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Amphidinolide N (1), a novel 26-membered macrolide possessing an unprecedented carbon framework, has been isolated as an extremely potent cytotoxic compounds from the cultured marine dinoflagellate Amphidinium sp., which was living inside of the Okinawan marine flatwork, Amphiscolops sp., and its structure elucidated by extensive analyses of its spectroscopic data.

Nine species of benthic dinoflagellates isolated at Ishigaki Island, Okinawa, were grown unialgally. They were Prorocentrum lima, prorocentrum concavum, prorocentrum rhathymum, Amphidinium carteri, Amphidinium klebsii, Coolia monotis, Ostreopsis siamensis, Ostreposis ovata, and Gambierdiscus toxicus. The harvested cells were extracted with boiling methanol and the extracts were fractionated into diethyl ether soluble, 1-butanol soluble, and water soluble fractions. Each fraction was tested by mouse and fish assays and by blood cell hemolysis test. The extracts of P. lima, P. concavum, A. carteri, A. klebsii, O. siamensis, O. ovata, and G. toxicus were confirmed to show toxicity to mice. Hemolytic activity was recognized in all the species tested. Ichthyotoxicity was demonstrated by A. carteri, A. klebsii, and P. concavum, the last being the most potent. With the exception of the water soluble toxin of O. siamensis, all the toxins were found in either diethyl either diethyl ether soluble fraction or 1-butanol soluble fraction or in both.

A technique using 35SO42− was developed to assess the physiological state, with respect to division rate and rate of protein synthesis, of marine phytoplankton. Radiosulfur is incorporated predominantly into protein and was ≈ 50% of total sulfur uptake for Thalassiosira weissflogii (Grunow) G. Fryxell and Hasle, comb. nov. (= T. fluviatilis Hustedt). Rates of protein synthesis calculated from the rate of 35S incorporation (S-inc) agreed with measured rates during active cell growth, but generally exceeded those measured during the stationary phase. Positive correlations were found between S-inc and changes in cell biomass in batch culture. S-inc per cell declined as T. weissflogii progressed from the exponential to the late stationary phase. Cultures of Amphidinium carteri Hulburt, Dunaliella tertiolecta Butcher and Pavlova (= Monochrysis) lutheri (Droop) Green behaved similarly. Changes in S-inc detected the onset of the stationary phase during growth with nitrate at 18 μM at least 24 h before it was observed by measuring 14C uptake. Molar ratios of S-inc in the dark to S-inc in the light, and 14C uptake rate to S-inc by T. weissflogii were low during exponential growth and elevated during the stationary phase. Relationships were found between each of these ratios and division rates. Incubation of natural populations from coastal waters of Nova Scotia gave results comparable to those obtained in laboratory batch cultures.

Sulphate uptake by Amphidinium carterae, Amphidinium klebsii and Gymnodinium microadriaticum grown on artificial seawater medium with sulphate, cysteine, methionine or taurine as sulphur source occurred via an active transport system which conformed to Michaelis-Menten type saturation kinetics. Values for Km ranged from 0.18–2.13 mM and Vmax ranged from 0.2–24.2 nmol · 105 cells−1 · h−1. Km for symbiotic G. microadriaticum was 0.48 mM and Vmax was 0.2 nmol · 105 cells−1 · h−1. Sulphate uptake was slightly inhibited by chromate and selenate, but not by tungstate, molybdate, sulphite or thiosulphate. Cysteine and methionine (0.1 mM), but not taurine, inhibited sulphate uptake by symbiotic G. microadriaticum, but not by the two species of Amphidinium. Uptake was inhibited 45–97% under both light and dark conditions by carbonylcyanide 3-chlorophenylhydrazone (CCCP); under dark conditions sulphate uptake was 40–60% of that observed under light conditions and was little affected by 3-(3,4-dichlorophenyl) 1,1-dimethylurea (DCMU).

The flagellar apparatus of the marine dinoflagellate Amphidinium rhynchocephalum Anissimowa was examined using the techniques of rapid freezing/freeze substitution and serial thin section three dimensional reconstruction. The flagellar apparatus is composed of two basal bodies that are offset from one another and lie at an angle of approximately 150° The transverse basal body is associated with two individual microtubules that extend from the proximal end of the basal body toward the flagellar opening. One of these microtubules is closely appressed to a striated fibrous root that also extends from the proximal base of the transverse basal body. The longitudinal basal body is associated with a nine member microtubular root that extends from the proximal end of the basal body toward the posterior of the cell. The longitudinal microtubular root and the transverse striated fiber are connected by a striated connective fiber. In addition to the microtubules associated with the transverse and longitudinal basal bodies, a group of microtubules originates adjacent to one of the transverse flagellar roots and extends into the cytoplasm. Vesicular channels extend from the flagellar openings to the region of the basal bodies where they expand to encompass the various connective structures of the flagellar apparatus. The possible function and evolutionary importance of these structures is discussed.

