Toxic dinoflagellate Centrodinium punctatum (Cleve) F.J.R. Taylor: An examination on the responses in growth and toxin contents to drastic changes of temperature and salinity.

To understand environmental effects affecting paralytic shellfish toxin production of Centrodinium punctatum, this study examined the growth responses, and toxin contents and profiles of a C. punctatum culture exposed to drastic changes of temperature (5-30 °C) and salinity (15-40). C. punctatum grew over a temperature range of 15-25 °C, with an optimum of 20 °C., and over a salinity range of 25-40, with optimum salinities of 30-35. This suggests that C. punctatum prefers relatively warm waters and an oceanic habitat for its growth and can adapt to significant changes of salinity levels. When C. punctatum was cultivated at different temperature and salinity levels, the PST profile included four major analogs (STX, neoSTX, GTX1 and GTX4, constituted >80 % of the profile), while low amounts of doSTX and traces of dc-STX and dc-GTX2 were also observed. Interestingly, though overall toxin contents did not change significantly with temperature, increases in the proportion of STX, and decreases in proportions in GTX1 and GTX4 were observed with higher temperatures. Salinity did not affect either toxin contents or profile from 25 to 35. However, the total toxin content dropped to approximately half at salinity 40, suggesting this salinity may induce metabolic changes in C. punctatum.

Food web structure for high carbon retention in marine plankton communities.

Total annual net primary productions in marine and terrestrial ecosystems are similar. However, a large portion of the newly produced marine phytoplankton biomass is converted to carbon dioxide because of predation. Which food web structure retains high carbon biomass in the plankton community in the global ocean? In 6954 individual samples or locations containing phytoplankton, unicellular protozooplankton, and multicellular metazooplankton in the global ocean, phytoplankton-dominated bottom-heavy pyramids held higher carbon biomass than protozooplankton-dominated middle-heavy diamonds or metazooplankton-dominated top-heavy inverted pyramids. Bottom-heavy pyramids predominated, but the high predation impact by protozooplankton on phytoplankton or the vertical migration of metazooplankton temporarily changed bottom-heavy pyramids to middle-heavy diamonds or top-heavy inverted pyramids but returned to bottom-heavy pyramids shortly. This finding has profound implications for carbon retention by plankton communities in the global ocean.

Bloom development of toxic dinoflagellate Alexandrium catenella (Group I) in Jinhae-Masan Bay, Korea: Germination strategy of resting cysts in relation to temperature and salinity.

To better understand the role of resting cysts in the outbreak of paralytic shellfish poisoning and bloom dynamics in Jinhae-Masan Bay, Korea, this study investigated the germination features of ellipsoidal Alexandrium cysts isolated from sediments collected in winter and summer under different combinations of temperature and salinity. Morphology and phylogeny of germling cells revealed that the ellipsoidal Alexandrium cysts belong to Alexandrium catenella (Group I). The cysts could germinate across a wide range of temperature (5-25 °C) with germination success within 5 days, indicating that continuous seeding for the maintenance of vegetative cells in the water column may occur through the year without an endogenous clock to regulate germination timing. In addition, the cyst germination of A. catenella (Group I) was not controlled by seasonal salinity changes. Based on the results, this study provides a schematic scenario of the bloom development of A. catenella (Group I) in Jinhae-Masan Bay, Korea.

Assessing the utility of mitochondrial gene markers in the family Suessiaceae (Dinophyta) with phylogenomic validation.

