Phototaxis, gravitaxis and vertical migrations in the marine dinoflagellate Prorocentrum micans

Abstract The phototactic orientation of the marine dinoflagellate Prorocentrum micans was studied at three different ages and at several light intensities. High irradiances caused the cells to show negative phototaxis and low irradiances caused positive phototaxis. The precision of negative phototaxis reached a maximum in the early afternoon, while the precision of positive phototaxis was found to peak in the morning and at night. The cells also showed a pronounced negative gravitactic orientation, which had a maximum in precision in the early afternoon. The degree of gravitaxis was found to be constant over time when the cells were confined to a closed cuvette for up to 9 h. As a consequence of the orientation strategies, populations of Prorocentrum micans showed daily vertical migrations in a 3-m Plexiglas column. They accumulated in the top layers in the afternoon and were almost randomly distributed during the rest of the day.     

Action of the organophosphorous insecticide parathion on the free-living marine dinoflagellate Prorocentrum micans Ehrbg

Growth of cultures of the dinoflagellate Prorocentrum micans Ehrbg. was slowed by parathion greater than 1 ppm. Parathion also decreased chlorophyll content and perturbed cellular ultrastructure, eliciting especially plastoglobuli in their chloroplasts. Toxicity of this organophosphorous insecticide is unlikely to be due to its anticholinesterase activity since P. micans appears not to contain cholinesterase. Fluorescence kinetics show that parathion affects the photosynthetic system, particularly photosystem II.     

Distinctive features of dinoflagellate chromatin. Absence of nucleosomes in a primitive species Prorocentrum micans E

The absence of nucleosome-like structures from purified nuclei of the primitive dinoflagellate Prorocentrum micans was demonstrated by three means. i) Electron microscopy revealed mostly thin, smooth 6-nm nucleofilaments in chromatin incubated at various ionic strengths and either fixed in 0.1% glutaraldehyde or unfixed. No "beads-on-a-string" structure was found. ii) Analysis of nuclear proteins showed that low amounts of basic proteins were present (basis proteins: DNA less than 0.1), the two major one with molecular weights 12 000 and 13 000 and that histones characteristic of eucaryotes were absent. iii) Digestion of the nuclei with micrococcal endonuclease of DNase I did not result in partially digested DNA fragment repeats. Only about 10% of the bulk of the nuclear DNA was digested by micrococcal endonuclease. The high molecular weight of the remainder suggests particular protection against this type of nuclease. In the light of these distinctive nuclear features, we discuss the evolutionary position of the dinoflagellate protists with respect to the procaryotes and eucaryotes.     

Cytotoxicity in the marine dinoflagellate Prorocentrum mexicanum from Brazil

The microscopic algae in the oceans are crucial food for filter feeding bivalve shellfish (oysters, mussels, scallops, clams, etc.) as well as for the larvae of commercially important crustaceans. Some species of microalgae have the capacity to produce potent toxins, such as saxitoxins and ciguatoxins, which may intoxicate humans. Among the marine phytoplankton, the dinoflagellates are the main toxin producers. Studies on the marine phytoplankton from the S?o Sebasti?o Channel, southeastern coast of Brazil, showed a great diversity of dinoflagellates. Some species were collected and cultured at the Marine Biology Center of the S?o Paulo University (USP). The polar (PEs) (aqueous) and apolar (AEs) (methylene chloride) extracts of the cultivated dinoflagellate species were tested on different stages of the sea urchin development, on mouse erythrocytes and on microfilaments organization in a neuroblastoma cell line. Prorocentrum mexicanum PE and AE induced cells anomalies and cell division inhibition of sea urchin eggs at EC50 of 78.75 microg/mL (95% CI from 32.56 to 190.50) and 22.50 microg/mL (95% CI from 2.96 to 170.80) respectively (n=3). Both AE and PE of P. mexicanum induced hemolysis with EC50 of 65.07 microg/mL (95% CI from 27.40 to 154.60) and 84.29 microg/mL (95% CI from 53.26 to 133.40 microg/mL), respectively. P. mexicanum PE was tested in immunofluorescence for actin filaments organization in neuroblastoma cultured cell.     