Summary The nomenclature of symbiotic dinoflagellates harboured by animal hosts is reviewed with regard to its history and employment. Zooxanthella, Philozoon, Zoorhabdella, and Endodinium may be regarded as synonyms of Amphidinium which has priority. Gymnodinium is considered to be incorrectly employed instead of Symbiodinium when applied to S. microadriaticum. Chrysidella is illegitimate. It is proposed to reject Zooxanthella as a confusing name widely applied to taxa not including its type.

Amphidinium cryophilum sp. nov. was found in the fall of 1979 in a small pond near Madison, Wisconsin. During the ensuing winter, it became the dominant phytoplankter. Cell numbers remained high despite a thick layer of ice and snow. After the ice melted in the spring the organism disappeared from plankton samples. A successful culture of A. cryophilum was established only when isolates were incubated at 5–7° C. It is compared with two morphologically similar species, A. amphidinioides (Geitler) Schiller and Gymnodinium inversum Nygaard. Amphidinium cryophilum is distinguished from the former by its pigmentation (golden-yellow vs. blue-green), the location of the cingulum, and its lack of an eyespot. It differs from the latter in cell shape, the route of the sulcus and position of the nucleus.

Taxonomical study on eleven species of benthic dinoflagellates was conducted. They were collected from algal samples harvested on coral reefs of French Polynesia, New Caledonia and the Ryukyu Islands, Japan. They were classified into 4 species of Prorocentrum, 2 species of Amphidinium, 3 species of Ostreopsis, coolia monotis and Gambierdiscus toxicus, including 4 new species, Prorocentrum emarginatum sp. nov., Prorocentrum concavum sp. nov., Ostreopsis lenticularis sp. nov. and Ostreopsis ovata sp. nov.

The planula larvae and young polyp stages of the West Indian gorgonian Pseudopterogorgia bipinnata (Verrill) do not have symbiotic zooxanthellae. Planulae were allowed to settle in water free of any algae and presented with a number of strains of dinoflagellates. Motile forms of these algae were attracted to the polyps and in some cases were seen to swim into the polyp's open mouth. Successful infection was obtained only with Gymnocdinium (probably microadriaticum (Freudenthal)). Algae of the genus Amphidinium were apparently not able to infect polyps. The differences in transmission of zooxanthellae in symbiotic animals are discussed.

The carotenoids of the photosynthetic dinofiagellates Amphidinium carterae (two strains), Glenodinium sp.,Gymnodinium splendens, G. nelsoni and Gyrodinium dorsum have been investigated, quantitatively and qualitatively. Peridinin is the principal carotenoid in all species; also present are β-carotene, diadinoxanthin, dinoxanthin, pyrrhoxanthin, astaxanthin, peridininol, diatoxanthin and pyrrhoxanthinol. New structures have been assigned to dinoxanthin and pyrrhoxanthin while peridininol and pyrrhoxanthinol are new carotenoids not previously reported. A carotenoid glycoside, P-457, found in four species, is a hexoside. Dinoxanthin is the only, plausible biosynthetic precursor of peridinin that could be detected.

Dinoflagellates of the genus Dinophysis are responsible for diarrhetic shellfish poisoning. Phototrophic species have an orange primary fluorescence indicating the presence of phycobilins. The chloroplasts greatly resemble cryptophycean chloroplasts having pairs of thylakoids and electron-dense material in the thylakoid lumen. They are bound by only two membranes, in contrast to the blue-green chloroplasts of Amphidinium wigrense Woloszynsk, which are enveloped by three membranes (Wilcox and Wedemayer, 1985). Possible ways of evolution of the Dinophysis chloroplasts, phylogenetical questions and implications for the monitoring of toxic dinoflagellates are discussed.

Summary In the late autumn 1977 there was a very dry weather. There were no affluents to the ponds. The density of plankton was low. Only in the melting period in January 1978 the ponds got water supply and the effect was a strong development of algae, especially of the genus Mallomonas, Synum, Chrysococcus and Chrysamoeba. New for science: Chrysamoeba bizarra n. sp. During the period of breaking of ice in March the development of Mallomonas schwemmlei has been observed. New for science: Synechococcus ferrunginosus n. sp. A few interesting algae are discused: Amphidinium geitleri, Chlorogonium peterhofiense (Oogamie), Chloromonas fusiformis, Ch. plurivacuolata, Cryptomonas sp. (Hologamie), Mallomonas insignis, M. insignis v. lacustris, Massartia woloszynscae, Phacus similis, Phytodinium sp. (?), Pseudokephyrion klarnetii var. triangularis, Siderocelis kolkwitzii, Strombomonas fluviatilis, Synura petersenii (Hologamie).

