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Marine benthic dinoflagellates are interesting not only because some epiphytic genera can cause harmful algal blooms but also for understanding dinoflagellate evolution and diversification. Our understanding of their biodiversity is far from complete, and many thecate genera have unusual tabulation patterns that are difficult to relate to the diverse known phytoplankton taxa. A new sand‐dwelling genus, Pachena gen. nov., is described based on morphological and DNA sequence data. Three species were discovered in distant locations and are circumscribed, namely, P. leibnizii sp. nov. from Canada, P. abriliae sp. nov. from Spain, and P. meriddae sp. nov. from Italy. All species are tiny (about 9–23 μm long) and heterotrophic. Species are characterized by their tabulation (APC 4′ 3a 6′′ 5c 5s 5′′′ 2′′′′), an apical hook covering the apical pore, an ascending cingulum, and a sulcus with central list. The first anterior intercalary plate is uniquely "sandwiched" between two plates. The species share these features and differ in the relative sizes and arrangements of their plates, especially on the epitheca. The ornamentation of thecal plates is species‐specific. The new molecular phylogenies based on SSU and LSU rDNA sequences contribute to understanding the evolution of the planktonic relatives of Pachena, the Thoracosphaeraceae. [ABSTRACT FROM AUTHOR]

A new thecate, photosynthetic, sand‐dwelling marine dinoflagellate, Laciniporus arabicus gen. et sp. nov., is described from the subtidal sediments of the Omani coast in the Arabian Sea, northern Indian Ocean, based on detailed morphological and molecular data. Cells of L. arabicus are small (16.2–30.1 μm long and 13.1–23.2 μm wide), dorsoventrally compressed, with a small apical flap‐shaped projection pointing to the left. The thecal plate pattern is distinguished by minute first precingular plate and sulcus, which extends into the epitheca, with large anterior and right sulcal plates. The Kofoidian thecal tabulation is Po, X, 4′, 2a, 7′′, 6c, 6s, 5′′′, 2′′′′. Morphologically, the revealed plate pattern has an affinity to the Peridiniales, and LSU rDNA based phylogenetic analyses placed L. arabicus within the Thoracosphaeraceae, close to calcareous‐cyst producing scrippsielloids, predatory pfiesteriaceans, and photosynthetic freshwater peridinioids Chimonodinium lomnickii and Apocalathium spp. However, the thecal plate arrangement of L. arabicus differs noticeably from any currently described dinoflagellates, and the species stands out from closely related taxa by extensive differences in physiology and ecology. [ABSTRACT FROM AUTHOR]

A new thecate, photosynthetic, sand‐dwelling marine dinoflagellate, Laciniporus arabicus gen. et sp. nov., is described from the subtidal sediments of the Omani coast in the Arabian Sea, northern Indian Ocean, based on detailed morphological and molecular data. Cells of L. arabicus are small (16.2–30.1 μm long and 13.1–23.2 μm wide), dorsoventrally compressed, with a small apical flap‐shaped projection pointing to the left. The thecal plate pattern is distinguished by minute first precingular plate and sulcus, which extends into the epitheca, with large anterior and right sulcal plates. The Kofoidian thecal tabulation is Po, X, 4′, 2a, 7′′, 6c, 6s, 5′′′, 2′′′′. Morphologically, the revealed plate pattern has an affinity to the Peridiniales, and LSU rDNA based phylogenetic analyses placed L. arabicus within the Thoracosphaeraceae, close to calcareous‐cyst producing scrippsielloids, predatory pfiesteriaceans, and photosynthetic freshwater peridinioids Chimonodinium lomnickii and Apocalathium spp. However, the thecal plate arrangement of L. arabicus differs noticeably from any currently described dinoflagellates, and the species stands out from closely related taxa by extensive differences in physiology and ecology. [ABSTRACT FROM AUTHOR]

