bluuebunny/crossref_metadata_2025 huggingface dataset:
STEROLS AS BIOMARKERS IN GYMNODINIUM BREVE: DISTRIBUTION IN DINOFLAGELLATES
Authors: Leblond J.D. , Chapman P.J.
Published: March 2003

The sterol composition of marine microalgae has been shown to be a chemotaxonomic property potentially of value in distinguishing members of different algal classes. For example, members of the class Dinophyceae display sterol compositions ranging from as few as two (cholesterol and dinosterol in Alexandrium tamarense) to as many as twelve in certain Heterocapsa species. Certain of these are 4‐methyl sterols rarely found in other classes of algae. The ability to use sterol biomarkers to distinguish certain dinoflagellates such as the toxic species Gymnodinium breve, responsible for red tide events in the Gulf of Mexico, from other species within the same class would be of considerable scientific and economic value. Gymnodinium breve has been shown by others to possess two principal novel sterols, (24S)‐4a‐methylergosta‐8(14), 22‐dien‐3b‐ol (ED) and its 27‐nor derivative (NED), not previously known to be present in other dinoflagellates. Characterization of free and esterified sterols from laboratory cultures of G. breve and of samples from a recent bloom in the Gulf of Mexico has confirmed the predominance of these two sterols. This has prompted a study of the sterol signatures of more than 30 dinoflagellates. ED and NED were shown also to be the primary sterols of the closely related dinoflagellates G. mikimotoi and G. galatheanum. They are also found as minor components of the more complex sterol profiles of other members of the Gymnodinium‐Peridinium‐Prorocentrum (GPP) taxonomic group. The more widespread distribution of this sterol pattern is consistent with the known close relationship between G. breve and G. mikimotoi.
PHYLOGENY OF THE EUGLENOPHYTES: ANALYSIS USING SSU RDNA AND ULTRASTRUCTURAL CHARACTERS
Authors: Linton E.W. , Triemer R.E.
Published: March 2003

The use of both molecular and morphological data to determine relationships among the euglenoids is vital for a complete understanding of their phylogeny, and the development of an accurate taxonomy. Analyses of the SSU (18S) rDNA from 12 euglenoid genera have resulted in tree topologies that are in agreement with many defining morphological characters. The euglenoid lineage is formed by phagotrophic euglenoids at its base, followed by the divergence of phototrophs that in‐turn gave rise to osmotrophs. The photosynthetic lineage is anchored by euglenoids with two emergent flagella, Eutreptia and Eutreptiella, while the remainder of the lineage is composed of euglenoids with a single emergent flagellum. Among the photosynthetic euglenoids with a single emergent flagellum those that secrete mucilaginous stalks, Colacium, or form a lorica, Trachelomonas and Strombomonas, are closely associated. The remaining photosynthetic genera Euglena, Phacus, and Lepocinclis are intermixed with each other and the osmotrophic genera Astasia, and Khawkinea. Hence, they are not monophyletic, sensu Hennig. To reinforce molecular phylogenies, a robust morphological character database is necessary. For taxa with complex internal structures complete serial reconstruction is required. Serial reconstruction of the flagellar and feeding apparatuses in Ploeotia costata illustrate this necessity. Originally described as having both an MTR (Type I) and a Type II feeding apparatus, reconstruction has shown P. costata to have a single, Type II, feeding apparatus. Moreover, the Type II now appears to be an autapomorphy for Ploeotia species, while euglenoid feeding apparatuses, in toto, appear to form a continuum of structural types.
COMBINED EFFECTS OF MACRONUTRIENTS AND METALS ON THE ADRIATIC GREEN ALGA ULVA RIGIDA C.AG.
Authors: Munda I. M. , Veber M.
Published: March 2003

The ephemeral green alga Ulva rigida C. Ag. is common in polluted and eutrophicated sites of the northern Adriatic. Its tolerance and responses to the combined effects of excess macronutrients (nitrates, phosphates) and metals (Mn, Co, Zn) that are essential micronutrients were studied in vitro regarding growth expressions, survival, elemental composition (N, C, P), and metal accumulation. Plants belonging to vernal/estival and autumnal populations were compared. Excess nutrients were applied together with the single metals. Nitrate and phosphate were used separately and in a dual combination. In control samples that lacked metals, it was obvious that plants belonging to vernal and estival populations grew better in phosphate than in nitrate enriched media and that the opposite was true for autumnal plants. The presence of metals altered the responses of U. rigida to excess nutrients. In some of the samples a relationship between Mn accumulation and growth was indicated, Mn promoting growth. Metal accumulation was greater in the autumnal than in the vernal and estival plants, being the highest for Mn and lowest for Zn. A comparison between experimental series of different duration revealed that the metal accumulation increases time‐dependently for Mn and Co. The N and P content of the plants followed the nutrient enrichment of the media. Autumnal plants accumulated more N and P than vernal and estival ones. It was obvious that the presence of metals influences the nitrogen uptake of U. rigida, in the sequence Mn‐Co‐Zn. The presence of Mn promotes nitrogen uptake and that of Zn is inhibitory.
THE PHYLOGENY OF CAULERPA BASED ON RDNA INTERNAL TRANSCRIBED SPACER SEQUENCES
Authors: Nemeth S. , Mai T.T. , Zechman F.W.
Published: March 2003

