A NOVEL PATTERN OF APICAL CELL POLYPLOIDY,SEQUENTIAL POLYPLOIDY REDUCTION AND INTERCELLULAR NUCLEAR TRANSFER IN THE RED ALGA POLYSIPHONIA

Nearly a century ago, Rosenvinge published a now-classic paper reporting nuclear transfer between cells of Polysiphonia during secondary pit connection (SPC) formation. While reinvestigating this phenomenon, we discovered that the uninucleate apical cell, which is the progenitor of all cells in the plant, has many times (ca. 64–128 ×) the level of nuclear DNA characteristic of nuclei of gametes or mature pericentral cells. Via a regular sequence of cell divisions, the polyploid apical cell gives rise to tiers of cells, each composed of a number of pericentral cells which surround a single central cell. A large proportion of the nuclear divisions are not accompanied by DNA replication. Thus, as the number of nuclei within elongating pericentral cells increases, the DNA level of nuclei in these cells “cascades” down to the DNA level expected for the particular life history generation (i.e., gametophyte or tetrasporophyte). In mature pericentral cells, the number of nuclei is proportional to the volume of the cell. The pattern of nuclear division, reduction in ploidy level and the timing of intercellular nuclear transfer via SPC formation is regular and characteristic of a species. Nuclei transferred from one cell to an adjacent cell participate in the further nuclear divisions of the recipient cell. The degree of polyploidy in apical cells may determine the number of cells in a “determinant” branch or even the number of cells in “indeterminant” axes. In addition, the highly polyploid state of the germinating spore and its pattern of development may provide for the rapid initial growth so characteristic of this taxon.     

ELECTRON MICROSCOPIC OBSERVATIONS ON THE DIFFERENTIATION AND RELEASE OF SPERMATIA IN THE MARINE RED ALGA POLYSIPHONIA HENDRYI (CERAMIALES,RHODOMELACEAE)

Spermatial differentiation in Polysiphonia hendryi begins after nonpolar, avacuolate spermatia are cleaved from their mother cells. The spermatia and their mother cells are embedded within the spermatangium, a confluent wall matrix of the male branch. As the young spermatium enlarges and becomes ellipsoid, the wall fibrils of the spermatangium are compressed, forming a separating layer. Spermatia become polar with rough endoplasmic reticulum coalescing to form a large, fibrillar spermatial vacuole that becomes extracytoplasmic in later development. Following spermatial vacuole formation, dictyosomes form and deposit a spermatial wall, severing the spermatial mother-cell pit connection. Enlargement of younger spermatia, which are lateral to the older ones, squeezes the maturing spermatia, pushing them from the male branch, and leaving a scar that compresses and heals. Through this release mechanism, new sites are created for additional spermatial proliferation.     

ISOLATION, PURIFICATION, AND CHARACTERIZATION OF DMSP LYASE (DIMETHYLPROPIOTHETIN DETHIOMETHYLASE (4.4.1.3)) FROM THE RED ALGA POLYSIPHONIA PANICULATA1

Polysiphonia paniculata Montagne is an intertidal red alga known to produce large amounts of the compound dimethylsulfoniopropionate (DMSP). Conversion of this substrate into dimethylsulfide is accomplished in P, paniculata by an enzyme called DMSP lyase (dimethylpropiothetin dethiomethyla.se (4.4.1.3)). DMSP lyase has been purified and characterized from P. paniculata. Enzymie activity is found in two different proteins: the larger with a molecular weight of 9.26 ± 10⁴ daltons and the smaller with a molecular weight of 3.65 ± 10⁴ daltons. Specific activity of the enzyme is 526 μmols min⁻¹mg⁻¹ for the smaller protein a nd 263 μmols min ⁻¹ mg⁻¹ for the la rger protein. The Michaelis-Menten constant (K_m) is 72.8 μM ± 17.15 and the v_max is 1.62 μmols min⁻¹± 0.928 for the 92.6-kDa protein. The p1 of the larger protein is 5.8 and 5.9 for the smaller protein. Interaction with cysteine protease inhibitors L-trans-epoxysuccinyl-leucylamido (4-guanidino)-butane, dithiobis-(2-nitrobenzoate), or N -ethylmaleimide inactivated enzyme activity. The presence of either magnesium or calcium with DMSP lyase enhanced activity al concentrations between 20 and 40 μM but had little effect above these levels. Addition of the divalent chelators ethylenebis(oxyethylenenitrilo) tetraacetic acid and ethylenediaminetetraacetate decreased activity of the enzyme, but activity was restored when either chelator was removed and magnesium or calcium was added to the enzyme .     