Nine species of benthic dinoflagellates collected in subtropical waters were cultured, extracted, and tested for mouse lethality, ichthyotoxicity, and hemolytic activity. Hemolytic activity was detectable in all species, but the activities of Amphidinium carteri, A. klebsi, and Gambierdiscus toxicus were outstanding. G. toxicus showed the most potent mouse lethality. Two hemolytic constituents of A. carteri were determined to be mono- and di-galactoglycerolipids. Maitotoxin, produced by G. toxicus, was suggested to have a molecular weight of 3402 ± 2 (m/z). Two potent toxins against mice were isolated from Prorocentrum lima and identified as okadaic acid and 5-methylene-6-hydroxy-2-hexen-1-okadaate.

The general ultrastructure of A. poecilochroum is typical of dinoflagellates. The proximal part of the longitudinal flagellum possesses a previously undescribed structure consisting of three dense ...

The relationship between flow cytometric fluorescence signals and photosynthetic pigments was investigated in three species of marine eucaryotic phytoplankton, ThaZassiosiru weissflogii, Hymenomonas carterae, and Amphidinium carteri. The species were grown over a range of light intensities to provide a spectrum of pigment compositions for the study. Both interspecific and intraspecific differences were observed. Variations among the species in fluorescence per unit of chlorophyll a (Chl a) could be explained by differences in the relative abundance of Chl a and accessory pigments. Amphidinium carteri had much greater fluorescence per unit of Chl a than the other two species and it had the highest Chl c : Chl a ratio. Fluorescence per unit of Chl a decreased as Chl a per cell increased in H. carterae and A. carteri, whereas it remained the same in T. weissflogii. We interpret these differences to have their origins in the “package” effect on light absorption. This effect seems to be least evident in the diatom because cell size increased as Chl a per cell increased in low-light-grown cells. In H. carterae and A. carteri the opposite was true, such that the intracellular concentration of Chl a increased substantially in the low-light cells. Based on these data, we find that to interpret fluorescence signals among species, differences in the relative abundances of Chl a and accessory pigments must be considered, while for intraspecific fluorescence differences, the package effect may be more important.

SUMMARY Ammonia concentration between 10–300 μM in 75% seawater in which Amphidinium carterae Hulb, was allowed to photosynthesize caused an increased rate of photosynthesis. In addition, these same concentrations caused the dinoflagellate to release to the medium up to 50% of the carbon fixed during the 30 min period of photosynthesis used in the experiments.

October field collections from a salt water marsh maintained in the laboratory revealed stages of cell fusion and nuclear cyclosis in Amphidinium klebsii Kofoid & Swezy. Cells were observed with one enlarged nucleus and two epicones oriented at 90° to 180° relative to each other. Such a configuration is not typical of dividing cells, suggesting that these cells represent planozygotes. Over time, the two epicones fuse. The product of the fusion is a pigmented cell exhibiting the normal vegetative cell morphology but possessing two trailing flagella. These latter cells enlarge in size and exhibit nuclear cyclosis (rotation of the contents of the nucleus). This rotation has been linked to meiosis I in other dinoflagellate zygotes. Within this same field collection, cells enclosed by a smooth cyst wall composed of a single layer of electron-translucent material were observed. These encysted cells exhibited the same morphology as free-swimming forms of Amphidinium observed in the collection. Transfer ...

Nineteen sterols isolated from the cultured zooxanthella of the planktonic foraminifer Orbulina universa were identified. All main sterols are either Δ 5 -4-demethyl sterols or 4α-methyl sterols with saturated skeletons. The absence of 4α-methyl sterols with Δ 8(14)-unsaturated skeletons characteristic of Amphidinium subsp. and the presence of large amounts of E -(24 R )-27-norergosta-5,22-dien-3β-ol (24-epioccelasterol) and (23 R :24 R )-4 α ,23- dimethyl -5 α - ergostan -3 β - ol (dinostanol), which have never been detected in cultured strains of Symbiodinium microadriaticum , strongly suggests that the symbiont of O. universa is taxonomically different from all known dinoflagellate symbionts of marine invertebrates.

