bluuebunny/crossref_metadata_2025 huggingface dataset:
Soil Algae in Brown Coal and Lignite Post‐Mining Areas in Central Europe (Czech Republic and Germany)
Authors: Lukešová Alena
Published: March 2003

Algal communities were investigated in two contrasting chronosequences established on reclaimed spoils in the west Bohemian brown coal mining district near Sokolov (Czech Republic) and in the Lusatian lignite mining district near Cottbus (Germany). The Sokolov chronosequence was characterized by tertiary cypric clay substrate, afforestation with Alnus glutinosa (L.) Gaertn., and high pH of deposited spoil material, Cottbus chronosequence by tertiary carboniferous and pyritic sand of extremely low pH ameliorated by fly ash, and afforestation with Pinus sylvestris L. and P. nigra Arnold. A total of 122 species of algae was found in both areas. Although the same species number (80) was identified from Sokolov and Cottbus, both proportion of individual algal groups and species composition were different. Green algae prevailed in both areas, but in Sokolov cyanobacteria and diatoms were also quite diverse, and in younger sites they were also abundant. Total abundance of algae ranged mostly between 104–107 cells/g dry soil, and was one order higher in Cottbus than in Sokolov. Species number was high in young sites, decreased with increasing age, and was the lowest in control forests. In Sokolov, the highest abundance was recorded in the youngest alder plantation. In Cottbus, sludge and compost fertilization used in the youngest pine plantations resulted in rapid formation of visible algal crusts dominated by Klebsormidium crenulatum (Kütz) Lokhorst.
Use of Shrubs as Nurse Plants: A New Technique for Reforestation in Mediterranean Mountains
Authors: Castro Jorge , Zamora Regino , Hódar José A. , Gómez José M.
Published: March 2003

Common techniques currently used for afforestation in the Mediterranean basin consider the pre‐existing vegetation (mainly shrubs) as a source of competition for trees, and consequently it is generally eliminated before planting. Nevertheless, it has been demonstrated that woody plants can facilitate the establishment of understory seedlings in environments that, like the Mediterranean area, are characterized by a pronounced dry season. In this study, we experimentally analyze the usefulness of shrubs as nurse plants for afforestation of two native conifers,Pinus sylvestrisL. (Scots pine) andPinus nigraArnold (black pine). Two‐year‐old seedlings were planted in four microhabitats: (1) open interspaces without vegetation (which is the usual method used in afforestation programs), (2) under individuals ofSalvia lavandulifolia, (3) under the north side of spiny shrubs, and (4) under the south side of spiny shrubs. Pine survival was remarkably higher when planted under individuals of the shrubS. lavandulifolia(54.8% for Scots pine, 81.9% for black pine) compared with open areas (21.5% for Scots pine, 56.8% for black pine; chi square,p< 0.05). The survival of both pines was also higher when planted on the north side of spiny shrubs, although the survival on the south side was similar to that found in open areas. In addition, pine growth was not inhibited when planted in association with shrubs. This pattern appears to result from the combination of abiotic conditions imposed by the presence of a nurse shrub, which leads to improvement in seedling water status and therefore reduced summer mortality by drought. The results show that the use of shrubs as nurse plants is a technique that offers both economic and ecological advantages, in terms of savings in labor and plant material and reduced and even negligible impact on the pre‐existing vegetation.
A Comparative Assessment of Genetic Diversity among Differently‐Aged Populations ofSpartina alternif loraon Restored Versus Natural Wetlands
Authors: Travis Steven E. , Proffitt C. Edward , Lowenfeld Robin C. , Mitchell Timothy W.
Published: March 2003

We collected naturally recolonizingSpartina alterniflora(smooth cord grass) from each of three restored sites and one undisturbed reference site in southwestern Louisiana to assess the impact of wetland restoration on genetic diversity. We used amplified fragment length polymorphisms (AFLPs) to produce 94 polymorphic genetic markers, which were used to characterize genetic diversity as average heterozygosity  and the proportion of polymorphic loci . Overall our findings indicate that restored populations of S. alterniflora maintain levels of genetic diversity comparable to natural populations, which should provide some measure of resistance against environmental disturbances. Diversity estimates were lowest for the natural reference site ( = 0.1059;  = 0.2763), whereas estimates for the three restored sites ranged from= 0.1148 to 0.1256 and  = 0.3114 to 0.3202. All sites maintained sufficiently high diversity levels to suggest significant rates of outcrossing. Overall, genetic differentiation among populations was small (Weir and Cockerham's Θ = 0.0645), with the values from each pairwise comparison among the populations increasing with the geographic distance between sites (range = 0.0490–0.1101). These values indicate an average migration rate of 3.6 migrants, either pollen or seeds, per generation.
Peripheral neuropathy and antiretroviral drugs
Authors: Dalakas Marinos C.
Published: March 2003