ULTRASTRUCTURE OF EARLY DEVELOPMENT IN THE FEMALE REPRODUCTIVE SYSTEM OF POLYSIPHONIA HARVEYI BAILEY (CERAMIALES,RHODOPHYTA)1

Prefertilization and immediate postfertilization development in the female reproductive branch of Polysiphonia harveyi (Bailey) was studied with the electron microscope. Results pertaining to prefertilization morphology and development are consistent with those established in earlier light microscopic studies, but several unexpected ultrastructural characteristics were discovered. The mature carpogonium was found to have double membrane-bound vacuoles of nuclear origin and the carpogonial nucleus contained a nucleolus with a distinctive crystalline lattice. Trichogynes lacked a nucleus. Of particular interest was the discovery of a highly structured channel of smooth endoplasmic reticulum (SER) which extended uninterrupted, except for pit connections, through the carpogonial branch. It is suggested that the message of fertilization is conducted through the SER channel from the carpogonium to the support cell. Few observations were made on postfertilization branches, but evidence of direct fusion between the carpogonium and auxiliary cell was fairly conclusive. Pit plugs in the female branch were found to be of three morphological types differing by the presence and number of pit membranes. We have designated these plugs Type I–III since differential functioning was not fully ascertained. Our data suggest that pit membranes may serve to stabilize the plug and that those plugs without membranes are more readily dismantled to allow cytoplasmic continuity between cells.     

REPRODUCTIVE, CULTURE AND REGENERATION STUDIES OF THE EDIBLE RED ALGA CALLOPHYLLIS IN CHILE

In Chile, the demand of edible seaweeds has increased during recent years and Callophyllis variegata is one of the most demanded species. This study summarizes information on phenology, aspects, in vitro culture and vegetative propagation methods for Callophyllis. Results indicate that spore production occurs mainly during winter, and recruitment of new plants appear in nature in the spring. Culture studies indicate that spores presented higher germination and growth rates at 8° C and 10 to 12 μmol m⁻² s⁻¹. Furthermore, these results indicate that this species presents a high potential for regeneration from its holdfast. The manipulation of temperature, light and culture medium enhances the regeneration process and growth of Callophyllis in the laboratory.     

A FREEZE-ETCHING STUDY OF THE RED ALGA PORPHYRIDIUM

Freeze-etched cells of Porphyridium cruentum and P. aerugineum closely resemble those fixed with glutaraldehyde and post-fixed with osmium tetroxide. Freeze-etching reveals diversity in the non-membranous and membranous parts of the cell. All the membranes are asymmetrical. The application of a double-replica technique illustrates how the two sides of several cell membranes fit together. Interpretation of fracture patterns through the thylakoids and stroma leads to the suggestion that the thylakoids are composed of repeating structural units. A model of the photosynthetic apparatus is proposed. It is suggested that the thylakoids of Porphyridium and other red algae are not always “free” but can be stacked much like those of other plants.     

