Effects of temperature,salinity and their interaction on growth of the benthic dinoflagellate Ostreopsis cf. ovata (Dinophyceae) from Japanese coastal waters

Benthic dinoflagellates of the genus Ostreopsis produce palytoxin (PTX)‐like compounds. The worldwide distributed Ostreopsis ovata/O. cf. ovata is potentially responsible for outbreaks of human health problems around the coasts of tropical, subtropical, and temperate regions. The present study examined growth responses of an O. cf. ovata strain s0662 collected from coastal waters of Japan with 35 different combinations of temperature (15–35°C) and salinity (20–40) and discusses the bloom dynamics of the organism in Japanese coastal environments. The O. cf. ovata strain s0662 tolerated a wide range of temperature (17.5–35°C) and salinity (25–40). Results of a two‐way ANOVA showed significant effects of temperature‐salinity interaction on growth rates and biomass yields of the O. cf. ovata strain (F(24,70) > 127, P < 0.001). The strain showed a maximal growth rate (1.03 divisions day^?1) and biomass yield (240 relative fluorescence) at temperature 25°C and salinity 30. The high growth rates of over 1.0 division day^?1 were obtained in conditions of temperature 25–30°C and salinity 30–35, which indicates that strain s0662 prefers high temperature and salinity conditions. The growth rates of O. cf. ovata under the optimal conditions were higher than those of other benthic toxic‐dinoflagellates, Coolia monotis, Gambierdiscus toxicus, and Prorocentrum lima (Dinophyceae) previously reported. Taken together, we suggest that O. cf. ovata is able to grow faster than the other benthic dinoflagellates in waters of high temperature and salinity. The physiological feature probably confers an ecological advantage on O. cf. ovata in the bloom development during warmer seasons in Japan and may be responsible for outbreaks of PTX‐like poisoning in the region especially during the warmer seasons.     

Blooms of benthic dinoflagellates of the genus Ostreopsis; an increasing and ecologically important phenomenon on temperate reefs in New Zealand and worldwide

Blooms of benthic dinoflagellates belonging to the tropical genus Ostreopsis are an increasingly common phenomenon in temperate regions worldwide. This is reflected in the rapid upsurge of publications on Ostreopsis from temperate regions since 2000. Relatively little is known about these blooms or their effects on other organisms. An unprecedented bloom of Ostreopsis siamensis occurred on shallow reefs in northern New Zealand in 2004 providing an opportunity to examine the dynamics of an O. siamensis bloom and its effect on community structuring sea urchins (Evechinus chloroticus). The bloom occurred following a period of calm sea conditions with warmer than average water temperatures. The cover of O. siamensis was highly ephemeral and strongly related to temporal and spatial variation in wave action. Blooms were most prevalent at sites protected from prevailing swells where O. siamensis covered 30–60% of the reef with the concentrations on macroalgae reaching 1.4 × 10⁶ cells g⁻¹ wet weight, some of the highest recorded worldwide. Surveys of the health of sea urchins in relation to the cover of O. siamensis suggested strong negative effects on this ecologically important herbivore and urchin densities declined by 56–60% at bloom sites over the study period. Further research is needed to examine the factors controlling the distribution and intensity of this new phenomenon, and into the ecological effects of such blooms on marine communities and the potential mechanisms responsible.     

Long‐standing environmental conditions,geographic isolation and host–symbiont specificity influence the relative ecological dominance and genetic diversification of coral endosymbionts in the genus Symbiodinium