Phylogenetic hypotheses for the pantropical marine green algal genus, Caulerpa, were inferred based on analyses of nuclear‐encoded rDNA internal transcribed spacer (ITS) sequences. Results of these analyses were used to assess the correspondence between rDNA phylogeny and traditional sectional taxonomy, to identify synapomorphic morphological characters (including assimilator morphology and chloroplast ultrastructure), and to examine marine biogeographic hypotheses for the genus. Ribosomal DNA ITS sequences were aligned for thirty‐three species and intraspecific taxa of Caulerpa. Results indicate limited correspondence between phylogeny and sectional taxonomy for the genus, (e.g., the sections Filicoideae and Sedoideae were not monophyletic). In contrast, chloroplast morphology could be mapped to the tree topology with limited homoplasy. Pantropical isolates of the filicoidean species, Caulerpa sertularioides and Caulerpa mexicana each formed monophyletic groups. Caulerpa reyesii was included as a derived taxon within the Caulerpa taxifolia clade, suggesting that these species were conspecific and affirmed the lack of correspondence between phylogeny and assimilator morphology. Isolates and various intraspecific taxa of Caulerpa racemosa did not form a monophyletic group. Instead, these taxa formed a heterogeneous assemblage with other sedoidean and filicoidean taxa. Within the C. sertularioides clade, Caribbean and Atlantic isolates formed a basal paraphyletic group, whereas eastern and western Pacific isolates formed a more derived monophyletic group. Therefore, these results are not consistent with an Indo‐West Pacific origin of this species.
FINE STRUCTURE OF PHACUS SPLENDENS POCHMAN (EUGLENOPHYTA)
Authors: Nudelman  , Leonardi P. , Farmer  , Conforti V.
Published: March 2003

The general fine structure of P. splendens Pochman (Section Pleurapsis) is described. This Section comprises a series of species with very distinctive features unshared by the majority of the members of the genus. The cells are pear‐shaped in frontal view, rounded at the anterior end, narrowed posteriorly tapering in a long twisted tail. In lateral view, the anterior margins are asymmetric, undulate to serrate. The pellicle is strongly striated, with ribs helically arranged, oriented to the left, concavely depressed between adajcent ribs. In transverse section, the pellicle outline shows a single microtubule in the middle of each rib, on the base of a central sulcus. The other two are located one at each side of the sulcus. Among other distinguishing characteristics, the most remarkable feature is the presence of a single chloroplast, a fact never reported in this genus before since the minimal observed number is two and most of the Phacus species have been described as having numerous, small and discoid chloroplasts. In longitudinal section, a large, leaf‐like parietal chloroplast is observed. It extends along the entire cell, bearing three prominent cup‐shaped paramylon caps on the external face. In transverse section is C‐shaped. The unusual shape and localization of the chloroplast and paramylon in this species resemble descriptions of Cryptoglena pigra, suggesting a closer relationship to this organism than to other members of Phacus.
TAXONOMIC REASSESSMENT OF THE GENUS PADINA (DICTYOTALES, PHAEOPHYTA) IN THE GULF OF CALIFORNIA, MÉXICO
Authors: Paul‐Chávez L. , Riosmena‐Rodriguez R. , Angeles‐Pérez A.
Published: March 2003

Padina is one of the most important genera in the coastal zone of the Gulf of California because of their biomass. Eight species have been recorded for the area: P. tetrastromatica, P. durvillaei, P. gymnospora, P. mexicana, P. caulencens, P. concrescens, P. crispata y P. vikeersiae based on taxonomic and floristic studies. Unfortunately, until today, a comparative study of all these species in a modern context was not available. Intensive surveys in 100 localities around the area yield more than 1000 specimes and 500 slides were analyzed and compared with relevant types. Taxonomic evaluations were developed using 16 characters commonly used in the literature. As a result of our analysis, only five characters can discriminate species. Based on character analysis and comparisons with proper type material, only three species can be recognized in the zone: P. concrencens, P. durvillaei and P. mexicana. In the case of P. crispata, we conclude that it is a heterotypic synonym for P. mexicna. But in the case of P. gymnospora, P. tetrastromatica and P. vikersiae, all previous records represent mis‐identifications.
SONDERELLA, LEMBERGIA AND THE NEW TRIBE SONDERELLEAE (RHODOMELACEAE, RHODOPHYTA)
Authors: Phillips L.E. , Nelson W.A. , Kraft G.T.
Published: March 2003

The monospecific genus Sonderella is endemic to Australia and has been the subject of speculation with regard to its taxonomic position. When the anatomy and reproduction of this genus were comprehensively described by Womersley in 1965, he recommended its inclusion in the Rhodomelaceae and foreshadowed that it would warrant its own tribe. Recent molecular investigation has confirmed its position within the Rhodomelaceae. Classical anatomical investigation of the rare and poorly‐known New Zealand endemic genus Lembergia has shown that it shares many features with Sonderella, including vegetative construction and position and construction of the reproductive structures. Molecular investigations of the 18S rRNA gene support the close relationship of the two genera and their inclusion within the Rhodomelaceae as a separate tribe, the Sonderelleae tribus novum.
ANALYSIS OF NUCLEAR MUTANTS OF CHLAMYDOMONAS DEFICIENT IN THE ACCUMULATION OF SPECIFIC CHLOROPLAST RNAS
Authors: Rochaix J.D. , Boudreau E. , Nickelsen J. , Lemaire S. , Vaistij F. , Goldschmidt‐Clermont M.
Published: March 2003