REPRODUCTION AND SYSTEMATICS OF THE MARINE ALGA DERBESIA (CHLOROPHYCEAE) IN NEW ENGLAND1,2

The morphology, gross cytology, reproduction, and habitat ecology are described for Derbesia marina based on observations of New England field populations and laboratory cultures of this plant. These data, and additional observations on cultures of several other species of Derbesia from elsewhere and on type and other important collections, have been used to evaluate the systematic relationship of New England Derbesia with other species of this genus. The single Derbesia species in New England is referred to D. marina. The systematic criteria previously used to distinguish species within Derbesia are reviewed and interpreted within the context of the present investigation. In systematic studies, we stress the importance of the use of sporangial and chloroplast morphology, the presence or absence of pyrenoids, and reproductive history. Two types of life history are reported for D. marina in New England: (1) A form of D. marina collected at 20 m reproduces directly with stephanokontous zoospores growing into sporophytic plants of Derbesia morphologically identical to their parent thalli. (2) On the other hand, at least some New England, populations of D. marina have retained the genetic potential for producing a sexual generation (Halicystis ovalis), even though the latter is unknown for the coast of northeastern North America.³ Gametophytes (H. ovalis) were produced directly from enlargement and subsequent differentiation of uncleaved lateral sporangia in 2 cultured populations of New England D. marina. A single female and numerous male vesicles formed in this manner produced gametes, but neither fertilization nor parthenogenesis occurred; thus the entire life history was not completed in culture. The occurrence of the directly reproducing deep water form of D. marina is presented as evidence for speciation of a sporophyte (Derbesia) independent of its alternate gametophyte (Halicystis). An hypothesis is advanced to explain the source and means for expression of genetic variability necessary for speciation in a population of nonsexually reproducing Derbesia.     

MORPHOLOGY AND REPRODUCTION OF THE RED ALGA ACROCHAETIUM PECTINATUM IN CULTURE12

The life history of the marine red alga Acrochaetium pectinatum (Kylin) Hamel was studied in unialgal culture using supplemented natural seawater media. The tetrasporophytes are larger than the gametophytes, have a compact filamentous basal system, and produce monosporangia and tetrasporangia. Mono-spores give rise to tetrasporophytes. Tetraspores develop into small gametophytes with unicellular bases. The gametophytes are heterothallic when small (usually less than 500 μ) but as some females become larger (2-3 mm) they produce spermatangia as well as carpogonia. Gametophytes may bear mono-sporangia in addition to carpogonia or spermatangia. These monospores give rise to gametophytes. Fertilization of the carpogonia has not been observed. The tetrasporophytes produce only monosporangia in day-lengths of 12-16 hr, but both tetrasporangia and monosporangia are formed in daylengths of 6–10 hr. Tetrasporangial production is reduced at 15 C compared with 10 C. Light intensity in the range of 5-200 ft-c (cool white fluorescent lighting) has no apparent influence on induction of tetrasporangia. Induction of tetrasporangia is not a photoperiodic response because their development is not inhibited by a brief light break in the middle of the dark period in short daylengths. Plastid morphology, origin, and frequency of sporangia and vegetative branching are variable during the ontogeny, and consequently are somewhat unreliable as taxonomic criteria. Differences in basal systems between gametophytes and tetrasporophytes also indicate that this feature, which is used to distinguish major subgeneric groupings in Acrochaetium, may not be as useful as previously thought.     

SULFUR AND THE TOXICITY OF THE RED ALGA CERAMIUM RUBRUM TO BACILLUS SUBTILIS1,2

Crystalline sulfur has been isolated from the red seaweed Ceramium rubrum and shown to be responsible for the toxicity of this alga to the growth of Bacillus subtilis. This alga was unusual in that it contained a much higher free sulfur content than other red and brown algae tested.     

SIGNIFICANCE OF PHYLOGENETIC SYSTEMATICS FOR THE BIOGEOGRAPHY OF THE MARINE RED ALGAE

Hovencamp (1997) recommends that geographical information can be extracted from cladistic analyses of phylogenetic data in which the Earth's history is resolved in terms of vicariance events that established barriers to migration. Nodes in a cladogram that specify two sister groups which do not overlap in their distributions are taken as evidence for a vicariance event and the sequential order of cladogram nodes leads to a procedure whereby the sequence of vicariance events can be reconstructed. For red algae, two such events are the persistence of the northward extension of the eastern end of Gondwanaland across a cool to warm temperature gradient with the formation of present‐day Australasia, and the opening of the Tethyan Ocean followed by closure of the Tethyan Seaway between Africa and Eurasia. Phylogenetic hypotheses related to the first of these events are seen among genera belonging to the Bonnemaisoniaceae, Gracilariaceae, Kallymeniaceae, Gigartinaceae, and Delesseriaceae. A Tethyan origin and distribution is exemplified in part by families that comprise the Solieriaceae complex. Orders such as the Rhodymeniales, Halymeniales and the families Ceramiaceae and Rhodomelaceae contain taxa that fall partly into the first and partly into the second category. Phylogenies are constructed from rbcL sequence data and compared to the morphological evidence. The biogeographical speculations resulting from these observations are preliminary in nature and can only be confirmed or refuted with addtional data and more refined analytical techniques.     