The dinoflagellate family Suessiaceae comprises cosmopolitan species distributed across polar and tropical waters in both marine and freshwater ecosystems, encompassing free-living forms, symbionts, and parasites. Recently, species diversity within the family has rapidly expanded, now including a few species reported to cause red tides. Despite their ecological and evolutionary importance, classifying them within Suessiaceae is difficult due to the limitations of the existing molecular markers-the highly conserved small subunit ribosomal gene (SSU rDNA) and the presence of two indel regions of sequence fragments of the large subunit ribosomal gene (LSU rDNA)-resulting in poorly resolved phylogenetic relationships. We assessed mitochondrial cytochrome b (cob) and cytochrome c oxidase 1 (cox1) genes to develop robust molecular markers that can reveal the genetic diversity of the family Suessiaceae. The divergences of cob and cox1 sequences among the species in the family were greater than the SSU rDNA but less than the LSU rDNA and the ITS region. Moreover, the distinctive topology inferred from the mitochondrial genes provided high resolution among the suessiacean species. We examined the validity of the genetic markers using phylogenomics based on 2,023 core proteins. The divergence of the cob phylogeny was most consistent with that of the phylogenomic results. Taken together, the cob gene can be a novel marker reflecting topology at the genome-scale within the family Suessiaceae.

Evolutionary Dynamics and Lateral Gene Transfer in Raphidophyceae Plastid Genomes.

The Raphidophyceae is an ecologically important eukaryotic lineage of primary producers and predators that inhabit marine and freshwater environments worldwide. These organisms are of great evolutionary interest because their plastids are the product of eukaryote-eukaryote endosymbiosis. To obtain deeper insight into the evolutionary history of raphidophycean plastids, we sequenced and analyzed the plastid genomes of three freshwater and three marine species. Our comparison of these genomes, together with the previously reported plastid genome of Heterosigma akashiwo, revealed unexpected variability in genome structure. Unlike the genomes of other analyzed species, the plastid genome of Gonyostomum semen was found to contain only a single rRNA operon, presumably due to the loss of genes from the inverted repeat (IR) region found in most plastid genomes. In contrast, the marine species Fibrocapsa japonica contains the largest IR region and overall plastid genome for any raphidophyte examined thus far, mainly due to the presence of four large gene-poor regions and foreign DNA. Two plastid genes, tyrC in F. japonica and He. akashiwo and serC in F. japonica, appear to have arisen via lateral gene transfer (LGT) from diatoms, and several raphidophyte open reading frames are demonstrably homologous to sequences in diatom plasmids and plastid genomes. A group II intron in the F. japonica psbB gene also appears to be derived by LGT. Our results provide important insights into the evolutionary history of raphidophyte plastid genomes via LGT from the plastids and plasmid DNAs of diatoms.

Ovataline: A Polyketide Isolated from the Benthic Dinoflagellate Ostreopsis cf. ovata with 5α-Reductase Inhibitory Activity in RWPE-1 Prostatic Cells.

Ovataline (1), which is a polar metabolite containing a hexahydroquinoline moiety, was isolated from cultures of the marine dinoflagellate Ostreopsis cf. ovata. 1 was characterized as a zwitterionic compound with hexahydroquinoline and tetrahydropyran rings. The configurations of the chiral centers in 1 were established using ROESY correlations, J-based configurational and Mosher reaction analyses, and density functional theory calculations. 1 exhibited a 78% (1 µM) inhibition of type II 5α-reductase in testosterone propionate-induced RWPE-1 human prostatic cells.

Voratins A-C: Pyridinium Alkaloids from the Marine Dinoflagellate Effrenium voratum with Inhibitory Effects on Biomarkers for Benign Prostatic Hyperplasia.

Three voratin compounds (1-3) were isolated from the symbiotic marine dinoflagellate Effrenium voratum. The planar structures of 1-3 were determined by 1D and 2D NMR spectroscopy and HRESIMS, and the relative and absolute configurations were established using ROESY correlations, Mosher's method, and quantum calculations. All of the compounds are zwitterionic and contain a dihydroindolizinium ring and a spiroketal moiety. Compounds 1-3 were found to exhibit therapeutic effects against benign prostatic hyperplasia (BPH), as evaluated using testosterone propionate-treated LNCap and RWPE-1 human prostate cells. This excellent activity suggests that 1-3 are promising for the development of BPH treatments.

Feeding diverse prey as an excellent strategy of mixotrophic dinoflagellates for global dominance.