Genetic analysis has revealed that the accumulation of several chloroplast mRNAs of the green alga Chlamydomonas reinhardtii requires specific nucleus‐encoded functions. We have characteized three nuclear mutants, nac2, 222E and F24 which lack psbD, psbB and psaB mRNA, respectively. In each case we have shown that the target of the nucleus‐encoded function affected in these mutants is the 5′ untranslated region of the corresponding mRNA (3, 4, 5). We have cloned the nuclear Nac2 and Mbb1 genes by rescue of the mutants which are deficient in the accumulation of the mRNAs of psbD and the psbB/psbT/psbH chloroplast transcription unit.. Nac2 encodes a hydrophilic polypeptide of 1385 amino acids with 9 tetratricopeptide repeats (TPR) in its C‐terminal half whereas Mbb1 encodes a polypeptide of 662 amino acids which also contains 9 TPRs. Both proteins contain a putative chloroplast transit peptide at their N‐terminal end. They have been tagged with the HA epitope and localized in the stromal compartment of the chloroplast. Nac2 and Mbb1 are part of a high molecular weight complex of 500 and 250 kDa, respectively, which is associated with RNA in the case of Nac2. A change of a conserved Ala residue of the fourth TPR motif by site‐directed mutagenesis completely abrogates Nac2 function indicating that this TPR is important for psbD mRNA stability, processing and/or translation.
POPULATION PARAMETERS AND PHOTOSYNTHETIC CAPABILITIES OF CORALLINE RHODOLITHS: BIOGEOGRAPHIC IMPLICATIONS
Authors: Steller D. L. , Cabello‐Pasini A. , Riosmena‐Rodriguez R.
Published: March 2003

Rhodoliths are bed forming, unattached coralline algae that incorporate large quantities of carbonate into their thalli in oceans worldwide. Lithophyllum margaritae and Neogoniolithon tricotomun are common Rhodoliths from the Gulf of California, however, little is known about their biogeographic distribution, and their ecological and physiological characteristics. As a consequence, the objective of this study was to define the temporal population dynamics, growth rates and photosynthetic capabilities of L. margaritae and N. tricotomun from the Gulf of California. The Gulf of California is characterized by annual temperature fluctuations that can exceed 20° C. Rhodolith beds exceeding one km in length were observed from the intertidal zone to a depth of approximately 20 m at the southern Gulf. Percent cover estimates for spherical unattached individuals of L. margaritae and N. tricotomun ranged from 10 to 100%. Growth rates were determined by staining the rhodoliths with Alizarine red and evaluating the linear increment of calcium carbonate after an incubation period in the field. Annual growth rates averaged 1.8 mm year−1 in L. margaritae and 3.4 mm year−1 in N. tricotomun, however, growth rates varied seasonally. The photosynthetic response of both species as a function of temperature was evaluated in the laboratory from 10° to 30° C. Maximum net photosynthetic rates peaked at approximately 25 to 30° C in both species, suggesting that maximum growth rates occur during the warmest months of the year. These results lead to a better understanding of the biogeographic ranges of subtidal coralline algae.
THE EVOLUTION OF RNA POLYMERASE II IN RED ALGAE
Authors: Stiller J.W. , Riley J. L. , Hall B.D.
Published: March 2003

Whether red algae are the sister group to green plants has been an intriguing question for over a century. We are investigating both the evolutionary and functional significance of differences in DNA‐dependent RNA polymerase II between rhodophytes and other eukaryotic organisms. Results of both phylogenetic and genetic complementation studies are consistent with an origin of the Rhodophyta that was independent of the common ancestor of green plants, animals, fungi and several related protistan groups. Examination of long‐branch attraction among Pol II gene sequences indicates that this separate emergence of red algae is not the result of an artifactual grouping of rhodophytes with more rapidly evolving taxa. The absence in red algal pol II largest subunits of a canonical C‐terminal domain (CTD), an essential component of mRNA transcription in plants, animals and fungi, further supports the proposition that red algae diverged independently of these groups, and before CTD function was incorporated fully into Pol II function. Evolutionary complementation, that is, in vivo replacement of the wild‐type CTD from yeast with RPB1 C‐terminal sequences from a red alga, further supports the hypothesis that fundamental differences exist in Pol II function between red algae and organisms with a CTD‐based mRNA transcription cycle.
BIOCHEMISTRY OF SILICA BIOMINERALIZATION IN DIATOMS
Authors: Sumper M.
Published: March 2003

Diatoms are well known for the intricate patterns of their silica‐based cell walls. The complex structures of diatom cell walls are species specific and become precisely reproduced during each cell division cycle, indicating a genetic control of silica biomineralization. Therefore, the formation of the diatom cell wall has been regarded as a paradigm for controlled production of nanostructured silica. However, the mechanisms allowing biosilicification to proceed at ambient temperature at high rates have remained enigmatic. Recently, we have shown that a set of highly cationic peptides (called silaffins) isolated from Cylindrotheca fusiformis shells are able to generate networks of silica nanospheres within seconds when added to a solution of silicic acid. Different silaffin species produce different morphologies of the precipitated silica. Silaffins contain covalently modified Lys‐Lys elements. One of these lysine residues bears a novel type of protein modification, a polyamine consisting of 6–11 repeats of the N‐methyl‐propylamine unit. In addition to the silaffins, additional polyamine‐containing substances have been isolated from a number of diatom species that may be involved in the control of biosilica morphology. Scanning electron microscopic analysis of diatom shells isolated in statu nascendi provide insights into the processes of pattern formation in biosilica. A model will be discussed that explains production of nanostructured biosilica in diatoms on the basis of these experimental results.
THE ROLE OF CALCIUM IN FLOW‐STIMULATED BIOLUMINESCENCE OF THE RED TIDE DINOFLAGELLATE LINGULODINIUM POLYEDRUM
Authors: Von Dassow P. , Latz M.I.
Published: March 2003

