摘要:

ABSTRACTUsing rhodamine‐phalloidin to detect F‐actin/microfilaments and indirect immunofluorescence to detect tubulin/microtubules, we studied the cytoskeleton in axial cells ofCeramium strictumHarv., especially microfilaments and microtubules associated with cytoplasmic strands (trabeculae) that extend longitudinally through the central vacuole. As axial cells attained mature size, trabeculae became progressively thinner, branched, and then broke down. An extensive microfilament array was present in peripheral parts of axial cells as well as in trabeculae. Microfilament arrays were highly disrupted by cytochalasin‐B; this resulted in small irregular actin structures in axial cell peripheries and occasional dense aggregations at the base of cells. No actin‐fluorescence was detected in intact trabeculae after cytochalasin‐B treatment. Microtubules formed a primary structural component in trabeculae, which were disrupted by griseofulvin (5 to 0.005 μM) but reformed after two days in griseofulvin

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00085.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTIn some cultures of the flagellateChrysochromulina polylepisManton et Parke, established from cells isolated from the massive bloom in Skagerrak and Kattegat in 1988, we observed, two motile cell types. They were termed authentic and alternate cells and differed with respect to scale morphology. To investigate whether or not the two cell forms were joined in a sexual life cycle, the relative DNA content per cell and relative size of cells of several clonal cultures ofC. polylepiswere determined by flow cytometry. Percentages of authentic and alternate cells in the cultures were estimated by transmission electron microscopy.Pure authentic cultures (α) contained cells with the lowest level of DNA and were termed haploid. Two pure alternate cultures (β) contained cells with double the DNA content of authentic cells and were termed diploid. Other pure alternate cultures contained haploid cells only, or both haploid and diploid cells. Three cell types were observed, each capable of vegetative propagation: authentic haploid, alternate haploid, and alternate diploid cells. Both the haploid and diploid alternate cells were larger than the haploid authentic cells. Cultures containing diploid cells appeared unstable: cell type ratio and ploidy ratio changed during the experiment where this cell type was present, particularly when grown in continuous light. In contrast, cultures with only haploid cells remained unchanged at all growth conditions tested. Light condition may influence cell type ratio and ploidy ratio. Our attempt to induce syngamy by mixing different authentic haploid clones did not result in mating. Assuming that the authentic and alternate cell types are of the same species, the life cycle ofC. polylepisincludes three flagellated scale‐covered cell forms. Two of the cell types are haploid and may function as gametes, and the third is diploid, possibly being the result of syng

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00094.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTTo provide insights into the occurrence, evolution, and phylogenetic distribution of discontinuous mitochondrial and chloroplast large subunit ribosomal RNAs (LSU rRNAs) among green algae, we surveyed 12 taxa representing three classes of green algae: the Chlorophyceae, Pleurastrophyceae, and Micromonadophyceae (sensu Mattox and Stewart 1984). We present evidence that discontinuous mitochondrial and chloroplast LSU rRNAs are quite widespread among green algae. Mitochondrial LSU rRNAs appear discontinuous in zoosporic chlorophycean lineages displaying a clockwise or directly opposed configuration in their flagellar apparatus, as well as in chlorococcalean autosporic taxa phylogenetically related to them, but are continuous among zoosporic green algal lineages with a counterclockwise flagellar apparatus configuration, as well as among chlorococcalean autosporic taxa phylogenetically related to them. Chloroplast LSU rRNAs appear discontinuous in all of the lineages investigated. Discontinuous mitochondrial LSU rRNA represents a molecular trait that might have originated at or near the base of Chlorophyceae, whereas discontinuous chloroplast LSU rRNA might have developed very early in the evolutionary history of the green algal group itself. We suggest, therefore, that the presence of discontinuous mitochondrial but not chloroplast LSU rRNA can be used as an additional character in assessing phylogenetic affiliations among green algae.

