Showing papers in "Phycologia in 2000"
TL;DR: Evidence from partial large-subunit (LSU) rDNA sequencing has been combined with ultrastructure, including details of the flagellar apparatus, in a number of phototrophic dinoflagellates to try to solve some of the most pressing taxonomic problems and to contribute to an improved understanding of the phylogeny within the group.
Abstract: Evidence from partial large-subunit (LSU) rDNA sequencing has been combined with ultrastructure, including details of the flagellar apparatus, in a number of phototrophic dinoflagellates, with the aim of trying to solve some of the most pressing taxonomic problems and to contribute to an improved understanding of the phylogeny within the group. Special attention has been paid to the unarmoured (naked) genera, many of which were described during the 1800s or early 1900s and whose taxonomy is artificial and misleading. This is particularly unsatisfactory because many of the species cause extensive plankton blooms, fish kills and other harmful events. Our studies have indicated that the path of the so-called apical groove (acrobase) is of particular importance for the taxonomy of the unarmoured genera of dinoflagellates. Features presently used to characterize many of the genera, such as the relative size of the epicone and hypocone, are misleading. Our data have resulted in the splitting of the large genus Gymnodinium into four genera. The fish-killing species are confined to two genera, Karenia G. Hansen & Moestrup gen. nov. and Karlodinium J. Larsen gen. nov. The paralytic shellfish poisoning-producing species Gymnodinium catenatum is retained within Gymnodinium, together with a number of harmless species. The fourth genus, Akashiwo G. Hansen & Moestrup gen. nov., presently comprises only the large nontoxic species previously known as Gymnodinium sanguineum. The genus Gyrodinium is redefined. The genus Amphidinium is artificial, but more data are needed before redescription of the genus can be made with any confidence. Within the armoured dinoflagellates, LSU and previously published small-subunit rDNA data show the Gonyaulacales to be a natural group. Peridiniella catenata, sometimes included in the Gonyaulacales based on gross morphology, falls outside this order both genetically and ultrastructurally. Based on the DNA data, the genus Peridinium appears to be artificial. Ultrastructure as well as gene sequences confirm that the genus Heterocapsa is unusual, since it includes both apparently unarmoured species (but with very thin plates) and armoured species.
627 citations
TL;DR: Based on 18S ribosomal DNA sequence data and available information on morphological structure and ultrastructure, it is proposed that the class Prymnesiophyceae be divided into four orders: Phaeocystales ord. nov., PrymNESiales, Isochrysidales, and Coccolithales.
Abstract: Most haptophytes are unicellular, photosynthetic flagellates, although some have coccoid, colonial, amoeboid, or filamentous stages. Nearly all have a characteristic filamentous appendage, the haptonema, arising between the two flagella. The small subunit ribosomal RNA gene (l8S ribosomal DNA) from 18 haptophyte species has been sequenced, and the sequences aligned with those of more than 300 published and unpublished chlorophyll a + c algae. Phylogenies were constructed using maximum likelihood, neighbor-joining, and weighted maximum parsimony analyses. The high divergence (6%) between members of Pavlova and the remaining haptophytes supports the division of Haptophyta into two classes: Prymnesiophyceae and Pavlovophyceae. Three major clades that correspond to known taxa within the Prymnesiophyceae were identified: one clade embraces Phaeocystis spp.; the second includes members of the genera Chrysochromulina, Prymnesium, and Imantonia; and the third includes coccolithophorid genera and the genu...
196 citations
TL;DR: Detailed morphological examination of field specimens and cultured cells of A. ostenfeldii showed that in most major aspects specimens from the western Atlantic coast closely resemble this species as described from Scandinavian waters, confirming it as the primary source of spirolides in this region.
Abstract: A suite of biologically active compounds, fast-acting toxins called spirolides, were recently isolated and characterized from shellfish and plankton samples collected from southeastern Nova Scotia, Canada. Circumstantial evidence from natural plankton assemblages has linked spirolides to gonyaulacoid dinoflagellates, particularly athecate cells (GB-42) that are derived from motile stages from this group. After repeated attempts to isolate spirolide-producing taxa from enriched size-fractionated field samples, numerous isolates of potential source organisms, including Alexandrium ostenfeldii (Paulsen) Balech et Tangen, Alexandrium tamarense (Lebour) Balech, Fragilidium subglobosum (von Stosch) Loeblich III, Gonyaulax spinifera (Claparede et Lachmann) Diesing, Protoceratium reticulatum (Claparede et Lachmann) Butschli, and Scrippsiella trochoidea (Stein) Loeblich III were successfully cultured. Among all cultured dinoflagellate species harvested in late exponential growth phase and analyzed for spi...