Deciphering interactions between the marine dinoflagellate Prorocentrum lima and the fungus Aspergillus pseudoglaucus

The comprehension of microbial interactions is one of the key challenges in marine microbial ecology. This study focused on exploring chemical interactions between the toxic dinoflagellate Prorocentrum lima and a filamentous fungal species, Aspergillus pseudoglaucus, which has been isolated from the microalgal culture. Such interspecies interactions are expected to occur even though they were rarely studied. Here, a co-culture system was designed in a dedicated microscale marine-like condition. This system allowed to explore microalgal–fungal physical and metabolic interactions in presence and absence of the bacterial consortium. Microscopic observation showed an unusual physical contact between the fungal mycelium and dinoflagellate cells. To delineate specialized metabolome alterations during microalgal–fungal co-culture metabolomes were monitored by high-performance liquid chromatography coupled to high-resolution mass spectrometry. In-depth multivariate statistical analysis using dedicated approaches highlighted (1) the metabolic alterations associated with microalgal–fungal co-culture, and (2) the impact of associated bacteria in microalgal metabolome response to fungal interaction. Unfortunately, only a very low number of highlighted features were fully characterized. However, an up-regulation of the dinoflagellate toxins okadaic acid and dinophysistoxin 1 was observed during co-culture in supernatants. Such results highlight the importance to consider microalgal–fungal interactions in the study of parameters regulating toxin production.     

Prorocentrum属涡鞭毛虫核仁的观察

迄今未能在光学显微镜下观察到Prerocentrum属的涡鞭毛虫有核仁。本文作者用伊红的酒精溶液和用甲基缘—派若宁法染色,也未能在Prerocentrum micans和Proro-centrum cassubica的细胞核中显示出核仁来。但是在用专门为显示单细胞生物的核仁组织者区（NOR）而改进了的Ag—1法进行染色时,这两种涡鞭毛虫的核仁都会被染作鲜明的深褐色或深黑色,而身体的所有其他部份,包括染色体,全都不着色。染色适当时可以看出,实际上只是核仁的中央部分被染上色。在电镜下可见,此时所有的银粒全部是集中在核仁的纤维区中。染色的结果表明,Prorocentrum cassbica只有一个扁园形的小核仁,后者是贴附在核膜上,其NOR通常是作O形或C形。与P.cassubica不同,P.micans的核仁的数量变化很大,可以有一个至七个;其核仁的大小与形状同样也变化很大;其NOR的形状也复杂多变。发现P.micans的核仁数量与个体的生活状况有一定的关联:向老的培养液中加入等量的新的培养液一天以后,具有三个核仁的个体是最多的（占三分之一）,具有4—6个核仁的个体占28.5％,只有一个核仁的个体只占8.6％;加入新培养液三天后,具两个核仁的个体变成是最多的（占38.8％）,具4—6个核仁的个体降为占18.4％;加入新培养液一个月以后,只有一个核仁的个体是最多的（占3     

On the nucleoli of the dinoflagellate Prorocentrum

To date no nucleolus had been observed in Prorocentrum under the light microscope. The author failed to show the nucleoli of P. micans and P. cassubica with eosin in 70% alc or with methyl green-pyronin. But when these dinoflagellates were treated with an Ag-1 technique which had been improved for demonstrating NORs in unicellular organisms, nucleoli were stained dark brown or black, while all other parts showed no colour. When the materials were stained well, only the central part of the nucleolus was stained. Under the electron microscope, it was observed that all the silver grains were concentrated in the pars fibrosa of the nucleolus. P. cassubica had only one small oblate nucleolus attached to the nuclear envelope, with NOR usually in the shape of the letters O or C. P. micans had 1–7 nucleoli of various sizes and shapes with NORs in various complicated forms. The number of nucleoli bore a certain relationship to the living state of the dinoflagellate. One day after fresh medium was added, cells with 3 nucleoli were most common, and 28.5% of the individuals had 4–6 nucleoli. Cells having only one nucleolus accounted for 8.6%. 3 days after, cells with 2 nucleoli became dominant, and those with 4–6 decreased to 18.4%. After a month, cells with 1 nucleolus became most abundant, cells having 4 nucleoli decreased to 2.4%, and no cells had 5 or 6 nucleoli.     

