Chlorophycean Algae Research Articles

OCCURRENCE OF CODIUM FRAGILE SUBSP. TOMENTOSOIDES (CHLOROPHYTA: BRYOPSIDALES) IN MARINE EMBAYMENTS OF SOUTHEASTERN AUSTRALIA

Codium fragile (Sur.) Hariot subsp. tomentosoides (van Goor) Silva, a widespread weedy species, is reported from Australia for the first time. Specimens were initially found in June 1996 in Corner Inlet, Victoria, where the species fouled fishing nets. This invasive chlorophycean alga was subsequently found in large numbers on 30 January 1997 in Port Phillip Bay and on 9 March 1998 in Western Port, Victoria. Presumably the species is native to Japan. The alga formed dense stands on rocky substrata in intertidal or in subtidal regions. In Port Phillip Bay, the species was also found attached to the common blue mussel Mytilus edulis planulatus Lamarck, and in Western Port it was found attached to the mud oyster Ostrea angasi Sowerby. Results of this study suggest that recruitment of juvenile germlings and growth of C. fragile subsp. tomentosoides differs between populations in Port Phillip Bay and those in Western Port.

BOTRYOLEPRARIA, A NEW MONOTYPIC GENUS SEGREGATED FROMLEPRARIA

The monotypic genusBotryoleprariaCanalset al. is described. The type species,B. lesdainii(Hue) Canalset al. is a sterile, cottony, pale green lichen, made of hyphae supporting subterminal bunches of chlorophycean algae.

Study of Molecular Karyotypes in Amoeboaphelidium protococcarum,the Endotrophic Parasite of Chlorophycean alga Scenedesmus

On the basis of the pulsed field gel electrophoresis(PFGE) technique, molecular karyotypes in Amoeboaphelidiumprotococcarum (the endotrophic parasite of chlorophycean algae, whichcombines protozoon- and fungus-type characters) were determined. Molecularkaryotypes in the strains X1, X5, and X31, which differ in the host range andoriginate from Western, Central, and Eastern Euro-Asia respectively,demonstrate the intrageneric polymorphism-from 7 to 13 chDNA bands-with theestimated molecular size of 0.3-2.2 Mb were resolved, and the genome sizewas determined to be between 7.4 and 10.2 Mb. The molecular karyotype patternin A. protococcarum is different from that in Protozoa. The low-gradedistinction in molecular karyotypes between X1 and X5, on one hand, andhigh-grade distinction between X1/X5 and X31, on the other hand, makes itpossible to place X31 in a separate taxon.

Phylogeny of wall‐less green flagellates inferred from 18SrDNA sequence data

SUMMARYTo elucidate the phylogeny of the Dunaliellalessensu Ettl.the taxon often thought to be intermediate between primitive green flagellates such as the prasinophytes and the advanced chlorophycean algae, the sequences of the nuclear‐encoded small subunit ribosomal RNA gene (18SrDNA) were determined and analyzed for five green algae, including three dunaliellalean algae. Phylogenetic trees based on 18SrDNA suggest thatOltmannsiellopsis viridis(Margraves et Steele) Chihara et Inouye represents an early divergence in the Ulvophyceae/Trebouxio‐phyceae/Chlorophyceae clade and has no close relationship to any other green algae, as also suggested from ultrastructural characters. We propose Oltmannsiellopsidates ord. nov. for this genus.HafniomonasandPolytomellaare included in the clade which is characterized by clockwise basal bodies (CW group). The 18SrDNA trees suggest that multiple losses of the cell wall of the flagellate cell occurred in the CW group, and that the Dunaliellales sensu Ettl has a polyphyletic nature. This study also suggests thatPlanophita terrestnsGroover et Hof‐stetter (Chaetopeltidales) andChaetophora incras‐sata(Hudson) Hazen (Chaetophorales) are distinct lineages in the Chlorophyceae.

Transcript mapping and processing of mitochondrial RNA in the chlorophyte alga Prototheca wickerhamii.