193 citations
TL;DR: There was a strong negative correlation between CYL content and temperature, and when cultures of isolates that normally produce CYL were transferred from 35°C to a lower temperature, production of CYL was restored.
Abstract: This study investigates the effect of temperature (range, 20–35°C) on the growth and cylindrospermopsin (CYL) content of seven isolates of Cylindrospermopsis raciborskii grown in batch culture. The concentration of CYL, measured late in the exponential growth phase for cultures grown at 25°C, ranged from below detection (< 2 × 10−5% freeze-dried weight) for isolates from Lake Julius (20°08'S; 139°44'E) and an aquaculture pond in Townsville (19°16'S; 146°49'E) up to 0.46% for an isolate from Solomon Dam, Palm Island (18°45'S; 146°35'E). Maximum growth rates for all isolates occurred at temperatures between 25 and 30°C. Only one isolate failed to grow at 20°C. For isolates containing undetectable concentrations of CYL, the production of this compound could not be induced by an increase in temperature. For strains producing detectable concentrations, there was a strong negative correlation between CYL content and temperature. While all the isolates grew well at 35°C, none produced any detectable amount of CYL. When cultures of isolates that normally produce CYL were transferred from 35°C to a lower temperature, production of CYL was restored. In the cultured isolates, less than 10% of the total CYL was released from exponentially growing cells. In one CYL-producing isolate, extracellular CYL accounted for c. 50% of the total in stationary phase (20 day old) cultures.
162 citations
TL;DR: Morphological observations and molecular analysis of a red alga, which has been known as Grateloupia filicina var.
Abstract: Morphological observations and molecular analysis of a red alga, which has been known as Grateloupia filicina var. lomentaria, G. filicina var. porracea f. lomentaria, or Sinotubimorpha porracea (Cryptonemiales, Halymeniaceae) in the western Pacific, were made for field-collected and cultured plants. The auxiliary-cell ampullae lack tertiary filaments and are of the Grateloupia-type. Morphologically, this alga can be distinguished from G. filicina by (1) the hollow axis; (2) the numerous short proliferations with Lomentaria-like constrictions that densely cover the surface of erect axes in mature plants; and (3) a tendency for reproductive structures to be restricted to the proliferations. The presence of 4.2–4.6% (62–67 bp) nucleotide substitutions in the ribulose-1,5-bisphosphate carboxylase/oxygenase gene (rbcL) between G. filicina and the alga in question also strongly supports the differentiation of these two entities at the species level. The form of the proliferations distinguishes the alg...
101 citations
TL;DR: It is proposed that spore dispersal from fixed stands of Undaria results primarily in short-range spread, with dispersal of fragments or whole sporophytes facilitating spread at scales of hundreds of metres to kilometres.
Abstract: The Asian kelp Undaria pinnatifida (Laminariales, Phaeophyceae) was first recorded in New Zealand in 1987 and has since spread via shipping traffic and other vectors to a number of ports and harbou...
100 citations
TL;DR: Prey size spectrum and food preference in the thecate heterotrophic dinoflagellates Protoperidinium pallidum, P. steinii, and Zygabikodinium lenticulatum are determined, showing some degree of food niche differentiation, with preference for different prey types.
Abstract: Laboratory experiments were conducted to determine prey size spectrum and food preference in the thecate heterotrophic dinoflagellates Protoperidinium pallidum, P. steinii, and Zygabikodinium lenticulatum. Algal cultures of different taxonomic groups and different size were offered as prey. In addition to observations of feeding, growth rate was used as a measure of the quality of the different prey for population maintenance. The two Protoperidinium species show some degree of food niche differentiation, with preference for different prey types. Protoperidinium pallidum showed a preference for diatoms over dinoflagellates, and only diatom prey was able to support population growth. The smaller P. steinii had positive population growth on both dinoflagellates and diatoms, but the highest growth rate was supported by dinoflagellates, and P. steinii showed a preference for this prey type. A common feature of the Protoperidinium species was the failure of small flagellates to support growth. The thi...
