bluuebunny/crossref_metadata_2025 huggingface dataset:
INTERGENERIC HYBRIDIZATION AMONG FIVE GENERA OF THE FAMILY LESSONIACEAE (PHAEOPHYCEAE) AND EVIDENCE FOR POLYPLOIDY IN A FERTILE PELAGOPHYCUS×MACROCYSTIS HYBRID
Authors: Lewis Raymond J. , Neushul Michael
Published: October 2004

Hybridization was attempted by combining gametophytes between intergeneric pairs among the following taxa in the Lessoniaceae: Macrocystis pyrifera (L.) C. Agardh, M. integrifolia Bory, M. angustifolia Bory, Pelagophycus porra (Leman) Setch., Nereocystis luetkeana (Mert.) Post & Rupr., Dictyoneurum californicum Rupr., and Dictyoneuropsis reticulata (Saud.) Smith. Hybrid sporophytes were produced in some combinations involving Macrocystis × Pelagophycus and Macrocystis × Dictyoneurum, and in all combinations of Dictyoneuropsis × Dictyoneurum. This is the first report of intergeneric hybrids involving Dictyoneurum. Gametophytes of P. porra had 16–24 chromosomes. Gametophytes from a fertile Macrocystis‐Pelagophycus hybrid were crossed with Macrocystis and Pelagophycus gametophytes. Hybrid male gametophytes and Pelagophycus female gametophytes produced sporophyte progeny, but hybrid males with Macrocystis females did not. A single hybrid female gametophyte did not produce gametophytes in combination with hybrid males, Pelagophycus males or Macrocystis males. The hybrid gametophytes had approximately 30 chromosomes. It is hypothesized that the hybrid is an alloploid, containing a complete set of Macrocystis and Pelagophycus chromosomes, which may have allowed meiosis and sporogenesis to proceed normally in the hybrid sporophyte found in the sea. Thus, reproductive isolating mechanisms appear to operate at both pre‐ and postzygotic stages, and both can be overcome in intergeneric hybrids.
ISOLATION AND FLOW CYTOMETRIC CHARACTERIZATION OF PROTOPLASTS FROM MARINE MACROALGAE
Authors: Corzo Alfonso , Vergara Juan J. , García‐Jiménez M. Carmen
Published: October 2004

Protoplasts were isolated from Ulva rigida C. Agardh (Chlorophyta) and two species of Rhodophyta, Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Folvik and Gracilaria tenuistipitata Chang et Xia var. liui with minor modifications (the inclusion of 0.01% agarase in the set of cell‐wall‐degrading enzymes for the two red algae). Flow cytometric characteristics of freshly isolated protoplasts were determined on a FACScan flow cytometer (FC). The most useful parameters for characterizing protoplasts from marine algae were forward angle light scatter (FSC), orange fluorescence (FL2) and red fluorescence (FL3). Protoplasts from all the species were easily distinguishable when their FSC, FL2, and FL3 signals were combined in the bivariate plots FL3 vs. FSC and FL3 us. FL2. Two alternative techniques to help identify protoplasts from debris in the FC computer screen were developed (for FC without sorting capability). Both techniques were based on the ability of new FCs to record time. The first one was based on the induction of rapid changes of cell volume in response to osmotic stress. Only intact protoplasts responded to changes in the osmotic pressure. The second one was based on the uptake and hydrolysis of fluorescein diacetate by intracellular esterases. Viable protoplasts showed a hyperbolic accumulation of fluorescein with time. Semimaximal fluorescein accumulation was attained in 30.5±9.5 s. Debris was easily recognized since, contrary to protoplasts, it did not show a time‐dependent accumulation of fluorescein.
FACTORS ASSOCIATED WITH HOST SPECIFICITY IN SPOROCLADOPSIS NOVAE‐ZELANDIAE (CHLOROPHYTA)1
Authors: Correa Juan A. , Martínez Enrique A.
Published: October 2004

This study tests the hypotheses that substrate stability and rugose microtopography are the main factors that determine the tissue‐specific epiphytism in the chlorophyte Sporocladopsis novae‐zelandiae Chapman. Both in vitro and field experiments showed that the epiphyte did not develop on stable algal surfaces nor on artificial (smooth or rugose) substrata. In field experiments, however, other macroalgae settled more abundantly on rugose substrata. Similarly, our field experiments did not support the hypothesis that the physical environment provided by the spatial location of the host in the intertidal or subtidal was a relevant factor associated with specificity. In contrast, our laboratory experiments suggested that some component of the host cell wall might trigger the formation of penetrating rhizoids. These did not develop in isolated cultures of the epiphyte but were detected when the epiphyte contacted its natural host. Also, preliminary results showed that rhizoid‐like structures developed, although at very low frequency, only in plants grown in culture medium containing a crude extract of sorus cortical tissue.
RECONSIDERING PREY SPECIALIZATIONS IN AN ALGAL‐LIMPET GRAZING MUTUALISM: EPITHALLIAL CELL DEVELOPMENT INCLATHROMORPHUM CIRCUMSCRIPTUM(RHODOPHYTA, CORALLINALES)1
Authors: Pueschel Curt M. , Miller Theresa J.
Published: October 2004

