PIGMENTS,FATTY ACIDS,AND STEROLS OF THE TOXIC DINOFLAGELLATE GYMNODINIUM CATENATUM1

Cultures and field samples of the toxic dinoflagellate Gymnodinium catenatum Graham from Tasmania, Australia, were analyzed for pigment, fatty acid, and sterol composition. Gymnodinium catenatum contained the characteristic pigments of photosynthetic dinoflagellates, including chlorophyll a, chlorophyll c₂, and the carotenoids peridinin, dinoxanthin, diadinoxanthin, diatoxanthin, and β,β-carotene. In midlogarithmic and early stationary phase cultures, the chlorophyll a content ranged 50–72 pg · cell^?1, total lipids 956–2084 pg · cell^?1, total fatty acids 426–804 pg · cell^?1, and total sterols 8–20 pg · cell^?1. The major fatty acids (in order of decreasing abundance) were 16:0, 22:6(n-3), and 20:5(n-3) (collectively 65–70% of the total fatty acids), followed by 16:1(n-7), 18:2(n-6), and 14:0. This distribution is characteristic of most dinoflagellates, except for the low abundance (<3%) of the fatty acid 18:5(n-3), considered by some authors to be a marker for dinoflagellates. The three major sterols were 4α-methyl-5α-cholest-7-en-3β-ol, 4α,23,24-trimethyl-5α-cholest-22E-en-3β-ol (the dinoflagellate sterol, dinosterol), and 4α,23,24-trimethyl-5α-cholest-7-en-3β-ol. These three sterols comprised about 75% of the total sterols in both logarithmic and early stationary phase cultures, and they were also found in high proportions (22–25%) in natural dinoflagellate bloom samples. 4-Desmethyl sterols, which are common in most microalgae, were only present in trace amounts in G. catenatum. The chemotaxonomic affinities of G. catenatum and the potential for using specific signature lipids for monitoring toxic dinoflagellate blooms are discussed.     

Intra- and extracellular osmotic regulation in the hololimnetic Caridea and Anomura: a phylogenetic perspective on the conquest of fresh water by the decapod Crustacea

We investigate extra- and intracellular osmoregulatory capability in two species of hololimnetic Caridea and Anomura: Macrobrachium brasiliense, a palaemonid shrimp, and Aegla franca, an aeglid anomuran, both restricted to continental waters. We also appraise the sharing of physiological characteristics by the hololimnetic Decapoda, and their origins and role in the conquest of fresh water. Both species survive salinity exposure well. While overall hyperosmoregulatory capability is weak in A. franca and moderate in M. brasiliense, both species strongly hyporegulate hemolymph [Cl⁻] but not osmolality. Muscle total free amino acids (FAA) increase slowly but markedly in response to the rapid rise in hemolymph osmolality consequent to hyperosmotic challenge: 3.5-fold in A. franca and 1.9-fold in M. brasiliense. Glycine, taurine, arginine, alanine and proline constitute ≈85% of muscle FAA pools in fresh water; taurine, arginine, alanine each contribute ≈22% in A. franca, while glycine predominates (70%) in M. brasiliense. These FAA also show the greatest increases on salinity challenge. Muscle FAA titers correlate strongly (R = 0.82) with hemolymph osmolalities across the main decapod sub/infraorders, revealing that marine species with high hemolymph osmolalities achieve isosmoticity of the intra- and extracellular fluids partly through elevated intracellular FAA concentrations; freshwater species show low hemolymph osmolalities and exhibit reduced intracellular FAA titers, consistent with isosmoticity at a far lower external osmolality. Given the decapod phylogeny adopted here and their multiple, independent invasions of fresh water, particularly by the Caridea and Anomura, our findings suggest that homoplastic strategies underlie osmotic and ionic homeostasis in the extant freshwater Decapoda.     