80 citations
TL;DR: In this paper, the authors present a method to solve the problem of homonymity in the context of homophysics, and no abstracts available, but no abstract available.
Abstract: Abstract No abstract available.
72 citations
TL;DR: The results suggest that the metabolic stress due to UV-B radiation has little impact on the seasonal growth cycle of U. olivascens but has significant impact on pigments and internal carbon and nitrogen content.
Abstract: Relative growth rate, photosynthetic pigment content, and internal carbon and nitrogen levels of Ulva olivascens P.A. Dangeard, were examined on a seasonal basis under natural conditions from December 1994 to February 1996. Biotic variables were correlated with abiotic factors, including phosphate and nitrate/nitrite [(NO3− + NO2−)] concentrations in the seawater, temperature, photosynthetically active radiation (PAR), and UV-A and UV-B radiation. The relative growth rate of the alga was 68% higher in spring and early summer than in mid summer. In the same spring-to-summer period, photosynthetic pigment concentrations (chlorophyll a, chlorophyll b, and carotenoids) decreased by 70–80%. From March to July, nitrogen and carbon content declined by 62% and 11%, respectively, which yielded a change in the carbon: nitrogen mass ratio from 12.9 to 39.4. In late summer, the alga disappeared from the field site. Seasonal variations in relative growth rate of U. olivascens were governed by changes in prima...
66 citations
TL;DR: A new species, N. limnetica Krienitz, Hepperle, Stich & Weiler sp.
Abstract: High densities of Nannochloropsis, reaching up to 5.7 × 109 cells per litre, were observed in small inland water bodies in Germany. This is one of the few evidences of a Nannochloropsis species in a freshwater habitat. We describe a new species, N. limnetica Krienitz, Hepperle, Stich & Weiler sp. nov, for which the critical taxonomic characterization is based upon 18S rRNA sequence data. The ultrastructure of this species is characterized by the absence of a plastidial girdle lamella and pyrenoids. The plastid-bounding endoplasmic reticulum is continuous with the nuclear envelope, and the protoplasm contains numerous rodlike, doubly refringent lamellate vesicles. The pigment content of N. limnetica corresponds to that of other Nannochloropsis, but echinone was also found. The fatty acid composition of N. limnetica is similar to that of marine species; however, the total amount of fatty acids (351 μg mg−1 C−1) is higher than in marine species.
65 citations
TL;DR: A hitherto unrecognized kind of green picoplanktonic alga from a saline pond, now isolated in pure culture, suggests that this alga might be assigned to a new lineage within the Chlorophyta.
Abstract: We describe Picocystis salinarum R.A. Lewin, gen. et sp. nov., a hitherto unrecognized kind of green picoplanktonic alga from a saline pond, now isolated in pure culture. The cells are normally sph...
TL;DR: Qualitative measures of the abundance of macroalgal species having different thallus form, longevity and taxonomy are more sensitive and robust than qualitative measures in reflecting changes in the communities brought about by cultural eutrophication, suggesting that the impact of eutrophic on coastal macroalgae will follow a geometric series similar to that established for lakes of different trophic levels.
Abstract: Long-term studies of the composition of marine macroalgal communities are rare because of the lack of quantitative investigations in the past. In Denmark, a single quantitative study was performed in 1941–1943 in the nontidal estuary Isefjord–Roskilde Fjord, at several sites of variable salinity (10–22 ‰) and nutrient availability. This study was used as a reference for evaluating changes in the richness and relative abundance of macroalgal species from different taxonomic groups and functional forms at sites experiencing increasing concentrations of nitrate and light attenuation during the 50 years elapsed since then. Qualitative measures showed no, or few, changes over the period. In contrast, quantitative measures showed a significant increase in the relative abundance of small, opportunistic green algae (e.g. species of Chaetomorpha, Cladophora, Enteromorpha and Ulva) and a significant decrease in the relative abundance of large, perennial brown algae (e.g. Fucus serratus and F. vesiculosus)....
TL;DR: An increase in toxin concentration from 0 to 4423 μg saxitoxins g−1 dry weight cells was observed over a 3-month period in a series of samples collected from a persistent bloom of A. circinalis at Wongulla Lagoon, South Australia.