The association of the limpetTectura testudinalis(Müller 1776) and the crustose coralline red algaClathromorphum circumscriptum(Strömfelt) Foslie (Melobesioideae) is considered a species‐specific mutualism between grazer and prey. Anatomical features ofC. circumscriptum, especially those associated with epithallial cells, have been viewed as being unusual and directly related to the mutualism. Transmission and scanning electron microscopic methods were used to investigate the structure and development of epithallial cells inC. circumscriptum.Contrary to prior reports, terminal cells of the epithallial filaments ofC. circumscriptumundergo senescence and shedding much like epithallial cells in other members of the Corallinales; hence, multicellular epithallial filaments did not evolve in this alga simply because epithallial cells were unable to slough. Although epithallial cells in many coralline algae are lightly calcified, those inC. circumscriptumare heavily mineralized, more so than the underlying initial cells and cells comprising the cortex. As in other coralline algae, starch is absent from the epithallial cells ofC. circumscriptum.The feature of having abundant chloroplasts in the epithallial cells of C. circumscriptum is shared by other species with multi‐cellular epithallial filaments and transiently by species with single epithallial cells. Except for having a thick epithallus, a feature found in other genera and in other species ofClathromorphum, the anatomy ofC. circumscriptumis unexceptional.
LIGHT AND ELECTRON MICROSCOPY OF GRAZING BY POTERIOOCHROMONAS MALHAMENSIS (CHRYSOPHYCEAE) ON A RANGE OF PHYTOPLANKTON TAXA1
Authors: Zhang Xiaoming , Watanabe Makoto M. , Inouye Isao
Published: October 2004

Grazing of fluorescent latex beads, bacteria, and various species of phytoplankton by Poterioochromonas malhamensis (Pringsheim) Peterfi (about 8.0 μm in diameter) was surveyed. The alga ingested fluorescent beads and various live or killed and nomnotile or motile organisms including bacteria, blue‐green algae, green algae, diatoms, and chrysomonads. The size range of grazed prey was from 0.1 to 6.0 μm for latex beads and from 1.0 μm (bacteria) to about 21 μm (Carteria inverse) for organisms. As many as 17 latex beads (2.0 μm) or more than 10 Microcystis cells (5–6 μm) were ingested by a single P. malhamensis cell. Following such grazing, the cell increased in volume by up to about 30‐fold. The range of cell volume of ingested prey was from 0.52 μm3 (bacteria) to about 3178 μm3(Carteria inversa). This study demonstrates for the first time that P. malhamensis is capable of grazing algae 2–3 times larger in diameter than its own cell and of grazing intact motile algae. Poterioochromonas malhamensis is an omnivorous grazer. Food vacuole formation and digestion processes were examined. The membrane that was derived from the plasma membrane and surrounded the prey disappeared sometime after ingestion. The food vacuole was then formed by successive fusion of numerous homogeneous vesicles accumulated around the prey. The prey was enclosed in a single membrane‐bound food vacuole and then digested.
EFFECTS OF CADMIUM ON GROWTH AND SUPEROXIDE DISMUTASE ACTIVITY OF THE MARINE MICROALGA TETRASELMIS GRACILIS (PRASINOPHYCEAE)1
Authors: Okamoto Oswaldo Keith , Asano Cristina S. , Aidar Elisabeth , Colepicolo Pio
Published: October 2004

Marine planktonic algae are frequently exposed to metallic contaminants. Because heavy metals can be assimilated and accumulated by algal cells, they can then be transferred to higher trophic levels of food chains. We studied the effects of cadmium on protein production and the growth of the marine prasinophyte Tetraselmis gracilis (Kylin) Butcher. By means of toxicological assays, we estimated the LC50 of cadmium as 3.2 ppm and 1.8 ppm after 48 h and 96 h of exposure to this heavy metal, respectively. The growth curves and survival percentages of cell cultures in the presence of cadmium were determined, and a proportional reduction of both parameters with increasing metal concentrations was found. When chronically exposed to sublethal concentrations of cadmium, T. gracilis contained high levels of superoxide dismutase (SOD) activity, one of the main enzymes of the cell's antioxidant defense mechanism. Under these growth conditions, total SOD activity in crude extracts was increased by 41% (at 1.5 ppm) and 107% (at 3.0 ppm). Assays of SOD activity in nondenaturing polyacrylamide gels also showed a similar induction by cadmium. These results show that cadmium has potentially toxic properties since it significantly inhibited the growth of T. gracilis at low concentrations and promoted the induction of SOD activity, suggestive of an oxidative stress state. Besides being the first report of SOD in T. gracilis, this work describes experimental evidence of SOD induction by cadmium in this species.
WHY DO DINOFLAGELLATES HAVE LOWER GROWTH RATES?1
Authors: Tang Evonne P. Y.
Published: October 2004

Dinoflagellates have substantially lower growth rates than other taxa of similar size. These low growth rates have been suggested to reflect the lower chlorophyll a to carbon ratio (Chl a:C) in dinoflagellates, but that speculation has never been widely tested. This study tests if the variations in growth rates among taxa are related to differences in Chl a:C using published data. I collected 92 data entries from the literature representing 31 species, mostly from two divisions (Chrysophyta and Pyrrophyta), and found a significant relation (r2= 0.39) between growth and Chl a:C. Since Chl a:C is almost independent of C content, I also developed a growth model using both C and Chl a:C. Together, the two variables explain 68% of variation in algal growth. However, a further 6.4% of the variance in growth can still be attributed to phyletic differences. Low Chl a:C is only a partial explanation for the low growth rates of the dinoflagellates.
FLUORESCENT LABELLING OF THE CYTOSKELETON IN CERAMIUM STRICTUM (RHODOPHYTA)1,2
Authors: Garbary David J. , McDonald A. Rosa
Published: October 2004