Evaluation of crystalline amino acids,betaine and AMP as food attractants of the giant tiger prawn (Penaeus monodon)

Laboratory observations of substrate probing by the chelate walking legs (chelipeds), antennular flicking rate and maxilliped activity of the prawn Penaeus monodon were used to evaluate various chemicals at seven different concentrations between 10⁻¹M and 10⁻⁷M as feeding stimulants. Exposure to amino acids (alanine, arginine, glutamine, glycine, isoleucine, serine and taurine) and betaine resulted in higher rates of substrate probing, antennular flicking and maxilliped activity in P. monodon at higher pipette concentrations (>10⁻²M) than at lower concentrations. Least response occurred in prawns which were exposed to nucleotide, adenosine 5′-monophosphate. Glutamine, betaine and taurine were the most effective single compounds tested, and stimulated significantly higher activities (p < 0.05) in prawns at concentrations above 10⁻⁶M than did controls (seawater only).An equimolar mixture of amino acids and betaine was also found to be an effective stimulant to P. monodon at concentrations above 10⁻⁶M and continued to elicit search responses in prawns at concentrations lower than that of any of the single chemicals. Such a strong response is consistent with synergistic interactions of the mixtures. All four molt stages tested (C, D₀, D₁, D₂) were equally responsive to food attractants.     

Characterization of mycosporine‐serine‐glycine methyl ester,a major mycosporine‐like amino acid from dinoflagellates: a mass spectrometry study

Several unknown mycosporine‐like amino acids (MAAs) have been previously isolated from some cultured species of toxic dinoflagellates of the Alexandrium genus (Dinophyceae). One of them, originally called M‐333, was tentatively identified as a shinorine methyl ester, but the precise nature of this compound is still unknown. Using a high‐resolution reversed‐phase liquid chromatography mass spectrometry analyses (HPLC/MS), we found that natural populations of the red tide dinoflagellate Prorocentrum micans Ehrenberg showed a net dominance of M‐333 together with lesser amounts of other MAAs. We also documented the isolation and characterization of this MAA from natural dinoflagellate populations and from Alexandrium tamarense (Lebour) Balech cultures. Using a comparative fragmentation study in electrospray mass spectrometry between deuterated and non‐deuterated M‐333 compounds and synthesized mono and dimethyl esters of shinorine, this novel compound was characterized as mycosporine‐serine‐glycine methyl ester, a structure confirmed by nuclear magnetic resonance. These isobaric compounds can be differentiated by their fragmentation patterns in MS³ experiments because the extension and the specific site of the methylation changed the fragmentation pathway.     

Alanine and taurine transport by the gill epithelium of a marine bivalve: Effect of sodium on influx

Summary Marine mussels can accumulate amino acids from seawater into the epithelial cells of the gill against chemical gradients in excess of 5×10⁶ to 1. Uptake of both alanine and taurine into gill tissue isolated fromMytilus californianus was found to be dependent upon Na⁺ in the external solution. Uptake of these amino acids was described by Michaelis-Menten kinetics, and a reduction in external [Na⁺] (from 425 to 213mm) increased the apparent Michaelis constants (alanine, from 8 to 17 m; taurine, from 4 to 39 m) without a significant influence on theJ _max's of these processes. Fivemm harmaline, an inhibitor of Na-cotransport processes in many systems, reduced both alanine and taurine uptake by more than 95%; this inhibition appeared to be competitive in nature, with an apparentK _i of 43 m for the interaction with alanine uptake. Increasing the external [Na⁺] from 0 to 510mm produced a sigmoid activation of alanine and taurine uptake withK _Na's of approximately 325mm. The apparent Hill coefficients for this activation were 7.3 and 7.4 for alanine and taurine, respectively. These data are consistent with uptake mechanisms which require comparatively high concentrations of Na⁺ to activate transport, and which couple several Na⁺ ions to the transport of each amino acid. These characteristics, in conjunction with the previously demonstrated low passive permeability of the apical membrane to amino acids, result in systems capable of i) accumulating amino acids from seawater to help meet the nutritional needs of this animal, and ii) maintaining the high intracellular amino-acid concentrations associated with volume regulation in the gill.     