Many marine planktonic dinoflagellates emit flashes of light in response to either laminar or turbulent flows as well as direct mechanical stimulation. The production of a flash of light is known to be mediated by a proton‐mediated action potential across the vacuolar membrane; the mechanotransduction process initiating this action potential is unknown. Here we report on an investigation into the role of Ca+2 in the mechanotransduction process regulating bioluminescence in the red tide dinoflagellate Lingulodinium polyedrum. Calcium ionophores and low concentrations of the membrane‐disrupting agent digitonin stimulated bioluminescence only when calcium was present in the media or added with the agent, indicating that the flash‐triggering vacuolar action potential is specifically stimulated by a calcium influx. A variety of known calcium channel blockers or antagonists inhibited mechanically stimulated bioluminescence but did not affect cellular bioluminescent capacity. In many cases the inhibitory affect occurred after only a brief exposure. In addition, gadolinium (Gd+3), a blocker of many stretch‐activated ion channels, caused potent inhibition of mechanically stimulated bioluminescence. The order of potency of the transition metals tested was La+3 > Gd+3 > Co+2 > Mn+2 > Ni+2, similar to their potency as blockers of known calcium channels. Experiments with a quantified shear flow demonstrated that flow‐stimulated bioluminescence depended on the level of extracellular calcium. Future work will elucidate the signaling pathway involving calcium‐mediated flow‐stimulated mechanotransduction. Our goal is to use bioluminescence as a proxy for the initial cellular mechanotransduction events triggered by fluid flow.
MITOSIS, CELL WALL AND FLAGELLA SYNTHESIS IN SYNCHRONIZED CULTURES OF THE PRASINOPHYTE, SCHERFFELIA DUBIA
Authors: Wustman  , Becker B. , Melkonian M.
Published: March 2003

Cell division occurs within the parental cell wall, yielding two progeny cells. Since Scherffelia dubia sheds all four flagella prior to cell division, the maturing progeny cells must regenerate new cell walls and flagella during and/or after cytokinesis. To better understand these processes, we have synchronized cell division in cultures of S. dubia and observed all stages of mitosis, cytokinesis, and progeny cell maturation, including flagella and cell wall formation, via DAPI staining of fixed cells, DIC microscopy of live cells embedded in agarose and standard TEM. Microscopical observations revealed the following sequence of events: 1) Golgi stacks divide during late interphase and immediately begin producing theca scales; 2) deflagellation and release of the parental cell wall from the plasma membrane occurs during early prophase; 3) synthesis of theca and flagella scales within the Golgi and/or scale reticulum continues throughout mitosis; 4) during cytokinesis, a coalescence of vesicles containing theca scales at the posterior end of the cell results in a cleavage furrow slightly diagonal to the cells' longitudinal axis (40 min); 5) post‐mitotic nascent basal body formation and flagella elongation at the inherited basal bodies (and later at the mature nascent basal bodies) occurs concurrently with continued cell wall synthesis; 6) the cleavage furrow rotates into a transverse position (35 min); 7) reorientation of the nuclei results in a “head to tail” orientation of the maturing progeny cells; and 8) matured progeny cells emerge from the posterior end of the parental theca not before 8 hrs after the onset of mitosis.
KELP ECOLOGY AND THE POINT LOMA KELP FOREST: A BLEND OF THE OLD AND THE NEW
Authors: Dayton P.K. , Tegner M.J.
Published: March 2003

The history of the Point Loma kelp forest parallels that of the earlier pioneers in Europe, with an early descriptive focus moving quickly toward mechanistic studies. At Point Loma, research was initiated because of large‐scale loss of kelps, so from the beginning there was an urgency to restore the kelp forest with a concomitant focus on sea urchin grazing. We review the evolving relationships between new questions and long‐term observations that emphasize both small and large‐scale events in time and space. For example, the early descriptive work grew into small‐scale experimental work that demonstrated problems of scaling up from experiments. As we repeated experiments over larger spatial and temporal scales we learned that the low frequency variation at both scales is extremely important and must be understood before small‐scale results are generalized. Regime shifts in the physical environment and the increasing effects of fishing represent continuing challenges to the kelp community structure that make it critically important to consider scaling problems.
ADVANCES IN A MONOGRAPH OF THE GENUS GRACILARIA (RHODOPHYTA) IN THE MEXICAN ATLANTIC
Authors: Dreckmann K. M. , De Lara‐Isassi G. , Alvarez‐Hernández S.
Published: March 2003

Some species of the genus Gracilaria Greville (Gracilariales, Rhodophyta) are the main source of agar. For that reason, the taxonomic study of the taxon has become relevant for many scholars. In order to bring the Mexican floristics knowledge of the genus into the state‐of‐the‐art about it, we have initiated the needed monography. The character definition has proved to be the most important task. We have found that the most reliable characters for the species delimitation are: general form of the thallus, length and width; form of the axes, length and width; branching pattern; number of axes from the holdfast; form of the holdfast; presence of constrictions at the base of the branches or not; color; length of the segments; consistency; form of the apices; length and thickness of the stipes; surface texture of the branches, smooth, crispidous, etc; adherency to herbarium paper; cellular forms of the transition from cortex to medulla, size and thickness of celular walls of the cells involved; number of celular layers of the cortex, subcortex (if present) and medulla; form, number and distribution of the spermatangial conceptacles; form and size of the cystocarps, if constricted at the base or sessile; diameter of the ostiole and if it is apiculated or not; disposition of the carposporangial chains; form of the gonimoblastic cells, and form and number of tetrasporangia. A diagramatic description for each is provided.
RELATIVE IMPORTANCE OF RECRUITMENT VERSUS REGENERATION IN MAINTAINING THE POPULATIONS OF SARGASSUM HENSLOWIANUM IN PING CHAU, HONG KONG
Authors: Ang P.O.
Published: March 2003

