bluuebunny/crossref_metadata_2025 huggingface dataset:
NUCLEOTIDE SEQUENCES OF SMALL‐SUBUNIT AND INTERNAL TRANSCRIBED SPACER REGIONS OF NUCLEAR rRNA GENES SUPPORT THE AUTONOMY OF SOME GENERA OF THE GELIDIALES (RHODOPHYTA)
Authors: Patwary Mohsin U. , Sensen Christoph W. , MacKay Ron M. , van der Meer John P.
Published: March 2003

The lack of homogeneity in all previously proposed, distinguishing characteristics has left the relationships of taxa within the Gelidiales as one of the most enduring taxonomic uncertainties in the Rhodophyta. Although a precise knowledge of the taxonomy of commercially harvested members of the Gelidiales would assist resource management, agronomic practices, and marketing, even the distinction between two major groups, Gelidium and Pterocladia, has long remained controversial. In this study, the 18S ribosomal RNA (rRNA), internal transcribed spacer 1 (ITS1), 5.8S rRNA, and ITS2 regions of Gelidium latifolium (Greville) Bornet et Thuret, G. sesquipedale (Clemente) Thuret in Bornet et Thuret, G. vagum Okamura, Pterocladia lucida (Brown ex Turner) J. Agardh, and a recent segregate from Pterocladia, Pterocladiella capillacea (Gmelin) Santelices et Hommersand, were sequenced and analyzed. The ITS1, 5.8S rRNA, and ITS2 regions of G. arbuscula (Montagne) B=orgesen, G. canariensis (Grunow) Seoane‐Camba, G. capense (Gmelin) Silva, and G. pristoides (Turner) Kützing were also sequenced. Phylogenetic analyses based on the 18S rRNA genes from four Gelidium species, Pterocladia lucida, and Pterocladiella capillacea, compared with 18S rRNA genes from several other red algae confirmed the division between Gelidium and the Pterocladia/Pterocladiella isolates and were consistent with the recently proposed segregation of Pterocladiella from Pterocladia. Analyses based on the ITS regions of seven Gelidium species, Pterocladia lucida, and Pterocladiella capillacea were completely consistent with the conclusions drawn from the 18S rRNA data. There were extensive length and sequence differences between Gelidium and Pterocladia/Pterocladiella. In addition, there were larger sequence differences between Pterocladiella and Pterocladia than exist among Gelidium isolates, in keeping with the recently proposed separation of the former two taxa.
IDENTIFICATION AND ENUMERATION OF CULTURED AND WILD PSEUDO‐NITZSCHIA (BACILLARIOPHYCEAE) USING SPECIES‐SPECIFIC LSU rRNA‐TARGETED FLUORESCENT PROBES AND FILTER‐BASED WHOLE CELL HYBRIDIZATION
Authors: Miller Peter E. , Scholin Christopher A.
Published: March 2003

Efforts to understand the ecologic and environmental parameters that govern harmful algal blooms (HABs) require rapid and specific identification of causative species. Traditional methods of species identification using light and electron microscopy are useful in this regard but are also time consuming, making routine analysis of a large number of samples difficult. Techniques that speed and ease the detection of HAB species as they occur in natural populations are therefore desirable. In this paper, we continue efforts to develop species‐specific large subunit ribosomal RNA (LSU rRNA)‐targeted fluorescent DNA probes for a variety of Pseudo‐nitzschia H. Peragallo species, a group of marine pennate diatoms that includes representatives linked to production of domoic acid and amnesic shellfish poisoning (ASP). A custom filter tube and filtration manifold that has utility for both whole cell (in situ) hybridization as well as preparing samples for scanning electron microscopy (SEM) is described. Filter‐based whole cell hybridization was used to identify a variety of newly isolated Pseudo‐nitzschia clones, and probe results were confirmed using SEM. Some isolates of P. pungens (Grunow) Hasle exhibited variable (intraclonal) reactivity toward the P. pungens‐specific probe. Three isolates of P. subpacifica (Hasle) Hasle were found to cross‐react with probes designed for P. fraudulenta (Cleve) Hasle and P. heimii Manguin. Four isolates did not react with any species‐specific probes; this group comprised three distinct morphotypes whose fine‐scale morphologic features did not agree with published descriptions of Pseudo‐nitzschia species. Evaluation of the filter method using cultured cells added to natural (whole water) samples indicated quantitative recovery of target species. Confirming results of probe assays using SEM was difficult when the target species was less than 104 cells·L−1 in the presence of greater than 106 cells·L−1 of other nontarget diatom species. A variety of Pseudo‐nitzschia, including P. australis Frenguelli, P. fraudulenta, P. heimii, P. pseudodelicatissima (Hasle) Hasle, P. pungens, P. multiseries (Hasle) Hasle, and Nitzschia americana Hasle, were identified using whole cell hybridization in a variety of field samples containing mixed assemblages of plankton, and these results were confirmed using SEM. The filter tube method of applying probes was used onboard ship for near real‐time identification and enumeration of a variety of Pseudo‐nitzschia species.
ISOLATION, CHARACTERIZATION, AND CHROMOSOME MAPPING OF AN ACTIN GENE FROM THE PRIMITIVE GREEN ALGA, NANNOCHLORIS BACILLARIS (CHLOROPHYCEAE)
Authors: Arai Sayaka , Takahashi Hidenori , Takano Hiroyoshi , Sakai Atsushi , Kawano Shigeyuki
Published: March 2003