Behavioural responses of sablefish, Anoplopoma fimbria, to bait odour

A behavioural bioassay was used to determine the response threshold to squid extract of sablefish, Anoplopoma fimbria, held at three different feeding regimens. Sablefish responded to the odour of bait by changing swimming activity and turning behaviour. The response threshold to bait odour was influenced by both the amount of food eaten and the duration of food deprivation. The total concentration of amino acids in the bait extract was assumed to determine the response threshold as chemical fractionation studies have shown that this class of compounds is essential for the stimulatory capacities of food extracts. When fed to satiation (9.4% wet body weight) and tested after one day of food deprivation, the mean response threshold to total dissolved free amino acids was 4.4 × 10^?8m (range=7.6 × 10^?8 to 3.6 × 10^?8m ). When fed at 1.6-2.3% wet body weight, the threshold sensitivity had increased to a mean value of 1.8 × 10^?10m (range=8.4 × 10^?10 to 7.0 × 10^?11m ) after one day of food deprivation; after four days of deprivation, the sensitivity had increased even further to a mean value of 1.4 × 10^?11m (range=1.6 × 10^?10 to 1.4 × 10^?12m ). It was also apparent that the intensity of behavioural responses to the bait odour increased with both stimulus concentration and duration of food deprivation. These results suggest that sablefish intensify their search for prey under increased feeding motivation. The active space of a bait source was estimated from the threshold values obtained. Depending on state of food deprivation, rate of chemical release from the bait and the current velocity, maximum lengths of active space within which sablefish would exhibit food searching responses vary from 10 m to several km. Stock assessment based on catch data from baited gear will need techniques that take into account those factors influencing active space for food searching.     

Concentrations of dimethylsulphoniopropionate and activities of dimethylsulphide-producing enzymes in batch cultures of nine dinoflagellate species

Dinoflagellates are recognised as one of the major phytoplankton groups that produce dimethylsulphoniopropionate (DMSP), the precursor of the marine trace gas dimethylsulphide (DMS) which has climate-cooling potential. To improve the prospects for including dinoflagellates in global climate models that include DMSP-related processes, we increased the data base for this group by measuring DMSP, DMS-producing enzyme activity (DPEA), carbon, nitrogen and Chl a in nine clonal dinoflagellate cultures (1 heterotrophic and 8 phototrophic strains). Growth rates ranged from 0.11 to 1.92?day^?1 with the highest value being for the heterotroph Crypthecodinium cohnii. Overall, we observed two orders of magnitude variability in DMSP content (11–364?mM) and detected DPEA in five of the nine strains (0.61–59.73?fmol?cell^?1?h^?1). Cell volume varied between 454 and 18,439?μm³ and whilst C and N content were proportional to the cell volume, DMSP content was not. The first DMSP measurements for a dinoflagellate from Antarctic waters and a species with diatom-like plastids are included. Lower DMSP concentrations were found in three small athecate species and a dinoflagellate with haptophyte-like plastids. The highest concentrations and production rates tended to be in globally distributed dinoflagellates and the heterotroph. Photosynthetic species that are distributed in temperate to tropical waters showed low DMSP concentrations and production rates and the polar representative showed moderate concentration and a low production rate. Estuarine species had the lowest concentrations and production rates. These data should help refine the inclusion of dinoflagellates as a functional group in future global climate models.     

EFFECTS OF SMALL‐SCALE TURBULENCE ON NET GROWTH RATE AND SIZE OF TEN SPECIES OF MARINE DINOFLAGELLATES1

Field observations and results from previous laboratory studies on the effects of turbulence on dinoflagellates have led to a paradigm in phytoplankton ecology that dinoflagellate growth is negatively affected by turbulence. To test the paradigm, 10 species of autotrophic dinoflagellates were exposed to quantified three‐dimensional turbulence generated by vertically oscillating cylindrical rods in 20‐L rectangular culture tanks. Turbulence was quantified in the tanks (as the turbulent energy dissipation rate, ε ) using an acoustic Doppler velocimeter. Dinoflagellates were exposed to two turbulence treatments: high turbulence ( ε ～ 10 ^{? 4} m²·s ^{? 3}), low turbulence ( ε ～ 10 ^{? 8} m²·s ^{? 3}), and an unstirred control. In accord with the paradigm, Ceratium fusus (Ehrenberg) Dujardin had lower net growth rates in high turbulence, whereas Pyrocystis noctiluca Murray ex Haeckel and Ceratium tripos (O. F. Müller) Nitzsch did not increase their numbers in high turbulence. However, Alexandrium tamarense (Lebour) Balech, Pyrocystis fusiformis Wyville‐Thomson ex Murray, Alexandrium catenella (Whedon and Kofoid) Balech, and a Gyrodinium sp. Kofoid and Swezy were apparently unaffected by turbulence and had the same net growth rates across all turbulence treatments. Contradicting the paradigm, Lingulodinium polyedrum (Stein) Dodge (= Gonyaulax polyedra), Gymnodinium catenatum Graham, and Alexandrium fundyense Balech had increased net growth rates in high turbulence treatments. Cross‐sectional area (CSA) varied little across turbulence treatments for 8 of 10 dinoflagellate species tested, CSA in C. fusus increased when net growth rate decreased in high turbulence, and, conversely, CSA decreased in L. polyedrum when net growth rate increased in high turbulence.     