Populations S. henslowianum dominate the shallow subtidal waters of Ping Chau Island, Hong Kong. A study was carried out to evaluate the relative importance of recruitment vs regeneration from the holdfast in the maintenance of these populations. The number of recruits on clearings, artificial and natural substrata as well as the density of the natural populations were evaluated on a periodic basis from March 1998 to March 2000. The results indicated that although up to 85 to 100% of the individuals of this species may be reproductive during the winter reproductive season (Nov to Feb), only up to a maximum mean density of 17 recruits 0.25 m−2 were found in the cleared areas or artificial substrata provided. Less than 10% of these eventually survived the following growth season. In the natural stands, new individuals (recruits) constituted only less than 15% of the mean density. The number of new recruits was particularly low around older individuals. Thus, these populations were mainly made up of older individuals regenerating from their perennating holdfasts. It appears that regeneration from the holdfast is a far more important strategy than recruitment in the maintenance of these populations.
PHYLOGENY, BIOGEOGRAPHY AND LIFE HISTORY EVOLUTION IN THE RED ALGAL FAMILY PHYLLOPHORACEAE (GIGARTINALES)
Authors: Fredericq S. , Lopez‐Bautista J. M.
Published: March 2003

Red algae are exceptional for the great diversity in reproductive morphology and for their complex life histories. In particular, the family Phyllophoraceae, consisting of ∼100 species worldwide, stands out in exhibiting a wide spectrum of unique life history types that makes it unusually interesting for assessing the phylogenetic importance of reproductive traits relative to classification criteria. Type of life history and position of the reproductive structures on the plant body have traditionally formed the basis for separating eleven genera in the Phyllophoraceae; however, phylogenetic analyses inferred from three sets of DNA sequences [chloroplast‐encoded rbcL, nuclear large‐subunit ribosomal RNA gene (LSU), and internal transcribed spacer regions (ITS) of nuclear ribosomal DNA], instead indicate a lack of correlation between type of life history and phylogenetic relationships among the established taxa. This lack of correlation dramatically challenges all of the traditional taxonomy. The study will answer the question which morphological features and which aspects of life history evolution can be used as meaningful indicators of phylogenetic relationships in the Phyllophoraceae. The results are addressed in light of global biogeographic hypotheses for the family.
HIGH BREVETOXIN CONCENTRATIONS IN GYMNODINIUM BREVE BLOOMS ALONG THE NORTHWEST FLORIDA COAST DURING 1999
Authors: Greene R. M. , Walker C.C. , Murrell M.C. , Kurtz J.C. , Stanley R.S. , Genthner F.J.
Published: March 2003

Blooms of the dinoflagellate Gymnodinium breve (i.e. red tides) produce brevetoxins (PbTx) that negatively impact the Gulf of Mexico ecosystem, human health, and local economies. Characterizing and predicting bloom events and their impacts requires knowledge of G. breve abundance and PbTx concentrations in the water column. We report results from a bloom that occurred during the fall and winter of 1999 in NW Florida coastal waters. Data were collected from 16 stations on 3 sampling dates (29 Sept., 9 Nov., 1 Dec.), including basic hydrography, nutrient concentrations, G. breve abundances, and brevetoxin concentrations. G. breve cells were enumerated using flow cytometry and PbTx's were isolated from seawater using dichloromethane (DCM) partitioning. Brevetoxins were quantified by HPLC‐DAD using a C‐18 column and an acetonitrile‐water gradient elution. Literature estimates of total PbTx concentration (PbTx's 1, 2, 3) of cultured and field‐collected G. breve suggest a range in concentration from 7 to 17 pg cell−1. We measured total PbTx levels that greatly exceeded these values [Sept., 47–67 pg cell−1 (n=5); Nov., 59–126 pg cell−1 (n=3), Dec., 12–63 pg cell−1 (n=8)]. PbTx‐2 was the predominant (67–75%) PbTx isomer found in these blooms. PbTx‐1 and PbTx‐3 were found at 11–22% and ND–28% of total PbTx, respectively.
CULTURES OF CHYTRIDS ‐ PARASITES OF ALGAE IN BIOLOGICAL INSTITUTE OF PETERSBURG UNIVERSITY
Authors: Gromov B.V. , Mamkaeva K.A. , Pjusch A.V.
Published: March 2003

During our survey of chytrids occuring on algae in fresh waters in the northwestern part of the Russian Federation we never observed mass development of parasites, but if cultures of Chlorococcum minutum Starr or Tribonema gayanum Pasch. were inoculated with a sample of water (0.5 L), the parasites appeared in 10% of the cases. Two‐clonal (alga and parasite) cultures were obtained by plating of the material on the lawn of algal cells on the solid medium with benzyl penicillin. 22 cultures are now available. For the most part, cultures belong to Rhizophydium species. Chytridium lagenula (Braun) sensu Scherffel is grown on Tribonema gayanum cells. Cultures differ in possible host range, where some have a very wide host range, but others grow only on the cells of Chlorococcum minutum (from 40 strains of different clorococcalean algae examined). Only two Rhizophydium spp. cultures are opportunists and grow on dead algal cells and organic media. Collection is used for the examination of interaction between algae and fungi.
IMPACT OF STRESS CONDITIONS ON THE PHOTOSYNTHETIC MACHINERY
Authors: Grossman A.R. , Van Waasbergen L. , Schwarz S.
Published: March 2003