Historically, the genus Nannochloris has been classified using the morphology of cell division, although the mechanics of division remain relatively poorly understood. Nannochloris bacillaris reproduces by binary fission. Microscopic observation with fluorescein isothiocyanate‐phalloidin showed that actin filaments localized near the nucleus and appeared as a ring‐ or beltlike structure in the septum‐forming area in the middle of the cell during cell division. In primitive unicellular Chlorophyta such as N. bacillaris, actin is also thought to play important roles in nuclear migration and cell division. The N. bacillaris actin gene has three exons and two introns defined by two exon–intron junctions with splice site consensus sequences. The two introns are located at codons specifying amino acids 3/4 and 47/48. One of these, intron position 3/4, is conserved in the actin gene of Saccharomyces cerevisiae. The actin gene product was predicted to be 378 amino acids long with an estimated molecular weight of 42 kDa. There is only one copy of the actin gene in the N. bacillaris genome. Nannochloris bacillaris has 14 chromosomes that range in size from 230 kb to 3000 kb, and the total size of the genome was estimated to be 20.3 Mb. The actin gene is on either chromosome XI or XII. In a phylogenetic tree based on the actin gene sequence, N. bacillaris diverged before the divergence of Volvox, Chlamydomonas, and higher plants, and very shortly after the radiation of the Rhodophyta.
SELECTIVE PERMEABILITY OF THE EXTRACELLULAR ENVELOPE OF THE MICROALGA SPONDYLOSIUM PANDURIFORME (CHLOROPHYCEAE) AS REVEALED BY ELECTRON PARAMAGNETIC RESONANCE
Authors: Freire‐Nordi Cristina S. , Vieira Armando A. H. , Nascimento Otaciro R.
Published: March 2003

The aim of this work was to investigate the role of the polysaccharide sheath of the microalga Spondylosium panduriforme (Chlorophyceae, Desmidiaceae) in the selective permeability and transport of molecules into the interior of the cell. We have used the electron paramagnetic resonance (EPR) technique applied to a variety of spin labels of a hydrophobic nature with different substitutents on the ring (−OH, =O, −N=C=S, −NH3+, and others). The spin label EPR signals were destroyed as a consequence of metabolic processes once the spin probes had entered the cells. The decay time of the EPR signal was regulated by the diffusion mechanism across the polysaccharide sheath, cell wall, and membrane. To discriminate the effect of the polysaccharide sheath from that of the cell wall and membrane, the polysaccharide sheath was removed by ultrasonic treatment. The decay times for the cells without capsule were faster than those for intact cells, and a possible mechanism of interaction involving hydrogen bonds between the spin labels and the −OH groups of the polysaccharide sheath is presented. These were expressed by their diffusion and friction coefficients as derived from Ficks’ Second Law and the Einstein‐Stokes equation and were summarized in terms of diffusion coefficients (D1) for the capsule medium in the order: =O < −OH < −phe < −H < −N=C=S; and for cell wall and membrane (D2): −OH < −H < =O < −NH3+≅−phe < −N=C=S. For the friction coefficients (f1 and f2), the order was inverted. These results suggest the capsule plays a role in selectivity as a result of polar interactions with the spin labels.
PHOTOPHYSIOLOGICAL EVIDENCE OF NUTRIENT LIMITATION OF PLATELET ICE ALGAE IN MCMURDO SOUND, ANTARCTICA
Authors: Robinson Dale H. , Arrigo Kevin R. , Kolber Zbigniew , Gosselin Michel , Sullivan Cornelius W.
Published: March 2003

Seasonally changing photophysiological and biochemical characteristics of sea ice microalgae are interpreted with respect to light availability and measurements of nutrient concentration made at high vertical resolution (12.5 cm) during a dense bloom in the platelet ice layer of McMurdo Sound during a 6‐week study in austral spring of 1989. Platelet ice algae remained highly shade adapted throughout the spring as shown by their low photoadaptive index (Ek, 3.7–8.4 μmol photons·m−2·s−1), low mean specific absorption coefficient (<0.009 m2 mg−1 Chl a), high optical cross‐sectional area of photosystem II (σPSII, 3.0–8.2), and high molar ratio of fucoxanthin:chlorophyll a (mean = 1.62 ± 0.15 SD). Between 24 October and 8 November, the algae exhibited a photoacclimative response that was marked by a 30% decrease in photosynthetic efficiency (αB), a 75% decrease in maximum photosynthetic rate (PB/m), and a 60% increase in σPSII. The photochemical conversion efficiency at photosystem II (Fv/Fm= ca. 0.5) and the quantum yield of photosynthesis (ØC= 0.062– 0.078 mol C mol−1 photons) were ca. 80% of their maximal values. After 8 November, changes in algal photophysiology and biochemistry, which were inconsistent with a photoacclimation response, suggest that the platelet ice algae near the platelet/congelation ice interface became increasingly nutrient limited. The number of pennate diatoms increased threefold to 150 × 109 cells m−3 between 8 and 14 November, then remained unchanged throughout the remainder of the field season. Following the increase in cell number, Fv/Fm, ØC, and C:Chla decreased by >40%, σPSII increased by 70%; and the biochemical ratios C:N and C:Si increased 25%–30%. Nutrient depletion was apparent from the high‐resolution vertical profiles, but nutrient concentrations limiting algal growth were not observed. However, nutrient concentrations at the likely site of nutrient limitation near the platelet/congelation ice interface were not measured, indicating that higher resolution sampling is necessary to fully characterize this highly variable habitat.
SEQUENCES OF THE LARGEST SUBUNIT OF RNA POLYMERASE II FROM TWO RED ALGAE AND THEIR IMPLICATIONS FOR RHODOPHYTE EVOLUTION
Authors: Stiller John W. , Hall Benjamin D.
Published: March 2003