The detailed transcript map of the circular 55328 bp mitochondrial (mt) genome from the colourless chlorophycean alga Prototheca wickerhamii has been determined. On each half of this genome the genes are encoded only on one DNA strand, forming transcriptional units comprising variable numbers of genes. With the exception of four genes coding for ribosomal proteins, transcripts of the three rRNA genes and all protein-coding genes have been detected by both northern analysis and primer extension experiments. Polycistronic transcripts of protein coding and tRNA genes were verified by northern analyses, primer extension and RNAse mapping experiments. The 5' and 3' ends of different RNA species are often located in close proximity to putative stem-loop structures and some 5' termini of mRNAs coincide with the 3' end of tRNAs located immediately upstream. Transcript mapping in a putative promoter region revealed two different possible transcription initiation sites; no significant sequence homology to putative mt promoters from higher plants could be found. In addition, two out of three group I introns residing in the cox1 gene were found to be self-splicing in vitro under reaction conditions developed for related mt introns from a filamentous fungus. Mitochondrial gene expression of P. wickerhamii and of filamentous fungi has several features in common, such as intron splicing and the processing of longer polycistronic transcripts. The similarities in RNA maturation between higher-plant and P. wickerhamii mitochondria are less pronounced, since plants rarely use tRNAs as processing signals for their relatively short mitochondrial co-transcripts.

A chitin-like glycan in the cell wall of a Chlorella sp. (Chlorococcales, Chlorophyceae)

The stable amino-sugar fraction of the cell wall of the symbiotic Chlorella strain Pbi (Chlorophyceae) was isolated and investigated by sugar analysis, infra-red spectroscopy, lectin binding, enzymatic degradation, X-ray diffraction and electron microscopy. The results indicate the existence of a glycosaminoglycan which can be regarded as a chitin-like glycan. This carbohydrate structure is unusual for algae and reported here for the first time in unicellular chlorophycean algae.

Ultrastructural Aspects of the Cell Cycle in Planktosphaeria gelatinosa (Chlorophyceae), with Emphasis on the Flagellar Apparatus of the Zoospore

Summary The cell cycle of the multinucleate coccoid green alga, Planktosphaeria gelatinosa was studied with transmission electron microscopy. Young, uninucleate cells have a more or less cup-shaped, parietal chloroplast containing a pyrenoid. The nucleus is surrounded by the chloroplast, and penetrates into the pyrenoid by a finger-like lobe that is branched at its end. In maturing multinucleate cells, the parietal chloroplasts are lens-shaped or conical, each containing a pyrenoid associated with a nucleus. In vegetative cells, bundles of microtubules are present between the nuclei, radiating from the centre of the cell towards the plasma membrane. The processes of mitosis and cytokinesis are similar to those known from other chlorophycean algae, including a closed, centric spindle, a perinuclear envelope and centrifugal cleavage mediated by a phycoplast that probably is formed by the microtubular arrays present in the vegetative cell. Mitosis and cytokinesis may show overlap in time, so that Planktosphaeria is not considered as a true coenocyte. The flagellar apparatus of the zoospore is characterized by two basal bodies that essentially are directly opposed, oriented at a variable angle and connected by a distal fibre and two striated proximal fibres. The central part of the distal fibre is differentiated into a ribbed structure. The flagellar apparatus has a cruciate microtubular root-system, with the left root consisting of 4 microtubules in a 3/1 configuration. The 2-stranded right roots are covered by a system I fibre or SMAC (striated microtubule-associated component), which is continuous between the two opposite roots and connected to the ribbed structure. At their proximal end the basal bodies are covered by a partial terminal cap. The ultrastructure of the flagellar apparatus indicates a close affinity to the unicellular genera Neochloris, Tetraedron and Chlorotetraedron , and also to the coenobial genera Pediastrum and Hydrodictyon .