Organisms sense their environment and attempt to tune their metabolism to ambient conditions to efficiently utilize available resources. Cyanobacteria under conditions of stress (nutrient limitation, excess light) modify the photosynthetic apparatus by eliminating most photosystem II activity and degrading their light‐harvesting complex or phycobilisomes (PBS). We have identified cyanobacterial mutants that cannot acclimate normally to nutrient deprivation. One of these mutants has a lesion in a gene encoding a small polypeptide designated NblA that appears to target the PBS for degradation during nutrient limitation. A second lesion is in the nblB gene, which encodes a polypeptide with homology to a family of lyases involved in attaching chromophores to apophycobiliproteins. This protein may remove bilin chromophores from phycobiliprotein subunits prior to their degradation. A third mutant is defective in nblR, which encodes a transcription factor that controls some of the “general” responses that occur during any of a number of different stress conditions. It is required for degradation of PBS and appears to be necessary for controlling photosynthetic activity during both nutrient limitation and high light conditions; this control is critical for survival of cells during conditions of environmental stress. A fourth mutant is altered in nblS, which encodes a sensor kinase that plays a role in regulating both nutrient stress and high light responses. This sensor protein has a PAS domain, appears to binds a flavin, and integrates the response of the cell to a variety of stress conditions; it may sense the redox status of the cell. I will present a model that describes how cyanobacteria sense and respond to environmental change.
SIGNIFICANCE OF PHYLOGENETIC SYSTEMATICS FOR THE BIOGEOGRAPHY OF THE MARINE RED ALGAE
Authors: Hommersand M.H. , Fredericq S. , Freshwater D.W.
Published: March 2003

Hovencamp (1997) recommends that geographical information can be extracted from cladistic analyses of phylogenetic data in which the Earth's history is resolved in terms of vicariance events that established barriers to migration. Nodes in a cladogram that specify two sister groups which do not overlap in their distributions are taken as evidence for a vicariance event and the sequential order of cladogram nodes leads to a procedure whereby the sequence of vicariance events can be reconstructed. For red algae, two such events are the persistence of the northward extension of the eastern end of Gondwanaland across a cool to warm temperature gradient with the formation of present‐day Australasia, and the opening of the Tethyan Ocean followed by closure of the Tethyan Seaway between Africa and Eurasia. Phylogenetic hypotheses related to the first of these events are seen among genera belonging to the Bonnemaisoniaceae, Gracilariaceae, Kallymeniaceae, Gigartinaceae, and Delesseriaceae. A Tethyan origin and distribution is exemplified in part by families that comprise the Solieriaceae complex. Orders such as the Rhodymeniales, Halymeniales and the families Ceramiaceae and Rhodomelaceae contain taxa that fall partly into the first and partly into the second category. Phylogenies are constructed from rbcL sequence data and compared to the morphological evidence. The biogeographical speculations resulting from these observations are preliminary in nature and can only be confirmed or refuted with addtional data and more refined analytical techniques.
A SYSTEMATIC STUDY OF GIGAR‐TINACEAE FROM PACIFIC NORTH AMERICA BASED ON MOLECULAR AND MORPHOLOGICAL EVIDENCE
Authors: Hughey J.R. , Hommersand M.H.
Published: March 2003

Greater than 50 species of Gigartinaceae have been described from Pacific North America, about half of which are currently recognized. Although the family is treated extensively in the taxonomic literature, many of the species are still confused and a comprehensive revision is required. We sequenced the rbcL (RuBisCO) gene and ITS (Internal Transcribed Spacer) 1, 2, and 5.8S regions from a large number of recent collections and identified a discrete of number data sets. These were analysed in comparison with the morphological evidence for each of the taxa. Uncertain of the possibility that our operational taxonomic units may not correspond to the types, we developed a protocol for isolating PCR‐friendly DNA from herbarium specimens, some reaching back as far as 1670. The DNA profiles of types and historically important specimens were compared to those for recently collected silica gel‐dried and formalin‐fixed material and assigned correct names. Species studied ranged from Alaska to Mexico and the Gulf of California and were compared to outgroup taxa from Pacific South America and the Southern Ocean. Particular attention was paid to variations in morphology as they relate to habitat with emphasis on the presence or absence of different morphological forms among sympatric and allopatric populations. We recognize 10 species in Chondracanthus (including one new combination and one new species) and 16 species in Mazzaella (including two new combinations and two new species). Finally, we tested a phylogenetic hypothesis inferred for the Gigartinaceae from rbcL sequences for congruence with one generated from ITS sequences.
SUBCELLULAR LOCALIZATION OF IRON AND MANGANESE SUPEROXIDE DISMUTASE IN CHLAMYDOMONAS REINHARDTII (CHLOROPHYCEAE)
Authors: Kitayama Kaoru , Kitayama Masahiko , Osafune Tetsuaki , Togasaki Robert K.
Published: March 2003

Subcellular localization of superoxide dismutase (SOD) isozymes in Chlamydomonas reinhardtii Dangeard was investigated. From both biochemical and immunological studies, Fe‐ containing superoxide dismutase (Fe SOD) was localized in the chloroplast, and the major Mn‐containing SOD (Mn SOD) was localized in the mitochondria. We isolated cDNA clones, Sod1, and Sod2, which encode Mn SOD and Fe SOD, respectively. Genomic DNA hybridization with these SOD clones demonstrated that there are two additional sequences closely related to Sod1. The transcriptional levels of both genes were compared in light‐ and dark‐grown cells. Mn SOD was higher in heterotrophically grown cells, whereas the accumulation of Fe SOD transcripts was higher under phototrophic condition.
EVOLUTION OF THE FUCACEAE (PHAEOPHYCEAE) INFERRED FROM nrDNA‐ITS
Authors: Serrão Ester A. , Alice Lawrence A. , Brawley Susan H.
Published: March 2003