The Rhodophyta are a widespread group of multicellular eukaryotes that occupy a range of habitats and exhibit a broad variety of morphologies and life histories. Unlike green plants, animals, and even brown algae, the red algae have attained this diversity without having evolved true tissue differentiation. Moreover, the relationship of red algae to other multicellular lineages remains controversial, and the molecular and biochemical mechanisms of their development are largely unexplored. We have isolated the 3′ end of the gene encoding the largest subunit (RPB1) of RNA polymerase II (Pol II) from two divergent red algae, Porphyra yezoensis Ueda and Bonnemaisonia hamifera Heriot. The Pol II largest subunit lies at the catalytic center of the enzyme responsible for mRNA transcription in eukaryotic cells. In plants, animals, and fungi, the 3′ distal region of the RPB1 gene encodes a carboxyl‐terminal domain (CTD) that is the organizing center for assembly of the RNA Pol II holoenzyme essential for developmentally regulated transcription. Examination of rhodophyte RPB1 C‐terminal regions as well as phylogenetic analyses based on conserved gene sequences suggest that the red algae emerged in the course of eukaryotic evolution before the CTD had been codified in the remaining crown taxa. The possibility that a causal relationship underlies the correlated lack of a CTD and absence of tissue differentiation in red algae is proposed as an intriguing subject for further study.
POPULATION STRUCTURE, DYNAMICS, AND PRODUCTION OF THE MEDITERRANEAN MACROALGA CODIUM BURSA (CHLOROPHYCEAE)
Authors: Vidondo Beatriz , Duarte Carlos M.
Published: March 2003

The biochemical composition and metabolism of the balloonlike Mediterranean macroalga Codium bursa J. Agardh are strongly size dependent and constrained by the spherical geometry of its thallus. Changes in reproductive phenology, population structure, density, biomass, and production of this widespread alga were followed over an annual cycle to examine whether mortality rate was size and age dependent. Examination of size and age distributions showed the population to be in quasi‐steady state. A main recruitment event occurred in winter, with the highest gametangial densities observed in October, and the peak of recruits observed in December. The small recruits (0–2 cm in diameter) exhibited high growth (1 cm in <1 month) and mortality rates. High exponential mortality rate was also observed in the larger individuals (>12 cm, or 6 years old). Intermediate size C. bursa showed the lowest mortality rate, indicating that organisms within this size range (3–12 cm) escape advective and grazing losses that decimate small recruits and that they, unlike larger organisms, maintain an adequate physiological status. Asexual gemmation within the intermediate size classes may also contribute to maintain stable populations of this species in the NW Mediterranean littoral zone, since recruits derived from sexual reproduction experience extremely high mortality rates.
THE ENERGETICS OF EXTRACELLULAR FE(III) REDUCTION BY IRON‐LIMITED CHLAMYDOMONAS REINHARDTII (CHLOROPHYTA)
Authors: Xue Xiaoping , Collins Christopher M. , Weger Harold G.
Published: March 2003

Fe‐limited cells of the green alga Chlamydomonas reinhardtii (Fe‐limited growth rate = 0.3 d−1) reduced extracellular Fe(III) to Fe(II) when Fe(III) was supplied as ferricyanide or Fe(III)‐EDTA; Fe(III) reduction was stimulated by light. In both darkness and during photosynthesis, ferricyanide reduction was accompanied by a decrease in cellular NADPH levels, with a concomitant increase in NADP+. NADH and NAD+ levels were not measurably altered during ferricyanide reduction. Furthermore, cellular hexose monophosphate levels declined and 6‐phosphogluconate levels increased during ferricyanide reduction. Levels of most glycolytic and tricarboxylic acid cycle intermediates were mostly unaltered. Ferricyanide reduction was also associated with a decrease in cellular ATP levels, a concomitant increase in ADP and AMP, and increased extracellular acidification. The acidification was sensitive to inhibition by the H+‐ATPase inhibitor N,N′‐dicyclohexylcarbodiimide (DCCD). We conclude that the oxidative pentose phosphate pathway provides reducing equivalents for Fe(III) reduction in darkness and also contributes reducing equivalents to Fe(III) reduction during photosynthesis. The decline in ATP was likely due to activation of the plasma membrane H+‐ATPase during ferricyanide reduction and was not directly associated with provision of reducing equivalents.
DISTRIBUTION OF THE MITOCHONDRIAL DEVIANT GENETIC CODE AUA FOR METHIONINE IN HETEROKONT ALGAE
Authors: Ehara Megumi , Watanabe Kazuo I. , Kawai Hiroshi , Inagaki Yuji , Hayashi‐Ishimaru Yasuko , Ohama Takeshi
Published: March 2003

The DNA sequence of the cytochrome oxidase subunit I (COXI) gene (1059 bp), was determined in a number of heterokont algae, including five species of the Phaeophyceae [Chorda filum (Linnaeus) Stackhouse, Colpomenia bullosa (Saunders) Yamada, Ectocarpus sp., Pseudochorda nagaii (Tokida) Inagaki, Undaria pinnatifida (Harvey) Suringar], and a member of the Raphidophyceae [Chattonella antiqua (Hada) Ono]. The distribution of a deviant mitochondrial code, the AUA codon for methionine (AUA/Met), which was previously reported in the Xanthophyceae, was inferred from these COXI sequences. Comparative analyses of these sequences revealed that all the algae described above bear the universal genetic code, including the assignment for the AUA codon. A phylogenetic tree was constructed using the obtained sequences along with already‐published COXI sequences of various heterokont algae. The clusters of the Xanthophyceae and the Phaeophyceae were resolved as sister groups with high bootstrap support, excluding a bacillariophycean species, a raphidophycean species, and three species of the Eustigmatophyceae. Taking the distribution of the deviant code and the COXI phylogenetic tree together, the genetic code change most probably occurred in an ancestor of the Xanthophyceae after it had branched off from the Phaeophyceae.
EFFECTS OF CADMIUM TOXICITY ON GROWTH AND ELEMENTAL COMPOSITION OF MARINE PHYTOPLANKTON
Authors: Payne Chris D. , Price Neil M.
Published: March 2003