1. 1. The peridinin·chlorophyll a ·protein complex from Amphidinium carterae (Plymouth 450) shows spectroscopic characteristics (absorption, CD, fluorescence polarization, lifetime and energy transfer) essentially identical with peridinin·chlorophyll a ·protein complexes from Glenodinium sp., Gonyaulax polyedra and Amphidinium rhyncocephaleum . 2. 2. The apoprotein of peridinin·chlorophyll a ·protein complexes is globular, with an isotropic rotational relaxation time (e.g. 33 ns for the A. caterae peridinin·chlorophyll a ·protein), as deduced from the dynamic depolarization data. 3. 3. The chromophores (4 peridinins and 1 chlorophyll a for peridinin·chlorophyll a ·protein complexes from Glenodinium sp., G. polyedra and A. rhyncocephaleum and 9 and 2, respectively, for peridinin·chlorophyll a ·protein of A. carterae ) are accommodated in a hydrophobic crevice and not exposed to the solvent. The surface of the protein is highly hydrophilic. 4. 4. No evidence for chlorophyll-chlorophyll interactions in the A. carterae peridinin·chlorophyll a ·protein was obtained. This implies that binding crevices for two chlorophylls and half of peridinins (four to five) are located at some distance from each other. 5. 5. The peridinin·chlorophyll a ·protein complexes function as the photosynthetic antenna pigment. In addition, peridinins effectively protect chlorophyll a from photodecomposition.

Cell cycle dependent photosynthesis in the marine dinoflagellate Amphidinium carteri was studied under constant illumination and light/dark (L/D) photocycles to distinguish intrinsic cell cycle control from environmental influences. Cells were grown in constant light and on a 14:10 L:D cycle at light intensities that would yield a population growth rate of 1 doubling per day. In the former case division was asynchronous, and cells were separated according to cell cycle stage using centrifugal elutriation. Cells grown on the L:D cycle were synchronized, with division restricted to the dark period. Cell cycle stage distributions were quantified by flow cytometry. Various cell age groups from the two populations were compared as to their photosynthetic response (photosynthetic rate versus irradiance) to determine whether or not the response was modulated primarily by cell cycle constraints or the periodic L/D cycle. Cell cycle variation in photosynthetic capacity was found to be determined solely by the L/D cycle; it was not present in cells grown in constant light.

Cell division patterns in Thalassiosira weissflogii (Grun.), Hymenomonas carterae (Braarud and Fagerl), and Amphidinium carteri (Hulburl) grown in cyclostat culture were analyzed as functions of the periodic supply of light and the limiting nutrient (ammonium) and of combinations of these two factors. In all three species, division patterns were phased by light/dark cycles in N–limited as well as N–replte conditions, and also to ammonium pulses in N–limited growth in continuous light. Both the degree and timing of the cell cycle phasing varied among species. When both stimuli were present, the influence of the photocycle overrode the N–pulse stimulus in H. carterae and A. carteri. while in T. weissflogii, division was always phased by the timing of the N–pulse regardless of the phase angle between the photocycle and the pulse.

Axenic culture studies with the marine phytoplankton Skeletonema costatum, Dunaliella tertiolecta, and Amphidinium carteri demonstrated the ability of these species to adapt to and exhibit normal growth in relatively high concentrations of pulpmill effluent. Skeletonema costatum and A. carteri required a preadaptation period prior to commencement of exponential growth in high concentrations of kraft effluent (20–30%), while D. tertiolecta exhibited exponential growth in 90% kraft effluent with no requirement for preadaptation. Of six pulpmill effluent types tested, kraft was considered most inhibitory to growth, while combined kraft and newsprint effluent passed through an XAD-8 resin column was least inhibitory. The effects of the six effluent types on lag, exponential, and stationary growth phases are discussed in relation to in situ concentrations and relative ecological significance in the coastal marine environment.

A number of dinoflagellate species, previously reported to be toxic, were cultured and collected from natural blooms. Saxitoxin, detected by chemical assay and mouse bioassay, was absent in all dinoflagellates except Gonyaulax catenella and Gonyaulax excavata. Toxins other than saxitoxin were observed in Gymnodinium breve, Amphidinium carteri, Gonyaulax excavata and Gonyaulax catenella by means of fish and mouse bioassays. Most dinoflagellates tested were non-toxic. A sample of Mytilus edulis (blue mussels) collected during a red tide in Spain was found to contain an appreciable amount of a toxin which appears to be saxitoxin.

N-2-hydroxyethylpiperazine-N-2′-ethanesulfonic acid (Hepes) has been tested as an alternative to tris-(hydroxymethyl)aminoethane (Tris) for hydrogen-ion buffering of algal cultures. Hepes satisfactorily buffered both freshwater and artificial seawater media and has been used successfully to grow 25 species of microalgae from five classes. Electron microscopic fixations of Tetraselmis striata Butcher (Prasinophyceae) and Amphidinium rhyncocephalum Anissimowa (Dinophyceae) buffered by Hepes have given far superior ultrastructural preservation than fixations buffered by Tris. The substitution of Hepes for Tris allows a defined seawater medium to be used as a fixative vehicle for the first time.