Sequences of the internal transcribed spacer region (ITS‐1, 5.8S, and ITS‐2) of nuclear ribosomal DNA were obtained from 16 species representing all six genera of Fucaceae (Ascophyllum, Fucus, Hesperophycus, Pelvetia, Pelvetiopsis, and Xiphophora) plus one outgroup (Hormosira). Parsimony analysis indicated that the family Fucaceae is monophyletic and that the northern hemisphere taxa are highly divergent from the only southern hemisphere genus, Xiphophora. The genus Pelvetia is not monophyletic because the European P. canaliculata is more closely related to Fucus, Hesperophycus, and Pelvetiopsis than to other Pelvetia species. We establish Silvetia, gen. nov. and transfer the 3 Pacific species of Pelvetia to the new genus. Fucus is monophyletic and not ancestral in the Fucaceae. The ITS sequences identified two strongly supported lineages within Fucus, one with F. serratus sister to the clade containing F. gardneri, F. distichus, and F. evanescens and a second including F. vesiculosus, F. spiralis, F. ceranoides, and F. virsoides. The ITS was not useful for resolving relationships within each of these clusters and between populations of F. vesiculosus. Within‐individual variation in ITS sequences is high in Fucus, a derived genus, compared to Ascophyllum, a more ancestral genus. Mapping of the two characters that form the basis of Powell’s model for speciation in the Fucaceae showed that 1) number of eggs per oogonium has not followed a gradual reduction and that 2) monoecy/dioecy has changed several times during evolution of this family.
SILICON DEPOSITION IN DIATOMS: CONTROL BY THE pH INSIDE THE SILICON DEPOSITION VESICLE
Authors: Vrieling Engel G. , Gieskes W. W. C. , Beelen Theo P. M.
Published: March 2003

To test the hypothesis that silicification occurs under acid conditions in the silicon deposition vesicle (SDV), the acidity of the SDV of the pennate diatoms Navicula pelliculosa (Brébisson et Kützing) Hilse, N. salinarum (Grunow) Hustedt, and Nitzschia sigma (Kützing) Smith was determined during development of new frustule valves. Cells were incubated with the weak base 3‐(2,4‐dinitroanilino)‐3′‐amino‐N‐methylpropylamine (DAMP) followed by immunocytochemical localization in whole cells and on ultrathin sections. After resupplying silicate to cells synchronized by silicon depletion, the uptake of this nutrient from the medium was the same with or without DAMP; new valves developed without morphological aberrations that could conceivably have been caused by the probe. DAMP was found in cellular compartments known to be acidic, such as vacuoles active as lysosomes, the lumen of thylakoids, and microbodies. In the nucleus and mitochondria, which are circumneutral and basic compartments, the probe did not appear. Besides its presence in acidic compartments, DAMP was specifically accumulated within the SDV during formation of new valves; during the process of valve maturation, the SDV seemed to become increasingly acidic. In control experiments using the ionophores chloroquine, valinomycin, and nigericin, the compartmental location of DAMP was clearly disturbed, resulting in a random intracellular distribution. Accumulation of the fluorescent probe rhodamine 123, which can be translocated over membranes by a reducing potential, confirmed that the SDV can translocate weak bases. The results with DAMP suggest that the pH of the SDV is important in the silicification of diatoms: It facilitates a fast nucleation and aggregation of silica particles, thus increasing the rate of formation of the mature frustules. In addition, the acidic environment might protect the newly formed valves against dissolution before completion and coverage by the organic casing prior to their secretion.
THE ROLE OF F‐ACTIN DURING FERTILIZATION IN THE RED ALGA AGLAOTHAMNION OOSUMIENSE (RHODOPHYTA)
Authors: Kim Gwang Hoon , Kim Sung‐Ho
Published: March 2003

The actin cytoskeletons in spermatia and trichogynes of Aglaothamnion oosumiense Itono were studied using fluorescein isothiocyanate (FITC) conjugated phalloidin and the cytoskeletal inhibitors, potassium iodide (KI), cytochalasin‐B, and latrunculin‐A. Microfilaments were localized to the distal ends of elongated spermatia and trichogynes and were more prominent in the trichogyne before spermatium binding. The actin cytoskeleton in spermatia and trichogynes was disrupted by treatment with 0.6 M KI, 100 μM cytochalasin‐B, or 10 μM latrunculin‐A. The actin cytoskeleton in trichogynes recovered within 24 h of removal from the inhibitor, but no recovery was observed in spermatia. Spermatial nuclei entered mitosis as soon as spermatia attached to the trichogyne. The greatest percentage (50%– 60%) of spermatia having completed mitosis was obtained at 60 min after spermatial binding to trichogynes. During mitosis, actin accumulated in the center of the spermatium, thereby separating the two daughter nuclei. Cytoskeletal inhibitors did not affect initial binding of spermatia to trichogynes but did block subsequent stages of fertilization, including spermatial mitosis and gamete fusion. The accumulation of cellulose or β‐linked polysaccharide on the spermatial surface was also blocked by treatment with actin inhibitors. Exposure of the trichogyne to actin inhibitors after gamete fusion caused spermatial nuclei in trichogynes to stop moving and to condense. These results suggest that the microfilaments involved in nuclear division, cellulose deposition into the spermatial wall, gamete fusion, and migration of spermatial nuclei in trichogynes during fertilization in Aglaothamnion oosumiense.
PARTICULATE ORGANIC MATTER AS AN ALTERNATIVE NUTRIENT SOURCE FOR TROPICAL SARGASSUM SPECIES (FUCALES, PHAEOPHYCEAE)
Authors: Schaffelke Britta
Published: March 2003