Some classes of marine phytoplankton are believed to be more tolerant of high concentrations of trace metals than others, but the results of experimental tests of this hypothesis are ambiguous. Eleven species of phytoplankton representing five classes were grown in Aquil medium containing Cd concentrations between 10−8 and 10−5 M ([Cd2+]= 10−9.85 to 10−6.84 M), and growth rates and intracellular concentrations of Cd, C, N, and S were measured. The mean Cd2+ concentration (pCd50) that reduced the growth rate of each species to 50% of its maximum varied by 2.5 orders of magnitude, from 10−6.23 for Emiliania huxleyi to 10−8.79 for Synechococcus sp. Taxonomic trends in Cd resistance were not apparent in these data. Cadmium quotas (mol Cd·L−1 cell volume) were lowest in species of Bacillariophyceae (ANOVA, P < 0.001), suggesting that they might regulate Cd transport differently than other taxa. Cellular S:C molar ratios increased in four of seven phytoplankton grown at high pCd (7.37–6.84) compared to low Cd ion concentrations (no added Cd), a result of increases in S·L−1 cell volume. Nitrogen:carbon molar ratios were also higher in Cd‐exposed phytoplankton, as changes in N and S were highly correlated (r= 0.98, P < 0.0001). In two species that were examined, S:C ratios increased as a linear function of increasing Cd concentration. The results demonstrate large variability in Cd resistance among phytoplankton that is primarily a function of interspecific differences in Cd detoxification.
PHYLOGENETIC POSITION OF CHAETOSPHAERIDIUM (CHLOROPHYTA), A BASAL LINEAGE IN THE CHAROPHYCEAE INFERRED FROM 18S rDNA SEQUENCES
Authors: Sluiman Hans J. , Guihal Caroline
Published: March 2003

We sequenced the nuclear‐encoded small‐subunit ribosomal RNA gene (18S rDNA) of Chaetosphaeridium globosum (Nordst.) Klebahn, a microscopic freshwater epiphytic chlorophyte, to assess its phylogenetic affinities in the Chlorophyta. A phylogenetic analysis of a broad sampling of green algal taxa and Chaetosphaeridium confirmed that this alga is a member of the Charophyceae (Streptophyta) as earlier microscopical studies had suggested. However, more detailed phylogenetic analyses of the streptophyte lineage showed that contrary to expectations based on the ultrastructure of the zoospores, the presence of a unique type of setae, the oogamous mode of reproduction, and the occurrence of oscillatory rotations of the cytoplasm, Chaetosphaeridium and Coleochaete are not closely related and do not form a monophyletic clade. Instead, Chaetosphaeridium represents an early branch in the streptophyte lineage that had a near‐simultaneous origin as the Charalean clade and a clade formed by all remaining streptophytes examined (Klebsormidium, Coleochaete, Chlorokybus, Zygnematales, and bryophytes). All phylogenetic inference methods used (neighbor‐joining analysis of Kimura distances, maximum likelihood, and maximum parsimony) resulted in essentially the same tree topology. No Group I introns were found in the 18S rDNA coding region of Chaetosphaeridium. Our molecular phylogenetic analysis of Chaetosphaeridium supports a recent cladistic classification of the Streptobionta by Kenrick and Crane in which Chaetosphaeridium is placed in a monotypic division and class, Chaetosphaeridiophyta and Chaetosphaeridiophyceae, respectively.
AN OPTICAL DETECTION SYSTEM FOR THE STUDY OF FINE SCALE VERTICAL DISPLACEMENT OF MICROALGAE IN AN ARTIFICIAL WATER COLUMN
Authors: Erga Svein Rune , Omar Abdirahman M. , Singstad Ingar , Steinseide Egon
Published: March 2003

A proper knowledge of the vertical organization of the phytoplankton is of fundamental importance for our understanding of the functions of pelagic ecosystems. Essential in this context is the existence of vertical gradients in environmental parameters. However, little is known about how the fine vertical structures of phytoplankton species are formed and maintained. In situ study of phytoplankton is biased by the fact that submersing instruments can disturb or even destroy the fine vertical gradients in species composition and/or cell numbers. We have designed and constructed an optical instrumentation system by which fine‐scale vertical displacements of microalgae can be studied in an artificial water column without influencing fine physical, chemical, and biological structures of the water column. This enables us to find out more about the fine‐scale behavioral responses of microalgae to vertical gradients in environmental parameters. We describe the main system, present some test results, and conclude that our optical system is able to reveal fine‐scale vertical displacements of microalgae in an artificial water column and that the system can detect differences in cell densities down to 100 cells·mL−1.
LOW MOLECULAR WEIGHT CARBOHYDRATE PATTERNS IN THE BANGIOPHYCEAE (RHODOPHYTA)
Authors: Karsten Ulf , West John A. , Zuccarello Giuseppe C. , Nixdorf Oliver , Barrow Kevin D. , King Robert J.
Published: March 2003

The qualitative and quantitative occurrence of low molecular weight carbohydrates (LMWCs) in the Bangiophyceae is surveyed. Members of the orders Erythropeltidales (Sahlingia and Erythrotrichia), Compsopogonales (Compsopogon), and Bangiales (Bangia and Porphyra) all contain floridoside and, in some cases, D‐ and L‐isofloridoside, making the group chemotaxonomically the most homogeneous; L‐isofloridoside occurred only in the Bangiales. The Porphyridiales showed great variation in carbohydrate types: Chroodactylon contained only sorbitol, Porphyridium contained only floridoside, Dixoniella and Rhodella species exhibited only mannitol, and Rhodosorus showed digeneaside and sorbitol, whereas Stylonema contained floridoside, D‐isofloridoside, digeneaside, and sorbitol. The extensive variation in LMWC composition within and between the different orders suggests that the enzyme systems for each might have developed repeatedly in different Bangiophyceae and Florideophyceae. Nonetheless, a phylogenetic tree based on small‐subunit ribosomal RNA supports the LMWC patterns in the Bangiophyceae.
BRYOPSIS MAXIMA (CHLOROPHYTA) GLUTAMATE DEHYDROGENASE: MULTIPLE GENES AND ISOZYMES
Authors: Inokuchi Ritsuko , Motojima Kiyoto , Yagi Yukiko , Nakayama Katsumi , Okada Mitsumasa
Published: March 2003