Single species populations and natural populations of phytoplankton were grown in mixtures of surface sea water and deep ocean water. The yields of Phaeodactylum tricornutum and the natural species assemblages were positively correlated with the percentage of deep water in the mixture. Single species populations of Thalassiosira weissflogii and Amphidinum sp. showed yields which were positively correlated with per cent deep water at low deep water concentrations and negatively correlated at high deep water concentrations. Transition from the positive to the negative slope occurred at about 75% deep water for T. weissflogii and at about 25% deep water for Amphidinium. Populations were apparently limited by an inorganic nutrient, probably nitrogen, in the region of positive slope and by some other factor, probably organic, in the region of negative slope. The addition of EDTA increased the yields of T. weissflogii and Amphidinium in the presence of deep water and reduced lag times in the growth of the natural populations.

Five species of dinoflagellates and three microalgae of benthic habitat collected in French Polynesia were grown in unialgal state and tested for toxicity on mice and for hemolytic activity. Two diethyl ether soluble toxins (PL toxin-I, II) and one fast-acting toxin soluble in 1-butanlo (PL toxin-III) were found in Prorocentrum lima. The chromatographic behaviors of PL toxin-I and II closely resembled those of scaritoxin and ciguatoxin prepared from ciguateric fishes. Potent hemolytic substance was present in Amphidinium sp. This species was also toxic to mice. No remarkable activity was detected in the following species: Coolia monotis, Amphidinium sp.-2, and Gymnodinium sp. (dinoflagellates); Chloococcopsis sp. and Isochrysis sp. (blue-green algae); and Nitzschia panduriformis (diatom).

Distribution of nano-phytoplankton was studied during May–June 1971 in the subtropical northwestern Philippine Sea. Plankton samples were collected at various depths between 0 and 200 m. A gentle gravity filtration technique was employed to concentrate the samples. They were then examined without fixation under a microscope. The average cell number of total nano-phytoplankton was 1×104∼2×104/l, and nano-flagellate cell number often accounted for more than 90% of the total cell number of nano-phytoplankton, consisting mainly ofGymnodinium lacustre, Amphidinium sp., and unidentified small nano-flagellates. The distribution of nano-phytoplankton did not correlate with vertical profiles of chlorophylla.

The relative influence of the photoperiod and of periodic ammonium pulses in entraining the cell division cycle in nitrogen-limited cyclostat cultures differs dramatically in Hymenomonas carterae Braarud and Fagerl, Amphidinium carteri Hulburt and Thalassiosira weissflogii Grun. We examined how each species processes an NH4+ pulse at various times during the cell cycle and the L/D cycle. Rates of NH4+ uptake and changes in cellular concentrations of NH4+, free amino acids, and protein were examined after the addition of an NH4+ pulse. Depletion of NH4+ from the medium occurred earlier when the pulse was given at the beginning of the light period than at the beginning of the dark period in H. carterae and A. carteri. Depletion took longer in the T. weissflogii cultures and the kinetics were similar during both stages of the photocycle in this species. Similarly, the temporal phasing and maximum pool sizes varied with timing of the NH4+ pulse in H. carterae and A. carteri but complete assimilation was relatively rapid. More persistent pools of NH4+ and free amino acids accumulated in T. weissflogii, and the patterns of assimilation varied little as a function of the timing of the pulse with respect to the photocycle. Although nitrogen metabolism occurred rapidly in nitrogen-limited H. carterae and A. carteri, the entrainment of the cell division cycle by the photoperiod resulted in a large degree of uncoupling between completion of nitrogen assimilation and cell division. It is hypothesized that the strong entrainment of the cell division cycle of T. weissflogii by NH4+ pulses results from a relatively slow rate of nitrogen metabolism.

In experiments in a 10 m, thermally stratified seawater column, Cachonina niei crossed a 5°C gradient during a 4-m diurnal vertical migration, while Amphidinium carteri remained in the upper, isothermal, part of the water column during a 1-m diurnal vertical migration. The experiments confirm that some marine dinoflagellates have access to subthermocline nutrient pools. These same species may also exhibit spatial and temporal patchiness in response to countercurrent flow across the thermocline.

