SYNUROPHYCEAE CLASSIS NOV., A NEW CLASS OF ALGAE

The silica-scaled algae (Synuraceae, Chrysophyceae sensu lato) are compared to other Chrysophyceae, Phaeophyceae and Bacillariophyceae with occasional comparisons to other chlorophyll c-containing algae, scaled protozoa and oomycete fungi. The silica-scaled algae have several unique characters which separate them from the above groups and based upon these differences a new order, Synurales ord. nov., and a new class, Synurophyceae class. nov., are described. The major distinguishing characters of the Synurophyceae class. nov. are: they have chlorophylls a and c₁ but lack chlorophyll c₂; their flagellar apparatus includes a microtubular root that loops around two parallel flagella and a flagellar root system which occurs in four absolute orientations; the photoreceptor consists of paired flagellar swellings which are not associated with the cell membrane and chloroplast; no eyespot is present; the nuclear envelope is not or is only weakly associated with the chloroplast endoplasmic reticulum. The Synurophyceae class. nov. are about equally distinct from the Chrysophyceae sensu stricto, Phaeophyceae and Bacillariophyceae when the class level characters are compared. Although the Phaeophyceae have a long history of being placed by themselves in the division Phaeophyta, and the Bacillariophyceae and Chrysophyceae have recently been placed alone in the Bacillariophyta and Chrysophyta, respectively, the similarities found among these classes suggest these algae are not so distinct that they require separate divisions. Tentatively, therefore, the Synurophyceae are placed in the division Phaeophyta along with the Bacillariophyceae and Chrysophyceae sensu stricto.     

THE OCCURRENCE OF CHLOROPHYLL C1 AND C2 IN ALGAE1

Forty-two species of chlorophyll c-containing algae (diatoms, dinoflagellates, chrysomonads, haptophytes, cryptomonads and xanthophytes) were examined for their content of chlorophyll c₁ and c₂. This work, and recent studies on c₁/c₂ distribution in the literature (total 86 species), show that chlorophyll c₂ is universal to all algae examined. Chlorophyll c₁ occurs in addition to c₂ in brown seaweeds, diatoms, chrysomonads, haptophytes (coccolithophorids) xanthophytes and the, fucoxanthin-containing dinoflagellates; c₂ only occurs in dinoflagellates and cryptomonads. Two exceptions to the generalizations are one dinoflagellate and one cryptomonad containing c₁ in addition to c₂ No explanation can be offered on present knowledge for these exceptions. No alga was found containing only chlorophyll c₁. Chlorophyll c, far from being a minor accessory chlorophyll, occurred in amounts almost equal to chlorophyll a(some diatoms and dinoflagellates) or ranged from 50 to 20% of the chlorophyll a (diatoms, dinoflagellates, chrysomonads, cryptomonads, browns). Xanthophytes, however, contained only trace amounts of chlorophyll c with ratios of chlorophyll a:c ranging from 55:1 to 116:1 on a weight basis. In those algae with both chlorophyll c components, c₁ and c₂, occurred either in equal amounts, or chlorophyll c₂was twice the c₁ content.     

ULTRASTRUCTURE AND PIGMENTS OF TWO STRAINS OF THE PICOPLANKTONIC ALGA PELAGOCOCCUS SUBVIRIDIS (CHRYSOPHYCEAE)1

The organelle ultrastructure and photosynthetic pigments of a new isolate of the picoplanktonic alga Pelagococcus subviridis Norris from the East Australian Current was compared with the North Pacific Ocean type species. No differences in the ultrastructure of the two isolates were observed. Mitosis was studied in detail in the Australian strain, and showed two unusual features: the de novo appearance of centrioles prior to mitosis, and the formation of a small, extra-nuclear spindle. The major carotenoids in both strains were fucoxanthin and a 19′-butanoyloxyfucoxanthin-like pigment, with diadinoxanthin and diatoxanthin as secondary pigments. Several minor carotenoids have not yet been identified. In addition to chlorophylls a and c₂, a new chlorophyll c derivative (chlorophyll c₃), present in both strains, was separated by high-performance thin-layer chromatography (HPTLC). The Australian isolate, unlike the type material, showed no evidence of chlorophyllase activity during cell harvest and extraction. While the pigment composition suggests affinities with certain newly examined prymnesiophytes, organelle ultrastructure indicates Pelagococcus to be a member of the Chrysophyceae. Mitosis is, however, atypical of both Prymnesiophyceae and Chrysophyceae, and if this picoplanktonic alga is to be retained in the Chrysophyceae it must be seen as a most unusual member.     