The Mitochondrial DNA of the Amoeboid Protozoon, Acanthamoeba castellanii: Complete Sequence, Gene Content and Genome Organization

In phylogenetic trees based on comparison of nuclear small subunit rRNA sequences, Acanthamoeba castellanii(an amoeboid protozoon) is positioned near the base of the radiation leading to the animals, fungi and plants. However, the specific affiliation of this protist with the major multicellular lineages of eukaryotes is currently uncertain. To further explore the evolutionary position of A. castellanii, we have determined the complete primary sequence of its mitochondrial genome. We find that the circular mtDNA (41,591 bp; 70.6% A+T) encodes two rRNAs (small subunit and large subunit), 16 tRNAs and 33 proteins (17 subunits of the respiratory chain and 16 ribosomal proteins). As well, this genome contains eight open reading frames (ORFs) larger than 60 codons and of undefined function. Two of these ORFs ( orf124and orf142) have homologs in other mtDNAs ( “orf25”and “orfB”,respectively), three are unique to A. castellaniimtDNA ( orf83, orf115and orf349), and three are intronic ORFs. Among notable features of A. castellaniimtDNA are the following: (1) Genes and ORFs are all encoded on the same strand and are tightly packed, with only 6.8% of the total sequence not having an evident coding function and intergenic spacer sequences ranging from only 1 to 616 bp (average 64 bp). Ten pairs of protein-coding genes overlap by up to 38 bp and two subunits of cytochrome oxidase (COX1 and COX2) are specified by a single continuous ORF. (2) Only three introns, all group I and each containing a free-standing ORF, are present; these are localixzed in the 3′-half of the large subunit rRNA gene. (3) The genome encodes fewer than the minimal number of tRNA species required to support mitochondrial protein synthesis, suggesting that additional tRNAs are imported from the cytosol into A. castellaniimitochondria. O f the 16 tRNAs specified by A. castellaniimtDNA (one with an 8-nucleotide anticodon loop), 13 have been shown or are predicted to undergo a novel form of RNA editing within the acceptor stem. (4) A modified genetic code is used in which UGA specifies tryptophan. (5) Repeated sequences and obvious small sequence motifs that might represent regulatory elements are ab sent. In overall size, gene content and organizational pattern, A. castellaniimtDNA most closely resembles the mtDNA of the chlorophycean alga Prototheca wickerhamii(55,326 bp; 74.2% A+T), but is quite different in these respects from the mtDNA of Chlamydomonas reinhardtii(15,758 bp; 54.8% A+T), another chlorophysean alga, as well from characterized animal and fungal mitochondrial genomes. The mtDNAs of A. castellaniiand P. wickerhamiishare with those of land plants a virtually identical set of respiratory and ribosomal protein genes, with a number of these being arranged in the same way. In contrast, C. reinhardtiimtDNA lacks several of the standard respiratory genes and does not encode any ribosomal proteins. In addition, the mitochondrial genomes of A. castellaniiand P. wicker hamii(but not that of C. reinhardtii) contain homologs of two genes ( orf25and orfB) that have previously been found only in land plant mtDNA. These new genomic data provide additional phylogenetic markers linking the mitochondrial genomes of land plants, P. wickerhamiiand A. castellanii, to the exclusion of C. reinhardtii, fungi and animals. We suggest that land plant, P. wickerhamiiand A. castelaniimtDNAs are relatively conservative, slowly evolving genomes that retain a number of ancestral features that were present in a common mitochondrial progenitor. These features have largely been lost in mtDNAs such as that of C. reinhardtii, which appear to have evolved relatively rapidly and radically away from the ancestral pattern.

Chlorophycean algae from the Triassic of Australia

Among living green algae assigned to the order Chlorococcales and order Zygnematales certain species develop resistant outer organic walls and/or cysts during their life cycles; as such they have the potential to become fossils. Based on morphology, comparison between living algae and microfossil remains are made with varying degrees of confidence, and a possible evolutionary pathway for certain chlorococcalean coenobial families is suggested. Twelve genera are reviewed from earliest to latest Triassic palynological assemblages from northwestern Australia; and the following taxa are described as new: Plaesiodictyon mosellanum ssp. symmetricum ssp. nov.; Plaesiodictyon mosellanum ssp. variabile ssp. nov.; Plaesiodictyon decussatus sp. nov.; Plaesiodictyon decussatus ssp. decussatus ssp. nov.; Plaesiodictyon decussatus ssp. tetracornuta ssp. nov.; Tetraporina protrusa sp. nov.; Crucigeniella? torques sp. nov.; and Paleoraphidia akestra gen. et sp. nov. (type). Their suggested natural affinities are useful in palaeoenvironmental interpretations of mostly freshwater or low-salinity habitats.

