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Cryptophytes are known to vary widely in coloration among species. These differences in color arise primarily from the presence of phycobiliprotein accessory pigments. There are nine defined cryptophyte phycobiliprotein (Cr‐PBP) types, named for their wavelength of maximal absorbance. Because Cr‐PBP type has traditionally been regarded as a categorical trait, there is a paucity of information about how spectral absorption characteristics of Cr‐PBPs vary among species. We investigated variability in primary and secondary peak absorbance wavelengths and full width at half max (FWHM) values of spectra of Cr‐PBPs extracted from 75 cryptophyte strains (55 species) grown under full spectrum irradiance. We show that there may be substantial differences in spectral shapes within Cr‐PBP types, with Cr‐Phycoerythrin (Cr‐PE) 545 showing the greatest variability with two, possibly three, subtypes, while Cr‐PE 566 spectra were the least variable, with only ±1 nm of variance around the mean absorbance maximum of 565 nm. We provide additional criteria for classification in cases where the wavelength of maximum absorbance alone is not definitive. Variations in spectral characteristics among strains containing the same presumed Cr‐PBP type may indicate differing chromophore composition and/or the presence of more than one Cr‐PBP in a single cryptophyte species. [ABSTRACT FROM AUTHOR]

Microplastics are contaminants of global environmental concern. They can be ingested by a variety of organisms when they enter the food web. Several studies have reported trophic transfer of microplastics from low trophic levels to higher ones. Bioaccumulation has been suggested to occur but few studies have demonstrated it for marine environments. In this article, in controlled laboratory conditions, we exposed filter‐feeder ascidian juveniles to microplastics in the presence or in absence of mixotrophic cryptomonad flagellates. Cryptomonads can efficiently ingest microbeads, and their presence significantly increased the concentration of microplastics in the digestive tract of the ascidians. Our results demonstrate the occurrence of microplastic bioaccumulation in the lower levels of the marine trophic chain and suggest that unicellular organisms can be key actors in microplastic trophic transfer at the microscale level. Research Highlights: •Marine mixotrophic cryptomonad flagellates can ingest microbeads of polystyrene with a diameter of 10 µm. •The copresence of cryptomonads and microbeads significantly increased the microplastics in the digestive tract of filter‐feeding ascidians. [ABSTRACT FROM AUTHOR]

The underwater light field of lakes, estuaries, and oceans may vary greatly in spectral composition. Phytoplankton in these environments must contain pigments that absorb the available colors of light. If spectral quality changes, acclimation to the new spectral environment would confer an ecological advantage in terms of photosynthesis and growth. Here, we explored the capacity of eight marine cryptophytes to adjust pigmentation in response to changes in spectral irradiance and related effects on light absorption, photosynthetically useable radiation (PUR), and growth rate. The pigment composition of all species changed in some way in response to shifts in spectral irradiance, but not all pigment changes could be considered advantageous in the context of chromatic acclimation. For most species, absorption by chl‐a and chl‐c2 resulted in highest absorption in the blue region, highest PUR values for blue‐light grown cells, and highest growth rates in blue light. The exception was Chroomonas mesostigmatica (CCMP 1168), which contains a high percentage of Cryptophyte‐Phycocyanin (Cr‐PC) 645, absorbs strongly in the orange‐to‐red region of the spectrum, and grew fastest under red light. The position and magnitude of the maximum and secondary absorption peak of Cr‐PC 569, the phycobiliprotein pigment of Hemiselmis cryptochromatica, varied with spectral irradiance. The underlying cause remains unknown, but may represent a mechanism by which cryptophytes optimize photon capture. [ABSTRACT FROM AUTHOR]

Nucleomorphs are small nuclei that evolved from the nucleus of former eukaryotic endosymbionts of cryptophytes and chlorarachniophytes. These enigmatic organelles reside in their complex plastids and harbor the smallest and most compacted eukaryotic genomes investigated so far. Although the coding capacity of the nucleomorph genomes is small, a significant percentage of the encoded proteins (predicted nucleomorph-encoded proteins, pNMPs) is still not functionally annotated. We have analyzed pNMPs with unknown functions via Phyre2, a bioinformatic tool for prediction and modeling of protein structure, resulting in a functional annotation of 215 pNMPs out of 826 uncharacterized open reading frames of cryptophytes. The newly annotated proteins are predicted to participate in nucleomorph-specific functions such as chromosome organization and expression, as well as in modification and degradation of nucleomorph-encoded proteins. Additionally, we have functionally assigned nucleomorph-encoded, putatively plastid-targeted proteins among the reinvestigated pNMPs. Hints for a putative function in the periplastid compartment, the cytoplasm surrounding the nucleomorphs, emerge from the identification of pNMPs that might be homologs of endomembrane system-related proteins. These proteins are discussed in respect to their putative functions. [ABSTRACT FROM AUTHOR]