Aim This study examines the importance of geographic proximity, host life history and regional and local differences in environment (temperature and water clarity) in driving the ecological and evolutionary processes underpinning the global patterns of diversity and distribution of symbiotic dinoflagellates. By comparing and contrasting coral–algal symbioses from isolated regions with differing environmental conditions, we may assess the potential of coral communities to respond to significant changes in climate. Location Indian Ocean. Methods Community assemblages of obligate symbiotic invertebrates were sampled at numerous sites from two regions, the north‐eastern Indian Ocean (Andaman Sea, western Thailand) and the western Indian Ocean (Zanzibar, Tanzania). Molecular genetic methods, including denaturing gradient gel electrophoresis analysis of the ribosomal internal transcribed spacers, DNA sequencing and microsatellite genotyping, were used to characterize the ‘species’ diversity and evolutionary relationships of symbiotic dinoflagellates (genus Symbiodinium). Host–symbiont specificity, geographic isolation and local and regional environmental factors were evaluated in terms of their importance in governing the distribution and prevalence of certain symbiont taxa. Results Host‐generalist symbionts (C3u and D1‐4, formerly D1a now designated Symbiodinium trenchi) frequently occurred alone and sometimes together in hosts with horizontal modes of symbiont acquisition. However, the majority of Symbiodinium diversity consisted of apparently host‐specific ‘species’. Clade C Symbiodinium were diverse and dominated host assemblages from sites sampled in the western Indian Ocean, a pattern analogous to symbiont communities on the Great Barrier Reef with similar environmental conditions. Clade D Symbiodinium were diverse and occurred frequently in hosts from the north‐eastern Indian Ocean, especially at inshore locations, where temperatures are warmer, water turbidity is high and large tidal exchanges commonly expose coral populations to aerial desiccation. Main conclusions Regional and local differences in cnidarian–algal combinations indicate that these symbioses are ecologically and evolutionarily responsive and can thrive under various environmental conditions. The high temperatures and turbid conditions of the north‐eastern Indian Ocean partly explain the ecological success of Clade D Symbiodinium relative to Clade C. Phylogenetic, ecological and population genetic data further indicate that Clade D has undergone an adaptive radiation, especially in regions around Southeast Asia, during the Pleistocene.     

Sampling harmful benthic dinoflagellates: Comparison of artificial and natural substrate methods

This study compared two collection methods for Gambierdiscus and other benthic harmful algal bloom (BHAB) dinoflagellates, an artificial substrate method and the traditional macrophyte substrate method. Specifically, we report the results of a series of field experiments in tropical environments designed to address the correlation of benthic dinoflagellate abundance on artificial substrate and those on adjacent macrophytes. The data indicated abundance of BHAB dinoflagellates associated with new, artificial substrate was directly related to the overall abundance of BHAB cells on macrophytes in the surrounding environment. There was no difference in sample variability among the natural and artificial substrates. BHAB dinoflagellate abundance on artificial substrates reached equilibrium with the surrounding population within 24 h. Calculating cell abundance normalized to surface area of artificial substrate, rather than to the wet weight of macrophytes, eliminates complications related to the mass of different macrophyte species, problems of macrophyte preference by BHAB dinoflagellates and allows data to be compared across studies. The protocols outlined in this study are the first steps to a standardized sampling method for BHAB dinoflagellates that can support a cell-based monitoring program for ciguatera fish poisoning. While this study is primarily concerned with the ciguatera-associated genus Gambierdiscus, we also include data on the abundance of benthic Prorocentrum and Ostreopsis cells.     

A phylogeographical study of the toxic benthic dinoflagellate genus Ostreopsis Schmidt

Aim Ostreopsis is a benthic and epiphytic dinoflagellate producing potent toxins widespread in tropical and warm temperate coastal areas world‐wide. We tested the hypothesis that as it is benthic, it would show distinct biogeographical patterns in comparison with planktonic species. Here, we analyse sequence variability in ribosomal DNA markers to provide the first phylogeographical study of this toxic benthic dinoflagellate. Location Mediterranean Sea, Atlantic Ocean, Pacific Ocean. Methods Ribosomal DNA sequence data from partial nuclear LSU (D1/D2 domains) and 5.8S genes and non‐coding internal transcribed spacer (ITS) regions were obtained from 82 isolates of Ostreopsis species, collected at 26 localities throughout the world. Molecular sequence data were analysed using maximum parsimony, maximum likelihood and Bayesian methods for phylogenetic inference. A statistical parsimony network was obtained based on concatenated LSU and 5.8S rDNA–ITS region sequences of the Mediterranean/Atlantic Ostreopsis cf. ovata isolates to infer haplotype distribution over their geographical range. Light epifluorescence microscopy analyses were performed on cultured and field Ostreopsis material for taxonomic identification, while laboratory experiments for encystment induction were carried out on selected O. cf. ovata isolates. Toxin assays of Ostreopsis species isolates were carried out using the haemolytic‐based method. Results Analyses based on single and concatenated ribosomal genes gave substantially similar results. The rDNA phylogeny revealed different clades corresponding to different species within the genus Ostreopsis. In the species O. cf. ovata, different genetic lineages were correlated with macrogeographical distribution. A network of haplotypes inferred from the Atlantic and Mediterranean isolates of O. cf. ovata revealed that these two areas might host a single panmictic population. The Atlantic/Mediterranean population of O. cf. ovata was differentiated considerably from the Indo‐Pacific populations. Other species of Ostreopsis were found, but they turned out to be restricted to just one of the two main warm‐water oceanic basins, the Mediterranean/Atlantic and the Indo‐Pacific. Main conclusions Ostreopsis cf. ovata was found to be widely dispersed throughout the coastal areas of tropical and some warm temperate seas. In the Atlantic/Mediterranean region it may constitute a panmictic population that is highly distinct from Indo‐Pacific populations. Ostreopsis cf. siamensis was found only in the Mediterranean Sea, and strains identified as Ostreopsis lenticularis and Ostreopsis labens were found only in the Indo‐Pacific region.     