Abstract  Patients treated with nucleoside analogue reverse transcriptase inhibitors (NRTIs) develop a varying degree of myopathy or neuropathy after long‐term therapy. Zidovudine (AZT) causes myopathy; zalcitabine (ddC), didanosine (ddI) and lamuvidine (3TC) cause neuropathy; stavudine (d4T) and fialuridine (FIAU) cause neuropathy or myopathy and lactic acidosis. The tissue distribution of phosphorylases responsible for phosphorylation of NRTIs relates to their selective tissue toxicity. The myopathy is characterized by muscle wasting, myalgia, fatigue, weakness and elevation of CK. The neuropathy is painful, sensory and axonal. In vitro, NRTIs inhibit the gamma‐DNA polymerase, responsible for replication of mtDNA, and cause mtDNA dysfunction. In vivo, patients treated with AZT, the best studied NRTI, develop a mitochondrial myopathy with mtDNA depletion, deficiency of COX (complex IV), intracellular fat accumulation, high lactate production and marked phosphocreatine depletion, as determined with in vivo MRS spectroscopy, due to impaired oxidative phosphorylation. Animals or cultured cells treated with NRTIs develop neuropathy, myopathy, or cell destruction with similar changes in the mitochondria. There is evidence that the NRTI‐related neuropathy is also due to mitochondrial toxicity. The NRTIs (AZT, ddC, ddI, d4T, 3TC) contain azido groups that compete with natural thymidine triphosphate as substrates of DNA pol‐gamma and terminate mtDNA synthesis. In contrast, FIAU that contains 3′‐OH groups serves as an alternate substrate for thymidine triphosphate with DNA pol‐gamma and is incorporated into the DNA causing permanent mtDNA dysfunction. The NRTI‐induced mitochondrial dysfunction has an influence on the clinical application of these agents, especially at high doses and when combined. They have produced in humans a new category of acquired mitochondrial toxins that cause clinical manifestations resembling the genetic mitochondrial disorders.
Relative sensitivity to alfentanil and reliability of current perception threshold vs von Frey tactile stimulation and thermal sensory testing
Authors: Park Robert , Wallace Mark S. , Schulteis Gery
Published: March 2003

Abstract  Recent technological advances claim to allow quantitative measurement of the functional integrity of both large and small diameter sensory nerve fibers using the current perception threshold (CPT) sensory testing device. This device has yet to be validated against the corresponding gold standard references for sensory testing (thermal sensory testing [TST]) and von Frey tactile hair stimulation [VF]) to correlate its evaluation of similar sensory nerve perceptions. A baseline neurosensory examination using the CPT, TST and VF methods was performed on 19 healthy volunteers. Using a randomized, double‐blind, placebo‐controlled design, each subject received an alfentanil or diphenhydramine (as a placebo control) infusion in separate study sessions. The order of the study sessions was randomized and separated by 1 week. The 3 neurosensory examinations were repeated at 3 different targeted plasma levels of study drug. Changes in neurosensory thresholds were then compared between the 3 methods. All CPT measurements and the cold pain measurement showed a significantly higher degree of variability than the other TST and VF measurements. There appeared to be a correlation between the CPT 5 Hz pain threshold and the TST cold pain and warm sensation; intravenous alfentanil significantly elevated all 3 detection thresholds. In addition, there was no effect of alfentanil on the VF or the CPT 2000 Hz thresholds. However, we did not see the predicted relation between the 250 Hz CPT stimulus and cool sensation. From these studies, there is some evidence that similar fiber tracts may be measured between the CPT, TST, and VF methods, especially with the CPT 5 Hz measures and C‐fiber tract activity.
Tomacula in MAG‐deficient mice
Authors: Cai Zhao , Sutton‐Smith Peter , Swift Jeffrey , Cash Kathy , Finnie John , Turnley A. , Thompson Philip D. , Blumbergs Peter C.
Published: March 2003

Abstract  The pathogenesis of tomacula in mice with a null mutation of the myelin‐associated glycoprotein (MAG) gene is not well understood. This study, using a novel teased nerve fiber technique, demonstrates that tomacula in MAG‐deficient mice are formed by redundant myelin infoldings and outfoldings in the paranodal regions as early as 4 weeks after birth and increase in size and frequency with age. Although tomacula show degenerative changes with increasing age, there was no significant evidence of demyelination/remyelination. Longitudinal sections of normal teased nerve fibers show early redundant myelin foldings in externally normal paranodal regions. These data and the absence of internodal tomacula support a role for MAG in the maintenance of myelin at the paranodal regions.
Thermosensitivity Of Large Primary Sensory Neurons
Authors: Li HQ , Liu BG , Dobretsov M , Brull SJ , Zhang JM.
Published: March 2003

Spontaneous activity originating in the injured nerve or the dorsal root ganglion (DRG) has been implicated in the development and maintenance of neuropathic pain. The inherent characteristics of spontaneous activity and the causal factors that modulate its firing pattern and frequency are not fully understood. We attempted to assess the thermosensitivity of spontaneous activity in dorsal root ganglion (DRG) neurons in normal rats and in rat, with cl‐ironic compression of the DRG (CCD) in an in vitro nerve‐DRG preparation. Extracellular, dorsal root recording from 66 spontaneously active CCD Abeta fibers indicate that: (1) decreasing bath temperature from 37 to 36‐26 °C significantly decreased the firing rate (FR) in 85% (56/66) of fibers tested, of which 19 fibers (34%) responded to temperature change at physiological range (36‐37 °C), whereas the remaining fibers responded at lower temperature levels (26‐36 °C); (2) cooling of the DRG increased the FR in 12% (8/66) of fibers tested; (3) similarly, the firing rate of 21/26 spontaneously active Abeta fibers from normal rats was decreased following temperature decrease; (4) intracellular recordings from 38 normal neurons revealed that cooling the DRG significantly increased the action potential (AP) threshold, A‐P duration, AP amplitude and afterhyperpolarization (AHP) duration, but decreased AHP amplitude, maximal depolarizing and repolarizing rates. There was no significant change in the rheobase currents or the resting membrane potential. The present study indicates that large sensory neurons with myelinated axons are temperature dependent. It also suggests that maintenance of a stable temperature is critical for reliable characterization of spontaneous activity of sensory neurons.
Macrophage‐Related Demyelination In Peripheral Nerves Of Mice Deficient In The Gap Junction Protein Connexin 32
Authors: Kobsar I , Maurer M , Ott T , Martini R.
Published: March 2003