The DNA-structures of the chloroplast of Prorocentrum micans (Dinophyceae)

Summary DNA-regions of the chloroplasts of the dinoflagellate Prorocentrum micans were investigated by using serial sections. Prior to post-osmication the glutaraldehyde-fixed cells were treated with trypsin which results in a selective presentation of DNA-structures.For each of the two multilobed chloroplasts of the cell at least 80–100 individual DNA-regions could be calculated. Three-dimensional reconstructions of DNA-regions lead to models of usually flattened irregular discs which can differ markedly in size. It is concluded that the DNA-regions also differ in their DNA-content. Branched DNA-regions are regarded as possible division stages; they suggest a division into parts of different size.In some of the DNA-regions the DNA-fibrils seem to be attached to tube- or tongue-like evaginations of thylakoid membranes. The evaginations differ from normal thylakoids in their limited extension, enlarged loculus and their clearly visible unit membrane. A possible functional resemblance to bacterial mesosomes is discussed.Finally it is concluded that 1. the chloroplast of Prorocentrum is a polyenergidic organelle considering the number of DNA-regions, and that 2. the individual DNA-regions are polyploid to variable degrees with respect to their size.     

Evidence of a new toxin in the red-tide dinoflagellate Prorocentrum minimum

Several clones of Prorocentrum minimum were isolated from variousFrench Mediterranean and English Channel sites. Mouse testsperformed using methanolic extracts from cultures revealed aneurotoxic activity in four clones. The water-soluble toxindetected worked rapidly, killing mice within a few minutes athigh doses. Toxin production in cultures was observed duringthe phase of decline and appeared to be weak or nil during thegrowth phase. Toxin production was stimulated by associatedbacteria in the culture, but a clone rendered axenic remainedable to produce toxins. The potential risks of human poisoningfrom consumption of shellfish harvested during or after toxicblooms of P.minimum are discussed.     

Ultrastructural Damage by Cadmium in a Marine Dinoflagellate,Prorocentrum micans1

Prorocentrum micans Ehrenberg, a free-living marine dinoflagellate, was used to test the intracellular toxic action of cadmium. The cells were cultivated in Erdschreiber medium, with Cd concentrations of 10–100 ppb. Thin sections of treated cells, examined ultramicroscopically, exhibited vacuolations, increased numbers of lysosomes, and severe mitochondrial damage. The first two alterations are a general response to toxicity; the third is Cd specific. Although some chloroplasts were affected by Cd, they were not very sensitive to its action. The nuclear apparatus was not morphologically affected.     

Cell surface proteome of the marine planctomycete Rhodopirellula baltica

The surface proteome (surfaceome) of the marine planctomycete Rhodopirellula baltica SH1(T) was studied using a biotinylation and a proteinase K approach combined with SDS-PAGE and mass spectrometry. 52 of the proteins identified in both approaches could be assigned to the group of potential surface proteins. Among them are some high molecular weight proteins, potentially involved in cell-cell attachment, that contain domains shown before to be typical for surface proteins like cadherin/dockerin domains, a bacterial adhesion domain or the fasciclin domain. The identification of proteins with enzymatic functions in the R. baltica surfaceome provides further clues for the suggestion that some degradative enzymes may be anchored onto the cell surface. YTV proteins, which have been earlier supposed to be components of the proteinaceous cell wall of R. baltica, were detected in the surface proteome. Additionally, 8 proteins with a novel protein structure combining a conserved type IV pilin/N-methylation domain and a planctomycete-typical DUF1559 domain were identified.     

海水实验围隔中桡足类对海洋原甲藻摄食的研究

现场研究了发生严重海洋原甲藻（Ｐｒｏｒｏｃｅｎｔｒｕｍｍｉｃａｎｓ）水华后海水实验围隔中桡足类火腿许水蚤（Ｓｃｈｍａｃｋｅｒｉａｐｏｐｌｅｓｉａ）和长腹剑水蚤（Ｏｉｔｈｏｎａｓｐ．）的摄食强度．结果表明,体长在１２５ｍｍ以上的火腿许水蚤成体及其部分桡足幼体对海洋原甲藻的摄食率平均为１２１４０ｃｅｌｓ·ｉｎｄ－１·ｄ－１;体长不到１２５ｍｍ的部分火腿许水蚤桡足幼体和长腹剑水蚤成体及其桡足幼体的摄食率仅为１１３３ｃｅｌｓ·ｉｎｄ－１·ｄ－１．实验期间围隔中海洋原甲藻的浓度为８５０～１６１７０ｃｅｌｓ·ｍｌ－１,该藻的种群增长率为－０．００２～０．１５０．当海洋原甲藻细胞处于生长期时,桡足类的摄食不足以抑制该藻种群的增长,因此围隔中桡足类不可能阻止海洋原甲藻水华发生或使水华发生后迅速消退     