Algues chlorophycées calcifiéesdu Paléocène du Guatemala

Numerous works have been devoted to the Chlorophycean Algae from the Paleocene of Europe, Africa and Asia.However few studies deal with the Caribbean. The discovery in Guatemala, south of Polochic Fault, of a Paleocene carbonate platform with calc-alcalin volcanism clasts give importants data on the age of the volcanism arc near the boundary between the North American/Caribbean Plate. The inventory and the main characteristics of about ten species of these calcareous green algae, some of them with a large biogeographic distribution are given. The occurence of these algae in the Caribbean domain can be explained by a transatlantic migration from Mediterranean to Caribean Tethys and the settling of carbonate platforms and coral reefs in the Caribbean domain.

Evidence for independent acquisition of group I introns in green algae.

We report the occurrence of a group I intron, 452 nucleotides in length, in the nuclear small-subunit ribosomal gene of the benthic seaweed Urospora penicilliformis, a member of the green algal class Ulvophyceae. Group I introns have been reported in fungi, myxomycetes, the ciliate genus Tetrahymena, and recently in five unicellular chlorophycean algae. The sequence of the conserved core of the U. penicilliformis group I intron was aligned with that of 15 other introns of this type, and the evolutionary relationships among these introns were examined. Comparison of the "intron" tree with phylogenetic hypotheses of the intron-harboring organisms shows that nuclear group I introns in green algae have arisen several times and are not lineage specific.

Localization of glycolate dehydrogenase in two species of Dunaliella

The occurrence of glycolate oxidase in addition to glycolate dehydrogenase in Dunaliella salina and D. primolecta, as reported in the literature, could not be confirmed. Both species were demonstrated to possess only glycolate dehydrogenase. After separation of organelles by gradient centrifugation, glycolate dehydrogenase along with hydroxypyruvate reductase was found exclusively in the mitochondria. Thus the peroxisomes from Dunaliella are not of the leaf-type: because of their content of catalase, uricase and hydroxyacyl-CoA dehydrogenase they appear to be of the same type as in Eremosphaera and other chlorophycean algae. No activity of glycolate dehydrogenase was found in the chloroplast fraction when the 2,6-dichlorophenol-indophenol test was used.

TWO TYPES OF CYTOPLASMIC CLEAVAGE IN THE COENOCYTIC SOIL ALGA PROTOSIPHON BOTRYOIDES (CHLOROPHYCEAE)1

ABSTRACTCytokinesis in the coenocytic green alga Protosiphon botryoides (Kütz.) Klebs was studied with transmission electron microscopy. In vegetative cells, nuclei with associated basal bodies and dictyosomes are scattered throughout the cytoplasm. Mature cells may develop either multinucleate resting spores (coenocysts) or uninucleate zoospores. Cytokinesis may be preceded by contraction of the protoplast due to the disintegration of vacuoles that are present in larger, siphonous cells.The formation of coenocysts in ageing, siphonous cells, is signalled by cleavage of the chloroplast and the development of arrays of phycoplast microtubules in one or more transversely oriented planes through the cell. Nuclei with associated basal apparatuses stay dispersed throughout the cytoplasm; the basal bodies apparently are not involved in organization of the phycoplast. The plasma membrane invaginates, resulting in a centripetal cleavage of the protoplast into two or more multinucleate daughter protoplasts. Simultaneously, wall material is deposited along the outside of the daughter protoplasts by dictyosome‐derived vesicles, and finally two or more thick‐walled coenocysts are formed.The formation of zoospores, on the other hand, is signalled by clustering of the nuclei in one or more groups depending on the shape of the mother cell. The nuclei become arranged with the associated basal apparatuses facing toward the center of the cluster. Bundles of phycoplast microtubules develop between the nuclei, radiating from the center of a cluster toward the plasma membrane; basal apparatuses or associated structures apparently are involved in organization of the phycoplast. Cleavage furrows grow out centrifugally along these bundles of micro‐tubules, fed by dictyosome‐derived vesicles. No wall material is deposited. An additional mitotic division occurs during cleavage, and finally numerous uninucleate, wall‐less, biflagellate zoospores are formed. The ultrastructural features of the two different types of cytoplasmic cleavage associated with two different types of daughter cells have not previously been reported for chlorophycean algae.