Mice deficient in the gap junction protein connexin 32 (Cx32) develop a slowly progressing demyelinating neuropathy, with enlarged periaxonal collars, abnormal non‐compacted myelin domains and axonal sprouts. These mice serve as a model for the X‐linked form of inherited demyelin‐ ating neuropathies in humans. Based on our previous findings that macrophages are involved in demyelination in other myelin mutants (i.e. mice heterozygously deficient in P0), we considered the possibility that macrophages might be also mediators of demyelination in Cx32‐deficient mice. Indeed, we detected an age‐related increase in the number of macrophages in demyelinating nerves of Cx32‐deficient mice. In addition, immunoelectron microscopy revealed macrophages in an apposition to degenerating myelin reminiscent of a macrophage‐mediated demyelinating neuropathy. We conclude that involvement of macrophages might be a widespread phenomenon in genetically‐determined demyelination.
Structure Of Campylobacter Jejuni Lipopolysaccharides Determines Antiganglioside Specificity And Clinical Features Of Guillain‐Barre, And Miller Fisher Patients
Authors: Ang CW , Laman JD , Willison HJ , Wagner ER , Endtz HP , De Klerk MA , Tio‐Gillen AP , Van den Braak N  , Jacobs BC , Van Doorn PA.
Published: March 2003

Ganglioside mimicry in the lipopolysaccharide (LPS) fraction of Campylobacter jejuni isolated from Guillain‐Barré syndrome (GBS) and Miller Fisher syndrome (MFS) patients was compared with isolates from patients with an uncomplicated enteritis. The antibody response to C. jejuni LPS and gangliosides in neuropathy patients and controls was compared as well. LPS from GBS and MFS‐associated isolates more frequently contained ganglioside‐like epitopes compared to control isolates. Almost all neuropathy patients showed a strong antibody response against LPS and multiple gangliosides in contrast to enteritis patients. Isolates from GBS patients more frequently had a GM1‐like epitope than isolates from MFS patients. GQ1b‐like epitopes were present in all MFS‐associated isolates and was associated with anti‐GQ1b antibody reactivity and the presence of oculomotor symptoms. These results demonstrate that the expression of ganglioside mimics is a risk factor for the development of post‐Campylobacter neuropathy. This study provides additional evidence for the hypothesis that the LPS fraction determines the antiganglioside specificity and clinical features in post‐Campylobacter neuropathy patients.
A METHOD TO IMPROVE THE SPATIAL RESOLUTION OF PHOTOSYNTHETIC RATES OBTAINED BY OXYGEN MICROSENSORS
Authors: Lassen Carsten , Glud Ronnie N. , Ramsing Niels B. , Revsbech Niels Peter
Published: March 2003

To determine gross photosynthesis in benthic microalgal communities, oxygen microelectrodes were used to measure the rate of decrease within the first 4 s after extinction of light. Photosynthetic rates calculated from third‐order polynomial fits to the curve of decreasing O2 concentration were compared to the rates obtained by the traditional method, where rates were estimated from linear regression. When photosynthesis was calculated for the fitted initial rates of O2 decrease, maximum rates in microbial mats were up to 32% higher, and the depth‐integrated gross photosynthesis was 5%–10% higher than the rates determined by the traditional method. The determinations from fitted initial rates also resulted in a more detailed profile of photosynthetic rate than that normally obtained. Computer simulation based on diffusion models, where the estimated initial rates of O2 decrease were assumed to represent actual photosynthesis rates, verified the validity of the curve‐fitting procedure for obtaining high‐resolution photosynthesis profiles.
SEXUAL REPRODUCTION IN THE PENNATE DIATOMS PSEUDO‐NITZSCHIA MULTISERIES AND P. PSEUDODELICATISSIMA (BACILLARIOPHYCEAE)
Authors: Davidovich Nickolai A. , Bates Stephen S.
Published: March 2003

Clones of the domoic‐acid‐producing pennate diatom Pseudo‐nitzschia multiseries (Hasle) Hasle and of the potentially toxic P. pseudodelicatissima (Hasle) Hasle normally decrease in cell size in culture until they eventually die without undergoing sexual reproduction to regain the largest cell size. However, we induced sexual reproduction by mixing individual exponentially growing clonal cultures of the appropriate minimal cell size under the same conditions that are normal for vegetative growth. We observed pairing of parent cells (gametangiogamy); production of four morphologically isogamous, nonflagellated gametes per gametangial pair; rearrangement of the gametes and their fusion to form zygotes, revealing physiological anisogamy; enlargement of auxospores; and formation of long initial cells. Our observations of allogamous reproduction are consistent with those reported for other dioecious pennate diatoms. Clones of P. pseudodelicatissima from the Black Sea and from the CCMP culture collection failed to auxosporulate when mixed together, although they are the same species according to scanning electron microscopy. The range in apical length of P. multiseries was broader than that reported in the literature for field samples, necessitating a modification of the species description. Knowledge of the pattern and timing of sexual reproduction in Pseudo‐nitzschia spp. may provide insights into their bloom dynamics.
ISOLATION OF A NUCLEUS‐ASSOCIATED MICROTUBULE SCAFFOLD FROM SPIROGYRA (ZYGNEMATALES, CHAROPHYCEAE)
Authors: Schröder Jan , Grolig Franz
Published: March 2003

