The parasitic dinoflagellates of marine crustaceans

Parasitic dinoflagellates have recently emerged as significant disease agents of commercially important crustaceans. For example, epizootics of Hematodinium have seriously affected certain crab and lobster fisheries. The parasitic dinoflagellates of crustaceans are, however, relatively unknown. Marine crustaceans are parasitized by two orders of dinoflagellates: the Blastodinida and the Syndinida. Crustaceans are also parasitized by the Paradinida and the Ellobiopsidae, taxa that have close historical ties and possible taxonomic affinities with the dinoflagellates. The taxonomy and life history patterns of the different parasitic species are largely dictated by their host-parasite relationships. For example, sporulation in the blastodinids occurs internally but is completed externally with the expulsion of spores via the anus of the host. The egg-parasitic chytriodinids sporulate externally after destroying their host egg. The tissue-dwelling syndinids have plasmodia that sporulate internally and generally kill their hosts upon the expulsion of the dinospores. Unfortunately, complete life cycles have not been elucidated for any of the parasitic forms, hence characteristics of the life cycles must be applied cautiously to the systematics of the taxa. For example, gamogony and the presence of resting cysts are only known from a few species; they probably occur in most species. Further work on the life cycles of the parasitic dinoflagellates of crustaceans should concentrate on establishing the life cycles of representative species from each order or family. Parasitic dinoflagellates infect copepods, amphipods, mysids, euphausiids, and decapods. Their pathogenicity varies with their invasiveness in the host. The gut-dwelling blastodinids are relatively benign, while the chytriodinids kill their host egg. Members of the pervasive Syndinida and Paradinida are overtly pathogenic and insidiously ramify throughout the hemal sinuses and organs of their hosts. Members of the Ellobiopsidae vary from the commensal Ellobiocystis to the overtly parasitic Thalassomyces. Host castration and feminization are common pathologic results of infection by these parasites. The severity of the castration is dependent upon the invasiveness of the parasitic species and the duration of the infection, while the degree of feminization is related to the stage at which the host acquires the infection. Most of the parasitic dinoflagellates occur in epizootics in their host populations. Recent epizootics of Hematodinium spp. have had severe effects on crustacean fisheries in Alaska, Virginia, and Scotland, and may potentially result in changes to the benthic communities of the hosts. The epizootics are often associated with host-parasite systems that occur in regions with unique hydrological features, such as fjords or poorly draining estuaries with shallow sills. These regions are ideal for the application of a “landscape” ecology approach that could lead to a better understanding of the epizootiology of parasitic dinoflagellates and other marine pathogens.     

Biotechnological significance of toxic marine dinoflagellates

Dinoflagellates are microalgae that are associated with the production of many marine toxins. These toxins poison fish, other wildlife and humans. Dinoflagellate-associated human poisonings include paralytic shellfish poisoning, diarrhetic shellfish poisoning, neurotoxic shellfish poisoning, and ciguatera fish poisoning. Dinoflagellate toxins and bioactives are of increasing interest because of their commercial impact, influence on safety of seafood, and potential medical and other applications. This review discusses biotechnological methods of identifying toxic dinoflagellates and detecting their toxins. Potential applications of the toxins are discussed. A lack of sufficient quantities of toxins for investigational purposes remains a significant limitation. Producing quantities of dinoflagellate bioactives requires an ability to mass culture them. Considerations relating to bioreactor culture of generally fragile and slow-growing dinoflagellates are discussed. Production and processing of dinoflagellates to extract bioactives, require attention to biosafety considerations as outlined in this review.     

Genetic variability in growth rates of marine dinoflagellates

The growth rates of thirty clones of Prorocentrum micans, twenty-two clones of Gonyaulax excavata and fifteen clones of Scrippsiella trochoidea, isolated from eight different water samples were measured under two environmental conditions. There was significant genetic variability in growth rates between clones. The amount of genetic variability between clones ranged from 10–27% (coefficient of variation) in Prorocentrum micans, 31–52% in Gonyaulax excavata and 11–20% in Scrippsiella trochoidea. Unlike Gonyaulax excavata and Scrippsiella trochoidea many different Prorocentrum micans clones had identical growth rates.Supported by Spanish CAICYT, grant num. 2409/83.     