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00103.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTWe report six complete 18S ribosomal DNA (rDNA) sequences representing five brown algal orders: Sporochnus comosusC. A. Agardh (Sporochnales),Chorda tomentosaLyngbye (Chordaceae, Laminariales),Saccorhiza polyschides(Lightfoot) Batters (Phyllariaceae, Laminariales),Desmarestia ligulata(Lightfoot) Lamouroux (Desmarestiales),Ectocarpus siliculosus(Dillwyn) Lyngbye (Ectocarpales), andScytosiphon lomentaria(Lyngbye) J. G. Agardh (Scytosiphonales). These sequences were compared with published laminarialean(Alaria marginataPostel et Ruprecht [Alariaceae] andMacrocystis integrifoliaBory [Lessoniaceae]) and fucalean(Fucus gardneriSilva) rDNA sequences for phylogeny inference using both the distance‐matrix and parsimony methods. The inferred 18S phylogenies clusteredSporochnus, Desmarestia, Chorda, Saccorhiza, Alaria, andMacrocystisin an assemblage. This Sporochnales–Desmarestiales–Laminariales (S‐D‐L) complex was consistently separated from the Ectocarpales, Scytosiphonales, and Fucales by bootstrap analyses. The inferred phylogenies are consistent with several possible evolutionary processes leading to this S‐D‐L complex. Members in this assemblage lack eyespots in their sperm, and their sperm have the atypical brown algal flagellation: shorter anterior and longer posterior flagella. In addition, they are oogamous with a heteromorphic alternation of generations between a microscopic gametophyte and a macroscopic sporophyte. Members of the S‐D‐L complex can be separated into different phylogenetic lines based on the presence/absence of eyespots in their meiospores. Our findings support the contention that the Sporochnales, Desmarestiales, and Laminariales are closely related. In addition, our rDNA tree suggests that the Laminariale

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00112.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTComplete sequences of theRrn 18genes were obtained from 13 strains of the nonphotosynthetic algal genusPolytoma.Phylogenetic analyses showed that these strains formed two clades. One clade shows only modest sequence diversity but is represented by strains collected at widely dispersed sites in Europe and America. The other clade consists of a single isolate from the Canary Islands. Both clades lie well within the extended clade that includes all species ofChlamydomonasfor which sequence data are available. The twoPolytomaclades are separated from each other by several green species, suggesting that the extant nonphotosynthetic Chlamydomonadaceae arose from photosynthetic ancestors at least twice. These results suggest that nonphotosynthetic mutants are capable of establishing lineages that can spread widely but have a higher probability of extinction than their photosynthetic congeners.

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00119.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTDicroglossumgen. nov. (Delesseriaceae, Ceramiales) is a monotypic genus based onDelesseria crispatula, a species originally described by Harvey for plants collected from southwestern Western Australia. Distinctive features of the new genus include exogenous indeterminate branches; growth by means of a single transversely dividing, apical cell; absence of intercalary divisions in the primary, secondary, and tertiary cell rows; lateral pericentral cells not transversely divided; not all cells of the secondary cell rows producing tertiary cells rows; all tertiary initials reaching the thallus margin; midrib present but lateral nerves absent; determinate lateral bladelets arising endogenously; blades monostromatic, except, at the midrib; carpogonial branches restricted to primary cell rows, on both surfaces of unmodified blades; procarps produced on both blade surfaces, each procarp consisting of a supporting cell that bears two four‐celled carpogonial branches and one sterile‐cell group of three to four cells; and tetrasporangia borne in two layers, separated by a central row of sterile cells. The combination of exogenous indeterminate branching and bicarpogonial procarps is considered to warrant the recognition of a new tribe, the Dicroglosseae, within the subfamily Delesserioid