Honeydew amino acids in relation to sugars and their role in the establishment of ant-attendance hierarchy in eight species of aphids feeding on tansy (Tanacetum vulgare)

Abstract. The ratio of the concentration of honeydew total amino acids to total sugars in the honeydew of eight species of aphids, all feeding on tansy, Tanacetum vulgare (L.), was determined and correlated with honeydew production and ant‐attendance. The honeydew of the five ant‐attended aphid species [Metopeurum fuscoviride (Stroyan), Trama troglodytes (v. Hayd), Aphis vandergooti (Börner), Brachycardus cardui (L.), Aphis fabae (Scopoli)] was rich in total amino acids, ranging from 12.9 to 20.8 nmol µL^?1 compared with the unattended aphid Macrosiphoniella tanacetaria (Kalt.) with only 3 nmol µL^?1. Asparagine, glutamine, glutamic acid and serine (all nonessential amino acids) were the predominant amino acids in the honeydew of all species. The total concentration of amino acids in the phloem sap of tansy was much higher (78.7 nmol µL^?1) then in the honeydew samples, and the predominant amino acids were glutamate (34.3%) and threonine (17.7%). A somewhat unexpected result was the finding that those aphid species with the highest total amino acid concentration in the honeydew always had the highest concentration of sugars. The lowest amino acid–sugar combined value was 104–28.8 nmol µL^?1 in the non ant‐attended species M. tanacetaria, and the highest value was an average of 270–89.9 nmol µL^?1 for the three most intensely attended aphid species M. fuscoviride, A. vandergooti and T. troglodytes. There is no evidence that any single amino acid or group of amino acids in the honeydew acted as an attractant for ant‐attendance in these eight aphid species. The richness of the honeydew (rate of secretion × total concentration of sugars), along with the presence of the attractant sugar melezitose, comprised the critical factors determining the extent of ant‐attendance of the aphids feeding on T. vulgare. The high total amino acid concentration in sugar‐rich honeydews can be explained by the high flow‐through of nutrients in aphids that are particularly well attended by ants.     

Release of Endogenous Amino Acids from the Striatum from Developing and Adult Mice in Ischemia

In most other studies the release of amino acid neurotransmitters and modulators in vitro has been studied mostly using labeled preloaded compounds. For several reasons the estimated release may not reliably reflect the release of endogenous compounds. The magnitudes of the release cannot thus be quite correctly estimated using radioactive labels. The basal and K⁺-evoked release of the neuroactive endogenous amino acids γ-aminobutyrate (GABA), glycine, taurine, glutamate and aspartate was now studied in slices from the striatum from 7-day-old to 3-month-old mice under control (normoxic) and ischemic conditions. The release of alanine, threonine and serine was assessed as control. GABA and glutamate release was much greater in 3-month-old than in 7-day-old mice, whereas with taurine the situation was the opposite. Ischemia markedly enhanced the release of all these three amino acids. The release of aspartate and glycine was markedly enhanced as well whereas no effects were discernible in the release of glutamine, alanine, serine and threonine. K⁺ stimulation (50 mM) enhanced the release of GABA, glutamate, taurine, aspartate and glycine in most cases, except with taurine in 3-month-old mice under the ischemic conditions and with aspartate in 7-day-old mice under the control conditions. K⁺ stimulation did not affect the release of glutamine, alanine, serine or threonine. The results on endogenous amino acids are qualitatively similar to those obtained in our earlier experiments with labeled preloaded amino acids. In conclusion, in developing mice only inhibitory taurine is released in such amounts that may counteract the harmful effects of excitatory amino acids in ischemia.     