Symbiotic dinoflagellates in marine Cnidaria: diversity and function

Dinoflagellates of the genus Symbiodinium are the most common symbiotic algae in benthic marine Cnidaria. This review addresses our current understanding of the molecular diversity of Symbiodinium and the function of these algae in symbiosis. Ribosomal DNA sequence data indicate that Symbiodinium is a diverse but probably monophyletic group. They also provide a phylogenetic framework for the analysis of the functional diversity of Symbiodinium (i.e. the variation in phenotype among various Symbiodinium genotypes), especially in relation to their nutritional role in the symbiosis. Symbiodinium provides the animal host with photosynthetic carbon and may also recycle animal nitrogenous waste. These interactions are advantageous to animals in shallow, oligotrophic waters. Recent developments in understanding of both photosynthate release and nitrogen relations in the symbiosis are reviewed. They provide the basis to explore the variation in nutritional interactions among different Symbiodinium genotypes. This review highlights areas of current uncertainty and controversy and addressess possible fulture directions of research.     

Copepods induce paralytic shellfish toxin production in marine dinoflagellates

Among the thousands of unicellular phytoplankton species described in the sea, some frequently occurring and bloom-forming marine dinoflagellates are known to produce the potent neurotoxins causing paralytic shellfish poisoning. The natural function of these toxins is not clear, although they have been hypothesized to act as a chemical defence towards grazers. Here, we show that waterborne cues from the copepod Acartia tonsa induce paralytic shellfish toxin (PST) production in the harmful algal bloom-forming dinoflagellate Alexandrium minutum. Induced A. minutum contained up to 2.5 times more toxins than controls and was more resistant to further copepod grazing. Ingestion of non-toxic alternative prey was not affected by the presence of induced A. minutum. The ability of A. minutum to sense and respond to the presence of grazers by increased PST production and increased resistance to grazing may facilitate the formation of harmful algal blooms in the sea.     

Vectored introductions of marine endosymbiotic dinoflagellates into Hawaii

Endosymbiotic dinoflagellates belonging to the genus Symbiodinium associate with a diverse range of marine invertebrate hosts and also exist free-living in the ocean. The genus is divided into eight lineages (clades A–H), which contain multiple subclade types that show geographic and host specificity. It is commonly known that free-living dinoflagellates can and have been introduced to new geographic locations, primarily through shipping ballast water. In this study we sequenced the ITS2 region of Symbiodinium found in symbiosis with the coral Acropora cytherea in the Northwestern Hawaiian Islands Marine National Monument and from shipping ballast water. Identification of an unusual symbiont in Acropora cytherea and an analysis of the distribution of this symbiont suggests an introduction to Hawaii vectored by the scyphozoan host, Cassiopea sp. Symbiodinium were also detected in shipping ballast water. This work confirms that marine invertebrate endosymbionts can be introduced to new geographic locations vectored by animal hosts or the ballast water of ships.     

The temperature acclimatized swimming speed of selected marine dinoflagellates

Video measurements were used to monitor the temperature acclimatizedswimming speeds (24 hours exposure) of 11 species of marinedinoflagellates, some represented by different clones, on atemperature gradient plate. Although the inherent variabilityamong individuals within a population under the same treatmentwas high, each species or clone could be represented by a responsescatter plot that characterized its temperature-dependent swimmingability. A curve-fitting treatment of the data demonstratedthe similarity of the swimming speed versus temperature responsesfor repetitive trials on a single clone or for different clonesand the diversity of the swimming speed versus temperature responsesamong different species. Comparisons among populations includedviable temperature range, maximum swimming speed and responsecurve shape. All species swam over a broader temperature rangethan that over which growth was detected. Maximum swimming speedwithin the measured group occurred at a cell length of -35 µgThis possible optimum in cell size may result from the hydrodynamiccharacteristics of dinoflagellate swimming. Swimming speed variationamong dinoflagellate species can influence the competitive interactionswithin the group or with other kinds of phytoplankton and canaffect predator-prey interactions with herbivores.     

The fine structure and ontogeny of trichocysts in marine dinoflagellates

Long, rigid, rod-like structures found in the culture medium of several marine dinoflagellates are shown in this report to have fine transverse bandings characteristic of extruded trichocysts. These structures in genera such asGonyaulax are believed to pass through the heavily plated surface via narrow pores. In the resting or charged form, trichocysts are found to have an elaborate crystalline core connected by a series of fibers and still finer fibrils to the apex of an enclosing sac. The walls of this sac consist of a single membrane and fine thread-like hoops or spirals. The design of the whole charged trichocyst is suggestive of a mechanical sensing device. Trichocysts are found to originate in membrane-limited vesicles which are localized within a spherical shell composed of Golgi bodies. Initially these vesicles contain homogeneous materials, but with increasing development a crystal lattice appears and ultimately the resting trichocyst core evolves. At this point the trichocyst leaves the Golgi area and migrates elsewhere in the cytoplasm. The charged trichocyst core is found to be waterbut not acetone-soluble in contrast to the discharged trichocyst which is unaffected by either solvent. These facts together with the finding of shafts apparently polymerizing from amorphous contents are interpreted as supporting the hydration theory of trichocyst discharge. Finally, the striking similarities between the origin and structure of extruded trichocyst shafts and the origin and structure of collagen fibers are discussed briefly.     