PHOTOSYNTHETIC PIGMENTS IN FIFTY-ONE SPECIES OF MARINE DIATOMS1

The photosynthetic pigments of 51 species (71 isolates) of tropical and sub-tropical diatoms from 13 out of 22 families were examined. These were the Thalassiosiraceae, Melosiraceae, Coscinodiscaceae, Rhizosoleniaceae, Biddulphiaceae, Chaetoceraceae, Lithodesmiaceae, Eupodiscaceae, Cymatosiraceae, Diatomaceae, Naviculaceae, Nitzschiaceae and Phaeodactylinaceae. Pigments were analyzed by cellulose and polyethylene thin-layer chromatography (TLC) and reverse-phase high-performance thin-layer chromatography (HPTLC). All species contained chlorophylls a and c₂ and the carotenoids carotene, fucoxanthin, diatoxanthin and diadinoxanthin. In addition, 14 species (20 isolates) contained one or more of four minor carotenoids, which were not identified further. One species, Thalassiothrix heteromorpha, contained small amounts of a 19′-butanoyloxyfucoxanthin-like pigment, in addition to fucoxanthin. Chlorophyll c₂ was present in all the diatoms tested and occurred together with chlorophyll c₁ in 88% of them. The presence of both chlorophylls c₁ and c₂ therefore can no longer be considered a universal characteristic of the diatom class. Where chlorophyll c₁ was absent or occurred in trace amounts only (8 species, 11 isolates), it was usually replaced by a new chlorophyll c pigment designated chlorophyll c₃, recently characterized from several prymnesiophytes and one chrysophyte. Exceptions were Nitzschia closterium (CS-114), which contained only chlorophyll c₂, and Nitzschia bilobata (CS-47), which contained all three chlorophylls (c₁, c₂ and c₃) in approximately equal amounts. Five species that contained chlorophylls c₁ and c₂ also contained chlorophyll c₃ in trace quantities Quantitative pigment analyses of the 71 isolates showed that chlorophyll concentrations ranged from 0.02 μg. 10⁶ cells^?1 in the smallest diatom, Extubocellulus spinifer, to 174.4 μg. 10⁶ cells^?1 in one of the largest diatoms, Coscinodiscus sp. under the standard growth conditions used. The mean molar ratio of chlorophyll a:c in the 72 isolates was 3.33, with a range of 1.65–7.25. The close similarity between diatom and prymnesiophyte pigmentation was confirmed. Each class has three patterns of pigmentation: viz species with chlorophylls c₁ and c₂ and‘true’fucoxanthin, species with chlorophylls c₃ and c₂ and‘true’fucoxanthin, and species with chlorophylls c₃ and c₂ and fucoxanthin derivatives.     

SEPARATION OF CHLOROPHYLLS c1c2, AND c3 OF MARINE PHYTOPLANKTON BY REVERSED-PHASE-C18-HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY1

We separated chlorophylls c₁ c₂, and c₃ of marine phytoplankton together with other pigments by a modification of the commonly applied reversed-phase-C18-high-performance liquid chromatography (RP-C18-HPLC) method. However, the chlorophyll c-like pigment 2,4, Mg-divinylpheoporphyrin as monomethyl ester, co-eluted with chlorophyll c₁. The method involves optimization of the mobile phase by using a very high ion strength solvent in combination with a high carbon loaded RP-C18 column. Fingerprints of the various taxonomic groups of algae can thus be developed in a single run, including separation of the carotenoids lutein and zeaxanthin.     

Studies on generaMallomonas andSynura,and other plankton in freshwater with the electron microscope VIII. On three new species of chrysophyceae

Three new species (Chrysophyceae) which belong to the Torquata group of the genusMallomonas, to the Spinosa group of the genusSynura, and to the genusOhromonas were found from freshwater in the North-East of Japan by the aid of an electron microscope. They were namedMallomonas recticostata, Synura mammillosa, andOchromonas diademifera, respectively. The characteristics of the three new species are described here.     