Using rhodamine‐phalloidin to detect F‐actin/microfilaments and indirect immunofluorescence to detect tubulin/microtubules, we studied the cytoskeleton in axial cells of Ceramium strictum Harv., especially microfilaments and microtubules associated with cytoplasmic strands (trabeculae) that extend longitudinally through the central vacuole. As axial cells attained mature size, trabeculae became progressively thinner, branched, and then broke down. An extensive microfilament array was present in peripheral parts of axial cells as well as in trabeculae. Microfilament arrays were highly disrupted by cytochalasin‐B; this resulted in small irregular actin structures in axial cell peripheries and occasional dense aggregations at the base of cells. No actin‐fluorescence was detected in intact trabeculae after cytochalasin‐B treatment. Microtubules formed a primary structural component in trabeculae, which were disrupted by griseofulvin (5 to 0.005 μM) but reformed after two days in griseofulvin‐free medium.
PLOIDY ANALYSIS OF THE TWO MOTILE FORMS OFCHRYSOCHROMULINA POLYLEPIS(PRYMNESIOPHYCEAE)1
Authors: Edvardsen Bente , Vaulot Daniel
Published: October 2004

In some cultures of the flagellateChrysochromulina polylepisManton et Parke, established from cells isolated from the massive bloom in Skagerrak and Kattegat in 1988, we observed, two motile cell types. They were termed authentic and alternate cells and differed with respect to scale morphology. To investigate whether or not the two cell forms were joined in a sexual life cycle, the relative DNA content per cell and relative size of cells of several clonal cultures ofC. polylepiswere determined by flow cytometry. Percentages of authentic and alternate cells in the cultures were estimated by transmission electron microscopy.

Pure authentic cultures (α) contained cells with the lowest level of DNA and were termed haploid. Two pure alternate cultures (β) contained cells with double the DNA content of authentic cells and were termed diploid. Other pure alternate cultures contained haploid cells only, or both haploid and diploid cells. Three cell types were observed, each capable of vegetative propagation: authentic haploid, alternate haploid, and alternate diploid cells. Both the haploid and diploid alternate cells were larger than the haploid authentic cells. Cultures containing diploid cells appeared unstable: cell type ratio and ploidy ratio changed during the experiment where this cell type was present, particularly when grown in continuous light. In contrast, cultures with only haploid cells remained unchanged at all growth conditions tested. Light condition may influence cell type ratio and ploidy ratio. Our attempt to induce syngamy by mixing different authentic haploid clones did not result in mating. Assuming that the authentic and alternate cell types are of the same species, the life cycle ofC. polylepisincludes three flagellated scale‐covered cell forms. Two of the cell types are haploid and may function as gametes, and the third is diploid, possibly being the result of syngamy.
DISCONTINUOUS MITOCHONDRIAL AND CHLOROPLAST LARGE SUBUNIT RIBOSOMAL RNAs AMONG GREEN ALGAE: PHYLOGENETIC IMPLICATIONS1
Authors: Nedelcu Aurora M. , Spencer David F. , Denovan‐Wright Eileen M. , Lee Robert W.
Published: October 2004

To provide insights into the occurrence, evolution, and phylogenetic distribution of discontinuous mitochondrial and chloroplast large subunit ribosomal RNAs (LSU rRNAs) among green algae, we surveyed 12 taxa representing three classes of green algae: the Chlorophyceae, Pleurastrophyceae, and Micromonadophyceae (sensu Mattox and Stewart 1984). We present evidence that discontinuous mitochondrial and chloroplast LSU rRNAs are quite widespread among green algae. Mitochondrial LSU rRNAs appear discontinuous in zoosporic chlorophycean lineages displaying a clockwise or directly opposed configuration in their flagellar apparatus, as well as in chlorococcalean autosporic taxa phylogenetically related to them, but are continuous among zoosporic green algal lineages with a counterclockwise flagellar apparatus configuration, as well as among chlorococcalean autosporic taxa phylogenetically related to them. Chloroplast LSU rRNAs appear discontinuous in all of the lineages investigated. Discontinuous mitochondrial LSU rRNA represents a molecular trait that might have originated at or near the base of Chlorophyceae, whereas discontinuous chloroplast LSU rRNA might have developed very early in the evolutionary history of the green algal group itself. We suggest, therefore, that the presence of discontinuous mitochondrial but not chloroplast LSU rRNA can be used as an additional character in assessing phylogenetic affiliations among green algae.
ASTEROMENIA (RHODYMENIACEAE, RHODYMENIALES), A NEW RED ALGAL GENUS BASED ON FAUCHEA PELTATA1
Authors: Huisman John M. , Millar Alan J. K.
Published: October 2004

Asteromenia gen. nov. (Rhodymeniales, Rhodophyta) is proposed with a single species, Asteromenia peltata (W. R. Taylor) comb. nov. (basionym: Fauchea peltata W. R. Taylor). Thalli of the proposed new genus are stipitate with dorsiventral, peltate blades that are initially circular in shape but with age become stellate with ligulate arms. Internally, the blades have a polystromatic medulla of large, hyaline cells, grading into a cortex of smaller, pigmented cells. Clusters of translucent cells occur on the dorsal surface of the blade. Tetrasporangia are formed by transformations of intercalary midcortical cells. Mature tetrasporangia have cruciately arranged spores and are densely aggregated in the cortex, mostly on the ventral surface, but occasional tetrasporangia also arise on the dorsal surface. Carpogonial branches are four‐celled and arise on inner cortical cells. Auxiliary cells are borne on auxiliary mother cells attached to supporting cells of the carpogonial branches. Cystocarps are protuberant, with well‐developed, ostiolate pericarps that often have extended, proboscis‐like necks. The new genus differs from the previously described peltate or dorsiventral taxa in the Rhodymeniaceae by its polystromatic medulla (Maripelta and Sciadophycus have a monostromatic medulla), intercalary tetrasporangia formed in an unmodified cortex, and four‐celled carpogonial branches (Halichrysis, as typified by H. depressa (J. Agardh) F. Schmitz, has terminal tetrasporangia in nemathecia and three‐celled carpogonial branches).
PFIESTERIA PISCICIDA GEN. ET SP. NOV. (PFIESTERIACEAE FAM. NOV.), A NEW TOXIC DINOFLAGELLATE WITH A COMPLEX LIFE CYCLE AND BEHAVIOR1
Authors: Steidinger Karen A. , Burkholder JoAnn M. , Glasgow Howard B. , Hobbs Cecil W. , Garrett Julie K. , Truby Earnest W. , Noga Edward J. , Smith Stephen A.
Published: October 2004

