on the morphophysiological characteristics of the alga and its photosynthetic apparatus in different culture conditions still remained incomplete. In the present work, its growth was compared using low-salinity and brackish media with increasing nitrogen supply. The morphophysiological aspects, with a special attention on its photosynthetic apparatus, were analysed through light and transmission electron microscopy, photosynthetic pigment quantification, PSII maximum quantum yield measurements and evaluations of the chlorophyll-protein assembly state. In contrast to what has been reported in previous work on the positive effect of nitrate on N. oleobundans growth, we found negative or negligible effects in our samples cultivated in low-salinity or brackish media, respectively. Brackish conditions induced a better growth of the alga, which showed some morphological variations (cell volume enlargement, cell wall thickening, increased stromatic starch and polyphosphate grains). Furthermore, brackish cultured algae were characterized by a strong increase in cellular chlorophylls and carotenoids. Fluorimetric analyses pointed to the absence of disturbance to the photosynthetic apparatus and to a higher photosynthetic efficiency in brackish cultured samples with respect to controls in the low-salinity medium, indicating a somehow better photosynthetic performance. Interestingly, the behaviour of the F680/F685+694 ratio pointed to a possible positive correlation between nitrogen supply and PSII core stability. On the whole, morphological, biochemical and biophysical results confirmed the higher acclimatized growth of N. oleoabundans in brackish media, which seem more suitable for algal growth than low-salinity ones.
 
Top-cited authors
Gustaaf Hallegraeff
  • University of Tasmania
David G. Mann
  • Royal Botanic Garden Edinburgh
Linda K. Medlin
  • Marine Biological Association of the UK
Øjvind Moestrup
  • University of Copenhagen
John A. West
  • University of Melbourne