THE TOXIC DINOFLAGELLATE GYMNODINIUM CATENATUM (DINOPHYCEAE) REQUIRES MARINE BACTERIA FOR GROWTH1

Interactions with the bacterial community are increasingly considered to have a significant influence on marine phytoplankton populations. Here we used a simplified dinoflagellate‐bacterium experimental culture model to conclusively demonstrate that the toxic dinoflagellate Gymnodinium catenatum H. W. Graham requires growth‐stimulatory marine bacteria for postgermination survival and growth, from the point of resting cyst germination through to vegetative growth at bloom concentrations (10³ cells · mL^?1). Cysts of G. catenatum were germinated and grown in unibacterial coculture with antibiotic‐resistant or antibiotic‐sensitive Marinobacter sp. DG879 or Brachybacterium sp., and with mixtures of these two bacteria. Addition of antibiotics to cultures grown with antibiotic‐sensitive strains of bacteria resulted in death of the dinoflagellate culture, whereas cultures grown with antibiotic‐resistant bacteria survived antibiotic addition and continued to grow beyond the 21 d experiment. Removal of either bacterial type from mixed‐bacterial dinoflagellate cultures (using an antibiotic) resulted in cessation of dinoflagellate growth until bacterial concentration recovered to preaddition concentrations, suggesting that the bacterial growth factors are used for dinoflagellate growth or are labile. Examination of published reports of axenic dinoflagellate culture indicate that a requirement for bacteria is not universal among dinoflagellates, but rather that species may vary in their relative reliance on, and relationship with, the bacterial community. The experimental model approach described here solves a number of inherent and logical problems plaguing studies of algal‐bacterium interactions and provides a flexible and tractable tool that can be extended to examine bacterial interactions with other phytoplankton species.     

PHOTOINHIBITION OF MECHANICALLY STIMULABLE BIOLUMINESCENCE IN THE HETEROTROPHIC DINOFLAGELLATE PROTOPERIDINIUM DEPRESSUM (PYRROPHYTA)1

Photoinhibition of mechanically stimulable bioluminescence (MSL) in the heterotrophic dinoflagellate Protoperidinium depressum Bailey was investigated using samples collected from the Massachusetts and southern Texas coasts. The times for both photoinhibition of MSL (ca. 10 min) and dark recovery from photoinhibition of MSL (ca. 45 min) in this species were similar to those reported for autotrophic dinoflagellates. The degree of photoinhibition of MSL was a linear function of the logarithm of photon flux density (PFD). The threshold PFDs for the photoinhibition of MSL were 0.02, 0.6, and 21 μmol photons · m^?2· s^?1 for broad-band blue, green, and red light, respectively. These PFDs are lower than those required for photoinhibition of MSL by the autotrophic dinoflagellates Pyrocystis lunula and Ceratium fusus. We speculate that photosynthetic pigments in autotrophic dinoflagellates shield the photoreceptor that causes photoinhibition of MSL, thus lowering the sensitivity of these dinoflagellates to light. When field-collected P. depressum were kept in the laboratory without growth for a week, photoinhibition of MSL's sensitivity to light increased progressively along with 1) a decrease in its bioluminescence capacity (BCAP), 2) a decrease in the ratio of MSL to BCAP (MSL/BCAP), and 3) a decrease in the orange pigmentation (probably carotenoid) of the dinoflagellate. The action spectrum for photoinhibition of MSL in P. depressum was characterized primarily with a broad peak in the blue extending into the green. We suggest that carotenoid was not a photoreceptor for the photoinhibition of MSL in P. depressum because the peak of the action spectrum was too broad and extended too far into the green part of the spectrum, and because the orange pigment present decreased as photoinhibition of MSL became more sensitive to light.     

CHEMOSENSORY RESPONSES OF THE SYMBIOTIC DINOFLAGELLATE SYMBIODINIUM MICROADRIATICUM (DINOPHYCEAE)1

Motile Symbiodinium microadriaticum (Freudenthal 1962) were attracted to a variety of nitrogen-containing compounds, including ammonium, nitrate, urea and some amino acids. No chemosensory response to phosphate, sulphate, vitamins, trace metals or sugars was evident. Motile algae responded to concentrations of ammonium, nitrate, and urea at least as low as 10^?6 M. High concentrations (≥ 10^?2 M) of ammonium appeared to inhibit attraction of motile algae. Calculations using ammonium release rates from various aposymbiotic hosts suggest that motile S. microadriaticum can respond to released ammonium ca. 1 cm from the source. Cultured algae were not attracted to combined nitrogen cues for at least 2 days after inoculation into seawater with dissolved combined low nitrogen. Algae freshly isolated from starved animals were normally motile the day following isolation and attracted to ammonium and nitrate when maintained in seawater containing < 1 μM ammonium and nitrate. The algae lost their ability to orient to nitrogen attractants the day after incubation into culture medium containing high levels of ammonium and nitrate. These results suggest that chemosensory behavior is suppressed when nutrients are present in the ambient medium or are stored by the alga. There were few differences in chemosensory abilities in different strains of S. microadriaticum to the attractants assayed, suggesting that selection for a particular strain by a host species may not be due to differential chemosensory ability or cues. However, the absence of chemical attraction of motile S. microadriaticum to infected hosts may act to preserve strain selection occurring at other steps in the infection process of aposymbiotic hosts.     