A phragmosome‐like perinuclear scaffold attaches to helical chloroplast bands in the peripheral cytoplasm of Spirogyra crassa Kützing by rigid, stalk‐like cytoplasmic strands. Balanced integration of forces within this scaffold by microfilament‐based tension conveyed along stabilized microtubules (MTs) within the stalks controls transverse centering of the lenticular nucleus in the cylindrical cell prior to mitosis. Nuclei with their associated scaffolds were released from rapidly frozen, shattered cells upon thawing in a MT‐stabilizing buffer and could be purified by a procedure combining filtration, differential centrifugation, and isopyknic centrifugation in a linear density gradient. In the osmotically indifferent gradient medium Nycodenz™, nuclei with adhering scaffolds attained a buoyant density of 1.26–1.27 g·cm−3. The nuclei maintained their energetically unfavorable, lenticular shape in vitro and appeared structurally preserved as judged by video‐enhanced differential interference contrast and by fluorescent staining of DNA with 4′‐6′‐diamidino‐2‐phenylindole. The stalks of the scaffold, though still radiating from the nuclear rim, lost their straightness and were often severed during the isolation process. The distal ends of many unsevered stalks and of stalk fragments were still associated with chloroplast fragments. Persistent flexural rigidity of the scaffold stalks and indirect immunofluorescence indicated preservation of MTs. In addition to tubulin, both actin and an intermediate filament antigen of Mr≈ 68 kDa were detected in the isolated nuclei with associated scaffolds by immunoblot with monoclonal antibodies.
MOLECULAR AND MORPHOLOGICAL ANALYSIS OF ENTEROMORPHA INTESTINALIS AND E. COMPRESSA (CHLOROPHYTA) IN THE BRITISH ISLES
Authors: Blomster Jaanika , Maggs Christine A. , Stanhope Michael J.
Published: March 2003

The very common green seaweeds Enteromorpha intestinalis (L.) Nees and E. compressa (L.) Nees are important fouling organisms and have commonly been used as indicators of eutrophication, but their taxonomic status is problematic. The genus presents extreme difficulties because there is wide intraspecific variation in morphology, but morphological differences between species are small and difficult to detect. In this study, molecular data were used in parallel with morphological characters to resolve the taxonomic problems. Phylogenetic analysis of sequences of the internal transcribed spacers ITS1 and ITS2 and the 5.8S gene distinguished two groups of samples, which were identified by morphological characters as E. compressa (branched) and E. intestinalis (normally unbranched). There was a low level of sequence divergence within each group of samples, but divergence between groups was as great as that between either of the two species and the outgroup E. prolifera. Clades representing E. compressa and E. intestinalis were also found in analyses of an independent molecular data set, chloroplast DNA restriction fragment length polymorphisms (RFLPs). Enteromorpha intestinalis and E. compressa represent two distinct, genetically divergent species. Reinterpretation of published studies shows that these species are reproductively isolated. However, E. compressa and E. intestinalis are sometimes very difficult to distinguish from each other and could be regarded as cryptic species. The presence or absence of branching was the most useful character distinguishing these two species, but there was an element of ambiguity because low salinity or salinity shock can induce branching in E. intestinalis. If environmental factors such as salinity are taken into account, branching can be used to identify the great majority of thalli correctly. This study therefore provides a basis for identifying the two most important marine fouling macroalgae and for their use in environmental monitoring and experimentation. Typification of these two Linnaean species showed that current usage of the names accords with the lectotype and protologue of both species. Samples that resembled E. usneoides did not form a clade in any of the trees, and constraining the data to support the monophyly of this group incurred a penalty. Enteromorpha usneoides appears to be an ecotype of E. compressa.
CARRAGEENANS FROM AUSTRALIAN REPRESENTATIVES OF THE FAMILY CYSTOCLONIACEAE (GIGARTINALES, RHODOPHYTA), WITH DESCRIPTION OF CALLIBLEPHARIS CELATOSPORA SP. NOV., AND TRANSFER OF AUSTROCLONIUM TO THE FAMILY ARESCHOUGIACEAE
Authors: Chiovitti Anthony , Kraft Gerald T. , Bacic Antony , Craik David J. , Munro Sharon L. A. , Liao Ming‐Long
Published: March 2003

Ten Australian representatives from seven of the 10 genera presently constituting the family Cystocloniaceae have been analyzed for their cell‐wall galactans. Included in our survey are the monotypic Australian‐endemic genera Austroclonium, Gloiophyllis, Erythronaema, and Stictosporum, one species of Craspedocarpus, three species of Rhodophyllis, and two species of Calliblepharis. As one of the species of the latter genus is endemic to Western Australia and presently undescribed, we illustrate its habit and anatomical features in formally proposing to name it Calliblepharis celatospora Kraft, sp. nov. All the species surveyed essentially produce typical iota (ι)‐carrageenans, with the exception of Austroclonium. The sulfated galactans from Austroclonium predominantly contain the repeating units of ι‐, alpha (α)‐, and 6′‐O‐methylated ι‐ and α‐carrageenans; whether these exist as discrete polysaccharides or a complex hybrid structure was not resolved. Thus, Austroclonium carrageenans resemble the polysaccharides from Rhabdonia, Areschougia, and Erythroclonium. Although these latter three genera are currently included in the large gigartinalean family Solieriaceae, all produce significantly different carrageenans from Solieria itself and related genera such as Eucheuma, Kappaphycus, Betaphycus, Sarcodiotheca, Agardhiella, Sarconema, and Callophycus. In consideration of these findings, as well as of significant anatomical similarities, we provisionally recommend reestablishment of the family Rhabdoniaceae Kylin (as the family Areschougiaceae J. Agardh) for Rhabdonia, Areschougia, Erythroclonium, and Austroclonium.
FINE STRUCTURE OF ZOOSPOROGENESIS, ZOOSPORE GERMINATION, AND EARLY GAMETOPHYTE DEVELOPMENT IN CLADOPHORA SURERA (CLADOPHORALES, CHLOROPHYTA)
Authors: Cáceres Eduardo J. , Parodi Elisa R.
Published: March 2003