Subcellular localization of glutamate dehydrogenase (GDH) was investigated in the green alga Bryopsis maxima. Both intact and pure chloroplasts and mitochondria were isolated by two methods: successive centrifugation and continuous Percoll density gradient centrifugation. The NADP‐dependent GDH activities of the chloroplastic, mitochondrial, and cytosolic portions were estimated as 64.3, 9.8, and 25.9%, respectively, and NAD‐dependent GDH activity was observed only in the chloroplasts. Three organelle‐specific isozymes—chloroplastic NADP‐GDH1, cytosolic/mitochondrial NADP‐GDH2, and cytosolic/mitochondrial NADP‐GDH3—were purified. The molecular masses of these isozymes were estimated to be the same (280 kDa). Km values of NADP‐GDH1, NADP‐GDH2, and NADP‐GDH3 for NADPH in the amination reaction were 30, 110, and 34 μM, respectively, and those for NADH were 185, 1490, and 974 μM, respectively, showing different cofactor affinities. Several NADP‐GDHs and one NAD‐GDH were induced in the chloroplasts during incubation of the collected thalli in either continuous light or darkness in aerated seawater for 0 to 5 days, whereas the cytosolic and mitochondrial NADP‐GDHs decreased to an almost undetectable level in 5 days.  Two distinct DNA fragments (BmF‐1 and BmF‐2) encoding B. maxima Okamura GDH were identified and sequenced. They showed 90% homology in their deduced amino acid sequences, whereas synonymous nucleotide substitution was observed in the third position of 52% of the codons. Genomic Southern analysis suggested that the two genes are located at two different loci on the B. maxima chromosome. Thus, B. maxima GDH has been confirmed to be multiple in terms of both protein and gene.  The localization of other nitrogen‐assimilating enzymes was also determined. Glutamine synthetase was located in the chloroplasts and the cytosol, glutamate synthase was located in the chloroplasts, and nitrate reductase was located in the cytosol.
Comparative study ofGymnodinium mikimotoiandGymnodinium aureolum, comb. nov. (=Gyrodinium aureolum) based on morphology, pigment composition, and molecular data
Authors: Hansen Gert , Daugbjerg Niels , Henriksen Peter
Published: March 2003

Light and electron microscopy, nuclear‐encoded LSU rDNA sequences, and pigment analyses were performed on five geographically separate isolates ofGymnodinium mikimotoi.The morphological variation between the isolates equals that found within the isolates. The nuclear‐encoded LSU rDNA sequences were nearly identical in all isolates, and molecular analyses using maximum likelihood, parsimony, and neighbor joining showed the geographical isolates as an unresolved clade. Based on the available data it is concluded that the European isolates, formerly identified asGyrodinium aureolum,Gyrodiniumcf.aureolum, orGymnodiniumcf.nagasakiense, are conspecific with the JapaneseGymnodinium mikimotoi.An isolate from the Pettaquamscutt River, USA, is suggested to represent whatHulburt (1957)described asGyrodinium aureolum.The LSU rDNA sequence data and ultrastructural characters in this isolate closely resemble those ofGymnodinium fuscum, the type species ofGymnodinium, andGyrodinium aureolumHulburt is therefore renamedGymnodinium aureolum(Hulburt) G. Hansen, comb. nov.
DISPERSAL AND COLONIZATION OF THE EPIBIONT ALGA KORSHIKOVIELLA GRACILIPES (CHLOROPHYCEAE) ON DAPHNIA PULICARIA (CLADOCERA)
Authors: Pérez‐Martínez C. , Barea‐Arco J. , Sánchez‐Castillo P.
Published: March 2003

The dispersal and colonization of Korshikoviella gracilipes (Lambert) Silva on Daphnia pulicaria Forbes collected from a small high mountain lake in southern Spain were investigated in a series of laboratory experiments. Results of these laboratory experiments were related to previous field data. Massive release and detachment of zoospores, which is the dispersal stage of the epibiont, occurred just before molting. A lower number of zoospores was dispersed from the discarded molts and a scant number dispersed during the intermolt period. Release of cysts, which is the overwintering stage of the epibiont, mainly occurred immediately after the molt was discarded. The production of dispersal forms (zoospores and cysts) shows precise temporal synchronization with the molting process in Daphnia. The colonization of uninfected individuals from infected molts and from infected individuals was rapid. Our results suggest that colonization of field animals in this lake is efficient and is facilitated by the coincident aggregates of substrate and epibiont.
MOLECULAR PHYLOGENY OF THE HAPTOPHYTA BASED ON THErbcL GENE AND SEQUENCE VARIATION IN THE SPACER REGION OF THE RUBISCO OPERON
Authors: Fujiwara Shoko , Tsuzuki Mikio , Kawachi Masanobu , Minaka Nobuhiro , Inouye Isao
Published: March 2003