Nutrients,Signals, and Photosynthate Release by Symbiotic Algae (The Impact of Taurine on the Dinoflagellate Alga Symbiodinium from the Sea Anemone Aiptasia pulchella)

Exogenous concentrations of 10 [mu]M to 1 mM of the nonprotein amino acid taurine stimulated photosynthate release from the dinoflagellate alga Symbiodinium, which had been freshly isolated from the sea anemone Aiptasia pulchella. Photosynthate release, as induced by taurine and animal extract, was metabolically equivalent at both concentrations in that they (a) stimulated photosynthate release to the same extent and (b) induced the selective release of photosynthetically derived organic acids. A complex mixture of amino acids at 75 mM also promoted photosynthate release, but the release rate was reduced by 34% after the omission of taurine (3 mM) from the mixture, suggesting that much of the effect of amino acids was largely attributable to taurine. Exogenous 14C-labeled taurine was taken up by the cells, and more than 95% of the internalized 14C was recovered as taurine, indicating that taurine-induced photosynthate release was not dependent on taurine metabolism. Both taurine uptake and taurine-induced photosynthate release by Symbiodinium exhibited saturation kinetics, but with significantly different Km values of 68 and 21 [mu]M, respectively. The difference in Km values is compatible with the hypothesis that Symbiodinium has a taurine signal transducer that is responsible for photosynthate release and is distinct from the taurine transporter.     

PLANKTONIC SARCODINES: MICROHABITAT FOR OCEANIC DINOFLAGELLATES1

Two morphologically distinct species of free-swimming dinoflagellates belonging to the genus Gyrodinium utilize the spine and rhizopodial environments of planktonic foraminifera and colonial radiolaria as microhabitats. Up to 84% of the sarcodines examined in a given population were associated with these dinoflagellates at densities up to 20,000 cells per sarcodine in some radiolarian colonies. Both dinoflagellate species possess chloroplasts, indicating they are capable of autotrophy. ¹⁴C-labelling experiments with the radiolarian-associated dinoflagellate demonstrate that it can take up inorganic carbon under both light and dark conditions. Ultrastructural evidence suggests the foraminiferal dinoflagellate may be capable of phagotrophy. Hence, these algae should be considered mixotrophs. An unusual cytoplasmic extension used for attachment and possibly feeding occurs in the foraminiferal-associated Gyrodinium and is documented with electron microscopy. Ultrastructural examination suggests this organelle may be hydrostatically controlled and may be an extension of the sac pusule.     

Amino acid requirements for growth of the rabbit blastocyst in vitro

Ten amino acids, namely, arginine, histidine, lysine, tryptophane, methionine, phenylalanine, leucine, valine, threonine and serine were indispensable for growth of rabbit blastocysts in vitro; others were nonessential. Of all the essential amino acids, arginine and lysine were required in relatively high concentrations, 10^?2 M and 10^?3 M, respectively, for optimum growth. Complete omission of the non-essential amino acids from the medium markedly reduced blastocyst growth. Interaction between serine and glycine demonstrated a partial sparing action on serine by glycine, similar to that observed between methionine and cysteine. The amino acid composition of a culture medium capable of providing continuous and consistent growth of rabbit blastocysts in vitro is described.     