Abstract: Cyanobacterial samples were collected between April 1989 and May 1997 from six drainage divisions in coastal areas of Australia: the northeast coast, southeast coast, Tasmania, Murray–Darling Basin, South Australian coast and southwest coast. Saxitoxins were detected in approximately 70% of all field samples and 57% of cultured strains of Anabaena circinalis. Maximum saxitoxin concentrations were 4466 and 2553 μg g−1 dry weight cells in field samples and strains, respectively. Toxin profiles were similar in the majority of field samples and strains. The toxins were predominantly C-toxins (C1 and C2) and gonyautoxins (GTX2 and GTX3), with saxitoxin sensu stricto (STX), GTX5 and decarbamoyl gonyautoxins (dcGTX2 and dcGTX3) being present in minor amounts. A unique toxin composition (exclusively STX and GTX5) was found in a geographically isolated strain from the southwest coast of Australia. N1-hydroxy saxitoxins (neoSTX, GTX1 and GTX4) were not detected in any field sample or cultured strain. Anaba...
TL;DR: The feeding behavior of the heterotrophic dinoflagellate Polykrikos kofoidii Chatton on Gymnodinium catenatum Graham is described, suggesting that G.Catenatum populations may be controlled by P. kofoids predation in natural bloom conditions.
Abstract: This paper describes the feeding behavior of the heterotrophic dinoflagellate Polykrikos kofoidii Chatton on Gymnodinium catenatum Graham. Polykrikos kofoidii used a nematocyst to pull the prey into its body through the posterior sulcus, finally engulfing the prey completely. We measured growth rates of P. kofoidii on diverse assemblages of dinoflagellate prey. Gymnodinium catenatum was one of the best food sources for P. kofoidii, supporting a rapid growth rate in excess of one doubling per day. This suggests that G. catenatum populations may be controlled by P. kofoidii predation in natural bloom conditions. However, P. kofoidii cannot be a potential bloom-controlling factor in all toxic dinoflagellate blooms because it is rapidly killed by at least three Alexandrium strains.
TL;DR: A new unarmoured dinoflagellate that has bloomed in Hong Kong and Japan, and has caused significant fish kills and financial loss, is described on the basis of light and electron microscopy.
Abstract: A new unarmoured dinoflagellate, Karenia digitata Yang, Takayama, Matsuoka & Hodgkiss sp. nov., is described on the basis of light and electron microscopy. It has bloomed in Hong Kong and Japan, and has caused significant fish kills and financial loss. High ichthyotoxicity persisted for approximately one week after the blooms had subsided. Karenia digitata cells are 10–26.25 μm long and 10–22.5 μm wide. The epicone is hemispherical or broadly conical; the hypocone is hemispherical and is not concave at the antapex. The girdle displacement varies but is more than 20% of the body length. The sulcus continues into the epicone as small finger-like extensions; it does not reach the antapex. At its centre it is displaced by the girdle. Chloroplasts are numerous, irregular in shape and randomly distributed, though usually clumped. The nucleus is spherical to ovoid and centrally to posteriorly located. The cell has an apical groove, which lies to the right of the sulcal axis, extends in a straight line o...
TL;DR: Results from this study indicate that the most biologically successful light regimen in culture corresponds in nature to the day length of the fall bloom from which these clones were isolated.
Abstract: Sexual reproduction in the domoic acid–producing pennate diatom Pseudo-nitzschia multiseries (Hasle) Hasle is dioecious and involves pairing of two morphologically isogamous parent cells (gametangia) and the production of two gametes per gametangium. Gamete fusion leads to the formation of zygotes, which elongate into auxospores. Within each auxospore, a long initial cell is formed, thereby restoring the longer cell sizes in the population. Mating experiments were performed by mixing active “male” and passive “female” cells from pairs of clones and growing them under different light : dark (L : D) cycle regimes. Two pairs of clones were studied: one pair was ontogenetically older and therefore shorter than the other. After mating, the relative abundance of gametes, zygotes, auxospores, and initial cells was determined for a minimum of four consecutive days. Cell size, which reflects population age, influences sexualization. The short-celled clones had a lower maximum proportion of gametes per vegetative cell (4%) than the long-celled clones (49%), suggesting that the former were nearing the minimal cell length capable of sexualization. The size range within which P. multiseries is able to reproduce sexually is 23–70% of the maximum cell length. A positive correlation was found between hours of light exposure per 24 h at approximately 100 μmol photons m⁻² s⁻¹ and sexual cell production of the ontogenetically younger clones. Greatest production of initial cells per female gamete (26%) occurred in 10 h of light. Results from this study indicate that the most biologically successful light regimen in culture corresponds in nature to the day length of the fall bloom from which these clones were isolated.