The planktonic dinoflagellate Ptychodiscus noctiluca combined distinctive morphological features such as a disk-shaped anteroposteriorly compressed cell body and an apical carina, together with a flexible and tough cell covering, suggesting intermediate characteristics between thecate and naked dinoflagellates. Ptychodiscus noctiluca was examined by light, epifluorescence, and scanning electron microscopy from specimens collected in the Mediterranean Sea and the North and South Atlantic Ocean. Ptychodiscus noctiluca showed a straight apical groove that bisected the carina, a cell covering with a polygonal surface reticulum, nucleus without capsule, sulcal intrusion in the episome, sulcal ventral flange, and yellowish-green chloroplasts that are shared characters with Brachidinium/ Karenia. The cell division was the typical binary fission of gymnodinioid dinoflagellates, although exceptionally in an oblique transversal axis. We examined the intraspecific variability during incubation experiments. In the fattened cells, termed as Ptychodiscus carinatus, chloroplasts transformed into dark granules, and the cell acquired the swollen and smaller stage, termed as P. inflatus. Ptychodiscus carinatus, P. inflatus, and Diplocystis antarctica are synonyms of P. noctiluca. Molecular phylogeny based on the SSU rDNA sequence revealed that Ptychodiscus branched within the short-branching dinokaryotic dinoflagellates as an independent lineage with affinity to Brachidinium/Karenia and Karlodinium/ Takayama in a generally poorly resolved clade. Our results indicated that the order Ptychodiscales, established for unarmored dinoflagellates with a strongly developed pellicle, has artificially grouped thecate dinoflagellates ( Kolkwitziella, Herdmania), naked dinoflagellates with thick cell covering ( Balechina, Cucumeridinium) and other insufficiently known unarmored genera with typical cell coverings ( Brachidinium, Ceratoperidinium). [ABSTRACT FROM AUTHOR]

Symbiotic interactions between pelagic hosts and microalgae have received little attention, although they are widespread in the photic layer of the world ocean, where they play a fundamental role in the ecology of the planktonic ecosystem. Polycystine radiolarians (including the orders Spumellaria, Collodaria and Nassellaria) are planktonic heterotrophic protists that are widely distributed and often abundant in the ocean. Many polycystines host symbiotic microalgae within their cytoplasm, mostly thought to be the dinoflagellate S crippsiella nutricula, a species originally described by Karl Brandt in the late nineteenth century as Z ooxanthella nutricula. The free-living stage of this dinoflagellate has never been characterized in terms of morphology and thecal plate tabulation. We examined morphological characters and sequenced conservative ribosomal markers of clonal cultures of the free-living stage of symbiotic dinoflagellates isolated from radiolarian hosts from the three polycystine orders. In addition, we sequenced symbiont genes directly from several polycystine-symbiont holobiont specimens from different oceanic regions. Thecal plate arrangement of the free-living stage does not match that of S crippsiella or related genera, and LSU and SSU r DNA-based molecular phylogenies place these symbionts in a distinct clade within the Peridiniales. Both phylogenetic analyses and the comparison of morphological features of culture strains with those reported for other closely related species support the erection of a new genus that we name B randtodinium gen. nov. and the recombination of S . nutricula as B . nutricula comb. nov. [ABSTRACT FROM AUTHOR]

The diversity of extant calcareous dinophytes (Thoracosphaeraceae, Dinophyceae) is currently not sufficiently recorded. The majority of their coccoid stages are cryptotabulate or entirely atabulate, whereas relatively few forms exhibit at least some degree of tabulation more than the archeopyle. A survey of coastal surface sediment samples from the Mediterranean Sea resulted in the isolation and cultivation of several strains of calcareous dinophytes showing a prominent tabulation. We investigated the morphologies of the thecate and the coccoid cells and conducted phylogenetic analyses using Maximum Likelihood and Bayesian approaches. The coccoid cells showed a distinct reflection of the cingulum (and were thus cingulotabulate), whereas thecal morphology corresponded to the widely distributed and species-rich Scrippsiella. As inferred from molecular sequence data (including 81 new GenBank entries), the strains belonged to the Scrippsiella sensu lato clade of the Thoracosphaeraceae and represented two distinct species. Morphological details likewise indicated two distinct species with previously unknown coccoid cells that we describe here as new, namely S. bicarinata spec. nov. and S. kirschiae spec. nov. Cingulotabulation results from the fusion of processes representing the pre- and postcingular plate series in S. bicarinata, whereas the ridges represent sutures between the cingulum and the pre- and postcingular series in S. kirschiae, respectively. Bicarinate cingulotabulation appears homoplasious among calcareous dinophytes, which is further supported by a comparison to similar, but only distantly related fossil forms. [ABSTRACT FROM AUTHOR]