CHLOROPLAST PIGMENT PATTERNS IN DINOFLAGELLATES1

The chlorophylls and carotenoids of 22 species of dinoflagellates were analysed by thin layer chromatography, using 2-dimensional sucrose plates, and 1-dimensional polyethylene plates for chlorophylls c₁ and c₂. Peridinin was the major carotenoid in 19 of the species, while fucoxanthin was the major carotenoid in 3. In the peridinin-containing species, 5 carotenoid fractions, constituting more than 95% of the total carotenoids, were always present. These were peridinin (± neo-peridinin), averaging 64% of the total carotenoid, diadinoxanthin, dinoxanthin, β-carotene and a polar, unidentified pink xanthophyll. Six other carotenoid fractions occurred in minor or trace quantities among the species, but were not identified. Two of these had, a wide distribution; the other 4 were restricted to one or 2 species. The chlorophyll content of the dinoflagellate cultures ranged from 1–141 μg chlorophyll a + c/10⁶ cells, a pattern which was broadly correlated with cell size. In the peridinin-containing species the ratio of chlorophyll a to c on a molar basis was approximately 2 (range 1.60–4.39); in the fucoxanthin-containing species this ratio was approximately 4 (range 2.65–5.73). Both chlorophylls c₁ and c₂ occurred in the fucoxanthin-containing dinoflagellates, and only chlorophyll c₂ (one exception) occurred in the peridinin-containing dinoflagellates. These patterns of chlorophyll c and major carotenoid correspond to patterns previously observed in the Pyrrhophyta and the Chrysophyta, suggesting different phylogenetic origins for the “dinoflagellate” chloroplasts.     

PIGMENTS OF THE DINOFLAGELLATE PERIDINIUM BALTICUM AND ITS PHOTOSYNTHETIC ENDOSYMBIONT1

An examination of the pigments of the binucleate dinoflagellate Peridinium balticum (Levander) Lemmerman revealed the presence of chlorophylls a, c₁ and c₂ and the carotenoids: fucoxanthin (most abundant), diadinoxanthin, diatoxanthin, an unidentified fucoxanthin-like xanthophyll, β-carotene, γ-carotene and astaxanthin. A comparison of the pigments of P. balticum and P. foliaceum (Stein) Biecheler, also a binucleate dinoflagellate, demonstrated similar compositions. However P. balticum lacked the β-carotene precursors (e.g. phytoene) which accumulated outside the chloroplast in P. foliaceum. This study indicates that P. balticum and P. foliaceum are closely related; each species is a heterotrophic dinoflagellate with a photosynthetic endosymbiont taxonomically affiliated with the Chrysophyta (Chrysophyceae or Bacillariophyceae).     

A PHYTOL-SUBSTITUTED CHLOROPHYLL C FROM EMILIANIA HUXLEYI (PRYMNESIOPHYCEAE)1

A nonpolar chlorophyll c-like pigment was isolated by semi-preparative high performance liquid chromatography from the coccolithophorid Emiliania huxleyi (Lohm.) Hay and Mohler. The visible absorption spectrum of this pigment was similar to that of chlorophyll c₂. However, its nonpolar chromatographic properties were quite different from those of the relatively polar chlorophylls c₂ and c₃ in E. huxleyi and similar to those of chlorophyll a. Analyses by gas chromatography and gas chromatography-mass spectrometry showed that the nonpolar character of this new chlorophyll c was due to the presence of phytol, most likely on the acid side chain of the porphyrin macro-cycle. This is the first example of a phytol-substituted chlorophyll c-like pigment.     

ALGAE CONTAINING CHLOROPHYLLS a + c ARE PARAPHYLETIC: MOLECULAR EVOLUTIONARY ANALYSIS OF THE CHROMOPHYTA

Sequence comparisons of small subunit ribosomal RNA coding regions from 12 chlorophylls a + c-containing algae were used to infer phylogenetic relationships within the Chromophyta. Three chromophyte lines of descent, delineated by the Bacillariophyceae, the Phaeophyceae/Xanthophyceae, and the Chrysophyceae/Eustigmatophyceae/Synurophyceae are members of a complex evolutionary assemblage, which also includes representatives of the Oomycota (“lower” fungi). Maximum parsimony and distance matrix methods demonstrate a common evolutionary history for these lineages but their relative branching order could not be determined. Other algal species with chlorophylls a + c, including dinoflagellates and prymnesiophytes, are not members of this complex assemblage. Dinoflagellates are specifically related to apicomplexans and ciliates, and the prymnesiophyte, Emiliania huxleyi, represents an independent photosynthetic lineage that separated from other eukaryotes during the nearly simultaneous divergence of plants, animals, fungi, and a number of other protist lineages. The small subunit rRNA phylogenies of chromophytes/oomycetes were compared to those derived from comparisons of ultrastructural characters. Only tubular, tripartite mastigonemes (flagellar hairs) characterized all studied taxa of chromophytes/oomycetes as a monophyletic assemblage.     