The fine structure of zoosporogenesis, zoospore germination, and early gametophyte development in Cladophora surera Parodi et Cáceres were studied. Zoosporogenesis started with simultaneous meiosis in all nuclei of apical initial cells. The resulting haploid nuclei duplicated in turn by successive centric, closed mitoses. Then, each initial cell divided into two short zoosporangia. Numerous vacuoles appeared around each sporic nucleus. The delimitation of uninucleate zoosporocytes occurred by cytokinetic furrows produced by the coalescence of tiny, clear vesicles, without microtubules. Final shape of the zoospore resulted from gradual expulsion of vacuoles from the cell body. Mature biflagellate zoospores exhibited a conspicuous apical papilla containing fine granular globules, the basal apparatus, and a microtubular “umbrella” formed by numerous cortical microtubules that ran backward the length of the cell body. The chloroplast showed a conspicuous eyespot. The zoosporangial wall disorganized at the pore through which the zoospores were liberated. Zoospores settled on a substrate by their anterior papilla secreting an adhesive. Germination involved retraction of the apical papilla, loss of the “umbrella” microtubules and eyespot, and the lateral absorption of the entire flagellar apparatus, i.e. basal apparatus plus axoneme, into the cytoplasm. Early gametophyte development involved the synthesis of a thin, young cell wall, the development of outer peripheral vacuoles, the appearance of the marginal reticulate chloroplast, and the formation of the first central vacuoles derived from abundant endoplasmic reticulum. Close to the plasmalemma ran longitudinally oriented cortical microtubules. Eventually, the germling developed an achlorophylic, elongated rhizoidal portion.
SECRETION OF PHENOLIC SUBSTANCES INTO THE ZYGOTE WALL AND CELL PLATE IN EMBRYOS OF HORMOSIRA AND ACROCARPIA (FUCALES, PHAEOPHYCEAE)
Authors: Schoenwaelder Monica E. A. , Clayton Margaret N.
Published: March 2003

We have used light and electron microscopy to study the secretion of phenolic substances into the primary walls and cross walls of zygotes and embryos of the brown algae Hormosira banksii (Turner) Decaisne (Hormosiraceae) and Acrocarpia paniculata (Turner) Areschoug (Cystoseiraceae). Phenolic compounds packaged within physodes are a major cytoplasmic component of brown algae. Physodes accumulate at the zygote periphery early in development and are secreted into the primary zygote wall. At germination, physodes accumulate at the rhizoid tip. The first sign of impending cytokinesis is the lining up of these phenolic vesicles in the plane of cell division. This precedes the arrival of other wall constituents. Physodes, together with other wall components, contribute to the development of the cell plate. We conclude that phenolic compounds play an important role in cell‐wall construction in these species.
GRAZER‐INDUCED COENOBIAL FORMATION IN CLONAL CULTURES OF SCENENDESMUS OBLIQUUS (CHLOROCOCCALES, CHLOROPHYCEAE)
Authors: Lürling Miquel
Published: March 2003

Five strains of the phenotypically plastic alga Scenedesmus obliquus (Turpin) Kützing were cultured in standard medium or in medium containing filtered water from a Daphnia culture to examine grazer‐induced coenobia formation. Strains varied considerably in their response to Daphnia chemicals. A rapid formation of four‐ and eight‐celled coenobia was observed in the presence of Daphnia water in three strains. One strain showed numerous irregular aggregates with more than eight cells per colony, and no colony formation occurred in a fifth strain. In standard medium, all cultures remained unicellular. Growth rates were affected by Daphnia water in four strains and were different among strains. The chl a concentration was significantly different among strains but was not influenced by Daphnia water. The specific absorption coefficient was reduced at larger colony sizes, suggesting a possible cost associated with colony formation. The phenomenon of grazer‐induced coenobia formation seems widespread but not universal within the species S. obliquus.
NO EVIDENCE FOR AN ALLELOPATHIC ROLE OF OKADAIC ACID AMONG CIGUATERA‐ASSOCIATED DINOFLAGELLATES
Authors: Sugg Linda M. , VanDolah Frances M.
Published: March 2003

Serine/threonine protein phosphatases are regulatory enzymes critical to growth and replication in eukaryotes. Okadaic acid (OA), a potent serine/ threonine protein phosphatase inhibitor, has been well studied in vertebrates; however, little is known about the role this phycotoxin plays in the ecology of its producer, the benthic dinoflagellate Prorocentrum lima Ehrenberg. The frequency and diversity of toxins produced by benthic dinoflagellates suggests that toxin production might play a role in competition among algal species. To assess the role of OA in growth competition, dinoflagellate species that co‐occur with P. lima were grown in medium preconditioned by P. lima. Exudates from P. lima inhibited the growth of three of the four co‐occurring species. All four dinoflagellate species were found to possess protein phosphatases that are inhibited by low concentrations of OA (IC50∼5 nM). Furthermore, when treated in culture for 24 h with either purified OA or medium preconditioned by P. lima, their protein phosphatase activity was substantially inhibited. In contrast, P. lima’s protein phosphatase activity was refractory to OA both in vitro and in culture. To determine whether its growth inhibitory action was dependent on its phosphatase inhibitory activity, the P. lima‐preconditioned medium was fractionated by HPLC and fractions tested for growth‐inhibitory and protein phosphatase–inhibitory activity. We found that the two activities reside in different fractions. These results suggest that although OA has growth‐inhibitory potential against other microalgae, it does not represent the major growth‐inhibitory activity found in P. lima’s medium.
THE atpA GENE CLUSTER OF GUILLARDIA THETA (CRYPTOPHYTA): A PIECE IN THE PUZZLE OF CHLOROPLAST GENOME EVOLUTION
Authors: Leitsch Carola E. W. , Kowallik Klaus V. , Douglas Susan
Published: March 2003