DNA OF THE MARINE RED ALGA GRIFFITHSIA GLOBULIFERA12

A method has been given for isolating nuclei from red algae. The results are given for the isolation, purification, and analysis of Griffithsia globulifera DNA luith several methods. The G-C content is≈42%. A new DNase is also reported.     

REPRODUCTION AND LIFE HISTORY OF THE RED ALGA GALAXAURA OBLONGATA (NEMALIALES,GALAXAURACEAE)1

Culture and morphological studies showed that Galaxaura oblongata (Ellis et Solander) Lamouroux has a triphasic life history with conspicuous gametophytes and small filamentous tetrasporophytes. Development of male and female reproductive structures is very similar and both begin with the enlargement of a terminal cell of a filament branch occupying a normal vegetative position within the apical pit of a thallus branch. In male thalli this modified branch forms a conceptacle in which spermatangia are produced. In female thalli, this modified branch forms a three-celled carpogonial branch consisting of a carpogonium, hypogynous cell and basal cell. Filament branches from the basal cell form a pericarp and the gonimoblast develops directly from the carpogonium. Carposporangia are produced in conceptacles which resemble the male conceptacles. About the time the first carposporangia are produced, the carpogonium, hypogynous cell and basal cell form a large fusion cell. Released carpospores germinate in a unipolar or bipolar manner and form small filamentous thalli. Under short day conditions, cruciate tetrasporangia are produced in small clusters. Tetraspores germinate similarly to carpospores and also form small filamentous thalli. Under low nutrient conditions, small cylindrical thalli develop on the filaments and these appear similar to gametophytes collected in nature.     

INCORPORATION OF SULFATE INTO THE CAPSULAR POLYSACCHARIDE OF THE RED ALGA PORPHYRIDIUM

The accumulation of sulfate-³⁵S by Porphyridium aerugineum cells and subsequent appearance of solubilized capsular polysaccharide-³⁵S in the growth medium were examined The uptake of label by the cells was largely light dependent. Pulse-chase experiments using log phase cells revealed a rapid labeling of solubilized capsular polysaccharide, recovered from the medium as the cetylpyridinium chloride precipitate Polyacrylamide gel electrophoresis of the polysaccharide-³⁵S showed the sulfate to be firmly bound to an immobile fraction. Sephadex chromatography revealed the molecular weight of the polysaccharide to be in excess of 2 x 10⁵. Acid hydrolysis of the polysaccharide-³⁵S released sulfate-³⁵S ion as evidenced by radioautography of thin layer chromatographs Preliminary electron microscope evidence suggests that the synthesis, movement, and deposition of the capsular polysaccharide on the cell surface are Golgi complex-mediated processes     

ELECTRICAL CONTROL OF RHIZOID FORMATION IN THE RED ALGA,GRIFFITHSIA BORNETIANA

1. Direct galvanic current of 10 to 40 microamperes per square millimeter of cross-section of medium results in anodal determination of rhizoid origin in the differentiated cells of the red alga Griffithsia bornetiana. The current is most effective near the upper end of the range. 2. Within the range used there is an increase in the number of rhizoids produced with increase in current intensity and a decrease in size of rhizoids. 3. Currents of lower intensity require a longer time to produce these effects than comparatively high currents. 4. The orientation of the plants in the electrical field seems to affect the number of rhizoids produced, in that plants with apexes toward the anode produce more rhizoids. 5. Together with anodal rhizoid determination there is migration of chromatophores toward the anodal side of each cell. 6. Displacement of chromatophores (and other cytoplasmic bodies) by the centrifuge does not affect the point of rhizoid origin, but does affect the shoots. 7. Together with anodal determination of rhizoids the algal filaments become graded in color, from bright pink toward the cathode to pale tan toward the anode. 8. Evidence is presented to show that this is not due to a pH change, but to a loss of pigment by chromatophores toward the anode and electrophoresis of the pigment toward the cathode. 9. In conclusion the probability is pointed out that the current acts in morphogenesis by moving particles of different charge.     