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00127.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTAsteromeniagen. nov. (Rhodymeniales, Rhodophyta) is proposed with a single species,Asteromenia peltata(W. R. Taylor) comb. nov. (basionym:Fauchea peltataW. R. Taylor). Thalli of the proposed new genus are stipitate with dorsiventral, peltate blades that are initially circular in shape but with age become stellate with ligulate arms. Internally, the blades have a polystromatic medulla of large, hyaline cells, grading into a cortex of smaller, pigmented cells. Clusters of translucent cells occur on the dorsal surface of the blade. Tetrasporangia are formed by transformations of intercalary midcortical cells. Mature tetrasporangia have cruciately arranged spores and are densely aggregated in the cortex, mostly on the ventral surface, but occasional tetrasporangia also arise on the dorsal surface. Carpogonial branches are four‐celled and arise on inner cortical cells. Auxiliary cells are borne on auxiliary mother cells attached to supporting cells of the carpogonial branches. Cystocarps are protuberant, with well‐developed, ostiolate pericarps that often have extended, proboscis‐like necks. The new genus differs from the previously described peltate or dorsiventral taxa in the Rhodymeniaceae by its polystromatic medulla(MaripeltaandSciadophycushave a monostromatic medulla), intercalary tetrasporangia formed in an unmodified cortex, and four‐celled carpogonial branches(Halichrysis, as typified byH. depressa(J. Agardh) F. Schmitz, has terminal tetrasporangia in nemathecia and three‐celled carpogonial

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00138.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTDasya roslyniaesp. nov. (Dasyaceae, Rhodophyta) is described from subtidal habitats at Split Solitary Island (30°14′S, 153°11′E), New South Wales, Australia. The new species is distinct within the genus due to its strongly compressed and secondarily bilaterally branched axes, differing from the majority ofDasyaspecies that are terete and secondarily radially organized. Pseudolaterals are quickly caducous on ventral and dorsal (transverse) surfaces but are persistent on lateral surfaces for short distances from the apex, leaving the bulk of the plants flattened and denuded. Its gross morphological characters are thus similar to those displayed by the generaPogonophorella, Eupogodon(formerly known asDasyopsis), andRhodoptilum.Characters used for separating these genera andDasyaare, in some cases, overlapping and in need of critical evaluation. To the primarily radially organized taxa, determined by examination of divisions of the apical cell, are placed species ofDasya, six species now included inEupogodon, and the type and only species ofPogonophorella californica.Examination of the activity of the apical cells ofEupogodon planumandRhodoptilum plumosum, the type species of their genera, confirms the primary bilaterality of these two genera, and the traditional defining feature ofEupogodon(lack of discernible pericentral cells in cross‐section of indeterminate axes) is shown to be untenable. A secondary character that would separateEupogodonandRhodoptilumis the polysiphonous bases of otherwise monosiphonous laterals (pseudolaterals) inEupogodonand the monosiphonous bases inRhod

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00145.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTThe newly described toxic dinoflagellatePfiesteria piscicidais a polymorphic and multiphasic species with flagellated, amoeboid, and cyst stages. The species is structurally a heterotroph; however, the flagellated stages can have cleptochloroplasts in large food vacuoles and can temporarily function as mixotrophs. The flagellated stage has a typical mesokaryotic nucleus, and the theca is composed of four membranes, two of which are vesicular and contain thin plates arranged in a Kofoidian series of Po, cp, X, 4′, 1a, 5″, 6c, 4s, 5″′, and 2″″. The plate tabulation is unlike that of any other armored dinoflagellate. Nodules often demark the suture lines underneath the outer membrane, but fixation protocols can influence the detection of plates. Amoeboid benthic stages can be filose to lobose, are thecate, and have a reticulate or spiculate appearance. Amoeboid stages have a eukaryotic nuclear profile and are phagocytic. Cyst stages include a small spherical stage with a honeycomb, reticulate surface and possibly another stage that is elongate and oval to spherical with chrysophyte‐like scales that can have long bracts. The species is placed in a new family, Pfiesteriaceae, and the order Dinamoebal

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00157.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY

摘要:

ABSTRACTAulacoseira skvortzowiisp. nov. is a diatom taxon present in modern plankton assemblages and sedimentary deposits from Lake Baikal, Russia. It has been previously reported asA. islandica(O. Müll.) Simonsen,A. islandicassp.helvetica(O. Müll.) Simonsen, a sporangial frustule ofA. baicalensis(K. Meyer) Simonsen, andAulacoseira “spore”.However, its microstructure, ecology, and ability to form true resting spores provide ample criteria to describe this diatom asAulacoseira skvortzowiisp

ISSN:0022-3646    

DOI:10.1111/j.0022-3646.1996.00165.x

出版商:Blackwell Publishing Ltd    

年代:1996

数据来源: WILEY