We cloned and sequenced the genes of the atpA (atp1) cluster, together with its upstream and downstream sequences, of the chloroplast genome of the cryptomonad Guillardia theta Hill et Wetherbee and used gene signatures, predicted amino acid sequences, and gene arrangements for phylogenetic inferences. The Guillardia atpA cluster contains the genes atpI,H,G,F,D,A in the given order, thus reflecting the cyanobacterial/red algal/chromophyte gene arrangement. In addition, the order of both the upstream sequences rpoB,C1,C2,rps2,tsf and the downstream sequences ycf16/24, which is found exclusively in red algal chloroplast genomes, is conserved in Guillardia. This gene order, which presumably is the result of the reduction process of the cyanobacterial genome following primary endosymbiosis, provides strong evidence for a red algal ancestry of the Guillardia chloroplast and supports the hypothesis of secondary endosymbioses giving rise to chl a+c‐containing algae. The close evolutionary relationship of the chloroplasts of Guillardia and red algae is furthermore supported by the lack of introns, high degrees of sequence similarities, and additional gene signatures, including spacers, gene overlaps, and inverted repeats. Gene cluster analysis, including the ATPase genes together with their upstream and downstream genes, is consistent with a single primary photosynthetic eukaryote that gave rise to all extant algal lineages and land plants by either direct filiation or secondary endosymbioses.
SEXUALITY, INCOMPATIBILITY, SIZE VARIATION, AND PREFERENTIAL POLYANDRY IN NATURAL POPULATIONS AND CLONES OF SELLAPHORA PUPULA (BACILLARIOPHYCEAE)
Authors: Mann David G. , Chepurnov Victor A. , Droop Stephen J. M.
Published: March 2003

The capitate and rectangular demes of the freshwater epipelic diatom Sellaphora pupula (Kütz.) Mereschk. are dioecious, the first such report for any freshwater diatom. Sexual differentiation, which is probably determined genetically, involves recognition at the cell surface as well as differences in gamete behavior (one gametangium produces an active “male” gamete, the other a passive “female” gamete). In culture, successful sexual reproduction occurs only when compatible clones are mixed. All cells of a clone behave identically in interclonal crosses, being either male or female, regardless of the stage of the life cycle, in contrast to the sequential hermaphroditism of centric diatoms. Males and females have identical frustule morphology. As in other diatoms, there is an upper size threshold for sexual reproduction, below which cells become progressively easier to sexualize. In culture, sexual interactions occur in cells much smaller than those ever seen in natural populations, so that in nature the sexual size range is effectively open. Natural populations almost always contain sexualizable cells; often, most of the cells are below the upper sexual size threshold. Male gametangia are, on average, slightly larger than females in the capitate deme, which may be produced by preferential polyandry, depleting the population of males and making them younger at mating. Rarely, selfing occurs producing zygotes, but these abort before producing initial cells. The sizes of the gametangia and initial cells are correlated but this does not invalidate the use of “cardinal points” of the life cycle in taxonomy. No interbreeding occurs between the rectangular and capitate demes. However, when males of one deme are mixed with females of the other, there is a stimulation of activity, as during the early stages of pairing in compatible intrademic crosses.
THALASSIOSIRA ANDAMANICA SP. NOV. (BACILLARIOPHYCEAE), A NEW DIATOM FROM THE ANDAMAN SEA (THAILAND)
Authors: Gedde Anne Dorte
Published: March 2003

A new marine diatom, Thalassiosira andamanica, is described from light and electron microscopy. The specimens were collected in the vicinity of Phuket Marine Biological Center, Thailand, and later brought into clonal culture. Thalassiosira andamanica possess a rimoportula with a pronounced outer extension, one marginal ring of fultoportulae, and three rings of fultoportulae on the valve face. Cells are united into colonies by a single thread secreted through a central fultoportula. Marginal fultoportulae extensions are shortest on the inside of the valve. The areolae are arranged in sectors, and the valve margin is ribbed with approximately 38 ribs in 10 μm. The valvocopula and copula have rows of pores, four to six pores in 1 μm. Apparently, the pleurae are hyaline. Experiments with a clonal culture isolated at Phuket, Thailand, showed that growth (cell divisions·24 h−1) was reduced for cultures grown at 14° C compared to those grown at 19°, 24°, or 30° C. The maximum growth rate (2.2 divisions·24 h−1) was at 30° C. Thalassiosira andamanica is compared with morphologically similar taxa. On the basis of morphological features and the response to different temperature regimens, it is concluded that this taxon must be recognized as a new warm‐water species. In addition, T. andamanica does not clearly belong to any of the two subgroups of species of Thalassiosira. To accommodate the morphological characteristics of T. andamanica, the establishment of a possible third subgroup is discussed.
BOLIDOMONAS: A NEW GENUS WITH TWO SPECIES BELONGING TO A NEW ALGAL CLASS, THE BOLIDOPHYCEAE (HETEROKONTA)
Authors: Guillou Laure , Chrétiennot‐Dinet Marie‐Josèphe , Medlin Linda K. , Claustre Hervé , Goër Susan Loiseaux‐de , Vaulot Daniel
Published: March 2003