PHOTOSYNTHETIC LIGHT-HARVESTING FUNCTION OF VIOLAXANTHIN IN NANNOCHLOROPSIS SPP. (EUSTIGMATOPHYCEAE)1

Whole cell absorption spectra of the Eustigmatophycean algae Nannochloropsis salina Bourrelly and Nannochloropsis sp. reveal the presence of a distinct absorption peak at 490 nm. The lack of chlorophylls b and c in these species indicates that this peak must be attributed to carotenoid absorption. In vivo fluorescence excitation spectra for chlorophyll a emission show a corresponding maximum at 490 nm. This peak is more clearly resolved than carotenoid maxima in other algal classes due to the absence of accessory chlorophylls. The carotenoid composition of the two Nannochloropsis species shows that violaxanthin and vaucheriaxanthin are the main contributors to 490 nm absorption. Violaxanthin accounts for approximately 60% of the total carotenoid in both clones. We conclude that light absorption by violaxanthin, and possibly by vaucheriaxanthin, is coupled in energy transfer to chlorophyll a and that violaxanthin is the major light-harvesting pigment in the Eustigmatophyceae. This is the first report of the photosynthetic light-harvesting function of this carotenoid.     

A NEW PHYLOGENY FOR CHROMOPHYTE ALGAE USING 16S-LIKE RRNA SEQUENCES FROM MALLOMONAS PAPILLOSA (SYNUROPHYCEAE) AND TRIBONEMA AEQUALE (XANTHOPHYCEAE)1

The 16S-like ribosomal RNA genes from Mallomonas papillosa Harris et Bradley (Synurophyceae) and Tribonema aequale Pascher (Xanthophyceae) were sequenced and compared to those of other eukaryotes. Mallomonas is closely related to Ochromonas (Chrysophyceae) and supports the general hypothesis of a close phylogenetic relationship between the Synurophyceae and Chrysophyceae. Tribonema is specifically related to Costaria costata (C. A. Agardh) Saunders (Phaeophyceae) demonstrating an unexpected phylogenetic relationship between the Xanthophyceae and Phaeophyceae. Distance and parsimony analysis place these four chromophyte genera in a complex evolutionary assemblage that includes the Bacillariophyceae and Oomycetes but excludes the Dinophyceae. The close relationship between the chromophyte algae and the Öomycete fungi supports the hypothesis that protists with tripartite hairs form a natural assemblage.     

Chrysophyceae from freshwater localities near Nijmegen,The Netherlands

Scale-bearing Chrysophytes from nine freshwater bodies in the surroundings of Nijmegen, The Netherlands, have been studied using both scanning and transmission electron microscope.A comparison has been made with a previous study in the northern part of The Netherlands by Wujek & van der Veer (1976).This paper deals with three species of Mallomonopsis, twenty-one species and one variety of Mallomonas, four species and three formae of Synura, one species of Chrysosphaerella, two species of Spiniferomonas and three species and one form of Paraphysomonas. One species of Mallomonopsis, twelve species of Mallomonas, one form of Synura, Chrysosphaerella brevispina and one species and one form of Paraphysomonas are for the first time recorded from The Netherlands. One species of Mallomonopsis and one species of Spiniferomonas could not be identified.Some physical and chemical data of the sampling localities are given.     

A new form of chlorophyll C involved in light-harvesting

A new form of chlorophyll c has been isolated from the pyrmnesiophyte Pavlova gyrans Butcher. This pigment is spectrally similar to chlorophyll c₂, but all the absorption maxima (454, 583, and 630 nm in diethyl ether) are shifted 4 to 6 nanometers to longer wavelengths. The new pigment can be separated from other chlorophyll c-type pigments by reversed-phase high performance liquid chromatography and thin layer chromatography. Both chlorophylls c₁ and c₂ are found with the new chlorophyll c pigment in P. gyrans, and it has also been detected in the chrysophyte Synura petersenii Korsh. The light-harvesting function of the new chlorophyll c pigment is indicated by its presence along with chlorophyll c₁ and c₂ in a light-harvesting pigment-protein complex isolated from P. gyrans in which chlorophyll c pigments efficiently transfer absorbed light energy to chlorophyll a.     

A new spectrally distinct component in preparations of chlorophyll c from the micro-alga Emiliania huxleyi (Prymnesiophycease)

A new chlorophyll c pigment designated chlorophyll c₃ has been isolated from the coccolithophorid Emiliania huxleyi (Prymnesiophyceae) using reverse-phase high-performance thin-layer chromatography (HPTLC). Its spectral properties were compared with chlorophylls c₁ and c₂ from standard sources. Visible absorption maxima of the new pigment in diethyl ether were at 451, 585 and 625 nm with band ratios of 30.77, 3.79 and 1.00, respectively. Chlorophyll c₂ was present in approximately equal proportions to chlorophyll c₃, with maxima in diethyl ether at 447, 579 and 628 nm and band ratios of 12.26, 1.17 and 1.00, respectively. No chlorophyll c₁ was detected. The visible absorption spectra of the magnesium-free derivatives of both chlorophylls c₂ and c₃ from E. huxleyi in acetone were also recorded. The new chlorophyll c₃ pigment was chromatographically and spectrally distinct from a similar pigment, magnesium 2,4-divinylpheoporphyrin a₅ monomethyl ester, present in prasinophyte algae, with which it could have been confused.     