A phylogeny of 21 haptophyte algae was inferred by maximum parsimony, neighbor‐joining, and maximum likelihood analyses of sequences of the plastid‐encoded gene,rbcL. Sequence variation in the spacer region of the RUBISCO operon was also investigated. In all therbcL trees constructed, the haptophytes form two distinct clades: one includes the Pavlovales and the other includes the Prymnesiales, Coccosphaerales, and Isochrysidales (allsensuParke and Green 1976. This relationship coincides with the recent taxonomic treatment splitting the division into two subclasses, the Prymnesidae and Pavlovidae (Cavalier‐Smith 1989) or the Prymnesiophycidae and the Pavlovophycidae using botanical suffixes ( Jordan and Green 1994), or into two classes, the Patelliferea and the Pavlovea (Cavalier‐Smith 1993). In the Prymnesiophycidae, all the coccolithophorids examined are placed in a single clade, which suggests a single origin of the coccolithophorids and the ability of coccolith formation in the haptophytes. The genusChrysochromulinais polyphyletic. Species ofChrysochromulinawith a very long haptonema and a compressed cell body (typical of species including the typeC. parvaLackey) form a clade, includingImantonia, that is often classified in the Isochrysidales in the neighbor‐joining tree, whereas some species possessing a nontypical cell body and cell covering form a clade withPrymnesiumandPlatychrysisin all trees. It is suggested that loss of the haptonema inImantoniaand the reduction inPrymnesiumandPlatychrysisoccurred secondarily and independently in two different lineages. Within the coccolithophorids, four clades are recognized:Pleurochrysis,Calyptrosphaera‐Cruciplacolithus‐Calcidiscus‐Umbilicosphaera,Helicosphaera, andEmiliania‐Gephyrocapsa.A non‐coccolith‐bearing haptophyte,Isochrysis, is an ingroup of theEmiliania‐Gephyrocapsaclade, suggesting its secondary loss of the ability to form a coccolith. Sequence comparison of the spacer region of RUBISCO operon supports most results obtained in the analysis ofrbcL sequences. Monophyly of the Prymnesiales sensu Parke and Green is still unclear because of low (<50%) bootstrap support for this group.
QUANTITATIVE ANALYSIS OF SHAPE VARIATION IN TYPE AND MODERN POPULATIONS OFMERIDION(BACILLARIOPHYCEAE)
Authors: Rhode Kristina M. , Pappas Janice L. , Stoermer Eugene F.
Published: March 2003

Subtle differences in valve morphology can indicate sexually isolated populations in diatoms (Bacillariophyceae). Shape descriptors, like Legendre coefficients, have been used to quantify differences in valve outline so that morphologically distinct groups can be recognized. Legendre coefficients were used as shape descriptors to quantify differences in valve outline among five populations in the genusMeridionAg. Two novel populations ofMeridionfrom North America, a North American population ofM. constrictumRalfs, type material forM. circulare(Greve.) Ag., and type material ofM. constrictumwere included in this analysis. Results of a principle components analysis and discriminate analyses on the shape descriptors of all five populations support the hypotheses that the two novel North American populations are undescribed taxa withinMeridionand that the North AmericanM. constrictumcan be consideredMeridion constrictum sensu stricto.A new taxon,Meridion hohiiRhode, is described. There appears to be greater diversity within the genusMeridionthan is currently recognized.
A COMPARATIVE STUDY OF THE RED ALGA GRATELOUPIA FILICINA (HALYMENIACEAE) FROM THE NORTHWESTERN PACIFIC AND MEDITERRANEAN WITH THE DESCRIPTION OF GRATELOUPIA ASIATICA, SP. NOV.
Authors: Kawaguchi Shigeo , Wang Hong Wei , Horiguchi Takeo , Sartoni Gianfranco , Masuda Michio
Published: March 2003

Morphological observations and molecular analyses of the red alga Grateloupia filicina (Halymeniaceae) from two geographically distant regions, eastern Asia (Japan and northern China) in the northwestern Pacific and Italy in the Mediterranean, reveal the presence of two distinct entities. Morphologically, the eastern Asian entity differs substantially from the Italian entity in the following ways: 1) thin and soft thalli with wider axes, 2) denser medullary filaments, 3) scattered reproductive structures over the entire thallus, and 4) a mature auxiliary cell that is oval and slightly larger than other ampullary cells. Phylogenetic analysis based on the ribulose‐1,5‐bisphosphate carboxylase/oxygenase gene (rbcL) sequences revealed that the eastern Asian and Italian entities are phylogenetically far apart, strongly supporting the differentiation of these two entities at the species level. The eastern Asian entity is therefore described as a new species, Grateloupia asiatica. This species can be distinguished from most known species of Grateloupia that have widely flattened thalli by its compressed to narrowly flattened axes with numerous pinnate proliferations and from a few species with similar thalli by a particular combination of features, including a gelatinous texture, mostly simple and narrower axes, a thinner cortex, and the absence of catenate proliferations.
GENETIC VARIABILITY AND POTENTIAL SOURCES OFGRATELOUPIA DORYPHORA(HALYMENIACEAE, RHODOPHYTA), AN INVASIVE SPECIES IN RHODE ISLAND WATERS (USA)1
Authors: Marston Marcia , Villalard‐Bohnsack Martine
Published: March 2003