Dinoflagellates are the most abundant protists that produce bioluminescence. Currently, there is an incomplete knowledge of the identity of bioluminescent species arising from inter- and intraspecific variability in bioluminescence properties. In this study, PCR primers were designed to amplify the dinoflagellate luciferase gene ( lcf) from genetically distant bioluminescent species. One of the primer pairs was 'universal,' whereas others amplified longer gene sequences from subsets of taxa. The primers were used to study the distribution of lcf and assess bioluminescence potential in dinoflagellate strains representing a wide variety of taxa as well as multiple strains of selected species. Strains of normally bioluminescent species always contained lcf even when they were found not to produce light, thus demonstrating the utility of this methodology as a powerful tool for identifying bioluminescent species. Bioluminescence and lcf were confined to the Gonyaulacales, Noctilucales, and Peridiniales. Considerable variation was observed among genera, or even species within some genera, that contained this gene. Partial sequences of lcf were obtained for the genera Ceratocorys, Ceratium, Fragilidium, and Protoperidinium as well as from previously untested species or gene regions of Alexandrium and Gonyaulax. The sequences revealed high variation among gene copies that obscured the boundaries between species or even genera, some of which could be explained by the presence of two genetic variants within the same species of Alexandrium. Highly divergent sequences within Alexandrium and Ceratium show a more diverse composition of lcf than previously known. [ABSTRACT FROM AUTHOR]

Dinoflagellates are the most abundant protists that produce bioluminescence. Currently, there is an incomplete knowledge of the identity of bioluminescent species arising from inter- and intraspecific variability in bioluminescence properties. In this study, PCR primers were designed to amplify the dinoflagellate luciferase gene ( lcf) from genetically distant bioluminescent species. One of the primer pairs was 'universal,' whereas others amplified longer gene sequences from subsets of taxa. The primers were used to study the distribution of lcf and assess bioluminescence potential in dinoflagellate strains representing a wide variety of taxa as well as multiple strains of selected species. Strains of normally bioluminescent species always contained lcf even when they were found not to produce light, thus demonstrating the utility of this methodology as a powerful tool for identifying bioluminescent species. Bioluminescence and lcf were confined to the Gonyaulacales, Noctilucales, and Peridiniales. Considerable variation was observed among genera, or even species within some genera, that contained this gene. Partial sequences of lcf were obtained for the genera Ceratocorys, Ceratium, Fragilidium, and Protoperidinium as well as from previously untested species or gene regions of Alexandrium and Gonyaulax. The sequences revealed high variation among gene copies that obscured the boundaries between species or even genera, some of which could be explained by the presence of two genetic variants within the same species of Alexandrium. Highly divergent sequences within Alexandrium and Ceratium show a more diverse composition of lcf than previously known. [ABSTRACT FROM AUTHOR]

The possible role of cortical microtubules in dinoflagellates was studied using high-pressure treatments applied to nonmotile cells (just after ecdysis) of Scrippsiella hexapraecingula T. Horig. et Chihara. Whereas considerable disorganization of cortical microtubules was observed when cells were exposed to high-pressure treatments of 98 MPa or more for 5-15 min, they were mostly intact in cells exposed to a pressure of <98 MPa for 5 min. After nonmotile cells were exposed to high-pressure treatments sufficient to disorganize the cortical microtubules, they produced new motile cells with thecal plate patterns that differed considerably from the pattern known for this species. Increasing the intensity of high pressure applied to nonmotile cells resulted in an increase in the number of cells that exhibited disorganized cortical microtubules as well as a change in their thecal plate pattern, suggesting that high pressure disorganizes cortical microtubules leading to a change in the thecal plate pattern. [ABSTRACT FROM AUTHOR]