Contribution of external morphology in solving a species complex: The case of Prorocentrum micans, Prorocentrum gracile and Prorocentrum sigmoides (Dinoflagellata) from the Mexican Pacific Coast

Prorocentrum micans Ehrenberg, Prorocentrum gracile Schütt and Prorocentrum sigmoides Böhm are planktonic dinoflagellates present along the Mexican Pacific coast. These three species can be treated as a species complex because of similar shape and size. The taxonomy of the group has been based on cell form and size, the presence or absence of apical spines and the ornamentation of the main valves. A morphometric study of samples from 11 locations from the Mexican Pacific coast and from laboratory cultures is presented. The presence of a mucron (small tooth) in the antapical region of P. gracile and P. sigmoides morphotypes was recorded for the first time. Morphotypes were defined using as the main criteria the size of pores in relation to the size of the depressions on the cell’s surface, the presence of a mucron in the posterior end of the cell and the shape of the valve margins. Results show a clear distinction between the morphotype P. micans and the P. gracile–P. sigmoides. P. sigmoides is suggested to be a junior synonym of P. gracile as no convincing characters could distinguish these two morphotypes.     

Action of the Organophosphorous Insecticide Parathion on the Free-Living Marine Dinoflagellate Prorocentrum micans Ehrbg.

Growth of cultures of the dinoflagellate Prorocentrum micans Ehrbg. was slowed by parathion >1 ppm. Parathion also decreased chlorophyll content and perturbed cellular ultrastructure, eliciting especially plastoglobuli in their chloroplasts. Toxicity of this organophosphorous insecticide is unlikely to be due to its anticholinesterase activity since P. micans appears not to contain cholinesterase. Fluorescence kinetics show that parathion affects the photosynthetic system, particularly photosystem II.     

The dinoflagellate genus Prorocentrum along the coasts of the Mexican Pacific

We surveyed the dinoflagellate genus Prorocentrum Ehrenberg in Mexican Pacific waters, where it is rather common and sometimes causes red tides in coastal areas or shrimp farms. Material collected from Baja California and the Gulf of California was analyzed. Thirteen species were identified, all of them planktonic (although P. mexicanum is also epiphytic). All species are described by light microscopy, and most are also described by scanning electron microscopy; comments on morphology, taxonomy and distribution are made. Red tides were caused by P. dentatum, P. minimum and P. triestinum. Prorocentrum mexicanum and P. minimum were suspected of being toxic. Four species, previously reported in the Gulf of California, were not found. A total of 18 species, including the new records P. dactylum and P. lebourae have been to date reported from the Mexican Pacific.     

Detection of intracellular neutral lipid content in the marine microalgae Prorocentrum micans and Phaeodactylum tricornutum using Nile red and BODIPY 505/515

Diatoms and dinoflagellates not only have extensive distribution and a huge biomass in marine ecosystems, but also have high lipid accumulation in nature or after physiological and genetic modification, which indicates that these organisms may be optimal candidate algal strains for biodiesel production. In this study, we determined the content of intracellular neutral lipids (triacylglycerol [TAG]) in the dinoflagellate Prorocentrum micans and in the diatom Phaeodactylum tricornutum using NR and BODIPY 505/515 staining. The freshwater green alga Scenedesmus obliquus was used as a control. Optimum concentrations of 1.000 and 1.500 μg mL^?1 were determined for neutral lipid Nile red (NR) staining in P. micans and P. tricornutum. Unlike NR staining, the optimal concentrations of BODIPY 505/515 staining in P. micans and P. tricornutum were lower, at 0.100 and 0.075 μg mL^?1, respectively. High correlation coefficients of R ²?=?0.990 and R ²?=?0.989 were obtained for P. micans and P. tricornutum intracellular neutral lipid content and the relative fluorescence intensity with NR staining, while the reference alga, S. obliquus, had a relatively low correlation coefficient of R ²?=?0.908 when stained with NR. The neutral lipid content determined by thin-layer chromatography-flame ionization detector matched the analytical data from fluorescence measurements. These results indicated that NR and BODIPY 505/515 staining can be used as an excellent high-throughput approach to screen marine diatoms and dinoflagellates.