Microalgae fuel food webs and biogeochemical cycles of key elements in the ocean. What determines microalgal dominance in the ocean is a long-standing question. Red tide distribution data (spanning 1990 to 2019) show that mixotrophic dinoflagellates, capable of photosynthesis and predation together, were responsible for ~40% of the species forming red tides globally. Counterintuitively, the species with low or moderate growth rates but diverse prey including diatoms caused red tides globally. The ability of these dinoflagellates to trade off growth for prey diversity is another genetic factor critical to formation of red tides across diverse ocean conditions. This finding has profound implications for explaining the global dominance of particular microalgae, their key eco-evolutionary strategy, and prediction of harmful red tide outbreaks.

The Taxonomy and Diversity of Proschkinia (Bacillariophyta), A Common But Enigmatic Genus from Marine Coasts.

Detailed morphological documentation is provided for established Proschkinia taxa, including the generitype, P. bulnheimii, and P. complanata, P. complanatula, P. complanatoides and P. hyalosirella, and six new species. All established taxa are characterized from original material from historical collections. The new species described in this paper (P. luticola, P. staurospeciosa, P. impar, P. modesta, P. fistulispectabilis, and P. rosowskii) were isolated from the Western Pacific (Yellow Sea coast of Korea) and the Atlantic (Scottish and Texas coasts). Thorough documentation of the frustule, valve and protoplast architecture revealed the combination of characters diagnostic of the genus Proschkinia: a single-lobed chloroplast; a broad girdle composed of U-shaped, perforated bands; the position of the conopeate raphe-sternum relative to the external and internal valve surface; and the presence of an occluded process through the valve, termed the "fistula". Seven strains of Proschkinia were grown in culture and five of these were sequenced for nuclear ribosomal SSU and plastid-encoded rbcL. Phylogenetic analysis recovered a clade of Proschkinia with Fistulifera, another fistula-bearing diatom genus, and together these were sister to a clade formed of the Stauroneidaceae; in turn, all of these were sister to a clade composed of Parlibellus and two monoraphid genera Astartiella and Schizostauron. Despite morphological similarities between Proschkinia and the Naviculaceae, these two taxa are distant in our analysis. We document the variation in the morphology of Proschkinia, including significant variability in the fistula, suggesting that fistula ultrastructure might be one of the key features for species identification within the genus.

Relative Configurational Assignment of 4-Hydroxyprorocentrolide and Prorocentrolide C Isolated from a Benthic Dinoflagellate ( Prorocentrum lima).

Herein, we clarify the structure and relative configurations of two prorocentrolide analogues (1 and 2) isolated from the benthic marine dinoflagellate Prorocentrum lima. The results of NMR spectroscopy show that 1 is prorocentrolide substituted by a hydroxy group at C-4, while the newly isolated compound 2 can be thought of as 1 lacking one ether ring and having one extra double bond. The relative configurations of all stereogenic centers and the configurations of the double bonds in 1 and 2 were determined utilizing ROESY correlations and J-based configuration analysis. Furthermore, 2 was shown to exhibit cytotoxicity against HCT-116 and Neuro-2a cells (IC50 2.2 and 5.2 µM, respectively.

Effects of warming and eutrophication on coastal phytoplankton production.

Phytoplankton production in coastal waters influences seafood production and human health and can lead to harmful algal blooms. Water temperature and eutrophication are critical factors affecting phytoplankton production, although the combined effects of warming and nutrient changes on phytoplankton production in coastal waters are not well understood. To address this, phytoplankton production changes in natural waters were investigated using samples collected over eight months, and under 64 different initial conditions, established by combining four different water temperatures (i.e., ambient T, +2, +4, and + 6 °C), and two different nutrient conditions (i.e., non-enriched and enriched). Under the non-enriched conditions, the effect of warming on phytoplankton production was significantly positive in some months, significantly negative in others, or had no effect. However, under enriched conditions, warming affected phytoplankton production positively in all months except one, when the salinity was as low as 6.5. These results suggest that nutrient conditions can alter the effects of warming on phytoplankton production. Of several parameters, the ratio of initial nitrate concentration to chlorophyll a concentration [NCCA, µM (µg L-1)-1] was one of the most critical factors determining the directionality of the warming effects. In laboratory experiments, when NCCA in the ambient or nutrient-enriched waters was ≥1.2, warming increased or did not change phytoplankton production with one exception; however, when NCCA was <1.2, warming did not change or decreased production. In the time series data obtained from the coastal waters of four target countries, when NCCA was 1.5 or more, warming increased phytoplankton production, whereas when NCCA was lower than 1.5, warming lowered phytoplankton production, Thus, it is suggested that NCCA could be used as an index for predicting future phytoplankton production changes in coastal waters.