Six new species of unarmored dinoflagellates in the family Kareniaceae were isolated from the Australian sector of the Southern Ocean in March 2006: Takayama tuberculata de Salas sp. nov, Karlodinium antarcticum de Salas sp. nov., Karl. ballantinum de Salas sp. nov., Karl. conicum de Salas sp. nov., Karl. corrugatum de Salas sp. nov., and Karl. decipiens de Salas et Laza-Martínez sp. nov. These new taxa were characterized using light and electron microscopy and sequencing of the LSU rDNA and are well supported based either on their morphology or molecular phylogeny. Takayama tuberculata, isolated just north of the polar front (55°–57° S), is genetically close to T. tasmanica, but smaller, with a significantly reduced number of amphiesmal vesicles. Medium-sized Karl. antarcticum, also isolated from near the polar front, is characterized by its long ovoid cell outline and very long apical groove. The small Karl. ballantinum has a very short apical groove. The large Karl. conicum has a distinct conical epicone and spherical posterior nucleus. The small Karl. corrugatum, from just south of the polar front, has distinctive parallel striations on the epicone surface and a distinctively shaped and placed ventral pore. The large and widespread Karl. decipiens, distributed through Southern Ocean waters from the polar front to Tasmanian coastal waters, and coastal Spain, has a helicoidal chloroplast arrangement and a large central nucleus. This study represents the first description of species in the potentially ichthyotoxic family Kareniaceae recorded from the Southern Ocean. [ABSTRACT FROM AUTHOR]

A new genus of Pfiesteria-like heterotrophic dinoflagellate, Luciella gen. nov., and two new species, Luciella masanensis sp. nov. and Luciella atlantis sp. nov., are described. These species commonly occur with other small (<20 μm) heterotrophic and mixotrophic dinoflagellates in estuaries from Florida to Maryland and the southern coast of Korea, suggesting a possible global distribution. An SEM analysis indicates that members of the genus Luciella have the enhanced Kofoidian plate formula of Po, cp, X, 4′, 2a, 6″, 6c, PC, 5+s, 5‴, 0p, and 2″″. The two four-sided anterior intercalary plates are diamond shaped. The genus Luciella differs from the other genera in the Pfiesteriaceae by a least one plate in the plate tabulation and in the configuration of the two anterior intercalary plates. An SSU rDNA phylogenetic analysis confirmed the genus as monophyletic and distinct from the other genera in the Pfiesteriaceae. The morphology of Luciella masanensis closely resembles Pfiesteria piscicida Steid. et J. M. Burkh. and other Pfiesteria-like dinoflagellates in size and shape, making it easily misidentified using LM. Luciella atlantis, in contrast, has a more distinctive morphology. It can be distinguished from L. masanensis and other Pfiesteria-like organisms by a larger cell size, a more conical-shaped epitheca and hypotheca, larger rhombic-shaped intercalary plates, and an asymmetrical hypotheca. The genus Luciella is assigned to the order Peridiniales and the family Pfiesteriaceae based on plate tabulation, plate pattern, general morphology, and phylogenetic analysis. [ABSTRACT FROM AUTHOR]