Characterization of Prorocentrum elegans and Prorocentrum levis (Dinophyceae) from the southeastern Bay of Biscay by morphology and molecular phylogeny

Benthic Prorocentrum species can produce toxins that adversely affect animals and human health. They are known to co‐occur with other bloom‐forming, potentially toxic, benthic dinoflagellates of the genera Ostreopsis, Coolia, and Gambierdiscus. In this study, we report on the presence of P. elegans M.Faust and P. levis M.A.Faust, Kibler, Vandersea, P.A. Tester & Litaker from the southeastern Bay of Biscay. Sampling was carried out in the Summer‐Autumn 2010–2012 along the Atlantic coast of the Iberian Peninsula, but these two species were only found in the northeastern part of the Peninsula. Strains were isolated from macroalgae collected from rocky‐shore areas bordering accessible beaches. Morphological traits of isolated strains were analyzed by LM and SEM, whereas molecular analyses were performed using the LSU and internal transcribed spacer (ITS)1‐5.8S‐ITS2 regions of the rDNA. A bioassay with Artemia fransciscana and liquid chromatography–high‐resolution mass spectrometry analyses were used to check the toxicity of the species, whose results were negative. The strains mostly corresponded to their species original morphological characterization, which is supported by the phylogenetic analyses in the case of P. levis, whereas for P. elegans, this is the first known molecular characterization. This is also the second known report of P. elegans.     

101 Effect of Karlodinium Micrum Toxin on Success of the Parasitic Dinoflagellate Amoebophyra SP.

Parasitic dinoflagellates of the genus Amoebophrya infect and kill bloom‐forming dinoflagellates, including the toxic species Karlodinium micrum. Unlike non‐toxic hosts, K. micrum is partially resistant to infection, a trait that may be related to toxin production. Here we tested the hypothesis that parasitism of K. micrum is inversely related to toxin concentration in the culture medium. Time‐course studies were conducted to determine the influence of extracted toxin and toxin carrier (methanol) on host growth, parasite prevalence, and parasite load. Results indicate that methanol concentrations below 0.1% have no effect on these variables. When methanol concentration was maintained below 0.1%, extracted toxin equivalent to 100 to 10,000 K. micrum per ml had no effect on host abundance. We are currently analyzing sample to assess the fate of Amoebophrya dinospores when exposed to K. micrum toxin. We will also consider the effect of intracellular host toxin on parasite success, by examining the fate of Amoebophrya dinospores when inoculated to K. micrum cultures that express different levels of toxin production. Understanding the effect of toxins on parasite success will contribute to our knowledge of host‐parasite biology and provide insight into the role of dinoflagellate toxins as a defense against parasitism.     

Uvigerina proboscidea abundances and paleoceanography of the northern Indian Ocean DSDP Site 214 during the Late Neogene

This study attempts to understand the significance of Uvigerina proboscidea in paleoceanographic reconstructions at the northern (tropical) Indian Ocean DSDP Site 214 from the Late Miocene through the Pleistocene. In this interval at this site, U. proboscidea is the most abundant species of the benthic assemblage and shows abrupt frequency changes (about 1–74%). Based on relative percentages of U. proboscidea calibrated with oxygen and carbon isotope record and the sediment accumulation rates, the modern distribution of the species in the Indian Ocean, and other evidence, the peaks of abundance of U. proboscidea are inferred to represent times of high-surface productivity. This productivity is related to intensified trade winds during strong southwest (SW) Indian monsoons, causing widespread upwelling along equatorial divergence in the Indian Ocean. The sudden increase of U. proboscidea abundance at approximately 8.5–7.5 Ma reflects significant upwelling at the equatorial divergence. This event corresponds to the permanent build-up of West Antarctic ice sheets, and a major increase in SW Indian monsoons related upwelling in the northwestern Indian Ocean. The Chron-6 carbon shift at approximately 6.2 Ma is marked by another peak of abundance, reflecting widespread ocean fertility. The highest abundances of U. proboscidea and highest sediment accumulation rates occur between 5.8 and 5.1 Ma, which coincides with the greatest development of Antarctic ice sheets and strong southwest monsoons. The higher percentages at 3.2–3.1 Ma, approximately 2.4 Ma, and 1.6 Ma all represent phases of high productivity at the equatorial divergence.     