Gambierdiscus jejuensis sp. nov., an epiphytic dinoflagellate from the waters of Jeju Island, Korea, effect of temperature on the growth, and its global distribution.

The genus Gambierdiscus produces ciguatera toxins, which has led to extensive studies of this genus. Epiphytic dinoflagellate cells were isolated from coralline macroalgae collected from the coastal waters of Jeju Island, Korea, and two clonal cultures were established. The morphology of these cells was examined using light and scanning electron microscopy, and the sequences of the small subunit (SSU), large subunit (LSU), and internal transcribed spacer (ITS) region of rDNA were determined. The phylogenetic trees based on SSU, LSU (D1-D3), and LSU (D8-D10) rDNA showed the two Korean isolates forming a clade with unidentified strains named Gambierdiscus sp. type 2. This clade showed a clear divergence from the two closest clades containing of the G. caribaeus and G. carpenteri strains. Morphologically, the Korean isolates had an anteroposteriorly compressed cell shape having a smooth theca ornamentation. Growth of the Korean isolates ceased when water temperatures were <20 °C or >30 °C with an optimum at 26 °C. This temperature preference may account for why Gambierdiscus sp. type 2 has only been isolated from the temperate waters of Korea and Japan. However, the two most closely related species G. caribaeus and G. carpenteri have broader temperature ranges tolerating as high as 34-36 °C and are globally distributed. Based on these results, the Korean isolates are proposed as a new species in the genus Gambierdiscus and named Gambierdiscus jejuensis sp. nov. Furthermore, it is suggested that the unidentified strains belonging to the Gambierdiscus sp. type 2 be transferred to the new species, G. jejuensis.

Effects of light intensity, temperature, and salinity on the growth and ingestion rates of the red-tide mixotrophic dinoflagellate Paragymnodinium shiwhaense.

Among mixotrophic dinoflagellates, the maximum mixotrophic growth rate of the red-tide dinoflagellate Paragymnodinium shiwhaense is relatively high, whereas mortality due to predation is low. To investigate the effects of major environmental parameters on P. shiwhaense, growth and ingestion rates of one strain of P. shiwhaense on the algal prey species Amphidinium carterae (also a dinoflagellate) were determined under various light intensities (0-500 µE m-2s-1), water temperatures (5-30 °C), and salinities (5-40). Cells of P. shiwhaense did not grow well in darkness but grew well at light intensities ≥ 10 µE m-2s-1. There were no significant differences in either growth or ingestion rates of P. shiwhaense fed A. carterae at light intensities between 10 and 500 µE m-2s-1. Furthermore, P. shiwhaense did not grow at 5 °C or ≥ 28 °C. Its growth rates between 7 and 26 °C were significantly affected by temperature, and the optimal temperature for maximal growth was 25 °C. With increasing salinity from 5 to 20, the growth rate of P. shiwhaense fed A. carterae increased and became saturated at salinities between 20 and 40, while the ingestion rate at salinities between 10 and 40 did not significantly change. Thus, overall, the growth and ingestion rates of P. shiwhaense fed A. carterae were affected by temperature and salinity, but not by light intensity other than darkness. These findings provide a beginning basis for understanding the ecology of this potentially harmful algal species in marine coastal ecosystems.

Feeding and grazing impact by the bloom-forming euglenophyte Eutreptiella eupharyngea on marine eubacteria and cyanobacteria.