Pfiesteria shumwayaeGlasgow et Burkholder is assigned to a new genusPseudopfiesteriagen. nov. Plate tabulation differences betweenPfiesteriaandPseudopfiesteriagen. nov. as well as a maximum likelihood phylogenetic analysis based on rDNA sequence data warrant creation of this new genus. The Kofoidian thecal plate formula for the new genus is Po, cp, X, 4′, 1a, 6′′, 6c, PC, 5+s, 5′′′, 0p, 2′′′′. In addition to having six precingular plates,P. shumwayaecomb. nov. also has a distinctive diamond or rectangular-shaped anterior intercalary plate. BothPfiesteriaandPseudopfiesteriagen. nov. are reassigned to the order Peridiniales based on an apical pore complex (APC) with a canal (X) plate that contacts a symmetrical 1′, four to five sulcal plates, and the conservative hypothecal tabulation of 5′′′, 0p, and 2′′′′. These morphological characters and the life histories ofPfiesteriaandPseudopfiesteriaare consistent with placement of both genera in the Peridiniales. Based on the plate tabulations forP.shumwayae, P. piscicida, and the closely related“cryptoperidiniopsoid” and“lucy” groups, the family Pfiesteriaceae is amended to include species with the following tabulation: 4-5′, 0-2a, 5-6′′, 6c, PC, 5+s, 5′′′, 0p, and 2′′′′ as well as an APC containing a pore plate (Po), a closing plate (cp), and an X plate; the tabulation is expanded to increase the number of sulcal plates and to include a new plate, the peduncle cover (PC) plate. Members of the family have typical dinoflagellate life cycles characterized by a biflagellated free-living motile stage, a varying number of cyst stages, and the absence of multiple amoeboid stages. [ABSTRACT FROM AUTHOR]

Culture experiments on dinoflagellates from the Atlantic Ocean revealed Scrippsiella regalis (Gaarder) Janofske, nov. comb., a calciodinelloid species with a spherical spiny calcareous cyst. This calcareous cyst was collected previously from plankton and sediment samples, where it was described as the coccolithophorid Discosphaera regalis Gaarder or was often mistaken for the cyst of Scrippsiella trochoidea (von Stein) Loeblich III. The morphological features of both the cellulosic theca and the calcareous cyst of S. trochoidea and S. regalis were compared with respect to their systematic position and the emendation of taxa. Both species were found to have different distribution patterns. Scrippsiella trochoidea is known only from the neritic environment, whereas S. regalis has been found mostly in oceanic samples. The preservation of these spiny calcareous dinocysts in the (fossil) sediment was dependent on the ultrastructure of the calcareous layer of the cyst wall. [ABSTRACT FROM AUTHOR]

The paratabulate calcareous cyst of Calciodinellum operosum Deflandre was recorded in a sediment trap sample collected in the Bay of Naples (Tyrrhenian Sea, Italy). The germination of this resting stage produced a phototrophic vegetative cell that had the typical plate pattern of a Scrippsiella species. The cyst morphotypes, observed in a clonal culture of this species, ranged from cysts with well-developed paratabulation to cysts in which the paratabulation was barely visible, to cysts covered by irregularly shaped crystals. The analysis of thin sections of the calcareous cysts using the polarized light microscope equipped with crossed nicols and a gypsum plate showed that the optical orientation of the calcite crystals was tangential in all the morphotypes examined. We suggest that the crystallographic method we describe might provide insights for calcareous cyst taxonomy and phylogeny. [ABSTRACT FROM AUTHOR]

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 lenticularies Fukuyo 1981, Osteropsis ovata Fukuyo 1981, Ostreopsis heptagona Norris, Bomber, et Balech 1985, Ostreopsis mascarenensis Quod 1994, 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 six Ostreopsis species is P[suba], 3',7", 6C, 6S?, V[subP], R[subP] 5"', 1P, 2"", with differences in thecal plate size and shape. The cingulum in ventral view has two prominent structures: a ventral plate (V[subp]) with a ventral pore (V[aubo]) and a ridged plate (R[subp]) that distinguishes Ostreopsis species from any other dinoflagellate taxa. This paper also includes ecological and toxicity information regarding the six Ostreopsis species. [ABSTRACT FROM AUTHOR]