Eukaryotic genes are interrupted by introns that are removed in a conserved process known as pre-mRNA splicing. Though wellstudied in selectmodel organisms, we are only beginning to understand the variation and diversity of this process across the tree of eukaryotes. We explored pre-mRNA splicing and other features of transcription in nucleomorphs, the highly reduced remnant nuclei of secondary endosymbionts. Strand-specific transcriptomes were sequenced from the cryptophyte Guillardia theta and the chlorarachniophyte Bigelowiella natans, whose plastids are derived from red and green algae, respectively. Both organisms exhibited elevated nucleomorph antisense transcriptionand gene expression relative to their respective nuclei, suggesting unique properties of gene regulation and transcriptional control in nucleomorphs. Marked differences in splicing were observed between the two nucleomorphs: the few introns of the G. theta nucleomorph were largely retained in mature transcripts, whereas the many short introns of the B. natans nucleomorph are spliced at typical eukaryotic levels (>90%). These differences in splicing levels could be reflecting the ancestries of the respective plastids, the different intron densities due to independent genome reduction events, or a combination of both. In addition to extending our understanding of the diversity of pre-mRNA splicing across eukaryotes, our study also indicates potential links between splicing, antisense transcription, and gene regulation in reduced genomes. [ABSTRACT FROM AUTHOR]

Symbiosis between prokaryotes and microbial eukaryotes (protists) has broadly impacted both evolution and ecology. Endosymbiosis led to mitochondria and plastids, the latter spreading across the tree of eukaryotes by subsequent rounds of endosymbiosis. Present-day endosymbionts in protists remain both common and diverse, although what function they serve is often unknown. Here, we describe a highly complex community of endosymbionts and a bacteriophage (phage) within a single cryptomonad cell. Cryptomonads are a model for organelle evolution because their secondary plastid retains a relict endosymbiont nucleus, but only one previously unidentified Cryptomonas strain (SAG 25.80) is known to harbor bacterial endosymbionts. We carried out electron microscopy and FISH imaging as well as genomic sequencing on Cryptomonas SAG 25.80, which revealed a stable, complex community even after over 50 years in continuous cultivation. We identified the host strain as Cryptomonas gyropyrenoidosa , and sequenced genomes from its mitochondria, plastid, and nucleomorph (and partially its nucleus), as well as two symbionts, Megaira polyxenophila and Grellia numerosa , and one phage (MAnkyphage) infecting M. polyxenophila. Comparing closely related endosymbionts from other hosts revealed similar metabolic and genomic features, with the exception of abundant transposons and genome plasticity in M. polyxenophila from Cryptomonas. We found an abundance of eukaryote-interacting genes as well as many toxin-antitoxin systems, including in the MAnkyphage genome that also encodes several eukaryotic-like proteins. Overall, the Cryptomonas cell is an endosymbiotic conglomeration with seven distinct evolving genomes that all show evidence of inter-lineage conflict but nevertheless remain stable, even after more than 4,000 generations in culture. • A cryptomonad hosts two distinct bacterial endosymbionts and a bacteriophage • The bacteriophage infects the endosymbiont, Megaira polyxenophila • Both bacterial endosymbionts and bacteriophage encode eukaryotic-like proteins • Seven distinct genomes are present in the single-celled cryptomonad George et al. describe the genomic and metabolic complexity of two bacterial endosymbionts and an endosymbiont-infecting bacteriophage in the single-celled alga, Cryptomonas gyropyrenoidosa. This complex symbiosis involves seven genomes within a single eukaryotic cell and has been retained in culture for over 50 years. [ABSTRACT FROM AUTHOR]

The cryptomonad nucleomorph is a vestigial nucleus of a eukaryotic red alga engulfed by a phagotrophic protist and retained as a photosynthetic endosymbiont. This review recounts the initial discovery and subsequent characterisation of the cryptomonad nucleomorph focusing on the key role of Peter Sitte and his protégés in our understanding of secondary endosymbiosis to create complex plastids, one of the major transition events in the evolution of life on Earth. [ABSTRACT FROM AUTHOR]