THE FREE AMINO ACIDS OF HUMAN SPINAL FLUID DETERMINED BY ION EXCHANGE CHROMATOGRAPHY

(1) The free amino acids in human CSF from eighteen subjects have been determined. The analyses were performed on 0-75 ml of CSF by an ion exchange chromatographic method which is capable of detection to the 10^?10 mole level. (2) The amino acids always found in readily detectable amounts were: taurine, threonine, serine, glutamine, glutamic acid, citrulline, glycine, alanine, α-NH₂-n- butyric acid, valine, methionine, isoleucine, leucine, tyrosine, phenylalanine, ethanolamine, ornithine, lysine, histidine and arginine. Urea was present. Aspartic acid and cystine, though always present, occurred in small or trace amounts. Proline was found in four cases and tryptophan in thirteen cases. In addition, twelve unknown peaks were nearly always evident in every chromatogram. (3) Filtrates 10 times more concentrated than those used regularly were prepared from pooled CSF and analysed. These analyses clearly confirmed the presence of those amino acids which were normally in very low concentration and they also served to distinguish the twelve unknown compounds from confusion with baseline artifacts. (4) The distribution of free amino acids in CSF was different from their distribution in blood plasma. (5) Despite a variety of neurological conditions and a wide age span few marked deviations were found in any of the amino acid concentrations.     

THE FATTY ACID AND STEROL COMPOSITION OF FIVE MARINE DINOFLAGELLATES

The fatty acid and sterol compositions of five species of marine dinoflagellates (Scrippsiella sp. Symbiodinium microadriaticum Freud, Gymnodinium sp., Gymnodinium sanguineum Hirasaki, and Fragilidium sp.) are reported. All contained the major fatty acids that are considered common in dinoflagellates, but the proportions were quite variable, and some species contained low contents of some polyunsaturated fatty acids. Concentration ranges for the major fatty acids were: 16:0 (9.0%–24.8%), 18:4(n-3) (2.5%–11.5%), 18:5(n-3) (7.0%–43.1%), 20:5(n-3) (EPA) (1.8%–20.9%), and 22:6(n-3) (DHA) (9.9%– 26.3%). Small amounts of novel very-long-chain highly unsaturated C₂₈ fatty acids occurred in all species. Each dinoflagellate contained a complex mixture of 4-methyl sterols and 4-desmethyl sterols. Four species contained cholesterol, although the amounts were highly variable (from 0.2% of total sterols in Scrippsiella sp. to 45.6% in Fragilidium sp.). All but G. sanguineum contained the 4-methyl sterol dinosterol, and all species contained sterols lacking a double bond in the ring system (i.e. stanols); in Scrippsiella sp. cholestanol composed 24.3% of the total sterols. Other common features of the 4-methylsterol profiles were the presence of 23,24-dimethyl alkylation and unsaturation at Δ²² in the side chain. In Scrippsiella sp., four steroidal ketones were identified: cholestanone, dinosterone, 4α,23,24-trimethyl-5α-cholest-8(14)-en-3-one, and dinostanone. The structures of these corresponded to the major sterols in this species, suggesting that the sterols and steroidal ketones are biosynthetically linked. Steroidal ketones were not detected in the other species. Although fatty acid profiles can be used to distinguish among algal classes, they were not useful for differentiating among dinoflagellate species. In contrast, whereas some taxonomic groupings of dinoflagellates display similar sterol patterns, others, such as the gymnodinoids studied here, clearly do not. The combination of fatty acid, sterol, and steroidal ketone profiles may be useful complementary chemotaxonomic tools for distinguishing morphologically similar species. The identification of steroidal ketones supports earlier suggestions that certain dinoflagellates might be a significant source of such components in marine environments.     

ACTIVE GROWTH OF THE OCEANIC DINOFLAGELLATE CERATIUM TERES IN THE CARIBBEAN AND SARGASSO SEAS ESTIMATED BY CELL CYCLE ANALYSIS1

The growth rate of an oceanic dinoflagellate, Ceratium teres Kofoid, was investigated in the Sargasso and Caribbean Seas from September 1989 to July 1990 using the cell cycle analysis method. Estimated growth rates ranged from 0.29 to 0.58 day^?1 and were 1.5–7.2 times higher than generally accepted rates for oceanic dinoflagellates. The higher rates in this report were mainly due to an improvement in techniques that determine the duration of a terminal cell cycle phase in situ. The day-to-day variation in growth rates was surprisingly small, but, from long-term measurements, a weak correlation was found among temperature, daily irradiance, and seasonal growth rate. The calculated species-specific primary production ranged from 0.5 to 1.8 mg C·m^?2·day^?1, about 1% of the estimated total production. Ceratium teres may be an important carbon source at the base of the grazing food chain.