The phototrophic euglenophyte Eutreptiella eupharyngea often causes blooms in the coastal waters of many countries, but its mode of nutrition has not been assessed. This species has previously been considered as exclusively auxotrophic. To explore whether E. eupharyngea is a mixotrophic species, the protoplasm of E. eupharyngea cells were examined using light, epifluorescence, and transmission electron microscopy after eubacteria, the cyanobacterium Synechococcus sp., and diverse algal species were provided as potential prey. Furthermore, the ingestion rates of E. eupharyngea KR on eubacteria or Synechococcus sp. as a function of prey concentration were measured. In addition, grazing by natural populations of euglenophytes on natural populations of eubacteria in Masan Bay was investigated. This study is the first to report that E. eupharyngea is a mixotrophic species. Among the potential prey organisms offered, E. eupharyngea fed only on eubacteria and Synechococcus sp., and the maximum ingestion rates of these two organisms measured in the laboratory were 5.7 and 0.7 cells predator-1 h-1, respectively. During the field experiments, the maximum ingestion rates and grazing impacts of euglenophytes, including E. eupharyngea, on natural populations of eubacteria were 11.8 cells predator-1 h-1 and 1.228 d-1, respectively. Therefore, euglenophytes could potentially have a considerable grazing impact on marine bacterial populations.

Mixotrophy in the marine red-tide cryptophyte Teleaulax amphioxeia and ingestion and grazing impact of cryptophytes on natural populations of bacteria in Korean coastal waters.

Cryptophytes are ubiquitous and one of the major phototrophic components in marine plankton communities. They often cause red tides in the waters of many countries. Understanding the bloom dynamics of cryptophytes is, therefore, of great importance. A critical step in this understanding is unveiling their trophic modes. Prior to this study, several freshwater cryptophyte species and marine Cryptomonas sp. and Geminifera cryophila were revealed to be mixotrophic. The trophic mode of the common marine cryptophyte species, Teleaulax amphioxeia has not been investigated yet. Thus, to explore the mixotrophic ability of T. amphioxeia by assessing the types of prey species that this species is able to feed on, the protoplasms of T. amphioxeia cells were carefully examined under an epifluorescence microscope and a transmission electron microscope after adding each of the diverse prey species. Furthermore, T. amphioxeia ingestion rates heterotrophic bacteria and the cyanobacterium Synechococcus sp. were measured as a function of prey concentration. Moreover, the feeding of natural populations of cryptophytes on natural populations of heterotrophic bacteria was assessed in Masan Bay in April 2006. This study reported for the first time, to our knowledge, that T. amphioxeia is a mixotrophic species. Among the prey organisms offered, T. amphioxeia fed only on heterotrophic bacteria and Synechococcus sp. The ingestion rates of T. amphioxeia on heterotrophic bacteria or Synechococcus sp. rapidly increased with increasing prey concentrations up to 8.6×106 cells ml-1, but slowly at higher prey concentrations. The maximum ingestion rates of T. amphioxeia on heterotrophic bacteria and Synechococcus sp. reached 0.7 and 0.3 cells predator-1 h-1, respectively. During the field experiments, the ingestion rates and grazing coefficients of cryptophytes on natural populations of heterotrophic bacteria were 0.3-8.3 cells predator-1h-1 and 0.012-0.033d-1, respectively. Marine cryptophytes, including T. amphioxeia, are known to be favorite prey species for many mixotrophic and heterotrophic dinoflagellates and ciliates. Cryptophytes, therefore, likely play important roles in marine food webs and may exert a considerable potential grazing impact on the populations of marine bacteria.

Differential interactions between the nematocyst-bearing mixotrophic dinoflagellate Paragymnodinium shiwhaense and common heterotrophic protists and copepods: Killer or prey.