Cryptomonas curvata Ehrenberg is a photosynthetic freshwater flagellate and the type species of the genus Cryptomonas. We examined the flagellar apparatus of cryptomorphic C. curvata by transmission electron microscopy. The major components of the flagellar apparatus are the non-keeled rhizostyle (Rhs), striated fibrous root (SR), striated fiber-associated microtubular root (SRm), mitochondrion-associated lamella (ML), and two types of microtubular roots (3r and 2r). The non-keeled Rhs originate at the ventral basal body and consist of two types of microtubule bands extending together into the middle of the cell. The SR and SRm extend parallel to the left side of the cell. The ML originates from the ventral basal body and is a plate-like fibrous structure associated with mitochondria. The 3r extends from the dorsal basal body toward the dorsal anterior of the cell. The 2r originates between the two basal bodies and extends shortly to the left of the cell. The overall configuration of the flagellar apparatus is most similar to that previously reported for C. pyrenoidifera. These results demonstrate that the features of the flagellar apparatus are useful for distinguishing closely related species and inferring phylogenetic relationships among taxa. [ABSTRACT FROM AUTHOR]

Rhinomonas reticulata var. atrorosea G. Novarino is a photosynthetic marine flagellate that is known to have typical characteristics of cryptomonads. We examined the flagellar apparatus of R. reticulata var. atrorosea by transmission electron microscopy. The major components of the flagellar apparatus of R. reticulata var. atrorosea consisted of four types of microtubular roots (1r, 2r, 3r, and mr), a non-keeled rhizostyle (Rhs), mitochondrion-associated lamella (ML), two connections between basal bodies, a striated fibrous root (SR) and a striated fiber-associated microtubular root (SRm). Four types of microtubular roots originated near the ventral basal body and extended toward the left side of the basal bodies. The non-keeled Rhs originated at the Rhs-associated striated fiber, which was located between two basal bodies and extended into the middle of the cell. The ML was a plate-like fibrous structure associated with mitochondria and originating from a Rhs-associated fiber. It split into two parts and extended toward the dorsal-posterior of the cell to a mitochondrion. The SR and SRm extended parallel to the anterior lobe of the cell. The overall configuration of the flagellar apparatus in R. reticulata var. atrorosea was similar to the previously reported descriptions of those of Cryptomonas paramecium, C. pyrenoidifera, C. ovata, Hanusia phi, Guillardia theta, and Proteomonas sulcata. However, the flagellar apparatus system of R. reticulata var. atrorosea was more complex than those of other cryptomonad species due to the presence of an additional microtubular root and other distinctive features, such as a rhizostyle-associated striated fiber and large ML. [ABSTRACT FROM AUTHOR]

The morphology, ultrastructure, phylogeny, and ecology of a new red-tide-forming cryptomonad, Urgorri complanatus Laza-Martínez gen. et sp. nov., is described. U. complanatus has been collected in southwestern European estuaries, blooming in the inner reaches of several of them. The estuarine character of the species is also supported by its in vitro salinity preferences, showing a maximum growth rate at 10 psu. U. complanatus is a distinctive species and can be easily distinguished by LM from other known brackish and marine species. Cells are dorsoventrally flattened. The plastid has two anterior lobes. One pyrenoid is located in each of the lobes, and a third one on the posterior part. Thylakoids are arranged in pairs and do not penetrate pyrenoids. The plastid is reddish due to the presence of the phycoerythrin Cr-PE545. An orange discoidal eyespot lies beneath the nucleus, in the posterior ventral face of the plastid. A long furrow runs from the vestibulum, and a gullet is lacking. The periplast is composed of an inner sheet. The nuclear 18S rDNA based molecular analysis reveals U. complanatus is not related to any of the main cryptomonad lineages. Based on ultrastructural and pigment data, the most probable relatives are those merged under the family Geminigeraceae. Its lack of derived characters, together with the presence of characters proposed in previous studies to be primitive, suggests Urgorri could be considered representative of the cryptophycean ancestral character state. [ABSTRACT FROM AUTHOR]

The morphology, ultrastructure, phylogeny, and ecology of a new red-tide-forming cryptomonad, Urgorri complanatus Laza-Martínez gen. et sp. nov., is described. U. complanatus has been collected in southwestern European estuaries, blooming in the inner reaches of several of them. The estuarine character of the species is also supported by its in vitro salinity preferences, showing a maximum growth rate at 10 psu. U. complanatus is a distinctive species and can be easily distinguished by LM from other known brackish and marine species. Cells are dorsoventrally flattened. The plastid has two anterior lobes. One pyrenoid is located in each of the lobes, and a third one on the posterior part. Thylakoids are arranged in pairs and do not penetrate pyrenoids. The plastid is reddish due to the presence of the phycoerythrin Cr-PE545. An orange discoidal eyespot lies beneath the nucleus, in the posterior ventral face of the plastid. A long furrow runs from the vestibulum, and a gullet is lacking. The periplast is composed of an inner sheet. The nuclear 18S rDNA based molecular analysis reveals U. complanatus is not related to any of the main cryptomonad lineages. Based on ultrastructural and pigment data, the most probable relatives are those merged under the family Geminigeraceae. Its lack of derived characters, together with the presence of characters proposed in previous studies to be primitive, suggests Urgorri could be considered representative of the cryptophycean ancestral character state. [ABSTRACT FROM AUTHOR]