The newly described toxic dinoflagellate Pfiesteria piscicida is a polymorphic and multiphasic species with flagellated, amoeboid, and cyst stages. The species is structurally a heterotroph; however, the flagellated stages can have cleptochloroplasts in large food vacuoles and can temporarily function as mixotrophs. The flagellated stage has a typical mesokaryotic nucleus, and the theca is composed of four membranes, two of which are vesicular and contain thin plates arranged in a Kofoidian series of Po, cp, X, 4′, 1a, 5″, 6c, 4s, 5″′, and 2″″. The plate tabulation is unlike that of any other armored dinoflagellate. Nodules often demark the suture lines underneath the outer membrane, but fixation protocols can influence the detection of plates. Amoeboid benthic stages can be filose to lobose, are thecate, and have a reticulate or spiculate appearance. Amoeboid stages have a eukaryotic nuclear profile and are phagocytic. Cyst stages include a small spherical stage with a honeycomb, reticulate surface and possibly another stage that is elongate and oval to spherical with chrysophyte‐like scales that can have long bracts. The species is placed in a new family, Pfiesteriaceae, and the order Dinamoebales is emended.
AULACOSEIRA SKVORTZOWII SP. NOV. (BACILLARIOPHYTA), A POORLY UNDERSTOOD DIATOM FROM LAKE BAIKAL, RUSSIA1
Authors: Edlund Mark B. , Stoermer Eugene F. , Taylor Christine M.
Published: October 2004

Aulacoseira skvortzowii sp. nov. is a diatom taxon present in modern plankton assemblages and sedimentary deposits from Lake Baikal, Russia. It has been previously reported as A. islandica (O. Müll.) Simonsen, A. islandica ssp. helvetica (O. Müll.) Simonsen, a sporangial frustule of A. baicalensis (K. Meyer) Simonsen, and Aulacoseira “spore”. However, its microstructure, ecology, and ability to form true resting spores provide ample criteria to describe this diatom as Aulacoseira skvortzowii sp. nov.
STRESS TOLERANCE IN INTERTIDAL SEAWEEDS
Authors: Davison Ian R. , Pearson Gareth A.
Published: October 2004

Intertidal seaweeds are periodically exposed to air where they experience a variety of potentially stressful environmental conditions, including nutrient limitation, high light, high and low temperature, desiccation, and osmotic stress. This paper considers the current understanding of stress tolerance in intertidal seaweeds and discusses ways in which future research could increase our understanding of the role of environmental factors in the ecology and physiology of these algae. We believe research is required in at least three areas. 1) Laboratory physiological studies have established that correlations exist between stress tolerance and the vertical distribution of species. However, little information is available on the importance of stress in determining community structure in nature. Field experiments are essential to relate the impact of single or multiple stresses on the survival, growth, and reproductive output of macroalgae. In paticular, it is necessary to clarify the role of sublethal stress in determining the outcome of competitive interactions. 2) With the exception of obvious lethal effects or damage associated with extreme environmental conditions, such as unusually hot and dry weather, it is difficult to evaluate the occurrence and severity of stress in natural populations of seaweeds. There is a need to develop molecular and biochemical markers specific for individual stresses or groups of stresses to allow the unambiguous and direct determination of stressin situ.3) Despite the apparent importance of stress in intertidal seaweeds, we are largely ignorant of the mechanistic basis of tolerance. The application of currently available tools of molecular and cell biology to the investigation of stress‐induced transcriptional and translational changes could enormously increase our understanding of both the sites of, and pathways involved in, stress tolerance. In summary, there are numerous unanswered fundamental questions about the stress tolerance of intertidal seaweeds, providing opportunities for research ranging from field ecology to molecular biology and biochemistry.
SHORT‐TIME SCALE DEVELOPMENT OF A GYMNODINIUM CATENATUM POPULATION IN THE RIA DE VIGO (NW SPAIN)1
Authors: Fermín Eglée Gómez , Figueiras Francisco G. , Arbones Belén , Villarino María Luisa
Published: October 2004

Wind direction and fresh water runoff determine the circulation pattern of the Ría de Vigo (NW Spain), which in turn influence the selection and distribution of its phytoplankton populations. Coastal winds with a south–southwesterly component reverse the positive estuarine circulation in the Ría, causing an off‐shore to in‐shore flow of surface waters and, consequently, the outflow of inner waters via deeper layers. We found that this reversal imposed a selective force on the phytoplankton population: diatoms, which could not counteract the sinking movement of the surface waters, were diminished, while dinoflagellates remained in the water column. From the end of September to the beginning of October 1993, an accumulation of Gymnodimium catenatum Graham was observed coinciding with an intrusion of coastal water induced by westerly winds which provoked a reversal in the circulation of the Ría. The slow reestablishment of the positive estuarine circulation pattern, which was due to a weak coastal upwelling and considerable fresh water runoff, allowed the population of G. catenatum to flourish.
BIOENERGETIC PROCESSES ARE MODIFIED DURING NITROGEN STARVATION AND RECOVERY IN PHORMIDIUM LAMINOSUM (CYANOPHYCEAE)1
Authors: Ochoa de Alda Jesús A. G. , Tapia María I. , Llama María J. , Serra Juan L.
Published: October 2004