Grateloupia doryphora(Montagne) M.Howe is an invasive foliose alga that was reported for the first time in Rhode Island, USA in 1997. The population has since increased in size and expanded in range. In this study, the genetic variation and potential sources of the Rhode IslandG. doryphorapopulation were examined using three types of molecular markers: randomly amplified polymorphic DNA (RAPD), nuclear internal transcribed spacer (ITS) sequences, and mitochondrial cox2–cox3 intergenic spacer (COX) sequences. No variation was detected in ITS or COX sequences among Rhode IslandG. doryphoraindividuals. RAPDs, however, did reveal genetic variation, although banding patterns were similar, with RAPD genetic distances between individuals ranging from 0.00 to 0.17. The low level of genetic diversity observed within the Rhode Island population may be due to a small founder population or a founder population derived from a genetically uniform source. To identify possible sources of the Rhode Island invasion, individuals from nine geographically diverse populations of folioseGrateloupiawere compared. Phylogenetic trees inferred from RAPD distances and ITS and COX sequences had similar topologies; thus there was phylogenetic congruence among these independent loci. The Rhode IslandG. doryphoraspecimens were genetically similar to specimens fromG. doryphorapopulations located in Portsmouth, England; Tholen Island, The Netherlands; and Brittany and Hérault, France. Interestingly, theG. doryphorapopulation in each of these locations is itself due to an introduction event within the past 40 years.
PHOSPHORUS BIOAVAILABILITY MONITORING BY A BIOLUMINESCENT CYANOBACTERIAL SENSOR STRAIN 1
Authors: Gillor Osnat , Hadas Ora , Post Anton F. , Belkin Shimshon
Published: March 2003

Phosphorus (P) is widely considered to be the main nutrient limiting the productivity of freshwater phytoplankton, but an assessment of its bioavailability in natural samples is highly complex. In an attempt to provide a novel tool for this purpose, the promoter of the alkaline phosphatase gene, phoA, from Synechococcus sp. PCC 7942 was fused to the luxAB luciferase genes of the bioluminescent bacterium Vibrio harveyi. The resulting construct was introduced into a neutral site on the Synechococcus sp. PCC 7942 genome to yield strain APL, which emitted light when inorganic P concentrations fell below 2.3 μM. Light emission of P‐deprived cells decreased rapidly upon inorganic P readdition. The reporter was demonstrated to be a sensitive tool for monitoring the bioavailability of both inorganic and organic P sources. In water samples taken from a natural freshwater environment (Lake Kinneret, Israel), the luminescence measured correlated with total dissolved phosphate concentrations.
MULTIVARIATE ANALYSIS OF PERIPHYTON ASSEMBLAGES IN RELATION TO ENVIRONMENTAL GRADIENTS IN COLORADO ROCKY MOUNTAIN STREAMS1
Authors: Griffith Michael B. , Hill Brian H. , Herlihy Alan T. , Kaufmann Philip R.
Published: March 2003

We assessed relationships between chemical and physical characteristics and periphyton assemblages in stream reaches of the mineral belt in the Southern Rockies ecoregion of Colorado, United States. Using canonical ordination analyses, we contrasted results wherein assemblage structure was assessed using community metrics or species abundances. Our objectives were to identify community metrics or individual species diagnostic of the primary environmental stressors in these streams, to compare the sensitivity of these two approaches to determining the primary stressors, and to determine how these approaches may be used to differentiate the effects of these environmental stressors from other gradients. For periphyton metrics, the first axis extracted by redundancy analysis correlated with total phosphorus, substrate coarseness and embeddedness, and riparian vegetation condition, whereas the second axis correlated with dissolved metals. For species abundances, the three axes extracted by canonical correspondence analysis (CCA) were correlated with (1) stream size and types of in‐stream habitats; (2) total phosphorus, dissolved ions, and riparian disturbance by agriculture; and (3) sediment coarseness and embeddedness and riparian vegetation condition. Concentrations of dissolved metals were not correlated with the CCA axes. Analyses of species abundances were sensitive to effects associated with nutrients, substrates, and riparian vegetation, whereas analyses of periphyton metrics were sensitive not only to these nutrient and physical habitat effects but also to toxicological effects associated with metals. As a result, the analyses of periphyton metrics may be used to identify which metrics would be useful for a periphyton index of biotic integrity and would also be individually diagnostic of the larger scale stressors in these streams, nutrient, substrate, and riparian vegetation effects of livestock grazing and increased metal concentrations associated with metal mining.
ALLELOPATHIC GROWTH INHIBITION OF SELECTED PHYTOPLANKTON SPECIES BY SUBMERGED MACROPHYTES1
Authors: Körner Sabine , Nicklisch Andreas
Published: March 2003

Allelopathic effects of submerged macrophytes on the growth and photosynthesis of different unialgal cultures of planktonic cyanobacteria, a diatom, and a green alga were tested in coexistence experiments using dialysis cultures. The method applied allowed measurements under conditions similar to that in lakes but without nutrient and light limitation. Growth and photosynthesis were measured with a pulse amplitude modulated fluorometer as an increase of chlafluorescence and activity of PSII, respectively. Eurasian water milfoilMyriophyllum spicatumL. and rigid hornwortCeratophyllum demersumL. proved to inhibit the PSII activity and then growth of the investigated phytoplankton species, whereas sago pondweedPotamogeton pectinatusL. showed no effect. Growth inhibition was dependent on biomass ofM. spicatum. Considerable differences between phytoplankton groups and among species of cyanobacteria were found regarding their response toM. spicatum. Members of the Oscillatoriales andMicrocystis aeruginosaKütz. emend. Elenkin were more sensitive than the cyanobacteriumAphanizomenon flos‐aquaeRalfs ex Born. et Flah., the diatomStephanodiscus minutulus(Kütz) Cleve et Möller, and the green algaScenedesmus armatusChodat. A possible contribution of this result to changes in the phytoplankton succession of lakes after loss of macrophytes is discussed.
RELATIONSHIP BETWEEN PRESENCE OF A MOTHER CELL WALL AND SPECIATION IN THE UNICELLULAR MICROALGA NANNOCHLORIS (CHLOROPHYTA)1
Authors: Yamamoto Maki , Nozaki Hisayoshi , Miyazawa Yutaka , Koide Tomojiro , Kawano Shigeyuki
Published: March 2003