Abstract: Cryptophytes like the cryptomonad Guillardia theta are part of the marine phytoplankton and therefore major players in global carbon and biogeochemical cycles. Despite the importance for the cell in being able to cope with large changes in illumination on a daily basis, very little is known about photoprotection mechanisms in cryptophytes. Here, we show that Guillardia theta is able to perform non-photochemical quenching, although none of the usual xanthophyll cycle pigments (e.g., zeaxanthin, diadinoxanthin, diatoxanthin) are present at detectable levels. Instead, acclimation to high light intensity seems to involve an increase of alloxanthin. Guillardia theta has genes for 2 one-helix “light-harvesting-like” proteins, related to some cyanobacterial genes which are induced in response to high light stress. Both the plastid-encoded gene (hlipP) and the nucleomorph-encoded gene (HlipNm) are expressed, but transcript levels decrease rather than increase during high light exposure, suggesting that they are not involved in a high light stress response. The HlipNm protein was detected with a specific antibody; expression was constant, independent of the light exposure. [Copyright &y& Elsevier]

Cryptomonads are a ubiquitous and diverse assemblage of aquatic flagellates. The relatively obscure genus Hemiselmis includes some of the smallest of these cells. This genus contained only two species until 1967, when Butcher described seven new marine species mainly on the basis of observations with the light microscope. However, from these seven taxa, only H.  amylifera and H.  oculata were validly published. Additionally, the features Butcher used to distinguish species have since been questioned, and the taxonomy within Hemiselmis has remained clouded due to the difficulty in unambiguously applying his classification and validating many of his species. As a result, marine strains are often placed into one of three species— H.  rufescens Parke, H.  virescens Droop, or the invalid H.  brunnescens Butcher—based on cell color alone. Here we applied microscopic and molecular tools to 13 publicly available Hemiselmis strains in an effort to clarify species boundaries. SEM failed to provide sufficient morphological variation to distinguish species of Hemiselmis, and results from LM did not correlate with clades found using both molecular phylogenetic and nucleomorph genome karyotype analysis, indicating a high degree of morphological plasticity within species. On the basis of molecular characters and collection geography we recognize four new marine species of Hemiselmis— H.  cryptochromatica sp. nov., H.  andersenii sp. nov., H.  pacifica sp. nov., and H.  tepida sp. nov.—from the waters around North America. [ABSTRACT FROM AUTHOR]

Previous studies have shown that the nuclear internal transcribed spacer 2 (ITS2) is likely a good marker to identity biological species according to its degree of conservation. Dimorphic strains and a few reports of sexual reproduction indicate the presence of biological species also in cryptophyte taxa. In this study, a reverse (= DNA-based) taxonomy approach was used to predict putative biological species in the genus Cryptomonas. Of 49 Cryptomonas strains, nuclear ITS2 and partial large subunit (LSU) rDNA sequences were used to determine groups of genetically identical strains. From each group, representative strains (a total of 30 strains) were chosen for improved molecular phylogenetic analyses with combined data sets (nuclear ITS2 and LSU rDNA and nucleomorph small subunit rDNA). To predict putative biological species in Cryptomonas, the secondary structures of the nuclear ITS2 sequences were compared among clades and among strains of the same clade. Mapping light microscopically visible characters of the 49 strains onto the phylogenetic trees revealed conflicts between classical morphospecies and putative biological species. Strains that were identical or almost identical in nuclear ITS2, showed cell shapes representing different morphological species, whereas strains seemingly belonging to the same morphological species were genetically too diverse to represent one biological species. Most of the five putative biological species could solely be identified by molecular signatures. Therefore, five species descriptions were emended by adding molecular signatures as diagnostic characters including a new combination, Cryptomonas commutata (Pascher) Hoef-Emden comb. nov. [ABSTRACT FROM AUTHOR]

In this study, evidence for at least three independent losses of photosynthesis in the freshwater cryptophyte genusCryptomonasis presented. The phylogeny of the genus was inferred by molecular phylogenetic analyses of the nuclear internal transcribed spacer 2 (nuclear ITS2), partial nuclear large subunit ribosomal DNA (LSU rDNA), and nucleomorph small subunit ribosomal DNA (SSU rDNA, NM). Both concatenated and single data sets were used. In all data sets, the colorlessCryptomonasstrains formed three different lineages, always supported by high bootstrap values (maximum parsimony, neighbor joining and maximum likelihood) and posterior probabilities (Bayesian analyses). The three leukoplast-bearing lineages displayed differing degrees of accelerated evolutionary rates in nuclear and nucleomorph rDNA. Also an increase in A+T-content in highly variable regions of the nucleomorph SSU rDNA was observed in one of the leukoplast-bearing lineages. [ABSTRACT FROM AUTHOR]