Developments in the taxonomy of silica‐scaled chrysophytes – from morphological and ultrastructural to molecular approaches

Taxonomy in silica‐scaled chrysophytes has gone through three morphological phases. From primary studies of the cell morphology in the 18th century, the focus was in the 20th century replaced by studies of the silica structures of the cell envelope. Now, in the latest decades the importance of DNA sequencing has been recognized, not only to support the taxonomic framework but also to obtain new understanding of taxonomic relations among particular taxa. In the first part of this review, we provide a historical overview of the developments in the taxonomy of scale‐bearing chrysophytes. In the second part, we present a phylogenetic reconstruction of chrysophyte algae, updated by newly obtained SSU rDNA and rbcL sequences of several isolated Synura, Mallomonas and Chrysosphaerella species. We detected significant incongruence between the phylogenies obtained from the different datasets, with the SSU rDNA phylogram being the most congruent with the morphological data. Significant saturation of the first rbcL codon position could indicate the presence of positive selection in the rbcL dataset. Within the Synurales, the relationships revealed by the phylogenetic analyses highlight the artificial infragenetic classification of Mallomonas and Synura, and the occurrence of cryptic diversity within a number of traditionally defined species. Finally, three new combinations are proposed based on the phylogenetic analyses: Tessellaria lapponica, Synura asmundiae and S. bjoerkii.     

CHLOROPHYLL C PIGMENT PATTERNS IN 18 SPECIES (51 STRAINS) OF THE GENUS PSEUDO‐NITZSCHIA (BACILLARIOPHYCEAE)1

The pigment composition of 18 species (51 strains) of the pennate diatom Pseudo‐nitzschia was examined using HPLC. The carotenoid composition was typical for diatoms, with fucoxanthin (the major xanthophyll), diadinoxanthin, diatoxanthin, and β,β‐carotene. However, a diverse array of chl c pigments was observed in the studied strains. All Pseudo‐nitzschia strains contained chl a and chl c₂, traces of Mg‐2,4‐divinyl phaeoporphyrin a₅ monomethyl ester (MgDVP), and traces of a chl c₂–like pigment originally found in the haptophyte Pavlova gyrans. The distribution of chl c₁ and chl c₃ was variable among species (present in seven and 14 species, respectively). Based on chl c distribution, three major pigment types were defined: type 1 (chl c₁ + c₂, four species: P. australis, P. brasiliana, P. multiseries, and P. seriata), type 2 (chl c₁ + c₂ + c₃, three species: P. fraudulenta, P. multistriata, and P. pungens), and type 3 (chl c₂ + c₃, 11 species: P. arenysensis, P. calliantha, P. cuspidata, P. decipiens, P. delicatissima, P. galaxiae, P. mannii, P. pseudodelicatissima, P. subcurvata, P. cf. subpacifica, and a novel Pseudo‐nitzschia species). Type 1 and 2 species also shared the absence of a particular morphological character, the central nodule in the raphe, with the only exception of P. fraudulenta. The implications of such pigment diversity in chemotaxonomy, HAB monitoring, ecology, and phylogeny of Pseudo‐nitzschia species are discussed.     

DETECTION OF CHLOROPHYLL C1 AND MAGNESIUM-2,4-DIVINYLPHEOPORPHYRIN A5 MONOMETHYLESTER IN CRYPTOPHYTES1

Three different chlorophyll (chl) c-type pigments were isolated from two cryptophyte species by silica thin-layer chromatography or polyethylene high-performance liquid chromatography. Chroomonas sp. Hansgirg contained chl c₁ and magnesium-2,4-divinylpheoporphyrin a, mono-methylester; chl c₂ and magnesium-2,4-divinylpheoporphyrin a₅ monomethylester were found in Cryptomonas maculata (syn. Rhodomonas maculata Butcher). These identifications were based on spectral characteristics and on comparison with reference pigments isolated from the synurophycean Synura petersenii Korshikov and the prasinophyte Mantoniella squamata Manton & Park. Neither of the cryptophyte species contained chl c₁ and chl c₂. The significance of chl c₁ as a major pigment and the occurrence of magnesium-2,4-divinylpheoporphyrin a₅ monomethylester in cryptophytes are discussed.