Changes in the nutrient regime of phytoplankton cells induce variable time lags before the onset of cell division (quasi-instantaneous response to more than 24 h lags), dependent mainly on the algal species and the magnitude of the nutrient pulse. The latter parameter appears to be a main controlling factor in algal growth dynamics under transient conditions, overriding other variables such as temperature, irradiance and nutritional state. The presence of such phenomena puts intrinsic limits on primary production in a variable nutrient environment because algal cells are not made up of synthetic components only (sensu Williams 1971), but also of structural and genetic material. Under these conditions, high nutrient uptake rates over short time periods do not necessarily lead to high growth rates (defined as increase in cell numbers) over comparable time scales, even ~f cell quota increase very rapidly follow~ng nutrient resupply. Data from different groups of investigators on uptake-growth coupling, internal nutrient pools, growth lag, and carbon-nitrogen uptake interactions show consistent patterns as follows. for phytoplankton in a vanable nutrient environment, 2 essential strategies emerge at the genus level. One is the 'growth' response, exhibited by the genera Durialiella and Chaetoceros, which do not accumulate internal pools of inorganic nutrients, whose uptake and growth are closely coupled, and which therefore process nutrient pulses very rapidly into new cells. The other is the 'storage' response, found in genera such as Thalassiosira or Amphidinium, which have the capability of accumulating large internal nutrient pools, present extensive uncoupling between uptake and growth, and exhibit lags in cell v the first response type would provide a competitive advantage at high frequency pulses.

Summary Normally kinetochores have three-layered structures: the inner part containing DNA, the outer part RNA, and between them a transfer area. This structure can be observed as well in higher organisms as in Protozoa. But in some Dinoflagellates such as Apodinium and most of the free-living ones (Amphidinium …) this structure is quite different. Our observations allow us to conclude that only the chromosomes which bear histones may have typically trilaminar kinetochores.

SUMMARY Acrylylcholine, choline O-sulfate, and a yet unidentified choline ester have been isolated from cells of Amphidinium carteri. Natural and synthetic acrylyl choline had approximately 1/4,000 the activity of acetylcholine and choline O-sulfate about 1/20,000 the activity on isolated Mercenaria mercenaria heart.

Changes in mean cell size, DNA and cell density were monitored at 6-h intervals for 72 h in populations of six species (eight clones) of marine dinoflagellates to determine the temporal relationships between the cell cycle events of DNA replication and cytokinesis. Batch cultures were maintained at 15 or 20°C on a 12-h light: 12-h dark photoperiod. Cell densities and size frequency distributions were determined conductimetrically and the amount of DNA within populations was measured fluorometrically. A variety of intra- and interspecific relationships were observed, ranging from parallel phasing of cell cycle processes to variations which involved the temporal uncoupling of DNA synthesis from the phased pattern of cell division which is characteristic of dinoflagellate cell cycles. Daily growth rates of individual populations varied from 0.05 (Gymnodinium nelsoni) to 2.08 (Amphidinium carteri) cell divisions day-1 and DNA doubling rates ranged from 0 to 1.14 day-1. Mean doubling rates for DNA were usually 30–40% lower than those for cells. The degree of difference in these rates and the amount of variability evident in cell cycle sequences may be major factors in determining the rate and extent of development of dinoflagellate populations in nature.

Cultures of eleven unicellular algae were grown at various values of pH between 6 and 10, obtained by varying the supply of CO 2 . In this pH range, the value of the ratio photosynthesis: respiration showed a maximum. It is suggested that the algae may be placed in three groups according to the values of the ratio at these maxima. In the first there was only Amphidinium , which gave a mean ratio of only 2.7; in the second, Chaetoceros 3.3, Chroomonas 5.3, Gymnodinium 4.0, Nitzschia sp., 5.7, and Phaeodactylum 4.0; and in the third, Biddulphia 7.3, Cylindrotheca 7.0, Dunaliella 9.1, Monochrysis 8.3, and Nitzschia closterium 9.0. The highest rates of photosynthesis were found between pH 7.1 and 7.5, except for Nitzschia closterium pH 6.3, Amphidinium pH 8.2 and Phaeodactylum pH 10.0. Most algae gave an assimilation number of ??? 400 mol O 2 ?? mol ???1 , chlorophyll a ?? h ???1 .

When grown under a 12-12 light-dark regime, Amphidinium, Biddulphia, Chaetoceros, Chroomonas, Cylindrotheca, Dunaliella, Pavlova, and Phaeodactylum had a higher photosynthetic rate and photosynthesis: respiration ratio than when grown under constant illumination. The chlorophyll content was also higher (except for Biddulphia and Chaetoceros), the assimilation number was higher (except for Pavlova), but growth was less (except for Biddulphia which showed no difference and for Amphidinium which grew faster).