TL;DR: Parsimony and distance analyses of the rbcL and 18S rRNA sequences indicate that the Prasiolales is a well-defined order and provide moderate support for a relationship with the Trebouxiophyceae, which has been postulated in past studies based on cellular and ultrastructural characters.
Abstract: Partial sequences of the genes coding for the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (rbcL) and the nuclear ribosomal small subunit (18S rRNA) were used to determine the p...
TL;DR: One of the most unusual features of G. fuscum is the absence of a transverse striated flagellar root, a feature presently known only in the zoospores of the otherwise very different genus Noctiluca, and this feature, together with the lack of striated collars around the flageLLar canals, suggests a phylogenetically more isolated position for G.fuscum.
Abstract: Gymnodinium fuscum (Ehrenberg) Stein is the type species of Gymnodinium, one of the largest genera of dinoflagellates. It has the typical fine structure of dinoflagellates, but also possesses several unusual features. The nuclear envelope is specialized by having vesicular chambers in which the nuclear pores are located; the pusular complex includes an internal collectjon chamber; and a nuclear fibrous connective links the nucleus with the longitudinal microtubular root of the flagellar apparatus. A delicate horseshoe-shaped apical groove is visible by scanning electron microscopy. The same morphological features have been observed in a few other gymnodinioids, indicating a close phylogenetic relationship, and have recently been used, together with large subunit (LSU) rDNA data, in redefining the genus Gymnodinium [Daugbjerg et al. (2000) Phycologia 39: 302–317]. However, one of the most unusual features of G. fuscum is the absence of a transverse striated flagellar root, a feature presently know...
TL;DR: A new benthic dinoflagellate, Coolia areolata Ten-Hage, Turquet, Quod & Couté sp.
Abstract: A new benthic dinoflagellate, Coolia areolata Ten-Hage, Turquet, Quod & Coute sp. nov., was isolated from sandy substrata in La Possession Bay, La Reunion, and at various other sites in the western Indian Ocean. This new species is described and illustrated by light and scanning electron micrographs and drawings. The plate formula of C. areolata is P03′7″ 6c 6?s 5′″ 2″″. Cell size ranges are 30–36.5 μm long and 28–36.5 μm wide. Cells are spherical, areolate, and covered with scattered round pores. The surface of the apical plate 1′ is smooth. The apical pore is 9–10 μm long. Cells of C. areolata are distinguished from C. monotis and C.tropicalis by thecal surface morphology, thecal plate size and shape, and apical pore length.
TL;DR: Comparison with sequences obtained in the laboratory from other dinoflagellate genera such as Alexandrium and with those reported in the genomic databases suggests that the ITS–5.8S region could be used as a molecular marker for detection of D. sacculus.
Abstract: High-density blooms of Dinophysis sacculus Stein, a dinoflagellate that produces diarrhetic shellfish toxins, are reported from a brackish lagoon in Sicily, Italy. The diarrhetic shellfish poisonin...
TL;DR: Several freshwater phytoplanktonic species (eukaryotic and prokaryotic) were grown in batch cultures up to stationary phase and quantified by chlorophyll a analysis, revealing two classes of copper-complexing ligands, one weaker and the other stronger.
Abstract: Several freshwater phytoplanktonic species (eukaryotic and prokaryotic) were grown in batch cultures up to stationary phase and quantified by chlorophyll a analysis. The complexation properties (co...
TL;DR: There was little effect of bryozoan colonization on pigmentcontent at the N-poor site, but colonization significantly affected pigment content at theN-rich site, where concentrations of chlorophyll a and fucoxanthin were lower with bryozooan colonization.