A new algal class, the Bolidophyceae (Heterokonta), is described from one genus, Bolidomonas, gen. nov., and two species, Bolidomonas pacifica, sp. nov and Bolidomonas mediterranea, sp. nov., isolated from the equatorial Pacific Ocean and the Mediterranean Sea, respectively. Both species are approximately 1.2 μm in diameter and have two unequal flagella; the longer flagellum bears tubular hairs, whereas the shorter is smooth. The flagellar basal apparatus is restricted to two basal bodies, and there is no transitional helix. Cells are naked, devoid of walls or siliceous structures. The internal cellular organization is simple with a single plastid containing a ring genophore and a girdle lamella, one mitochondrion with tubular cristae, and one Golgi apparatus close to the basal bodies. The Mediterranean and the Pacific species differ in the insertion angle between their flagella and their pattern of swimming, these differences possibly being linked to each other. Analyses of the SSU rDNA gene place the two strains as a sister group to the diatoms. Moreover, pigment analyses confirm this position, as fucoxanthin is found as the major carotenoid in both lineages. These data strongly suggest that the ancestral heterokont that gave rise to the diatom lineage was probably a biflagellated unicell.
BIOVOLUME CALCULATION FOR PELAGIC AND BENTHIC MICROALGAE
Authors: Hillebrand Helmut , Dürselen Claus‐Dieter , Kirschtel David , Pollingher Utsa , Zohary Tamar
Published: March 2003

Microalgal biovolume is commonly calculated to assess the relative abundance (as biomass or carbon) of co‐occurring algae varying in shape and/or size. However, a standardized set of equations for biovolume calculations from microscopically measured linear dimensions that includes the entire range of microalgal shapes is not available yet. In comparison with automated methods, the use of microscopical measurements allows high taxonomic resolution, up to the species level, and has fewer sources of error. We present a set of geometric shapes and mathematical equations for calculating biovolumes of >850 pelagic and benthic marine and freshwater microalgal genera. The equations are designed to minimize the effort of microscopic measurement. The similarities and differences between our proposal for standardization and previously published proposals are discussed and recommendations for quality standards given.
THE MARINE AND TERRESTRIAL PRASIOLALES (CHLOROPHYTA) OF GALWAY CITY, IRELAND: A MORPHOLOGICAL AND ECOLOGICAL STUDY
Authors: Rindi Fabio , Guiry Michael D. , Barbiero Richard P. , Cinelli Francesco
Published: March 2003

Green algae belonging to the order Prasiolales have been reported frequently in terrestrial, freshwater, and marine habitats, generally in situations in which they are not submerged continuously and often in association with deposits of avian feces or other rich sources of nitrogenous compounds. Terrestrial habitats in Galway City on the west coast of Ireland have large populations of four such algae: Rosenvingiella polyrhiza (Rosenvinge) P. C. Silva, Prasiola calophylla (Carmichael ex Greville) Kützing, P. crispa (Lightfoot) Kützing, and P. stipitata Suhr ex Jessen, of which only the last is in any way fully associated with a tidal regime. The other species are found in an extraordinary range of nonmarine terrestrial habitats in the center of Galway, a city that still retains its narrow, medieval street plan. Width of the streets, proportion of residences, substratum type, and aspect are shown to be the main factors affecting the distribution of these algae, although a combination of consistent dampness and nitrogenous‐compound availability from animal wastes is likely to be the primary determining factor. Morphological and phenological data are presented for each entity, and it is concluded from field observations that R. polyrhiza should continue to be recognized as a separate entity, even though a close relationship with Schizogonium murale Kützing is probable.
A STUDY OF Si DEPOSITION SYNCHRONY IN RHIZOSOLENIA (BACILLARIOPHYCEAE) MATS USING A NOVEL 32Si AUTORADIOGRAPHIC METHOD
Authors: Shipe Rebecca F. , Brzezinski Mark A.
Published: March 2003

A 32Si autoradiographic technique using a liquid photographic emulsion was developed for the study of diatom silica deposition in culture or in natural water samples. The method was used in the Central North Pacific to study silica deposition by diatoms of the genus Rhizosolenia. The species examined form centimeter‐sized aggregates commonly referred to as mats. The Rhizosolenia mats examined were composed of a matrix of R. fallax Sundström chains, embedded with chains of larger cells, either R. debyana H. Peragallo or R. acuminata H. Peragallo. The autoradiographs revealed distinct rings of labeled intercalary bands and/or labeled valves. A greater proportion of the frustule of the larger species was labeled during the incubations with 32Si, implying higher rates of silicification by R. debyana and R. accuminata compared to R. fallax. A quantitative consideration of these differences in species‐specific Si production combined with abundance and surface area estimates for each species indicates that cells of the larger species carry out the majority of silica production in Rhizosolenia mats. The large cell size (pervalvar axis 240 to 3000 μm) and elongate frustule morphology of Rhizosolenia cells enabled us to localize the deposition of silica along the pervalvar axis. Positions of labeled bands along this axis indicate progress through the Si deposition cycle, and the results suggest that cell division is phased, with either a bimodal or unimodal age distribution of cells within the cell cycle for all species in a mat. Species‐specific doubling times from 25 to 60 h were implied by the mean fractions of frustule that were labeled. 32Si autoradiography revealed unique species‐specific differences in diel patterns of cell division and silica deposition and has potential for studies of Si deposition by other diatom species and assemblages.
VARIATION IN PATTERNS OF VALVE MORPHOGENESIS BETWEEN REPRESENTATIVES OF SIX BIRAPHID DIATOM GENERA (BACILLARIOPHYCEAE)
Authors: Cox Eileen J.
Published: March 2003