Type 1 (archaeal) rhodopsins and related rhodopsin-like proteins had been described in a few halophile archaea, γ-proteobacteria, a single cyanobacteria, some fungi, and a green alga. In exhaustive database searches, we detected rhodopsin-related sequences derived not only from additional fungal species but also from organisms belonging to three groups in which opsins had hitherto not been described: the α-proteobacterium Magnetospirillummagnetotacticum, the cryptomonad alga Guillardia theta, and the dinoflagellate Pyrocystis lunula. Putative plant and human type 1 rhodopsin sequences found in the databases are demonstrated to be contaminants of fungal origin. However, a highly diverged sequence supposedly from the plant Oryza sativa was found that is, together with the Pyrocystis sequence, quite similar to γ-proteobacterial rhodopsins. These close relationships suggest that at least one horizontal gene transfer event involving rhodopsin genes occurred between prokaryotes and eukaryotes. Alternative hypotheses to explain the current phylogenetic range of type 1 rhodopsins are suggested. The broader phylogenetic range found is compatible with an ancient origin of type 1 rhodopsins, their patchy distribution being caused by losses in multiple lineages. However, the possibility of ancient horizontal transfer events between distant relatives cannot be dismissed. [ABSTRACT FROM AUTHOR]

Fe deficiency has been documented in diverse marine environments ranging from pelagic high-nutrient, low chlorophyll (HNLC) regions to coastal systems. Detection of specific Fe-responsive proteins in phytoplankton has provided a sensitive approach to assessing Fe deficiency in natural waters. Here, we report on the development and applicability of taxon-specific polyclonal antisera to monitor the accumulation of two such Fe-responsive proteins, flavodoxin and ferredoxin (Fd) in cryptomonad algae. Reactivity of these immunoreagents was limited primarily to cryptomonads. Anti-Fd cross-reacted with a broad spectrum of both marine and freshwater cryptophytes whereas anti-flavodoxin recognized only flavodoxin from Rhodomonas lens . Assessment of Fd and flavodoxin accumulation in R. lens grown under various levels of Fe demonstrated an apparent uncoupling of flavodoxin expression from physiological Fe deficiency in this species. It appears that flavodoxin accumulates in response to external Fe availability as supported by results of a chelator addition experiment which demonstrated rapid accumulation of flavodoxin in Fe-replete cells of R. lens without concomitant physiological deficit following addition of the fungal siderophore desferrioxamine B. [ABSTRACT FROM AUTHOR]

A nuclear18S rDNA phylogeny for cryptomonad algae is presented, including 11 species yet to be investigated by molecular means. The phylogenetic positions of the cryptomonad genera Campylomonas and Plagioselmis are assessed for the first time. Campylomonas groups most closely with morphologically similar species with the same accessory pigment from the genus Cryptomonas. Plagioselmis groups with the genera Teleaulax and Geminigera forming a clade whose members are united by unusual thylakoid arrangement. Nuclear 18S rDNA phylogeny divides cryptomonads into seven major lineages, two of which consist of the monospecific genera Proteomonas and Falcomonas. Analysis of nuclear18S rDNA sequence supports suggestions that a Falcomonas -like cryptomonad gave rise to all other blue-green cryptomonads. New sequence from the plastid-lacking cryptomonad genus Goniomonas is also included, and the order of divergence of the major cryptomonad lineages is discussed. The morphology, number, and pigmentation of the cryptomonad plastidial complex are congruent with nuclear 18S rDNA phylogenies. Host cell features, such as periplast type, furrow/gullet system, and cell shape, can be more variable and may be markedly different in species that are closely related by nuclear 18S rDNA phylogeny. Conversely, some species that are not closely related by molecular phylogeny may display a very similar, possibly primitive, periplast and furrow morphology. [ABSTRACT FROM AUTHOR]