The mechanical triggering of bioluminescence in marine dinoflagellates: chemical basis

In both photosynthetic (Pyrodinium bahamense, Gonyaulax polyedra, Pyrocystis Iunula, P. noctiluca, P. fusiformis) and nonphotosynthetic (Noctiluca miliaris) bioluminescent dinoflagellates chemical stimulation can by-pass mechanical stimulation. The effective ions are Ca⁺⁺, K⁺, NH₄⁺ and H⁺. Other chemicals found effective are those implicated in Ca⁺⁺ transport or binding. There are interspecies differences in degrees of mechanical and chemical stimulability. Photoinhibition of mechanical stimulability is the result of two effects, the first a reduction in total bioluminescence potential and the second a decrease in mechanical stimulability resulting experimentally in a decreased rate of light emission. This latter effect can be reversed with Ca⁺⁺ ions. Chemicals which bind Ca⁺⁺ or displace Ca⁺⁺ can mimic the effects of photoinhibition. The chemical inhibition of mechanical stimulability is also reversed by Ca⁺⁺ ions. A scheme is proposed which is consistent for all species examined.     

The fatty acid and sterol composition of two marine dinoflagellates

The fatty acid, sterol and chlorophyll pigment compositions of the marine dinoflagellates Gymnodinium wilczeki and Prorocentrum cordatum are reported. The fatty acids of both algae show a typical dinoflagellate distribution pattern with a predominance of C₁₈, C₂₀ and C₂₂ unsaturated components. The acid 18:5ω3 is present at high concentration in these two dinoflagellates. G. wilczeki contains a high proportion (93.4%) of 4-methyl-5α-stanols including 4,23,24-trimethyl-5α-cholest-22E-en-3β-ol (dinosterol), dinostanol and 4,23,24-trimethyl-5α-cholest-7-en-3β-ol reported for the first time in dinoflagellates. The role of this sterol in the biosynthesis of 5α-stanols in dinoflagellates is discussed. P. cordatum contains high concentrations of a number of δ ²⁴⁽²⁸⁾-sterols with dinosterol, 24-methylcholesta-5,24(28)-dien-3β-ol, 23,24-dimethylcholesta-5,22E-dien-3β-ol, 4,24-dimethyl-5α-cholest-24(28)-en-3β-ol and a sterol identified as either 4,23,24-trimethyl- or 4-methyl-24-ethyl-5α-cholest-24(28)-en-3β-ol present as the five major components. The role of marine dinoflagellates in the input of both 4-methyl- and 4-desmethyl-5α-stanols to marine sediments is discussed.     

Long-term survival of marine planktonic diatoms and dinoflagellates in stored sediment samples

Sediment samples from Scottish coastal sites, taken over the last 9 years, were stored in closed containers at 5C. Slurry cultures were used to determine the survival of phytoplankton in these sediments. A range of diatom and dinoflagellate species survived for at least 27 months in these stored samples. A number of species grew for which no resting stage has yet been described: Thalassiosira angulata, T.pacifica, T.punctigera, T.eccentrica, T.minima and T.anguste-lineata. Notable results were survival times of 73 months for Skeletonema costatum, 96 months for Chaetoceros socialis, C.didymus and C.diadema, 109 months for Scrippsiella sp. and 112 months for Lingulodinium polyedrum. A single sample was stored and repeatedly cultured for diatoms over a period of 16 months. The number of species cultured from the sediment declined over this time. Lingulodinium polyedrum cysts isolated from sediments collected at least 18 months previously gave a hatching success of 97%, and cysts isolated from a 9-year-old sample gave a hatching success of 3%. The study indicated the potential importance of coastal sediments as a source of phytoplankton to their overlying waters. The validity of using marine planktonic diatoms and dinoflagellates for modelling geological events is discussed.      

Phased cell division in natural populations of marine dinoflagellates from shipboard cultures

In June 1975 samples were preserved every 2 h for 26 h from water collected from Santa Monica Bay, California and which was incubated on shipboard. The percentage of dividing dinoflagellate cells in the samples was determined by microscopic examination after applying a nuclear stain. The maximum proportion of dividing cells was at 03.30 h, 05.30 h, and 09.30 h for Ceratium dens Ostf. & Schmidt, C. furca (Ehrenb.) Claparède & Lachmann, and Dinophysis fortii Pavillard, respectively. Mean doubling times for these species, calculated from the percentage of dividing cells, were 3.3,4.6, and 1.4 days. Temporal stratification in the timing of cell division may reflect a selective process for minimizing interspecific competition.     