Extent chromophytic algae have been suggested to have originated via the engulfment of a photosynthetic alga by a colorless protist. The dinoflagellate Peridinium foliaceum (Stein) Biecheler contains a reduced chlorophyll c-containing endosymbiont and, thus, represents an evolutionary intermediate stage in the establishment of chloroplasts. Although the exact phylogenetic relationship of the symbiont to extent algal species is unknown, it had been suggested that the P. foliacum symbiont was either a diatom or a chrysophyte. Identification of the closest living relative of the P. foliaceum symbiont would provide a free-living model system with which the photosynthetic symbiont could be compared. Nucleotide sequence analysis of rbcL and rbcS (encoding the large and small subunits of ribulose-1,5 bisphosphate carboxlase/oxygenase) by the P. foliaceum symbiont was performed to provide insights into its identity, Cloned restriction fragments from a chloroplast DNA library6 were screened, and clones encoding the rbcLS operon were sequenced. Parsimony phylogenetic analysis was performed for each gene. Our data strongly suggest that the symbiont originated from a photosynthetic diatom. [ABSTRACT FROM AUTHOR]

Dinoflagellate associations, including toxic and potentially toxic benthic species, were examined in sand from South Water Cay and Carrie Bow Cay, Belize. The inshore sand habitat in localized areas of warm shallow lagoonal waters supported blooms of toxic assemblages of dinoflagellates. In the sand, the dominant microalgae were dinoflagellates; cyanobacteria were a minor component and diatoms were absent. Ciliates and nematodes were present. Assemblages of microorganisms in colored sand were examined for 4 consecutive days after which a storm washed away the patch. The sand-dwelling dinoflagellate assemblage included 16 species where densities ranged from as low as 1.3% to 15% of total cell densities. The dominant species was Scrippsiella subsalsa, having 1.8 × 10[sup5] to 2.3 × 10[sup5] cells · g[sup-1 sand. Toxic dinoflagellates indentified in the sand were Gambierdicus toxicus, Ostreopsis lenticularis, Prorocentrum lima, Prorocentrum mexicanum, and Amphidinum carteri. The potentially toxic Ostreopsis labens, Gambierdiscus belizeanus sp. nov., and Coolia tropicalis sp. nov. were also identified. Toxic and potentially toxic species represented 36% to 60% of total microalgal cell assemblage. The morphology of a new sand-dwelling species, Gambierdiscus belizeanus sp. nov., was examined with the scanning electron microscope. The plate formula was P[subo], 3′, 7′′, 6c, 8s?, 5′′′, 1p, and 2′′′′. Dimensions of G. belizeanus cells were 53-67 μm long, 54-63 μm wide, and 92-98 μm in dorsoventral depth. Cells were deeply areolated, ellipsoid in apical view, and compressed anteroposteriorly. The cells of G. belizeanus were identified by the cell's long, narrow, pentagonal, posterior intercalary plate (1p) wedged between the wide postcingular plates 2′′′ and 4′′′; 1p occupied 20% of the width of the hypotheca. The plate formula for Coolia tropicalis sp. nov. was P[subo], 3′, 7′′, 7c, 8s?. 5′′′, and 2′′′′. Cell size ranges were 23-40 μm long, 25-39 μm wide, and 35-65 μm in dorsoventral diameter. Cells were spherical, smooth, and covered with scattered round pores. The epitheca was smaller than the hypotheca. Precingular plates 1′ and 7′′ were small and narrow, and the first apical plate 1′ and precingular plate 6′′ were the largest plates on the epitheca. The apical pore was straight and 7 μm long, and was situated in the apical plate complex. Cells of C. tropicalis were distinguished from C. monotis by the wedge-shaped plate 1′, a four-sided 3′ plate, and a short apical pore. [ABSTRACT FROM AUTHOR]

Seventeen clones of the toxic, epiphytic-benthic dinofla-gellate Prorocentrum lima (Ehrenberg) Dodge isolated from three separate sites on the reef flats of Heron Island, Australia, were acclimated under the same set of environmental conditions. Morphological features examined for each clone included cell surface configuration, size, and dry weight. Physiological and biochemical features determined for each clone included reproduction rates, pigments (chloropyll a, chlorophyll c[sub2] peridinin, and other xanthophylls) toxins (okadaic acid and methyl-okadaic acid), and macromolecular compounds (total protein, lipid, and carbohydrate). Variation in morphological features and reproduction rates of clones within and between sites was minimal and not significant. Also, variation in biochemical features within an individual site was low, but pronounced differences existed among sites, the most notable of which was toxin content (okadaic acid and methyl-okadaic acid). The greatest difference in biochemical features was between clones isolated from the southern site and clones isolated from the northern and southeastern sites. Results of a cluster analysis of clonal characters support the view that these two groups represent distinct genotypes. We suggest that these groups originated from separate seed sources and that the genetic integrity of each is maintained through asexual reproduction. [ABSTRACT FROM AUTHOR]