CURRENT STATUS OF THE INVASIVE GREEN ALGA CODIUM FRAGILE IN EASTERN CANADA

Ten years after the initial discovery of Codium fragile in eastern Canada on the Atlantic coast of Nova Scotia, C. fragile has extended its range considerably to northern Nova Scotia, southern New Brunswick and Prince Edward Island (P.E.I.) in the Gulf of St. Lawrence. In all principal areas C. fragile subsp. tomentosoides is present. In two regions of Prince Edward Island, Codium is becoming extremely abundant, and is known by local fishers as the "oyster thief". A potential second taxon of Codium was collected in 1999 at three sites in Malpeque Bay where it is locally abundant. These plants are distinguished from C. fragile subsp. tomentosoides by their smaller frond size, flatter utricle tops, smaller mucrons, and smaller gametangia. Principal component analysis distinguishes plants of the two types. The abundance of C. fragile on both hard bottom and soft bottom substrata suggests that it will become the dominant alga in many subtidal algal communities in eastern Canada.     

THE INVASIVE GENUS ASPARAGOPSIS (BONNEMAISONIACEAE,RHODOPHYTA): MOLECULAR SYSTEMATICS,MORPHOLOGY, AND ECOPHYSIOLOGY OF FALKENBERGIA ISOLATES1

The genus Asparagopsis was studied using 25 Falkenbergia tetrasporophyte strains collected worldwide. Plastid (cp) DNA RFLP revealed three groups of isolates, which differed in their small subunit rRNA gene sequences, temperature responses, and tetrasporophytic morphology (cell sizes). Strains from Australia, Chile, San Diego, and Atlantic and Mediterranean Europe were identifiable as A. armata Harvey, the gametophyte of which has distinctive barbed spines. This species is believed to be endemic to cold‐temperate waters of Australia and New Zealand and was introduced into Europe in the 1920s. All isolates showed identical cpDNA RFLPs, consistent with a recent introduction from Australia. Asparagopsis taxiformis (Delile) Trevisan, the type and only other recognized species, which lacks spines, is cosmopolitan in warm‐temperate to tropical waters. Two clades differed morphologically and ecophysiologically and in the future could be recognized as sibling species or subspecies. A Pacific/Italian clade had 4–8° C lower survival minima and included a genetically distinct apomictic isolate from Western Australia that corresponded to the form of A. taxiformis originally described as A. sanfordiana Harvey. The second clade, from the Caribbean and the Canaries, is stenothermal (subtropical to tropical) with some ecotypic variation. The genus Asparagopsis consists of two or possibly three species, but a definitive taxonomic treatment of the two A. taxiformis clades requires study of field‐collected gametophytes.     

THE ULTRASTRUCTURE OF GALLS ON THE RED ALGA GRACILARIA EPIHIPPISORA1

A strain of Gracilaria epihippisora Hoyle produces gall-like cell proliferations in culture. These growths can be excised and grown separately, where they retain an undifferentiated morphology and reach 5mm in diameter. The gall tissue consists of a single morphological cell type without any differentiation between surface and internal cells as is characteristic of normal thallus tissue. Gall cells are typically 20–40 μm in diameter and contain the usual complement of organelles and a prominent vacuole, although there are several distinct features. The large multilobed plastids have an extensive proliferation of thylakoid membranes, which form an arrangement of loops and spirals. The thallus outer cell wall layer is highly reduced. The gall growths contain intracellular virus-like particles (ca. 80 nm in diameter) that occur in discrete groups.