To investigate interactions between the nematocyst-bearing mixotrophic dinoflagellate Paragymnodinium shiwhaense and different heterotrophic protist and copepod species, feeding by common heterotrophic dinoflagellates (Oxyrrhis marina and Gyrodinium dominans), naked ciliates (Strobilidium sp. approximately 35µm in cell length and Strombidinopsis sp. approximately 100µm in cell length), and calanoid copepods Acartia spp. (A. hongi and A. omorii) on P. shiwhaense was explored. In addition, the feeding activities of P. shiwhaense on these heterotrophic protists were investigated. Furthermore, the growth and ingestion rates of O. marina, G. dominans, Strobilidium sp., Strombidinopsis sp., and Acartia spp. as a function of P. shiwhaense concentration were measured. O. marina, G. dominans, and Strombidinopsis sp. were able to feed on P. shiwhaense, but Strobilidium sp. was not. However, the growth rates of O. marina, G. dominans, Strobilidium sp., and Strombidinopsis sp. feeding on P. shiwhaense were very low or negative at almost all concentrations of P. shiwhaense. P. shiwhaense frequently fed on O. marina and Strobilidium sp., but did not feed on Strombidinopsis sp. and G. dominans. G. dominans cells swelled and became dead when incubated with filtrate from the experimental bottles (G. dominans+P. shiwhaense) that had been incubated for one day. The ingestion rates of O. marina, G. dominans, and Strobilidium sp. on P. shiwhaense were almost zero at all P. shiwhaense concentrations, while those of Strombidinopsis sp. increased with prey concentration. The maximum ingestion rate of Strombidinopsis sp. on P. shiwhaense was 5.3ngC predator-1d-1 (41 cells predator-1d-1), which was much lower than ingestion rates reported in the literature for other mixotrophic dinoflagellate prey species. With increasing prey concentrations, the ingestion rates of Acartia spp. on P. shiwhaense increased up to 930ngCml-1 (7180cellsml-1) at the highest prey concentration. The highest ingestion rate of Acartia spp. on P. shiwhaense was 4240ngC predator-1d-1 (32,610 cells predator-1d-1), which is comparable to ingestion rates from previous studies on other dinoflagellate prey species calculated at similar prey concentrations. Thus, P. shiwhaense might play diverse ecological roles in marine planktonic communities by having an advantage over competing phytoplankton in anti-predation against potential protistan grazers.

Genetics and morphology characterize the dinoflagellate Symbiodinium voratum, n. sp., (Dinophyceae) as the sole representative of Symbiodinium Clade E.

Dinoflagellates in the genus Symbiodinium are ubiquitous in shallow marine habitats where they commonly exist in symbiosis with cnidarians. Attempts to culture them often retrieve isolates that may not be symbiotic, but instead exist as free-living species. In particular, cultures of Symbiodinium clade E obtained from temperate environments were recently shown to feed phagotrophically on bacteria and microalgae. Genetic, behavioral, and morphological evidence indicate that strains of clade E obtained from the northwestern, southwestern, and northeastern temperate Pacific Ocean as well as the Mediterranean Sea constitute a single species: Symbiodinium voratum n. sp. Chloroplast ribosomal 23S and mitochondrial cytochrome b nucleotide sequences were the same for all isolates. The D1/D2 domains of nuclear ribosomal DNA were identical among Western Pacific strains, but single nucleotide substitutions differentiated isolates from California (USA) and Spain. Phylogenetic analyses demonstrated that S. voratum is well-separated evolutionarily from other Symbiodinium spp. The motile, or mastigote, cells from different cultures were morphologically similar when observed using light, scanning, and transmission electron microscopy; and the first complete Kofoidian plate formula for a Symbiodinium sp. was characterized. As the largest of known Symbiodinium spp., the average coccoid cell diameters measured among cultured isolates ranged between 12.2 (± 0.2 SE) and 13.3 (± 0.2 SE) µm. Unique among species in the genus, a high proportion (approximately 10-20%) of cells remain motile in culture during the dark cycle. Although S. voratum occurs on surfaces of various substrates and is potentially common in the plankton of coastal areas, it may be incapable of forming stable mutualistic symbioses.

Feeding by heterotrophic dinoflagellates and ciliates on the free-living dinoflagellate Symbiodinium sp. (Clade E).