In the non‐N2‐fixing cyanobacterium Phormidium laminosum (Agardh) Gomont (strain OH‐I‐pCl1), N starvation induced an increase in the rate of respiration and a decrease in the rate of O2 evolution. When NO3− was added to illuminated N‐starved cells, O2 evolution immediately increased to levels shown by NO3− grown cells, even though N‐starved cells had lost most of their in vitro photosynthetic activities. Stimulation of noncyclic electron flow was maximal under light‐saturating conditions and after 2–3 days of N starvation. The respiratory rate of N‐starved cells was stimulated by the addition of NO3− or NH4+ and partially inhibited at very low irradiances, even in the presence of DCMU (3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea). Results indicate that N‐starved cells obtain the energy supply for N assimilation through a process different from that used by N‐sufficient cells. N‐starved cells were able to take up NO3− in the dark and when illuminated in the presence of DCMU under anaerobiosis. Following NO3− addition, the photosynthetic yield of the in vivo noncyclic electron transport slightly increased, whereas it decreased after NH4+ addition. Addition of NO3− or NH4+ favored photoinhibition of photosystem II, the effect being faster after NH4+ addition.
SYNTHESIS AND BINDING OF PHYCOERYTHRIN AND ITS ASSOCIATED LINKERS TO THE PHYCOBILISOME IN RHODELLA VIOLACEA (RHODOPHYTA): COMPARED EFFECTS OF HIGH LIGHT AND TRANSLATION INHIBITORS1
Authors: Bernard Cécile , Etienne Anne‐Lise , Thomas Jean‐Claude
Published: October 2004

We studied the synthesis and binding of phycoerythrin and its associated linkers to the phycobilisome (PBS) in Rhodella violacea (Kornmann) Wehrmeyer and compared the effects of high light and translation inhibitors on these processes. Rhodella violacea has a simple hemidiscoidal PBS structure with a well‐known composition. The number of PBSs per cell decreases when irradiance is increased, and at higher irradiances the rods are shortened with a specific loss of the terminal hexamer of phycoerythrin (PE) and its associated linker. To test whether or not the observed variations were due to a coordination between the expression of the chloroplast‐encoded PE and the nuclear‐encoded linkers, we inhibited the expression of the chloroplast genes by the translation inhibitor chloramphenicol. In the few PBSs synthesized, the linker associated to the terminal PE hexamer was missing while that associated with the intermediate PE hexamer was still present. The inhibition by cycloheximide of the translation of the nuclear‐encoded linkers did not influence the synthesis of the chloroplast‐encoded phycobiliproteins. The absence of linkers prevented the formation of PE hexamers and their binding to the PBSs.

We therefore propose the existence of two levels of regulation for PE and associated linkers: the intermediate PE hexamer and associated linker are always present even though their amount is reduced when irradiance is increased. In contrast, the terminal hexamer of PE and its associated linker are no longer present under high light. Their absence can be due to a feedback control between the level of PE and the synthesis of the linker: when the level of PE is lowered below a given value by the action of light on the chloroplast, a signal coming from the chloroplast reaches the nucleus and the synthesis of the linker is repressed. There is no sign of nuclear regulation of the synthesis of PE, but the nuclear‐encoded linkers have a structural role in the formation of PE hexamers.
EFFECT OF LOW TEMPERATURE ON THE STEREOISOMER COMPOSITION OF β‐CAROTENE IN THE HALOTOLERANT ALGA DUNALIELLA BARDAWIL (CHLOROPHYTA)1
Authors: Ben‐Amotz Ami
Published: October 2004

Dunaliella bardawil Ben‐Amotz & Avron, a β‐carotene‐accumulating halotolerant alga, was analyzed for the effect of growth temperatures on its pigment content and on the stereoisomeric composition of β‐carotene by the use of advanced liquid chromatography and photodiode array detection. Decreasing culture temperature from 30° to 10°C increased the β‐carotene content twofold and the ratio of 9‐cis to all‐trans β‐carotene fourfold, with no significant changes in the other cell pigments. The variation of total β‐carotene content by temperature was correlated with the integral irradiance received by the algal culture during a cell division cycle, whereas the 9‐cis stereoisomer increased over the amount expected by that integration. The massive accumulation of 9‐cisβ‐carotene within the β‐carotene globules is interpreted as indicating that the oily 9‐cis stereoisomer protects against the crystallization of all‐trans β‐carotene at low temperatures.
EFFECT OF TEMPERATURE ON TWO ENZYMES FROM A PSYCHROPHILIC CHLOROMONAS (CHLOROPHYTA)1
Authors: Loppes Roland , Devos Nathalie , Willem Sabine , Barthélemy Pascal , Matagne René F.
Published: October 2004

A psychrophilic green alga belonging to the Chloromonas genus and here named ANT1 was collected in Antarctica. The activities of two enzymes, nitrate reductase and argininosuccinate lyase, were measured at various temperatures and compared to the corresponding enzyme activities in the mesophilic species Chlamydomonas reinhardtii Dangeard. For both enzymes, the temperature for apparent optimal activity was about 20°C lower in ANT1 than in C. reinhardtii. The enzymes were also submitted to various heat treatments before measuring their activities. Both psychrophilic enzymes were more sensitive to heat than the corresponding mesophilic enzymes. It is worth stressing, however, that in both species nitrate reductase was much more sensitive to heat than argininosuccinate lyase, which probably indicates that the peculiar structure of each protein primarily determines its dependence to temperature. Secondary adaptations to low temperatures should then occur to confer the psychrophilic character.
WIDESPREAD PHAGOCYTOSIS OF CILIATES AND OTHER PROTISTS BY MARINE MIXOTROPHIC AND HETEROTROPHIC THECATE DINOFLAGELLATES1
Authors: Jacobson Dean M. , Anderson Donald M.
Published: October 2004