Ultrastructure of the flagellar apparatus of the gametes ofGongrosira papuasica(Chlorophyta)

Gongrosira papuasica is the only known filamentous, branching chlorophycean alga to produce biflagellate gametes. The flagellar apparatus of the gametes exhibits 180° rotational symmetry and clockwise absolute orientation. In addition, the gametes have a distal fibre and proximal sheaths similar to those of Chlorosarcinopsis. Other features include a double-banded, striated distal fibre, a 4-2-4-2 pattern of the microtubular rootlets with associated electron-dense material, two rhizoplasts, a mating structure, and a pyrenoid penetrated by thylakoid membranes. The 2s rootlet extends near to the eyespot in the chloroplast. The characteristics of trentepohlialean vegetative filaments and motile cells, including the pits and transverse walls of vegetative cells, and the multi-layered structures, overlap of basal bodies, and keeled flagella of motile cells were not observed. Although the vegetative morphologies of Gongrosira and Chlorosarcinopsis are dissimilar, the ultrastructure of G. papuasica gametes and t...

Microfacies zonation and spatial evolution of a carbonate ramp: Marginal Moroccan phosphate sea during the Paleogene

The paleoenvironment of the southwestern portion of the Paleogene Moroccan phosphate sea has been reconstructed in detail by microfacies studies for a complete transgressive-regressive cycle. In front of the Anti-Atlas, forming the southern border of the Atlantic gulf, a bioclastic and phosphatic carbonate ramp extended to the north. The ramp was a homoclinal, very gentle dipping surface. Four stages of ramp evolution can be distinguished. They are (1) the marginal marine initial stage, (2) the marine transgressive stage, (3) the marine regressive stage and (4) the final silting up stage. The ramp is characterized by a distinct facies zonation. A sabkha plain, documented by mudstones and dolocretes, was situated between the arid hinterland and the ramp. Nearshore, open lagoons existed, populated by chlorophycean algae and miliolid foraminifera. These environments were protected from the open sea by a chain of oyster banks. A belt of echinoid enrichments probably marked the wave base. Sea areas with deeper and only temporarily, highly-agitated water are characterized by a benthic faunal assemblage of varied molluscs, with bryozoans becoming more abundant to the east. The carbonates are intensively bioturbated and interfinger with phosphorite sands, which dominated in the deepest part of the ramp. All phosphorites studied are clastics, poor in matrix and are not associated with phosphate source rocks. A process of extensive reworking, transport and redeposition, which is related to transgressions and regressions, has to be assumed.

Verteilung und Tiefenzonierung von schalenbohrenden Endolithen in rezenten Riff- und Schelfbereichen: Cozumel, Yucatán (Mexiko)

Pelecypod shells from bottom sediments of the shelf and upper slope off Cozumel (Mexico), at depths ranging from 1 to 47 m, were studied with regard to the taxonomy, frequency and distribution of microborings produced by endolithic organisms. Scanning electron microscopy of plastic casts of the borings reveals the existence of 29 microboring types, distinguished on the base of shape, size, mode of branching, overall boring pattern and sporangia. The endoliths include cyanobacteria, chlorophycean algae, rhodophycean algae, fungi, sponges and several microborers of uncertain taxonomic affinities. Although most of the borings exhibit a wide bathymetrical range, a subdivision of the photic zone is indicated by the abundance and vertical distribution of some species. The upper part of the photic zone (1–30 m) is characterized by higher species diversity, by the green algaePhaeophila engleri andEntocladia testarum, and by the abundance of the cyanobacteriaHyella gigas. Fungi occur at all depths but are more common in the lower photic zone (30–47 m). The bathymetrical position of the boundary might be influenced by the vertical sampling distance. Generally, there is a good agreement with other bathymetrical patterns of recent endoliths, especially with those from the Puerto Rican carbonate shelf. There is no distinct difference in the frequency or taxonomic composition of shell-boring endoliths from reefs and interreef areas (platforms covered by bioclastic sands). Boring intensity, measured by point-counting of SEM photographs, is generally high; in 58% of the samples 60 to 99% of the outer shell surface is bored, predominantly by fungi and by the green algaPhaeophila engleri. Mean boring intensities show no relationship with water depths.