A nuclear18S rDNA phylogeny for cryptomonad algae is presented, including 11 species yet to be investigated by molecular means. The phylogenetic positions of the cryptomonad genera Campylomonas and Plagioselmis are assessed for the first time. Campylomonas groups most closely with morphologically similar species with the same accessory pigment from the genus Cryptomonas. Plagioselmis groups with the genera Teleaulax and Geminigera forming a clade whose members are united by unusual thylakoid arrangement. Nuclear 18S rDNA phylogeny divides cryptomonads into seven major lineages, two of which consist of the monospecific genera Proteomonas and Falcomonas. Analysis of nuclear18S rDNA sequence supports suggestions that a Falcomonas -like cryptomonad gave rise to all other blue-green cryptomonads. New sequence from the plastid-lacking cryptomonad genus Goniomonas is also included, and the order of divergence of the major cryptomonad lineages is discussed. The morphology, number, and pigmentation of the cryptomonad plastidial complex are congruent with nuclear 18S rDNA phylogenies. Host cell features, such as periplast type, furrow/gullet system, and cell shape, can be more variable and may be markedly different in species that are closely related by nuclear 18S rDNA phylogeny. Conversely, some species that are not closely related by molecular phylogeny may display a very similar, possibly primitive, periplast and furrow morphology. [ABSTRACT FROM AUTHOR]

There are two ways eukaryotic cells can permanently acquire chloroplasts. They can take up a cyanobacterium and turn it into a chloroplast or they can engulf an alga that already has a chloroplast. The second method is far more common and there are at least seven major groups of protists that have obtained their chloroplasts, this way. In most cases little remains of the engulfed alga apart from its chloroplast, but in two groups, the cryptomonads and chlorarachniophytes, a small remnant nucleus of the engulfed alga is still present. These tiny nuclei, called nucleomorphs, are the smallest and most compact eukaryotic genomes known and recently the nucleomorph of the cryptomonad alga Guillardia theta, was completely sequenced (551 kilobases). The nucleomorph of the chlorarachniophyte Bigellowiella natans (380 kilobases), is also being sequenced and is about half complete. We discuss some of the similarities and differences that are emerging between these two nucleomorph genomes. Both genomes contain just three chromosomes that encode mainly housekeeping genes and a few proteins for chloroplast functions. The bulk of nucleomorph gene coding capacity, therefore, appears to be devoted to self perpetuation and creating gene and protein expression machineries to make a small number of essential chloroplast proteins. We discuss reasons why both nucleomorphs are extraordinarily compact and why their gene sequences are evolving rapidly. [ABSTRACT FROM AUTHOR]

Occurrence of Dinophysis fortii, a causative organism of diarrhetic shellfish poisoning, in the Okkirai Bay, Sanriku was surveyed in 1995, 1996, 1998 and 1999. In each year, its major occurrence was detected from the late May or early June and continued until the late June or early July. Seawater temperature, salinity and nutrients measurements suggested that inflows of offshore water into the bay played key role on the first major occurrence of D. fortii. With an analysis of continuous temperature data in the Otsuchi Bay which locates north of the Okkirai Bay, this influent was considered to be intermittent inflow of the offshore water by internal tidal waves which propagated from north to south. First occurrence peak of D. fortii was synchronous with phycobilin containing microalgae, synechococcoid cyanobacteria and cryptomonad, in all years. In vivo fluorescence measurement of D. fortii cells in 1995 and 96 showed that the cells in these microalgal-rich water contained more phycobilin pigment than those in the microalgal-poor water. The result may support a hypothesis that D. fortii acquires phycobilin by an uptake of these microalgae. After the first major occurrence in the bay, D. fortii sometimes occurred in rather inshore waters where showed elevated ammonium level possibly due to increased heterotrophic activity. Together with another finding that D. fortii is mixotrophic, it could be assumed that the environment being suited to heterotrophic nutrition also stimulates D. fortii growth in the bay. [ABSTRACT FROM AUTHOR]

Guillardia theta is a cryptomonad alga, whose phototrophic symbiont was acquired by secondary endocytobiosis. The nucleomorph, the vestigial nucleus of the eukaryotic endosymbiont, harbors three linear chromosomes with a total coding capacity of 515 kb. Sequencing of the nucleomorph genome reveals that it encodes an ORF homologous to the bacterial cell division protein FtsZ, supporting the hypothesis that FtsZ is common in chloroplasts. We show that the nucleomorph-encoded ftsZ gene is transcribed. The transcript is polyadenylated and therefore shows features typical of eukaryotic transcripts. However, 3′ processing of nucleomorph mRNA is inaccurate. Transcripts of nucleomorph genes in G. theta overlap with neighboring UTRs and coding regions. We demonstrate that the reading frame encoding NmFtsZ is not interrupted by introns. Subcellular localization of the protein reveals that FtsZ is localized exclusively in the chloroplast of G. theta, demonstrating that FtsZ is imported into the organelle. [ABSTRACT FROM AUTHOR]

Provides evidence supporting that Amphidinium latum feeds specifically on cryptomonads. Observations on pigments and morphology of Gymnodinium aeruginosum; Evidence for a membrane-bound endosymbiont within the dinoflagellate Peridinium foliaceum; Classification of species of cryptomonads based on their color and ultrastructure features.