Distribution of Dinophysis species and their association with lipophilic phycotoxins in plankton from the Argentine Sea

Dinophysis is a cosmopolitan genus of marine dinoflagellates, considered as the major proximal source of diarrheic shellfish toxins and the only producer of pectenotoxins (PTX). From three oceanographic expeditions carried out during autumn, spring and late summer along the Argentine Sea (∼38–56°S), lipophilic phycotoxins were determined by liquid chromatography coupled to tandem mass spectrometry (LC–MS/MS) in size-fractionated plankton samples. Lipophilic toxin profiles were associated with species composition by microscopic analyses of toxigenic phytoplankton. Pectenotoxin-2 and PTX-11 were frequently found together with the presence of Dinophysis acuminata and Dinophysis tripos. By contrast, okadaic acid was rarely detected and only in trace concentrations, and dinophysistoxins were not found. The clear predominance of PTX over other lipophilic toxins in Dinophysis species from the Argentine Sea is in accordance with previous results obtained from north Patagonian Gulfs of the Argentine Sea, and from coastal waters of New Zealand, Chile, Denmark and United States. Dinophysis caudata was rarely found and it was confined to the north of the sampling area. Because of low cell densities, neither D. caudata nor Dinophysis norvegica could be biogeographically related to lipophilic toxins in this study. Nevertheless, the current identification of D. norvegica in the southern Argentine Sea is the first record for the southwestern Atlantic Ocean. Given the typical toxigenicity of this species on a global scale, this represents an important finding for future surveillance of plankton-toxin associations.     

Devastating farmed abalone mortalities attributed to yessotoxin-producing dinoflagellates

A large dinoflagellate bloom in Walker Bay (South Africa) in January 2017 impacted 3 land-based abalone farms resulting in the death of several million animals. Satellite-derived images of Chl-a from the Ocean and Land Colour Imager (OLCI) on board the European Space Agency Sentinel-3 A showed bloom initiation in late December 2016 and dispersal in mid-February 2017. The bloom was dominated by two dinoflagellate species identified by light microscopy as Gonyaulax spinifera (Claparède & Lachmann) Diesing, 1866 and Lingulodinium polyedrum (Stein) Dodge, 1989. These morphologically based identifications were confirmed by phylogenetic analysis using partial sequences of the large subunit rDNA of both dinoflagellates. The appearance of yessotoxins (YTX) in abalone clearly coincided with increases in dinoflagellate concentrations. Yessotoxins in both the plankton and abalone were dominated by the two analogues homo-YTX and 45-hydroxy-YTX. The absence of toxins in a clonal culture of L. polyedrum implicated G. spinifera as the likely source of YTX. Toxin concentrations were found to be highest in the gills which showed the most significant pathology, including severe, generalized disruption of the gill epithelium characterized by degeneration and necrosis of epithelial cells accompanied by a modest inflammatory response. Some farms undertook pre-emptive or emergency harvesting to reduce financial losses.     

Effects of temperature and salinity on the growth of Alexandrium (Dinophyceae) isolates from the Salish Sea