The cell division mechanisms of seven strains from six species of Nannochloris Naumann were analyzed and compared with those of three species of Chlorella Beijerinck and Trebouxia erici Ahmadjian using differential interference microscopy and fluorescence microscopy. Nannochloris bacillaris Naumann divides by binary fission and N. coccoides Naumann divides by budding. Distinct triangular spaces or mother cell walls were found in the dividing autosporangia of the other five strains from four species of Nannochloris, three species of Chlorella, and T. erici. In an attempt to infer an evolutionary relationship between nonautosporic and autosporic species of Nannochloris, we constructed a phylogenetic tree of the actin genes using seven strains from six species of Nannochloris, three species of Chlorella, and T. erici. Nannochloris species were polyphyletic in the Trebouxiophyceae group. Two nonautosporic species of N. bacillaris and N. coccoides were monophyletic and positioned distally. Moreover, to determine their phylogenetic position within the Trebouxiophyceae, we constructed phylogenetic tree of 18S rRNA genes adding other species of Trebouxiophyceae. Nannochloris species were polyphyletic in the Trebouxiophyceae and appeared in two different lineages, a Chlorella–Nannochloris group and a Trebouxia–Choricystis group. The nonautosporic species, N. bacillaris and N. coccoides, and three autosporic species of Nannochloris belonged to the Chlorella–Nannochloris group. Nannochloris bacillaris and N. coccoides were also monophyletic and positioned distally in the phylogenetic tree of 18S rRNA genes. These results suggest that autosporulation is the ancestral mode of cell division in Nannochloris and that nonautosporulative mechanisms, such as binary fission and budding, evolved secondarily.
A SINGLE ORIGIN OF PLASTIDS REVISITED: CONVERGENT EVOLUTION IN ORGANELLAR GENOME CONTENT1
Authors: Stiller John W. , Reel DeEtte C. , Johnson Jeffrey C.
Published: March 2003

In recent years a consensus has emerged from molecular phylogenetic investigations favoring a common endosymbiotic ancestor for all chloroplasts. It is within this conceptual framework that most comparative analyses of eukaryotic biochemistry and genetics now are interpreted. One of the first and most influential sources of data leading to this consensus is the remarkable similarity in genome content among all major plastid lineages. Here we report statistical analyses of two sequence data sets, genes encoding ribosomal proteins and transfer RNAs, from representatives of the three primary plastid lineages and a mitochondrion. The latter almost certainly originated in an independent endosymbiotic association and serves as a control for similarity due to convergent evolution. When genes related to organelle‐specific function are factored out, plastid genomes appear to be no more similar to each other than they are to the mitochondrion. Total similarities in gene content, measured as deviations from the expectation from a process of random gene loss, are correlated with the extent of reduction in the two genomes compared. They do not appear to reflect putative evolutionary relationships among plastids. These analyses indicate that similarities in plastid genome content are better explained by convergent evolution due to constraint on gene loss than by a shared evolutionary history. A review of other data cited as support for a single plastid origin suggests that the alternative hypothesis of multiple origins is at least equally consistent in most cases.
Biodiversity and Association of Dinoflagellates in Coral Reef Rubble, Carrie Bow Cay, Belize
Authors: Faust M. A.
Published: March 2003

The species diversity and distribution of benthic dinoflagellates are illustrated from the back reef sand habitats at Carrie Bow Cay. Sand appears an ideal environment for nurturing a variety of species. Sand supported blooms of toxic, nontoxic, and parasitic assemblages of dinoflagellates. Morphology of dinoflagellates is illustrated in SEM and LM pictures; including the life cycle of a parasitic dinoflagellate's vegetative stage, sporogenetic stages, and the morphology of the feeding organelle. The feeding organelle of the primary dinoflagellate cysts is a hold fast and a peduncle‐like infestation tube, a ‘sucker organelle’, that inserts itself into copepod eggs. The parasitic dinoflagellate continues feeding on crustacean eggs since it is the only food source during vegetative cell division within the cyst. This is the first observation of the presence of parasitic dinoflagellates in shallow coral reef water. The study attempts to provide new knowledge on dinoflagellate associations and morphology of sand‐welling species in the microscopic food web of shallow warm tropical waters. Even, sand‐inhabiting invertebrates are not exempt from parasitic dinoflagellates.
Effects of Outgroup Selection on Phylogenetic Hypotheses of the Heterokont Algae
Authors: Goertzen L. R. , Theriot E. C.
Published: March 2003

Nuclear ribosomal SSU and chloroplast rbcL data for heterokont algae and potential outgroups were analyzed separately and together under parsimony. A series of taxon sampling experiments were performed. Traditional heterokont classes (e.g. diatoms, phaeophytes, etc.) were monophyletic in most analyses of either dataset and in both together. Relationships among classes and of heterokonts to outgroup taxa are sensitive to taxonomic sampling. Stability of heterokont algae relationships was analyzed by deletion of outgroup classes, starting with those presumably most distant from the heterokonts to those closest. In only three analyses using SSU data were the heterokonts monophyletic: with all available outgroup taxa, with the outgroup being hyphochytrids alone or with the outgroup being hyphochytrids plus Developayella. For rbcL data, heterokonts were monophyletic when all available rhodophytes were used, when any combination of rhodophytes tested were used, and when rhodophytes plus bacteria were used. Any addition of cryptophyte and/or haptophyte sequence resulted in a nonmonophyletic heterokont algae. In both cases, distribution of heterotrophic stramenopiles among the heterokont algae changed as different outgroups were used. Combined data was similarly equivocal about monophyly of the heterokont algae. The literature suggests that this result is obtained regardless of whether parsimony or likelihood methods are used, and that is because taxon sampling affects all inference procedures. We suggest not only that more molecular data be obtained, but that morphological evidence for monophyly of the heterokonts be re‐examined. Finally, a community effort needs to be made to synchronize character sampling across different datasets to increase the number of taxa sampled and to create parallel datasets for all data types.