Ultrastructural examination of the freshwater, blue-green dinoflagellate Gymnodinium acidotum Nygaard revealed the presence of an endosymbiotic cryptomonad. Features of the endosymbiont allying it with the Cryptophyceae include mitochondria with flattened cristae, paired thylakoids with electron-dense contents, and nucleomorphs, bodies unique to the Cryptophyceae. This report is the first conclusive documentation of a symbiosis involving these two groups. [ABSTRACT FROM AUTHOR]

The extracellular starch released by autolysis of glycerolgrown Chroomonas salina (Wislouch) Buthcer was purified and chemically characterized. It contained 99% D-glucose, formed a blue complex (λmax at 605 nm) with iodine, and showed an optical rotation value more positive than that of potato starch. Methylation analysis established the presence of 1,4- and 1,4,6-glucoside linkages in the proportion 15:1. These properties indicate the cryptomonad starch to be an iodophilic α-(1,4)-glucan, composed of ca. 30% amylose with amylopectin, and broadly resembling potato, Chilomonas and other unicellular algal starches. [ABSTRACT FROM AUTHOR]

Extensive blooms of the autotrophic ciliate Mesodinium rubrum (Lohmann) occurred in the Peru coastal upwelling region at 15°S latitude in March through May 1977 and contributed significantly to the organic productivity of the region. From observations made during the JOINT-II oceanographic expedition, a budget of the carbon flux of these unusual photosynthetic organisms can be constructed. The light dependent C fixation was determined with short (1 h) incubations because of the organisms' sensitivity to confinement and rapid nutrient exhaustion. Maximum photosynthesis occurred at 50% of incident light with a maximum rate of particular C synthesis of 2187 mg C·m[SUP-3]·h[SUP-1]. The specific carbon uptake rates were also high with a maximum light saturated value of 16.8 mg C&midddot;(mg chl a)[SUP-1]·h[SUP-1]. The rate of excretion of dissolved organic C at the productivity maximum ranged from 16.1 to 181.1 mg C·m[SUP-3]·h[SUP-1]. The range of percent excretion was 1.8-12.5% the total C fixed, similar to the range found in both motile and nonmotile phytoplankton assemblages. Respiration, determined by the decrease in particulate C in the dark, averaged 4.6% of the previously fixed photosynthetic C·h[SUP-1]. M. rubrum actively took up amino acids and naturally occurring dissolved organic carbon. The C budget for this ciliate indicates that the daily contribution to the particulate food chain is large, although not as great as is indicated by short incubations. The contribution of M. rubrum to the productivity and elemental fluxes of upwelling and coastal ecosystems has been seriously underestiamted. [ABSTRACT FROM AUTHOR]

In zebra mussels ( Dreissena polymorpha) simultaneous release of gametes and peaks in larval densities at particular locations suggest that spawning is triggered by synchronizing stimuli. Furthermore, spawning tends to occur only after an adequate environmental temperature is reached. To test the hypothesis that phytoplankton and gamete-associated chemicals initiate spawning in zebra mussels and that the responsiveness to such chemicals is affected by ambient temperature, the spawning response of zebra mussels to extracts from algae, a cryptomonad, and a cyanobacterium and to water associated with released gametes was assayed in animals acclimated to 12 ^C and 17 ^C. For animals held at 12 ^C, only serotonin, a known activator of bivalve spawning used as a positive control, stimulated spawning. However, for animals acclimated to 17 ^C, extracts made from a diatom ( Phaeodactylum), a brown alga ( Fucus), and a cryptomonad ( Rhodomonas) stimulated spawning in both sexes; extracts from green algae ( Platymonas and Dunaliella) and a cyanobacterium ( Oscillatoria) did not cause spawning. Water associated with either released sperm or eggs elicited spawning in both females and males. Positive controls, stimulated with serotonin, spawned at a high (>90%) rate, whereas no negative control spawned. Thus, phytoplankton chemicals and gamete-associated factors may have a role in synchronizing spawning in zebra mussels once adequate ambient temperature is reached. [ABSTRACT FROM AUTHOR]