Scanning electron microscopic studies of silica valve formation in naviculoid diatoms representing six different genera revealed that the precise sequence of depositional events varied among genera. Valve deposition begins with the formation of the raphe sternum, from which virgae (lateral outgrowths) extend. Areolae (pores) are formed between the virgae by the fusion of cross‐extensions (vimines). In most of the species studied (Craticula ambigua (Kützing) D. G. Mann, Frustulia vulgaris (Thwaites) De Toni, Craspedostauros australis E. J. Cox, and Gomphonema truncatum Ehrenberg), areola (pore) formation began near the raphe sternum before completion of the valve margin, but in Pinnularia gibba Ehrenberg the valve margin fused before the areolae were formed. Silica deposition in all these taxa was mainly distal to proximal (with respect to the cytoplasm), but in Haslea sp. it was mainly proximal to distal. Haslea also differed in that areolae were defined as the valve margin was completed. These data have also contributed to the interpretation of taxonomically important features, such as raphe endings. In P. gibba the internal central raphe fissures were laterally deflected but subsequently obscured by additional silicification of the valve, whereas in G. truncatum they were initially straight, becoming laterally deflected as valves mature. External raphe fissures in Frustulia became Y‐shaped only just before maturity; in immature valves they were dotlike, as in Amphipleura Kützing. The comparison of developmental pathways in diatoms is a useful adjunct to morphological and other approaches in diatom systematics and warrants renewed attention.
AN ADDITIONAL PUNCTATE SPECIES OF PYRAMIMONAS, P. FORMOSA, SP. NOV., AND ITS IMPACT ON THE SUBGENERA PUNCTATAE AND PYRAMIMONAS (PRASINOPHYCEAE, CHLOROPHYTA)
Authors: Sym Stuart D. , Pienaar Richard N.
Published: March 2003

A new punctate species of Pyramimonas Schmarda from South Africa is described. This species is somewhat anomalous and, like P. chlorina Sym et Pienaar (subgenus Pyramimonas McFadden), has characters that bridge the divide between the subgenera Pyramimonas and Punctatae McFadden. Features of these two species, together with the lack of exclusive character sets for either subgenus derived from other species of these subgenera, lead to the conclusion that Punctatae now should be subsumed formally into the subgenus Pyramimonas.
The morphology, taxonomy, and molecular phylogeny of Heterocladia and Trigenea (rhodomelaceae, rhodophyta), with delineation of the little‐known tribe Heterocladieae*
Authors: Phillips Louise E. , Choi Hang‐Gu , Saunders Gary W. , Kraft Gerald T.
Published: March 2003

A morphological, anatomical, and molecular study of the two genera (Heterocladia and Trigenea) and three species of the tribe Heterocladieae (Rhodomelaceae, Ceramiales) is presented. First collections of male and female gametophytes of Heterocladia australis Decaisne and Trigenea umbellata J. Agardh and of tetrasporophytes of the type species of Trigenea, T. australis Sonder, have allowed a much clearer assessment of these taxa from a classical morphological standpoint. Reproductive and vegetative characters of the two Trigenea species are shown to be virtually identical to those of Heterocladia, which differs from Trigenea principally in having both flattened and terete lateral branches, as opposed to exclusively terete axes throughout. As a consequence, we propose to transfer the Trigenea species to the earlier‐named genus Heterocladia as H. caudata L. Phillips, H.‐G. Choi, G.W. Saunders et Kraft, nom. nov. and H. umbellata (   J. Agardh) L. Phillips, H.‐G. Choi, G.W. Saunders et Kraft, comb. nov. The close relationship of the three species is supported by molecular data, as nucleotide sequences of the 18S rRNA gene from each are nearly identical. The same sequences from species of eight other rhodomelaceous genera plus those from five outgroup taxa are analyzed to provide grounds for preliminary phylogenetic inferences about the position of the Heterocladieae in the Rhodomelaceae. Both the Heterocladieae and the Rhodomelaceae are monophyletic taxa in our analyses, the Heterocladieae grouping weakly with the Bostrychieae and the problematic Australian endemic genus Sonderella, the latter yet to be assigned to a tribe. Representatives of groups with which Heterocladia has been associated previously, such as the Lophothalieae and Brongniartelleae, appear to be only distantly related, although many more taxa need to be analyzed before the systematic position of the genus becomes clear.
COMPARISONS OF NITRATE UPTAKE, STORAGE, AND REDUCTION IN MARINE DIATOMS AND FLAGELLATES
Authors: Lomas Michael W. , Glibert Patricia M.
Published: March 2003

Diatoms, but not flagellates, have been shown to increase rates of nitrogen release after a shift from a low growth irradiance to a much higher experimental irradiance. We compared NO3− uptake kinetics, internal inorganic nitrogen storage, and the temperature dependence of the NO3− reduction enzymes, nitrate (NR) and nitrite reductase (NiR), in nitrogen‐replete cultures of 3 diatoms (Chaetoceros sp., Skeletonema costatum, Thalassiosira weissflogii) and 3 flagellates (Dunaliella tertiolecta, Pavlova lutheri, Prorocentrum minimum) to provide insight into the differences in nitrogen release patterns observed between these species. At NO3− concentrations <40 μmol‐N·L−1, all the diatom species and the dinoflagellate P. minimum exhibited saturating kinetics, whereas the other flagellates, D. tertiolecta and P. lutheri, did not saturate, leading to very high estimated K  s values. Above ∼60 μmol‐N·L−1, NO3− uptake rates of all species tested continued to increase in a linear fashion. Rates of NO3− uptake at 40 μmol‐N·L−1, normalized to cellular nitrogen, carbon, cell number, and surface area, were generally greater for diatoms than flagellates. Diatoms stored significant amounts of NO3− internally, whereas the flagellate species stored significant amounts of NH4+. Half‐saturation concentrations for NR and NiR were similar between all species, but diatoms had significantly lower temperature optima for NR and NiR than did the flagellates tested in most cases. Relative to calculated biosynthetic demands, diatoms were found to have greater NO3− uptake and NO3− reduction rates than flagellates. This enhanced capacity for NO3− uptake and reduction along with the lower optimum temperature for enzyme activity could explain differences in nitrogen release patterns between diatoms and flagellates after an increase in irradiance.