The response of carbonic anhydrase (CA) activity in Peridinium gatunense Nygaard, the natural bloom forming dinoflagellate in the Lake Kinneret, to diel and seasonal variations in environmental conditions was characterized under controlled laboratory experiments. Simulated diel cycles demonstrated large changes in the ambient concentration of dissolved CO[sub2] and parallel changes in CA activity. The CA activity depended on the total concentrations of inorganic carbon (C) and in particular on the dissolved CO[sub2] Lowering the C[subi] concentrations resulted in a large increase in CA activity within several hours. Light and photosynthesis were both required for the induction of CA activity. Under CO[sub2]-limited conditions, the dependence of the photosynthetic rate on CA (estimated from the ratio of photosynthetic rates in the presence or absence of CA inhibitors) was greater in P. gatunense than in other eukaryotic microalgae. This points to the ecological significance of CA inhibitors) was greater in P. gatunense than in other eukaryotic microalgae. This points to the ecological significance of CA in photosysntheic carbon uptake mechanisms of a large, dominant alga in a natural ecosystem. [ABSTRACT FROM AUTHOR]

Germination experiments demonstrate that the "hystrichosphere" called Hemicystodinium zoharyi, which previously has been found only as a microfossil organism, is the resting spore stage in the life history of Pyrodinium bahamense, a modern bioluminescent, thecate dinoflagellate. The morphology of this spore, together with new details of the thecal structure and ontogeny of P. bahamense, is described, and it is concluded that Pyrodinium is closely related to Gonyaulax but worthy of retention as a discrete genus. The geological history of P. bahamense is traceable to the Eocene through fossil occurrences of its spore, and it is suggested that additional pyrodinioid dinoflagellates which now are extinct were represented in Lower Tertiary seas by another hystrichosphere genus, called Homotryblium. Selected aspects of the physiology and ecology of modern dinoflagellate resting spores are discussed briefly with special reference to Pyrodinium. [ABSTRACT FROM AUTHOR]

A new thecate, photosynthetic, sand-dwelling marine dinoflagellate, Laciniporus arabicus gen. et sp. nov., is described from the subtidal sediments of the Omani coast in the Arabian Sea, northern Indian Ocean, based on detailed morphological and molecular data. Cells of L. arabicus are small (16.2-30.1 μm long and 13.1-23.2 μm wide), dorsoventrally compressed, with a small apical flap-shaped projection pointing to the left. The thecal plate pattern is distinguished by minute first precingular plate and sulcus, which extends into the epitheca, with large anterior and right sulcal plates. The Kofoidian thecal tabulation is Po, X, 4', 2a, 7'', 6c, 6s, 5''', 2''''. Morphologically, the revealed plate pattern has an affinity to the Peridiniales, and LSU rDNA based phylogenetic analyses placed L. arabicus within the Thoracosphaeraceae, close to calcareous-cyst producing scrippsielloids, predatory pfiesteriaceans, and photosynthetic freshwater peridinioids Chimonodinium lomnickii and Apocalathium spp. However, the thecal plate arrangement of L. arabicus differs noticeably from any currently described dinoflagellates, and the species stands out from closely related taxa by extensive differences in physiology and ecology., (© 2018 Phycological Society of America.)

The freshwater dinoflagellate Peridinium penardii (Lemm.) Lemm. fo. Californicum Javorn. has a positively phototactic diel migration. The extent of migration seems to vary with population density. [ABSTRACT FROM AUTHOR]