The effect of irradiance on the growth rate, macromolecular composition and photosynthetic carbon metabolism of Amphidinium carteri was studied in batch culture. Growth rate increased linearly with increasing irradiance up to a maximum growth rate of 0.04 h-1 at an irradiance of 80 μEm-2s-1. In contrast to a number of other studies on both prokaryotic and eukaryotic microorganisms, ours showed that cellular content of RNA, DNA, protein and carbohydrate of A. carteri were invariant with growth rate over the range μ=0.04 to 0.007 h-1. The invariant macromolecular composition was correlated with a constant modal cell volume. Chlorophyll and lipid per cell increased with decreasing irradiance. The distribution of [14C]-bicarbonate in the major end products of photosynthesis after incubation with isotope for 14% of a doubling time showed that the percentage carbon in the chloroform (lipids and pigments) fraction increased with decreasing irradiance while that of the trichloroacetic acid soluble (carbohydrate) fractions decreased. The percentage of isotope in the trichloroacetic acid insoluble (protein) fraction and methanol: water fraction (metabolites) remained constant. Because this species, under light-limited growth, differs from other organisms so far studied, more species must be similarly examined before nucleic acid content is used as an index growth rate in the field.

SUMMARY The activity of extracted NADH-NO3− reductase was measured in the marine dinoflagellates Amphidinium carteri Hulburt and Cachonina niei Loeblich. Its activity showed a diel periodicity and was ca. twice as great at midday as at midnight. The enzyme activity was unstable, with an in vitro half-life of 2–3 h. Values of enzyme activity were low or undetectable during lag phase but paralleled the instantaneous growth rate value during log phase. Nitrate reductase activity was not found in the stationary phase of growth, but additions of NO3− resulted in enzyme activity after 24h. When A. carteri was exposed to a series of light intensities for several weeks, the division rate and enzyme activity increased with increasing light intensity up to saturating intensities. In 6 h exposures, enzyme activity decreased with decreasing light intensities below light intensities saturating division rate. Additions of NH4+ (0.5–50 μm) to A. carteri cultures decreased the amount of extractable enzyme. The in vitro activity was not inhibited by similar NH+4 concentrations.

A novel 20-membered macrolide, amphidinolide-A with antineoplastic activity has been isolated from the marine dinoflagellate Amphidinium sp. and its structure was determined to be 1 by spectral data.

A fourth cytotoxic macrolide, amphidinolide D[1], together with known amphidinolide B[2], has been isolated from a different batch of the cultured dinoflagellate Amphidinium sp., which was symbiotically associated with an Okinawan flatworm Amphiscolops sp. Two-dimensional nmr experiments including 1H-detected heteronuclear multiple-bond correlation (HMBC) resulted in the structure assignment of 1 and structure revision of the diene moiety (C-13-C-15) of amphidinolide B.

An apparatus is described for exposing phytoplankton cultures to 64 different combinations of light and temperature. The light was of a known spectral energy resembling sunlight after passage through a few metres of clear coastal sea water and was measured in the energy units of cals/cm2/min (langlies/min or ly/min). The temperature range used varied in each experiment, the range of illumination was from about 0.005 to 0.4 ly/min, the latter being equivalent to bright summer sunlight at a depth of only a few metres in the sea.The growth of five bacteria-free cultures, Dunaliella tertiolecta, Amphidinium carteri, Monochrysis lutheri, Skeletonema costatum and Thalassiosira nordenskiöldii was followed for a period of 3–5 days using a cycle of 16 hr illumination and 8 hr of darkness every 24 hr. Growth was measured by counting cell numbers and the rate constants for cell division were evaluated at standard times.The resulting growth-response curves are reported and discussed in relation to their ecological significance. Except for T. nordenskiöldii cell division was relatively insensitive to temperature over a range exceeding 10 °C. Cell division showed a "stress" response, the growth rate being more susceptible to extremes of illumination when the cells were near to the extremes of temperature for a given species and to extremes of both temperature and light if the chemical nature of the medium was unsatisfactory. At optimum temperatures there was no inhibition of cell division at intensities of 0.4 ly/min of photosynthetically active light.

1. Instances of red water occurring in Delaware Bay and due to the swarming of Amphidinium fusiforme and other dinoflagellates are described. 2. It is suggested that the characteristic color of the water which gives the phenomenon its name is due to the reddish fluorescence of the chlorophyll present in such great quantities. 3. A factor tending to hold the cells together in dense masses, once they are brought together, may be the gelatinization of the outer envelope of the active cells, not heretofore noted in this connection.