Light and electron microscopy of Brachiomonas submarina Bohlin (Chlamydomonadales, Chlorophyceae)

Abstract Light and electron microscopic observations were made on Brachiomonas submarina Bohlin (Chlamydomonadales, Chlorophyceae). During development, cells change in morphology from a raindrop-like or ellipsoidal form to the diagnostic shape having arms and a tail-like process. Most ultrastructural characteristics are common to those of the unicellular chlorophycean algae, such as, multiple cell wall layers, clockwise absolute orientation of basal bodies and the three over one arrangement of the four-membered rootlets. Some unusual features were also found, including the extension of proximal sheaths connecting opposite basal bodies, branched rhizoplasts that extend to mitochondria, a layered structure associated with the four-membered rootlets, and hair-like projections radiating from the peripheral doublets of each flagellum. The process of flagellar replication is briefly discussed in regard to the accessory basal body–two-membered rootlet connection.

COCCOID EUKARYOTIC MARINE ULTRAPLANKTERS WITH FOUR DIFFERENT HPLC PIGMENT SIGNATURES

Pigment compositions of 16 coccoid eukaryotic ultraplanktonic clones isolated from coastal and oceanic waters were investigated by high-performance liquid chromatography (HPLC). Four distinct pigment signatures were observed, and clones were classified into subgroups based on the presence or absence and relative abundances of selected chlorphylls and carotenoids. The first subgroup (5 clones) was pigmented like chlorophyll b-containing higher plants and resembled true chlorophycean algae. The second subgroup (3 clones) contained chlorophyll b and relatively high levels of prasinoxanthin, a carotenoid characteristic of certain members of the Prasinophyceae (sometimes grouped as the Micromonadophyceae). The third subgroup (5 clones) was pigmented in a similar fashion but had a twofold lower prasinoxanthin-to-chlorophyll a ratio and an unidentified carotenoid. The fourth subgroup (3 clones) lacked chlorophyll b and was pigmented like certain members of the Chrysophyceae (e. g. 19′-butanoyloxyfucoxanthin-containing Pelagococcus subviridis Norris) Online diode array spectral analysis of selected clonal extracts revealed the presence of Mg 2,4-divinylphaeoporphyrin a5 monomethyl ester-like and chlorophyll c-like pigments in representatives of the prasinophyte-like and chrysophyte like clones, respectively. These findings plus the occurrence of chlorophyll b, prasinoxanthin and 19′-butanoyloxyfucoxanthin in the North Atlantic Ocean suggest that chrysophyte- and prasinophyte-like organisms can be important biomass components of marine phytoplankton.

On the restoration of fertility to a sexually inactive, heterothallic species ofChlamydomonas(Chlorophyta)

In our laboratory beginning in late 1977, a mating reaction could not be obtained for about 1 year using the heterothallic chlorophycean alga, Chlamydomonas eugametos Moewus. Mating potential was restored by long-term cultivation of the separate mating types on soil extract agar, demonstrating that the “loss” may not have been a mutation.

The algal flora of two distinct habitats along the Moa River in the state of Acre, Brazil

Twenty-eoght algal samples were collected in September-October, 1984, from two distinct habitats in the state of Acre, Brazil. Eleven were from the Moa River, and 17 were from a sulfur water spring which flows into the Moa River. A total of 74 species, representing 48 genera of algae, were identified from these samples. Forty-nine species were found in the Moa River and 67 in the sulfur water spring. Both coolection site had rich assemblages of cyanophycean algae, chlorophycean algae, and diatoms. Chlorophycean species dominated the algae flora at both sites, cut were more numerous at the sulfur water spring. There was also a definite difference in the relatives proportions of desmids to filamentous chlorophycean algae at the two sites.