An electron microscopic examination of large amorphous inclusions located in a variety of photosynthetic thecate dinoflagellates (Alexandrium ostenfeldii (Paulsen) Balech et Tangen, Gonyaulax diegensis Kofoid, Scrippsiella sp., Ceratium longipes (Bailey) Gran, and Prorocentrum micans Ehrenberg) and a nonphotosynthetic thecate species (Amylax sp.) revealed each inclusion to be a food vacuole, the majority of which were ingested ciliate prey. Recognizable features of these ciliates included linear arrays of basal bodies and cilia consistent with oligotrich polykinetid structure, characteristic macronuclei, chloroplasts (evidently kleptoplastids), cup‐shaped starch plates, and cylindrical extrusomes. Three species contained (apparent) nonciliate prey: Scrippsiella sp., whose food vacuoles consistently contained unusual and complex extrusome‐like cylindrical bodies having a distinctive six‐lobed, multilayered structure; P. micans, which contained an unidentified encysted cell; and a single A. ostenfeldii cell, containing a Dinophysis sp. dinoflagellate cell. Several food vacuoles of ciliate origin had a red hue. This, together with the resemblance of A. ostenfeldii cells to planozygotes, suggests that similar structures previously identified as accumulation bodies may in fact be food vacuoles and that feeding may in some cases be associated with sexual processes.
MOLECULAR IDENTIFICATION OF A BACTERIUM ASSOCIATED WITH GALL FORMATION IN THE MARINE RED ALGA PRIONITIS LANCEOLATA1
Authors: Ashen Jon B. , Goff Lynda J.
Published: October 2004

The polymerase chain reaction (PCR) was used to amplify eubacterial small‐subunit (16S) ribosomal DNA (rDNA) genes from galls of the marine red alga Prionitis lanceolata Harvey (Gigartinales). These tumors consist of hypertrophied algal cells containing large numbers of intercellular bacteria that remain uncultivable. PCR‐amplified 16S rDNAs from surface‐sterilized gall tissue plugs were cloned, sequenced, and analyzed by alignment to available small‐subunit rRNA sequences (University of Illinois Ribosomal Database Project). Variable regions were identified and used to construct a fluorescently labeled, species‐specific oligodeoxynucleotide probe for whole cell in situ hybridization to the gall symbiont. Probe 949 (PLANC.949) localized the P. lanceolata bacterial symbiont in preparations from mature gall tissue. This probe did not hybridize to the rDNA of closely related bacteria included as controls in the same hybridization reactions, In situ hybridization revealed the presence of the same bacterium in association with P. lanceolata gall formation from three central California localities. Distance and parsimony analyses suggest that this organism is a member of the Proteobacteria (alpha subdivision; Rhodobacter group) and is most closely related to Roseobacter denitrificans.
SPORELING COALESCENCE AND INTRACLONAL VARIATION IN GRACILARIA CHILENSIS (GRACILARIALES, RHODOPHYTA)1
Authors: Santelices Bernabé , Correa Juan A. , Meneses Isabel , Aedo Diego , Varela Daniel
Published: October 2004

This study evaluates the hypothesis that spore coalescence may cause intraclonal variation. Spore coalescence might allow the occurrence of unitary thalli that in fact correspond to genetically different, coalesced individuals. Plant portions simultaneously derived from these chimeric individuals may exhibit dissimilar growth responses even when incubated under similar abiotic conditions. Testing of the hypothesis included various approaches. Transmission electron microscopy observations of early stages of sporeling coalescence indicated that polysporic plantlets were formed by groups of spores and their derivatives. Even though adjacent cells in two different groups may fuse, these groups maintained an independent capacity to grow and form uprights. Laboratory‐grown plantlets showed a significant correlation between the initial number of spores and the total number of erect axes differentiated from the sporeling. Construction and growth of bicolor individuals indicated the chimeric nature of the coalesced individuals. Coalesced, bicolor holdfasts had green and red cells, which subsequently produced green and red uprights, respectively. Individuals fronds were also chimeric, as indicated by the production of green and red branchlets from single, red uprights. The existence of mixed tissues was further substantiated by random amplified polymorphic DNA analysis. The banding pattern produced by branchlets of a unisporic thallus was consistently monomorphic, whereas the patterns produced by the polysporic thallus were polymorphic. Growth rates of polysporic thalli had larger data dispersal and variation coefficients than oligosporic or monosporic thalli. Therefore, all results support the original hypothesis and suggest that coalescence might be ecologically more important than previously thought.
FURTHER OBSERVATIONS AND SOME COMMENTS ON THE FINE STRUCTURE OF THE CENTRIC DIATOM AULACOSEIRA ISLANDICA (BACILLARIOPHYCEAE)1
Authors: Le Cohu René
Published: October 2004

Using light and electron microscopy, the diatom species Aulacoseira islandica (O. Müll.) Sim. was examined with special emphasis on the following characteristics: structure of the valve areolae, heterovalvy, and distribution of the rimoportulae. The mantle and valve face areolae were pores containing volate occlusions. However, observations only using transmission electron microscopy may result in an incomplete interpretation because of the fragility of the dissected system of volae. Relief valves with a stepped mantle and intaglio valves with a plain mantle occurred. Another form of heterovalvy resulted from the formation of separation valves. Linking valves had spatulate spines while separation valves bore tapering spines. In Aulacoseira, the rimoportulae usually occurred near the “Ringleiste.” The presence of several rimoportulae on the mantle was one of the most striking features in Aulacoseira islandica.
DOES LIGHT QUALITY AFFECT THE SINKING RATES OF MARINE DIATOMS?1
Authors: Fisher Anne E. , Berges John A. , Harrison Paul J.
Published: October 2004