Toxin‐producing blooms of dinoflagellates in the genus Alexandrium have plagued the inhabitants of the Salish Sea for centuries. Yet the environmental conditions that promote accelerated growth of this organism, a producer of paralytic shellfish toxins, is lacking. This study quantitatively determined the growth response of two Alexandrium isolates to a range of temperatures and salinities, factors that will strongly respond to future climate change scenarios. An empirical equation, derived from observed growth rates describing the temperature and salinity dependence of growth, was used to hindcast bloom risk. Hindcasting was achieved by comparing predicted growth rates, calculated from in situ temperature and salinity data from Quartermaster Harbor, with corresponding Alexandrium cell counts and shellfish toxin data. The greatest bloom risk, defined at μ >0.25 d^?1, generally occurred from April through November annually; however, growth rates rarely fell below 0.10 d^?1. Except for a few occasions, Alexandrium cells were only observed during the periods of highest bloom risk and paralytic shellfish toxins above the regulatory limit always fell within the periods of predicted bloom occurrence. While acknowledging that Alexandrium growth rates are affected by other abiotic and biotic factors, such as grazing pressure and nutrient availability, the use of this empirical growth function to predict higher risk time frames for blooms and toxic shellfish within the Salish Sea provides the groundwork for a more comprehensive biological model of Alexandrium bloom dynamics in the region and will enhance our ability to forecast blooms in the Salish Sea under future climate change scenarios.     

FURTHER SEM STUDY OF MARINE DINOFLAGELLATES: THE GENUS OSTREOPSIS (DINOPHYCEAE)1

This paper presents a comprehensive examination of the taxonomy of the genus Ostreopsis Schmidt. The morphology of six species of marine dinoflagellates, Ostreopsis siamensis Schmidt 1902. Ostreopsis lenticularis Fukuyo 1981, Ostreopsis ovata Fukuyo 1981, Ostreopsis heptagona Norris, Bomber, et Balech 1985, Ostreopsis mascarenensis Quod 1994, and Ostreopsis labens Faust et Morton 1995 from three geographical regions (Japan, Southwest Indian Ocean, and the Caribbean) and three marine habitats (sand, water column, and macroalgal surfaces) are described from scanning electron micrographs. Differences in the following morphological characteristics differentiated the species: cell shape and size, and ornamentation of the epitheca, cingulum, and hypotheca. The thecal plate formula of the six Ostreopsis species is P_o, 3′, 7″, 6C, 6S?, V_p, R_p, 5′″, 1p, 2″″, with differences in thecal plate size and shape. The cingulum in ventral view has two prominent structures: a ventral plate (V_p) with a ventral pore (V_o) and a ridged plate (R_p) that distinguishes Ostreopsis species from any other dinoflagellate taxa. This paper also includes ecological and toxicity information regarding the six Ostreopsis species.     

Present and past genetic connectivity of the Indo‐Pacific tropical eel Anguilla bicolor

Aim The objective of this study was to reveal the present population structure and infer the gene‐flow history of the Indo‐Pacific tropical eel Anguilla bicolor. Location The Indo‐Pacific region. Methods The entire mitochondrial control region sequence and the genotypes at six microsatellite loci were analysed for 234 specimens collected from eight representative localities where two subspecies have been historically designated. In order to infer the population structure, genetic differentiation estimates, analysis of molecular variance and gene‐tree reconstruction were performed. The history of migration events and population growth was assessed using neutrality tests based on allelic frequency spectrum, coalescent‐based estimation of gene flow and Bayesian demographic analysis using control region sequences. Results Population structure analysis showed genetic divergence between eels from the Indian and Pacific oceans (F_ST = 0.0174–0.0251, P < 0.05 for microsatellites; Φ_ST = 0.706, P < 0.001 for control region), while no significant variation was observed within each ocean. Two mitochondrial sublineages that do not coincide with geographical regions were found in the Indian Ocean clade of a gene tree. However, these two sublineages were not differentiated at the microsatellite markers. The estimation of mitochondrial gene‐flow history suggested allopatric isolation between the Indian and Pacific oceans, and a possible secondary contact within the Indian Ocean after an initial population splitting. Bayesian demographic history reconstruction and neutrality tests indicated population growth in each ocean after the Indo‐Pacific divergence. Main conclusions Anguilla bicolor has diverged between the Indian and Pacific oceans, which is consistent with the classical subspecies designation, but is apparently genetically homogeneous in the Indian Ocean. The analysis of gene‐flow and demographic history indicated that the two mitochondrial sublineages observed in the Indian Ocean probably represent the haplotype groups of relict ancestral populations. A comparison with a sympatric congener suggested that absolute physical barriers to gene flow may not be necessary for population divergence in eels.     