Large Fucales are abundant on coastal coral reefs of the Great Barrier Reef, but are often limited by the availability of inorganic nutrients. Particle loads in these reef waters are high, which is generally perceived as detrimental for aquatic plants due to a reduction of light. Here, I provide evidence that several abundant Sargassum species supplement their nutrient supply with nutrients derived from the layer of particulate matter (PM) deposited on their thalli. In experiments involving removal or addition of PM, growth rates of Sargassum spp. were up to 180% higher when particles were present on the thalli. Tissue nitrogen and phosphorus levels of thalli with a surface PM layer were 10%–30% higher than those of thalli without PM. The amount of PM deposited in situ on thalli of five species of brown algae ranged from 0.6 to 0.9 g Corg·g−1 dry weight alga, depending on the species’ morphology. I suggest that a nutrient‐rich diffusive boundary layer is created on the thallus surface by an epiphytic microbial community that remineralizes the particulate nutrients. When algal growth is nutrient limited, the use of particle‐derived nutrients as a source alternative to nutrients in the water column may outweigh any potential adverse effects of the thallus particle layer.
THE PHYLOGENETIC RELATIONSHIP OF PFIESTERIA PISCICIDA, CRYPTOPERIDINIOPSOID SP. AMYLOODINOUM OCELLATUM AND A PFIESTERIA‐LIKE DINOFLAGELLATE TO OTHER DINOFLAGELLATES AND APICOMPLEXANS
Authors: Litaker R. Wayne , Tester Patricia A. , Colorni Angelo , Levy Michael G. , Noga Edward J.
Published: March 2003

The taxonomic relationship between heterotrophic and parasitic dinoflagellates has not been studied extensively at the molecular level. In order to investigate these taxonomic relationships, we sequenced the small subunit (SSU) ribosomal RNA gene of Pfiesteria piscicida (Steidinger et Burkholder), a Pfiesteria‐like dinoflagellate, Cryptoperidiniopsoid sp., and Amyloodinium ocellatum (Brown) and submitted those sequences to GenBank. Pfiesteria piscicida and Cryptoperidiniopsoid sp. are heterotrophic dinoflagellates, purportedly pathogenic to fish, and A. ocellatum, a major fish pathogen, has caused extensive economic losses in both the aquarium and aquaculture industries. The pathogenicity of the Pfiesteria‐like dinoflagellate is unknown at this time, but its growth characteristics and in vitro food preferences are similar to those of P. piscicda. The SSU sequences of these species were aligned with the other full‐length dinoflagellate sequences, as well as those of representative apicomplexans and Perkinsus species, the groups most closely related to dinoflagellates. Phylogenetic analyses indicate that Cryptoperidiniopsoid sp., P. piscicida, and the Pfiesteria‐like dinoflagellate are closely related and group into the class Blastodiniphyceae, as does A. ocellatum. None of the species examined were closely related to the apicomplexans or to Perkinsus marinus, the parasite that causes “Dermo disease” in oysters. The overall phylogenetic analyses largely supported the current class and subclass groupings within the dinoflagellates.
EVALUATING THE RELATIONSHIP BETWEEN PHOTOPIGMENT SYNTHESIS AND 2‐METHYLISOBORNEOL ACCUMULATION IN CYANOBACTERIA
Authors: Zimba Paul V. , Dionigi Christopher P. , Millie David F.
Published: March 2003

The relationship between photopigments and the terpene‐derived secondary metabolite, 2‐methylisoborneol (MIB), was analyzed in photoacclimated cultures of Pseudanabaena articulata Skuja throughout growth, during the diel cycle, and following chemical‐induced inhibition of the isoprenoid pathway. Accumulation of MIB coincided with the accumulation of lipophilic and phycobilin pigments during the early to mid‐exponential portion of the growth cycle with the greatest accumulation of MIB during the late‐exponential phase. Cellular release of MIB occurred as culture populations entered mid‐ to late‐logarithmic phase of growth and was greatest in irradiance‐stressed cultures. The greater correspondence of MIB accumulation with photopigments was seen in cultures transferred from a 12:12 h LD photoperiod alone and the consistent relationship between MIB and photopigment accumulation under varying irradiance suggested a photopigment‐dependent regulation for MIB synthesis. However, the consistent allocation of carbon into MIB during instances of phytofluene and tetrapyrrole biosynthetic inhibition within P. articulata and Oscillatoria perornata Skuja indicated that MIB accumulation is not limited by isopreniod‐carbon availability and does not appear to serve as an “overflow” product. Rather, MIB accumulation simply appears to reflect overall carbon accumulation resulting from increased cell metabolism.
Ecophysiological traits explain species dominance patterns in macroalgal blooms
Authors: Lotze Heike K. , Schramm Winfrid
Published: March 2003

Macroalgal blooms are a growing environmental problem in eutrophic coastal ecosystems world wide. These blooms are dominated typically by only one out of several co‐occurring opportunistic species, which are all favored by increased nutrient loads. We asked whether pronounced dominance of filamentous Pilayella littoralis Kjellm. (Phaeophyceae) over foliose Enteromorpha intestinalis L. (Chlorophyceae) in the Baltic Sea can be explained by interspecific physiological differences. In laboratory experiments, we analyzed uptake kinetics of nitrate, ammonium, and phosphate and the time dependency of uptake rates for both species. We further examined growth rates and nutrient assimilation in relation to single and combined enrichment with nitrate and phosphate, and three different nitrogen sources. Overall, we did not detect distinct differences in uptake, growth, and assimilation rates between P. littoralis and E. intestinalis. Minor differences and the related advantages for single species are discussed. Highest maximal uptake rates were found for ammonium, followed by nitrate and phosphate. Strong time dependency of uptake occurred, with the highest rates during the first 15 to 30 min. Nitrate enrichment had far more of an effect on growth than phosphate. Enrichment with urea, ammonium, and nitrate significantly increased growth rates without interspecific differences. A larger surface area to volume (SA/V) ratio in Pilayella compared with Enteromorpha did not translate into greater physiological capacity. We conclude that species dominance patterns in macroalgal blooms are not always a direct result of different ecophysiological traits among species. Ecological traits such as susceptibility to herbivory are important factors in determining species distribution in the field.