Abstract: The encrusting bryozoan Membranipora membranacea is the dominant epibiont on the giant kelp Macrocystis integrifolia. Previous studies suggest that bryozoans influence the nitrogen (N) and photosynthetic physiology of the underlying kelp. We predicted that for N-limited M. integrifolia, if bryozoans supply the underlying tissue with excreted ammonium, (1) the kelp tissue would utilize this N in chlorophyll synthesis, thereby compensating for reduced light levels that result from bryozoan colonization, and (2) levels of carbon-based secondary metabolites (polyphenolics) would be reduced. For N-replete M. integrifolia, we expected bryozoans to have little or no influence on kelp physiological parameters. Soluble tissue nitrate, tissue percent C and percent N, polyphenolic and chlorophyll a, c and fucoxanthin content, and ammonium uptake were determined for M. integrifolia tissue disks that (1) had no bryozoans (clean treatment); (2) were covered by bryozoans on one side of the disk (50% treatment);...
TL;DR: A new family is proposed to be established, the Akkesiphycaceae Kawai & Sasaki fam.
Abstract: Phylogenetic relationships of Akkesiphycus lubricum with the Laminariales and related taxa were assessed by molecular phylogenetic analyses based on the Rubisco large subunit gene (rbcL), internal transcribed spacer regions (ITS1 and ITS2), and 18S ribosomal DNA (18s rDNA) sequence data. Among the three data sets, rbcL gene sequences gave the best resolution for indicating familial and ordinal relationships within the Laminariales and related taxa. Using rbcL data, Akkesiphycus showed the closest phylogenetic relationship to the Pseudochordaceae (Laminariales) and this was also supported by ITS and 18S rDNA data. The clade of Akkesiphycus and the Pseudochordaceae formed a sister group to the Alariaceae/Laminariaceae/Lessoniaceae group and the Chordaceae of the Laminariales in maximum parsimony and neighbour-joining analyses. Morphologically, Akkesiphycus differs significantly from other Laminariales in having gametophytes with anisogamous planogametes. However, considering that some laminarialean...
TL;DR: Five marine sand-dwelling species of the dinoflagellate genus Thecadinium have been examined from intertidal and subtidal sand and illustrated with light and scanning electron microscopy and two species are described as new.
Abstract: Five marine sand-dwelling species of the dinoflagellate genus Thecadinium have been examined from intertidal and subtidal sand and illustrated with light and scanning electron microscopy. Additional information on the known species is provided. The type species, Thecadinium kofoidii, has the plate formula P 3′ 1a 4″ 5(6?)c 5s 4′″ 1″″ the sulcal plates and one more postcingular plate are described. Thecadinium kofoidii is so far the only Thecadinium species possessing chloroplasts. The first light microscopical observations of Thecadinium neopetasatum are reported, and the plate formula is emended to P 3′ 1a 6″ 6c ?s 5′″ 1 ″″, with one more epitheca and two more hypotheca plates. The first scanning electron microscopical observations of Thecadinium dragescoi are reported, and the plate formula is emended to P 5′ 2a 8″ 6(7?)c ?s 4′″ x 2p 1″″, with two newly described apical intercalary plates and the ‘x’ plate. Two species are described as new. Thecadinium ornatum Hoppenrath sp. nov. is flattened l...
TL;DR: Field observations of the synchronous formation and release of male gametes by the Mediterranean strain of C. taxifolia are reported, as in related species living in tropical regions, gamete release was synchronized by light intensity.
Abstract: Fifteen years after the first report of the presence of the tropical green alga Caulerpa taxifolia (Chlorophyta) in the Mediterranean Sea off the shores of Monaco, this alga is now present in the w...
TL;DR: Nuclear small-subunit rDNA sequences from three species of Ballia native to southern Australia have been investigated, initially to assess the tribal placement of the genus within the Ceramiaceae, but in distance and parsimony analyses, Ballia callitricha was strongly positioned in the ‘two-cap-layered pit-plug assemblage’ of the Florideo-phyceae as a distinct lineage.
Abstract: Nuclear small-subunit rDNA sequences from three species of Ballia (Ceramiales, Rhodophyta) native to southern Australia have been investigated, initially to assess the tribal placement of the genus...
TL;DR: Six marine species, four of them new, of the dinoflagellate Amphidiniopsis are described from intertidal sand and all species have a slightly ascending cingulum.