Phylogeny and biogeography of tropical carnivorous land‐snails (Pulmonata: Streptaxoidea) with particular reference to East Africa and the Indian Ocean

Rowson, B., Tattersfield, P. & Symondson, W. O. C. (2010). Phylogeny and biogeography of tropical carnivorous land‐snails (Pulmonata: Streptaxoidea) with particular reference to East Africa and the Indian Ocean. —Zoologica Scripta, 40, 85–98. A phylogeny is presented for the speciose, near pan‐tropical, carnivorous achatinoid land‐snail superfamily Streptaxoidea inferred from DNA sequences (two nuclear and two mitochondrial regions) from 114 taxa from Africa, the Indian Ocean, Asia, South America and Europe. In all analyses, Streptaxidae are monophyletic, while the (two to six) previously recognised subfamilies are polyphyletic, as are several genus‐level taxa including the most speciose genus Gulella, necessitating major taxonomic review. The Asian Diapheridae are sister to Streptaxidae, which forms several well‐supported clades originating in a persistent basal polytomy. Divergence dating estimates, historical biogeography, and the fossil context suggest a Cretaceous origin of these families, but suggest Gondwanan vicariance predated most radiation. The basal polytomy dates to the Paleogene and may correspond to a rapid radiation in Africa. There is evidence for multiple Cenozoic dispersals followed by radiation, including at least two from Africa to South America, at least two from Africa to Asia and at least two from Africa to Madagascar, indicating Cenozoic turnover in tropical snail faunas. The endemic Seychelles and Mascarene streptaxid faunas each are composites of early Cenozoic lineages and more recent dispersals from Africa, with no direct evidence for an Asian origin as currently proposed. Peak streptaxid diversity in East Africa is explained by Neogene speciation among a large number of coexisting ancient lineages, a phenomenon most pronounced in the Eastern Arc‐Coastal Forests centre of endemism. This includes Miocene diversification in Gulella, a primarily East and South‐East African group which remains strikingly diverse even after unrelated ‘Gulella’ species are reclassified.     

First report of fossilized cysts produced by the benthic Bysmatrum subsalsum (Dinophyceae) from a shallow Mexican lagoon in the Gulf of Mexico

Cysts belonging to the benthic dinoflagellate Bysmatrum subsalsum were recovered from palynologically treated sediments collected in the Alvarado Lagoon (southwestern Gulf of Mexico). The cysts are proximate, reflecting the features of the parent thecal stage, and their autofluorescence implies a dinosporin composition similar to the cyst walls of phototrophic species. This finding is important for our understanding of B. subsalsum life cycle transitions and ecology. Encystment may play an important role in the bloom dynamics of this species as it can enable the formation of a sediment cyst bank that allows reinoculation of the water column when conditions become favorable. This is the first report of a fossilized cyst produced by a benthic dinoflagellate recovered from sub‐recent sediments.     

Blooms of benthic dinoflagellates of the genus Ostreopsis; an increasing and ecologically important phenomenon on temperate reefs in New Zealand and worldwide

Blooms of benthic dinoflagellates belonging to the tropical genus Ostreopsis are an increasingly common phenomenon in temperate regions worldwide. This is reflected in the rapid upsurge of publications on Ostreopsis from temperate regions since 2000. Relatively little is known about these blooms or their effects on other organisms. An unprecedented bloom of Ostreopsis siamensis occurred on shallow reefs in northern New Zealand in 2004 providing an opportunity to examine the dynamics of an O. siamensis bloom and its effect on community structuring sea urchins (Evechinus chloroticus). The bloom occurred following a period of calm sea conditions with warmer than average water temperatures. The cover of O. siamensis was highly ephemeral and strongly related to temporal and spatial variation in wave action. Blooms were most prevalent at sites protected from prevailing swells where O. siamensis covered 30–60% of the reef with the concentrations on macroalgae reaching 1.4 × 10⁶ cells g⁻¹ wet weight, some of the highest recorded worldwide. Surveys of the health of sea urchins in relation to the cover of O. siamensis suggested strong negative effects on this ecologically important herbivore and urchin densities declined by 56–60% at bloom sites over the study period. Further research is needed to examine the factors controlling the distribution and intensity of this new phenomenon, and into the ecological effects of such blooms on marine communities and the potential mechanisms responsible.     