Adult Pseudocalanus elongatus have been kept in the laboratory, and fed with a variety of algal grazing media. The survival under conditions of starvation has also been determined, and in this respect, the overwintering generation has been found to differ from other generations.Isochrysis galbana, Phaeodactylum tricornutum, Gymnodinium veneficum, G. vitiligo, Chlamydomonas sp. and C. coccoides have been found to be satisfactory foods for Pseudocalanus elongatusDicrateria inornata, Nitzschia gotlandica, Amphidinium sp., Chlorella stigmatophora and Dunaliella tertiolecta were found to be unsatisfactory foods for Pseudocalanus elongatus.

The effects of DDT (2,2-bis-( p -chlorophenyl)-1, 1, 1-trichloroethane) on the growth of seven marine phytoplankters, representative of five algal divisions, were studied. At a concentration of 80 parts per billion (0.23 μm) DDT, growth of Dunaliella tertiolecta was unaffected, and there was slight, if any, influence on the development of Cyclotella nana, Thalassiosira fluviatilis, Amphidinium carteri, Coccolithus huxleyi , and Porphyridium sp. Skeletonema costatum exhibited a 9 day lag before cell division commenced, the rate of growth subsequently being the same as in the control (no DDT). A further inoculation of this culture of S. costatum into 80 parts per billion DDT gave another 9-day lag before initiation of normal growth. The ability of marine phytoplankton to metabolize DDT varied. DDE (2,2-bis-( p -chlorophenyl)-1, 1-dichloroethylene) was the only significant hexane-soluble metabolite detected. It occurred in cells of S. costatum, C. nana, T. fluviatilis and D. tertiolecta . Maximum degree of conversion was 7.5% and was based on the total DDT found in the cell-water system of 9-day D. tertiolecta cultures. The total amount of DDT recovered from cultures in 2- to 3-week experiments ranged from 63.5% for T. fluviatilis to 90.7% for S. costatum . The amount of DDT found associated with the cells, collected by centrifugation, in the cell-water system ranged from 70.8 to 99.5%. Chloroplast particles were isolated from a “resistant” species, D. tertiolecta . Noncyclic electron flow, as measured by ferricyanide reduction, was inhibited by DDT and DDE, and could explain growth inhibition in other phytoplankters. Fifty percent inhibition occurred at 20 μm DDT. Sensitivity of phytoplankton to toxic hydrophobic chlorinated hydrocarbons may be dependent upon penetration of the molecules to active sites within membranes.

Fructose diphosphate aldolase activity was examined in acetone powders and cell-free extracts of 15 photoautotrophically grown marine planktonic species belonging to 6 algal divisions as follows: Chlorophyta: Tetraselmis maculata, Dunaliella tertiolecta; Chrysophyta: Monochrysis lutheri, Isochrysis galbana, Prymnesium parvum, Coccolithus huxleyi; Bacillariophyta: Phaeodactylum tricornutum, Skeletonema costatum, Cyclotella nana; Cryptophyta: Cryptomonas sp., Rhodomonas lens, Hemiselmis virescens; Pyrrophyta: Amphidinium carteri; Cyanophyta: Anacystis marina, Agmenellum quadruplicatum. Indications of the types of aldolase (Rutter's classes) present in each alga were obtained from comparative studies of the effects of pH and of the following reagents on the activity: ethylenediamine tetraacetate, dithiothreitol, p-chloromercuriphenyl sulfonate. Type I (higher plant-animal type) aldolase only was indicated in the 2 chlorophytes, in I chrys-ophyte (M. lutheri), and in 1 bacillariophyte (P. tricornutum), while the remaining algae appeared to contain either exclusively or principally Type II (bacterial-fungal type) aldolase. The evolutionary implications of these findings are discussed.

Thirty-one species of marine unicellular algae in pure culture were tested for survival in darkness at 20 C in seawater buffered at pH 7.6–7.8 and enriched with nitrate, orthophosphate, silicate, vitamins (B12, thiamin, biotin), and trace-metal ions (chelated with ethylenediamine tetraacetate). None of the species showed any significant growth in darkness but six species [including two cyanophytes, two chlorophytes (Nannochloris oculata, Tetraselmis maculata), one rhodophyte (Porphyridium cruentum), and one diatom (Phaeodactylum tricornutum)] resumed growth in light after 24 weeks in darkness (the maximum period tested). Another chlorophyte survived 18 weeks, two chrysomonads and one cryptomonad 12–14 weeks, and most other algae (including ten diatoms) 6–8 weeks of darkness. Skeletonema costatum, Hemiselmis virescens, Coccolithus huxleyi, and Amphidinium carteri showed the lowest survival potential ranging from one to three weeks. The observed darkness-survival may have ecological relevance to th...