Abstract: Six marine species, four of them new, of the dinoflagellate Amphidiniopsis are described from intertidal sand. Amphidiniopsis hirsutum (Balech) Dodge has the plate formula Po 4′ 2a 7″ 8c 4s? 5′″ 2″″. The first scanning electron microscopy observations of Amphidiniopsis swedmarkii (Balech) Dodge are reported and the plate formula Po 4′ la 7″ 6c? 5s? 5′″ 2″″ is established. Amphidiniopsis arenaria Hoppenrath sp. nov. is flattened laterally with a cell size of 30.0–43.5 μm (37.8 ± 4.3 μm, mean ± s) long and 27.0–38.2 μm (33.8 ± 4.5) wide (dorsoventrally). The plate formula is Po 4′ 3a 7″ 6c? 4s? 5′″ 2″″. Amphidiniopsis dentata Hoppenrath sp. nov. is flattened laterally, 38.8–46.5 μm (43.0 ± 2.6) long and 33.7–38.8 μm (37.3 ± 1.7) wide (dorsoventrally). The plate formula is Po 4′ 3a 8″ 6c? 3s? 5′″ 2″″. Amphidiniopsis galericulata Hoppenrath sp. nov. is flattened laterally, 20.3–29.0 μm (24.9 ± 2.5) long and 18.0–25.4 μm (21.9 ± 2.7) wide (dorsoventrally). The plate formula is Po 4′ 3a 7(6)″ ?c 3s? 5′...
TL;DR: For all three predators, the best growth was achieved on dinoflagellate prey and Heterocapsa triquetra supported the highest growth rate and there was a tendency for predator cell volume to increase with increasing cell volume of the prey.
Abstract: Laboratory experiments were conducted to determine the prey size spectrum of the naked heterotrophic dinoflagellates Gyrodinium dominans, G. fusiforme and Katodinium glaucum. Dinoflagellates, diatoms, prymnesiophytes, a cryptophyte and a chlorophyte were offered as food. In addition to observations of feeding, growth rate was used as a measure of the quality of different prey for population maintenance. All the taxonomic groups, except the chlorophyte, were able to support growth in G. dominans, but not all species within the groups were. The prymnesiophytes and the chlorophyte were inadequate food for G. fusiforme, whereas the other groups tested supported growth. Fewer species were tested for K. glaucum, and only dinoflagellates and the cryptophyte yielded growth. For all three predators, the best growth was achieved on dinoflagellate prey and Heterocapsa triquetra supported the highest growth rate. There was a tendency for predator cell volume to increase with increasing cell volume of the pre...
TL;DR: The results show that physodes are formed in the perinuclear region of the cell, and the Golgi apparatus and the endoplasmic reticulum are implicated in physode formation.
Abstract: Phenolic compounds, packaged within vesicles known as physodes, are a major cytoplasmic constituent of eggs and zygotes of the Australasian fucoids Hormosira banksii (Turner) Decaisne and Phyllospora comosa (Labillardiere) C Agardh. Light and transmission electron microscopy in conjunction with the actin inhibitors cytochalasin and latrunculin and the Golgi disruptor Brefeldin were used to investigate physode biogenesis in Hormosira and Phyllospora zygotes and embryos. Our results show that physodes are formed in the perinuclear region of the cell. Contrary to many early reports, no evidence was found that physode genesis is associated with chloroplasts. Instead, the Golgi apparatus and the endoplasmic reticulum are implicated in physode formation. Physodes are produced in large quantities around the nucleus just before periods of active wall deposition, particularly during rhizoid initiation and crosswall formation. Subsequently, they move from their central location to the sites of wall deposition.
TL;DR: A new toxic benthic marine dinoflagellate, Prorocentrum borbonicum, isolated from the fringing coral reef of St Leu from La Réunion Island is described from light and scanning micrographs.
Abstract: A new toxic benthic marine dinoflagellate, Prorocentrum borbonicum Ten-Hage, Turquet, Quod, Puiseux-Dao & Coute sp. nov., isolated from the fringing coral reef of St Leu from La Reunion Island (France, southwest Indian Ocean) is described from light and scanning micrographs. The species was identified based on shape, size, surface micromorphology, ornamentation of thecal plates, and architecture of the periflagellar area and intercalary band. Prorocentrum borbonicum is a small species (18–24 μm long and 16–20 μm wide) with a broadly ovate shape. Thecal depressions are numerous (950–1020 per valve). Two sizes of valve pores were recognized: large pores, which are scattered on the valve surface, except in the central area, and smaller pores, which are localized chiefly in the centre of the valve and at the periphery, along the intercalary band. The periflagellar area is V-shaped and accommodates a flagellar pore and an auxiliary pore, the latter being the smaller of the two. Prorocentrum borbonicum...