Although the spectral quality of light in the ocean varies considerably with depth, the effect of light quality on different physiological processes in marine phytoplankton remains largely unknown. In cases where experiments are performed under full spectral irradiance, the meaning of these experiments in situ is thus unclear. In this study, we determined whether variations in spectral quality affected the sinking rates of marine diatoms. Semicontinuous batch cultures of Thalassiosira weissflogii (Gru.) Fryxell et Hasle and Ditylum brightwellii (t. West) Grunow in Van Huerk were grown under continuous red, white, or blue light. For T. weissflogii, sinking rates (SETCOL method) were twice as high (∼0.2 m·d−1)for cells grown under red light as for cells grown under white or blue light (∼0.08 m·d−1), but there were no significant differences in carbohydrate content (∼105 fg·μm−3) or silica content (∼ 17 fg·μ−3) to account for the difference in sinking rates. Thalassiosira weissflogii grown under blue light was significantly smaller (495 μm3) than cells grown under red light (661 μm3), which could contribute to its reduced sinking rate. However, cells grown under white light were similar in size to those grown under red light but had sinking rates not different from those of cells grown under blue light, indicating the involvement of factors other than size. There were no significant differences in sinking rate (∼0.054 m·d−1) or silica content (∼20 fg·μm−3) in D. brightwellii grown under red, white, or blue light, but cells grown under red light were significantly (20%) larger and contained significantly (20%) more carbohydrate per μm3 than cells grown under white or blue light. Spectral quality had no consistent effect on sinking rate, biochemical composition (carbohydrate or silica content), or cell volume in the two diatoms studied. The similarity in sinking rate of cells grown under white light compared to those grown under blue light supports the ecological validity of sinking rate studies done under white light.
DOES CARBOHYDRATE CONTENT AFFECT THE SINKING RATES OF MARINE DIATOMS?1
Authors: Fisher Anne E. , Harrison Paul J.
Published: October 2004

We tested the hypothesis that positive relationships between sinking rate and irradiance were due to increases in cell density caused by accumulations of carbohydrate. In semicontinuous batch cultures of Thalassiosira weissflogii (Gru.) Fryxell el Hasle and Ditylum brightwellii (t. West) Grunow in Van Huerk, carbohydrate content was varied by growing cells under diel cycles of high or low light. Sinking rate was measured at the end of the light period and the end of the dark period, on live and heat‐killed cells. No positive correlations were found between sinking rate (which varied from – 0.060 to 0.13 m·d−1) and carbohydrate content (which varied from 10 to 950 pg · cell−1), indicating that accumulations of carbohydrate did not significantly affect sinking rate. There were no large diel variations in the sinking rate of T. weissflogii, but sinking rates of D. brightwellii grown under high light ranged from being negative (i.e. cells were floating) at the end of the light period to positive at the end of the dark period. This is the first report of positive buoyancy in vegetative D. brightwellii, a phenomenon that may only occur in D. brightwellii grown under diel cycles.
OCCURRENCE OF A TEMPERATE CYANOPHAGE LYSOGENIZING THE MARINE CYANOPHYTE PHORMIDIUM PERSICINUM1
Authors: Ohki Kaori , Fujita Yoshihiko
Published: October 2004

A temperate cyanophage was found to lysogenize the marine cyanophyte Phormidium persicinum (Reinke) Com. (Provasoli strain). The lytic cycle was induced by the addition of mitomycin C or by brief illumination with ultraviolet light. The lytic process observed under the electron microscope showed that phage particles appeared in a nucleoplasm region 15 to 24 h after the addition of mitomycin C. The induction of the lytic process occurred simultaneously in almost all cells of every trichome. Matured phage particles were released to the medium 30 to 50 h after the addition of mitomycin C. Phage particles isolated from algal lysates had a polyhedral head (about 40 nm in diameter) with a long (about 300 nm) and noncontractile tail. The most abundant protein, presumably a structural protein, had an apparent molecular mass of about 38 kDa. The genome size estimated from restriction analysis was about 50 kbp. Phage DNA was digested with several restriction endonucleases including Sau3AI and DpnI. However, MboI failed to digest the phage DNA, suggesting that the phage DNA is highly methylated. Southern blot analysis suggested that some part of the phage was in the lytic cycle in algal cells growing under normal conditions. A possible role of temperate cyanophages in the regulation of cyanophyte populations in the marine environment is discussed.
CHANGES IN DOMOIC ACID PRODUCTION AND CELLULAR CHEMICAL COMPOSITION OF THE TOXIGENIC DIATOM PSEUDO‐NITZSCHIA MULTISERIES UNDER PHOSPHATE LIMITATION1
Authors: Pan Youlian , Subba Rao Durvasula V. , Mann Kenneth H.
Published: October 2004