Sterols with unusual nuclear unsaturation from three cultured marine dinoflagellates

Several new 4α-methyl sterols with unusual unsaturation in the Δ⁸⁽¹⁴⁾-or Δ¹⁴-positions, 4α,24S-dimethyl-5α-cholest-8 (14)-en-3β-ol, 4α-methyl-24ξ-ethyl-5α-cholest-8(14)-en-3β-ol, 4α-methyl-24(Z)-ethylidene-5α-cholest-8(14)- en-3β-ol, 4α,23 (or 22),24ξ-trimethyl-5α-cholesta-8(14),22-dien-3β-ol, 4α,24S(or 23ξ)-dimethyl-5α-cholest-14-en-3β-ol and 14-dehydrodinosterol, have been isolated from extracts of the cultured marine dinoflagellates Amphidinium carterae, A. corpulentum and Glenodinium sp. 4α-Methyl-24ξ-ethyl-5α-cholestan-3β-ol was isolated from the steryl ester fraction of Glenodinium sp. The structures of these new sterols are based upon extensive 360 MHz ¹H NMR and MS analyses.     

Esterases in marine dinoflagellates and resistance to the organophosphate insecticide parathion.

Esterases are involved in the susceptibility or resistance of organisms to organophosphate pesticides. We have examined the action of parathion on the marine dinoflagellates Crypthecodinium cohnii and Prorocentrum micans by looking at their esterases. One-dimensional gel electrophoresis, immunoblotting and cytochemistry plus image analysis were used to characterize the nature and distribution of the enzymes. Esterases were found in both species, but there appeared to be no particular intracellular localization. The esterase activity of the heterotrophic species Crypthecodinium cohnii was 30-fold greater than that of the autotrophic Prorocentrum micans and had an antigenic site in common with mosquito esterase. The resistance of Crypthecodinium cohnii to parathion was specific and reversible. Less parathion entered the parathion-resistant Crypthecodinium cohnii cells than the untreated control cells. Parathion-resistant cell extracts of Crypthecodinium cohnii analyzed after immunoblotting also contained an additional band of esterase activity. These results confirm the importance of esterases in toxicological studies of organophosphate insecticides, especially those of marine dinoflagellates.     

Extracellular L-glutaminase production by marine bacteria

Summary Four species of bacteria which includedPseudomonas fluorescens,Vibrio cholerae andVibrio costicola were observed to produce glutaminase both as extracellular and intracellular fractions. Comparatively both the fractions were higher in mineral media supplemented with 1% glutamine than in nutrient broth added with or without glutamine. Extracellular glutaminase production was about 2.6–6.8 times greater than the intracellular production by all the tested strains.     

Species range types of recent marine dinoflagellates recorded from the Arctic

On the basis of the geographic distribution of some 200 planktonic dinoflagellates recorded from the Arctic, species ranges were typified. Both original and literary data were considered and occurrences were mapped. The types are as follows: Arctic-boreal, boreal, Arctic-boreal-tropical, tropical-boreal, Antarctic-tropical-boreal, bipolar and cosmopolitan. Each type is discussed separately. Mostly, they correspond to the range types known for planktonic diatoms. The evidences of the unity of the Arctic-Boreal Biogeographic Zone are presented. No purely Arctic species have been found. Low endemism of the dinoflagellates of the Arctic-Boreal Zone at specific level (ca 2%) is noted for the Arctic Ocean. The Arctic-Boreal Biogeographic Zone can be subdivided into the Subarctic-Boreal-Atlantic, Subarctic-Boreal-Pacific and Euarctic Circumpolar subzones. As a whole, the Arctic dinoflagellate flora represents impoverished flora characteristic of temperate waters, mostly of the North Atlantic. The problems of bipolarity and bioindication of oceanic currents as well as the value of the so-called Ortmann and Dunbar lines are also discussed.     

Index of the Venezuelan marine microflora: diatoms, dinoflagellates and cocolithophorids

The marine phytoplankton of Venezuela has been studied on a regular basis since the mid 20th century. However, a species checklist that can be used as a framework for taxonomic studies is lacking. In this paper, an index of the marine microflora of Venezuela is presented for the first time. The index includes only those diatoms (89 centric and 186 pennate species), dinoflagellates (eight naked and 154 thecate species) and coccolithophores (24 species) for which formal diagnosis and illustrations (drawings and/or photographs) have been reported in the scientific literature (journals and/or first degree or master's theses). It is ordered alphabetically according to class, order, family, and species. It includes the author (s) of the taxa.