Characterization of Gambierdiscus and Coolia (Dinophyceae) isolates from Thailand based on morphology and phylogeny

The benthic dinoflagellates in the genus Gambierdiscus produce toxins that bioaccumulate in tropical and sub‐tropical fish causing ciguatera fish poisoning (CFP). Other co‐occurring genera such as Coolia have also been implicated in causing CFP. Little is known about the diversity of the two genera Gambierdiscus and Coolia along the Thai coasts. The results of morphological analyses based on observation under light microscopy and scanning electron microcopy showed that strains of Gambierdiscus from Thailand displayed the typical Gambierdiscus plate formula: Po, 4′, 0a, 6″, 6c,?s, 5′′′, 0p and 2′′′′. Morphological examination of Thai Gambierdiscus enabled it to be identified as Gambierdiscus caribaeus: round and anterior‐posteriorly compressed cell shape, broad 2′′′′ plate, rectangular 2′ plate, and symmetrical 3″ plate. The phylogenetic analyses based on the large subunit (LSU) rDNA D8/D10 sequences of Gambierdiscus from Thailand confirmed the morphological identification. The thecal plate formula for all of the Coolia isolates from Thailand was Po, 4′, 0a, 6″,?c,?s, 5′′′, 0p and 2′′′′. Most, but not all, of these isolates could be identified morphologically as Coolia malayensis. An LSU rDNA D1/D2 phylogenetic analysis confirmed identity of C. malayensis isolates identified morphologically. The remaining unidentified isolates fell in the C. tropicalis clade.     

COOLIA CANARIENSIS SP. NOV. (DINOPHYCEAE), A NEW NONTOXIC EPIPHYTIC BENTHIC DINOFLAGELLATE FROM THE CANARY ISLANDS1

A new photosynthetic dinoflagellate species, Coolia canariensis S. Fraga sp. nov., is described based on samples taken from tidal ponds on the rocky shore of the Canary Islands, northeast Atlantic Ocean. Its morphology was studied by LM and SEM. It is almost spherical and has a thick smooth theca with many scattered pores. Plate 1′ is the biggest of the epithecal plates, and 7″ is twice as wide as it is long. Phylogeny inferred from the D1/D2 regions of the LSU nuclear rDNA of three strains of C. canariensis and several strains of other Coolia species, C. monotis, C. sp., showed that C. canariensis strains clustered in a well‐supported clade distinct from the other species. No toxins were detected using mouse bioassay, liquid chromatography with Fluorescence detection (LC‐FLD) or liquid chromatography‐mass spectrometry (LC‐MS). Its pigment composition is of the peridinin type of dinoflagellates. Together with this new species, many other strains of C. monotis from the Atlantic Ocean and Mediterranean Sea have been analyzed for toxin presence, and no evidence of toxin production related to yessotoxins (YTXs) was found, as was previously suggested for C. monotis from Australia.     

New Insights on Cytological and Metabolic Features of Ostreopsis cf. ovata Fukuyo (Dinophyceae): A Multidisciplinary Approach

The harmful dinoflagellate Ostreopsis cf. ovata has been causing toxic events along the Mediterranean coasts and other temperate and tropical areas, with increasing frequency during the last decade. Despite many studies, important biological features of this species are still poorly known. An integrated study, using different microscopy and molecular techniques, Raman microspectroscopy and high resolution liquid chromatography-mass spectrometry (HR LC-MS), was undertaken to elucidate cytological aspects, and identify main metabolites including toxins. The species was genetically identified as O. cf. ovata, Atlantic-Mediterranean clade. The ultrastructural results show unique features of the mucilage network abundantly produced by this species to colonize benthic substrates, with a new role of trichocysts, never described before. The amorphous polysaccharidic component of mucilage appears to derive from pusule fibrous material and mucocysts. In all stages of growth, the cells show an abundant production of lipids. Different developmental stages of chloroplasts are found in the peripheral cytoplasm and in the centre of cell. In vivo Raman microspectroscopy confirms the presence of the carotenoid peridinin in O. cf. ovata, and detects in several specimen the abundant presence of unsaturated lipids structurally related to docosahexaenoic acid. The HR LC-MS analysis reveals that ovatoxin-a is the predominant toxin, together with decreasing amounts of ovatoxin-b, -d/e, -c and putative palytoxin. Toxins concentration on a per cell basis increases from exponential to senescent phase. The results suggest that benthic blooms of this species are probably related to features such as the ability to create a unique mucilaginous sheath covering the sea bottom, associated with the production of potent toxins as palytoxin-like compounds. In this way, O. cf. ovata may be able to rapidly colonize benthic substrates outcompeting other species.