Production of domoic acid (DA), a neurotoxin, by the diatom Pseudo‐nitzschia multiseries (previously Nitzschia pungens f. multiseries) Hasle and its cellular chemical composition were studied in phosphate‐limited chemostat continuous cultures and in subsequent batch cultures. Under steady‐state chemostat conditions, DA production increased from 0.01 to 0.26 pg DA · cell−1· d−1 as the growth rate decreased. When the nutrient supply was discontinued (to produce a batch culture), DA production was enhanced by a factor of ca. 3. DA production was temporarily suspended upon addition of phosphate to the batch cultures but resumed 1 d later at a higher rate coincident with the decline of phosphate uptake. In both steady‐state continuous culture and batch culture, more DA was produced when alkaline phosphatase activity (APA) was high. The association of high DA production with high levels of APA and high cellular N:P ratios strongly suggests that phosphate limitation enhances DA production. Also, DA production was high when other primary metabolism (e.g. uptake of carbon, nitrogen, phosphorus and silicon, and cell division) was low, but chlorophyll a and adenosine triphosphate were generally high. This suggests that the synthesis of DA requires a substantial amount of biogenic energy.
CHLAMYDOMONAS EUGAMETOS (CHLOROPHYTA) STORES PHOSPHATE IN POLYPHOSPHATE BODIES TOGETHER WITH CALCIUM1
Authors: Siderius Marco , Musgrave Alan , van den Ende Herman , Koerten Henk , Cambier Piet , van der Meer Pieter
Published: October 2004

When Chlamydomonas eugametos Moewus cells are starved of phosphate, they accumulate 32Pi much faster than before starvation. Phosphate accumulation is stimulated by calcium. Less than 5% of the 32Pi taken up by the cell is present in soluble molecules, suggesting that most is in a metabolically inactive, storage form. Nuclear magnetic resonance and X‐ray microanalysis data are presented to show that it is stored as polyphosphate in electron‐dense bodies hi the cytoplasm. The same bodies accumulate divalent cations, in particular calcium. The P/Ca ratio in the bodies was maintained between 5.4 (1‐week‐old cells) and 3.3 (5‐week‐old cells) during cultivation, suggesting that the calcium and phosphorus relations of the bodies are coupled. The possibility that these electron‐dense bodies represent calcium stores that can be released to activate calcium signaling is discussed.
POTENTIAL TOLERANCE MECHANISMS OF PROROCENTRUM MICANS (DINOPHYCEAE) TO SUBLETHAL LEVELS OF COPPER1
Authors: Lage Olga M. , Parente Ana M. , Vasconcelos M. Teresa S. D. , Gomes Carlos A. R. , Salema Roberto
Published: October 2004

We investigated how Prorocentrum micans Ehrenberg, a planktonic dinoflagellate common in Portuguese coastal waters, is able to tolerate and recover from sublethal concentrations of copper(II). The experimental design simulated events in inshore waters, where P. micans is subjected to high levels of pollutants, including copper. Decrease in growth rate, induction of a growth lag phase, temporary loss of motility, and potassium leakage were the effects induced in P. micans cultures by 90 nM labile copper. A 10–20‐fold increase in cellular copper concentration was observed in toxicity experiments. Copper efflux (representing a 50% decrease in cellular metal content) was a short‐term tolerance mechanism. A 25‐kDa protein was detected after only 3 h of exposure to copper, but there was no evidence of phytochelatin synthesis. Ultracytochemical labeling of metals with the sulfide‐silver procedure showed that copper was associated with the thecal plates, starch grains, and, to a lesser extent, lipid droplets. High values affixation capacities and average conditional stability constants for copper binding by starch, amylopectin, and cellulose support the location of copper in thecal plates and starch grains. We conclude that P. micans responds rapidly to copper toxicity and has two tolerance mechanisms for copper: copper efflux and sequestration in polymeric substances.
ASSESSING THE LIMITS OF RANDOM AMPLIFIED POLYMORPHIC DNAs (RAPDs) IN SEAWEED BIOGEOGRAPHY1
Authors: van Oppen Madeleine J. H. , Klerk Hans , de Graaf Martin , Stam Wytze T. , Olsenz Jeanine L.
Published: October 2004

As judged by comparison with other molecular data sets, random amplified polymorphic DNA (RAPD) data are robust in identifying large‐scale biogeographic populations that range from hundreds to thousands of kilometers apart. As the geographical scale is shifted downward, however, RAPD data often fail. This is because RAPD data are inherently “noisy” as a result of technical artifacts and reproducibility problems associated with non‐independence of bands, “missing” bands, and the presence of de novo bands, all of which contribute to scoring errors in the data set. To estimate the contribution of these error factors in algal phylogeographic studies, segregation of RAPD bands in tetrasphorophytic and gametophytic parents, their natural and synthetic offspring, and self‐cycled tetrasporophytes were compared in Lophocladia trichoclados (Mertens in C. Agardh) Schmitz and to a limited extent in Digenea simplex (Wulfen) C. Agardh. Wide‐ranging biogeographic populations of D. simplex were compared as were mixed populations of tetrasporophytes and gametophytes. Results show that nested priming can lead to some nonindependence of bands but that this probably does not significantly contribute to scoring error. Southern analysis using individual RAPD bands as probes revealed that up to 16% of visually nondetectable bands are actually present but that the random distribution of the error contributes uniformly across the data set. Non‐parental (de novo in offspring) and parental (not present in offspring) bands may contribute substantially to the scoring error in tetrasporophytes, gametophytes, and self‐cycled tetrasporophytes. The presence of tetrasporophytes and gametophytes in a sample is not important in large‐scale phylogeographic studies but does affect within‐clade variation at smaller scales. We conclude that the overall level of error remains roughly constant at probably between 5 and 10%, which is not a problem at large biogeographic scales where the phylogenetic signal is strong. Finally, some unexpectedly large abberations in RAPD banding patterns among life stages in L. trichoclados were observed that cannot be explained by methodological artifacts alone due to comparisons with synthetic offspring controls. The possibility that carpospore amplification may not always involve a simple mitotic process is discussed.