To investigate heterotrophic protists grazing on Symbiodinium sp., we tested whether the common heterotrophic dinoflagellates Gyrodinium dominans, Gyrodinium moestrupii, Gyrodinium spirale, Oblea rotundata, Oxyrrhis marina, and Polykrikos kofoidii and the ciliates Balanion sp. and Parastrombidinopsis sp. preyed on the free-living dinoflagellate Symbiodinium sp. (clade E). We measured the growth and ingestion rates of O. marina and G. dominans on Symbiodinium sp. as a function of prey concentration. Furthermore, we compared the results to those obtained for other algal prey species. In addition, we measured the growth and ingestion rates of other predators at single prey concentrations at which these rates of O. marina and G. dominans were saturated. All predators tested in the present study, except Balanion sp., preyed on Symbiodinium sp. The specific growth rates of O. marina and G. dominans on Symbiodinium sp. increased rapidly with increasing mean prey concentration < ca. 740-815 ng C/ml (7,400-8,150 cells/ml), but became saturated at higher concentrations. The maximum growth rates of O. marina and G. dominans on Symbiodinium sp. (0.87 and 0.61/d) were much higher than those of G. moestrupii and P. kofoidii (0.11 and 0.04/d). Symbiodinium sp. did not support positive growth of G. spirale, O. rotundata, and Parastrombidinopsis sp. However, the maximum ingestion rates of P. kofoidii and Parastrombidinopsis sp. (6.7-10.0 ng C/predator/d) were much higher than those of O. marina and G. dominans on Symbiodinium sp. (1.9-2.1 ng C/predator/d). The results of the present study suggest that Symbiodinium sp. may increase or maintain the populations of some predators.

Still acting green: continued expression of photosynthetic genes in the heterotrophic Dinoflagellate Pfiesteria piscicida (Peridiniales, Alveolata).

The loss of photosynthetic function should lead to the cessation of expression and finally loss of photosynthetic genes in the new heterotroph. Dinoflagellates are known to have lost their photosynthetic ability several times. Dinoflagellates have also acquired photosynthesis from other organisms, either on a long-term basis or as "kleptoplastids" multiple times. The fate of photosynthetic gene expression in heterotrophs can be informative into evolution of gene expression patterns after functional loss, and the dinoflagellates ability to acquire new photosynthetic function through additional endosymbiosis. To explore this we analyzed a large-scale EST database consisting of 151,091 unique sequences (29,170 contigs, 120,921 singletons) obtained from 454 pyrosequencing of the heterotrophic dinoflagellate Pfiesteria piscicida. About 597 contigs from P. piscicida showed significant homology (E-value

The newly described heterotrophic dinoflagellate Gyrodinium moestrupii, an effective protistan grazer of toxic dinoflagellates.

Few protistan grazers feed on toxic dinoflagellates, and low grazing pressure on toxic dinoflagellates allows these dinoflagellates to form red-tide patches. We explored the feeding ecology of the newly described heterotrophic dinoflagellate Gyrodinium moestrupii when it fed on toxic strains of Alexandrium minutum, Alexandrium tamarense, and Karenia brevis and on nontoxic strains of A. tamarense, Prorocentrum minimum, and Scrippsiella trochoidea. Specific growth rates of G. moestrupii feeding on each of these dinoflagellates either increased continuously or became saturated with increasing mean prey concentration. The maximum specific growth rate of G. moestrupii feeding on toxic A. minutum (1.60/d) was higher than that when feeding on nontoxic S. trochoidea (1.50/d) or P. minimum (1.07/d). In addition, the maximum growth rate of G. moestrupii feeding on the toxic strain of A. tamarense (0.68/d) was similar to that when feeding on the nontoxic strain of A. tamarense (0.71/d). Furthermore, the maximum ingestion rate of G. moestrupii on A. minutum (2.6 ng C/grazer/d) was comparable to that of S. trochoidea (3.0 ng C/grazer/d). Additionally, the maximum ingestion rate of G. moestrupii on the toxic strain of A. tamarense (2.1 ng C/grazer/d) was higher than that when feeding on the nontoxic strain of A. tamarense (1.3 ng C/grazer/d). Thus, feeding by G. moestrupii is not suppressed by toxic dinoflagellate prey, suggesting that it is an effective protistan grazer of toxic dinoflagellates.