A physical map of the circular plastid genome of Cryptomonas Φ has been constructed using the enzymes SacI, BamHI, SmaI, SalI, PstI and XhoI. In addition, fine-structural mapping of the inverted repeat region has been performed using AvaI, BglII, EcoRI and XbaI. The inverted repeat is very small, encompassing no more than 6 kb and containing only genes for the rRNAs. It divides the plastid genome into a small singlecopy region of 12-13 kb which contains genes for phycoerythrin and the 32 kd photosystem II polypeptide, and a large single-copy region of 93-94 kb, giving a total size of 118 kb. The genes for the large subunit of ribulose-1,5-bisphosphate carboxylase (Rubisco) and the beta subunit of ATP synthase CF are encoded in the large single-copy region. The evolutionary significance of the organization of this plastid genome, the first presented from the chlorophyll c-, phycobiliprotein-containing group of algae, is discussed. [ABSTRACT FROM AUTHOR]

Aquaculture of portunid crabs is hindered by high mortality during larval rearing, which is often attributed to inadequate nutrition. Live feed enrichment and greenwater are techniques used to improve the nutritional quality of feeds for larval fish and some invertebrates, but their usefulness for crab larvae is unclear. This study investigated the effects of live feed enrichment and three different microalgae as greenwaters on the development, growth, and survival of Portunus armatus from hatching to the megalopa stage. P. armatus reared in greenwater had superior development and survival compared to crabs reared without greenwater. Survival and development rates were better when larvae were reared in Nannochloropsis oculata or Proteomonas sulcata greenwaters compared to Tisochrysis lutea greenwater and the crab larvae. P. armatus were also largest when reared in P. sulcata greenwater. The carapace length of megalopa was positively correlated with the biologically important eicosapentaenoic acid (20:5n-3, EPA), but negatively correlated with oleic acid (18:1n-9, OA). This suggests the benefits of using greenwater to rear larval crabs may be tied to live feeds improving their nutritional value by consuming microalgae. Interestingly, enriching live feeds with a commercial lipid emulsion did not affect P. armatus larval development, survival, or growth, despite increasing levels of docosahexaenoic acid (22:6n-3, DHA) in megalopa to a point considered harmful for the larvae of other species of crabs. This study demonstrates the benefits of greenwater when rearing larval crabs as opposed to live feed enrichment, and highlights the potential effectiveness of cryptomonad microalgae as a greenwater media. • Portunus armatus reared without greenwater, i.e. in clear water, experienced high mortality and slow development. • P. armatus larvae developed quicker, were larger, and had better survival when Proteomonas sulcata was used as a greenwater compared to other microalgae. • Enriching live feeds with a commercial lipid emulsion increased DHA in P. armatus , but this did not affect larval development or survival. • The benefits of greenwater on larval crab development and survival may be linked to enhanced nutrition of live feeds. [ABSTRACT FROM AUTHOR]

High mortality during larval rearing is a persistent bottleneck in finfish aquaculture and is often caused by inadequate nutrition. Nutritional deficiencies in live feeds are usually overcome by enrichment with commercial lipid emulsions; however, enriching live feeds using microalgae may be more effective. This study investigated the efficacy of the microalga Proteomonas sulcata as a live feed enhancement for rearing larvae of the wide-band anemonefish, Amphiprion latezonatus. We found A. latezonatus larvae fed live feeds enhanced with P. sulcata had higher survival and better growth at 7 days post hatch (dph) compared to fish fed live feeds enriched with a commercial lipid emulsion or left unenriched. At 14 dph, A. latezonatus initially fed rotifers cultured on P. sulcata for several generations had the highest survival overall. These results may be due to the high phospholipid content in rotifers enhanced on P. sulcata compared to other diets. Survival, length, depth, and eye diameter of 7 dph A. latezonatus was also positively correlated with omega-6 docosapentaenoic acid (DPAn-6, 22:5n-6) and high ratios of DPAn-6 to docosahexaenoic acid (DHA, 22:6n-3) in their tissues, highlighting the need to better understand the role of DPAn-6 in larval fish ontogeny. Surprisingly, given their high survival and growth, A. latezonatus larvae fed P. sulcata enhanced live feeds had lower levels of DHA compared to the more poorly performing fish fed the commercial lipid emulsion enriched live feeds; this challenges the paradigm of a positive correlation between DHA and growth and survival that is documented in many other marine fish larvae. This study demonstrates the benefits of using P. sulcata to enhance the nutritional quality of live feeds and highlights the need for a better understanding of the role of n-6 long-chain polyunsaturated fatty acids in the early development of larval fish. • Larval Amphiprion latezonatus survived and grew best when fed live feeds enhanced with the microalga Proteomonas sulcata. • A. latezonatus fed live feeds enriched with a lipid emulsion contained the most DHA, but this did not correlate with survival or growth. • DPAn-6 and the ratio of DPAn-6 to DHA in A. latezonatus tissues was positively correlated with larval survival and growth. • High levels of dietary DHA may be less important for some marine fish larvae than previously thought. [ABSTRACT FROM AUTHOR]