261 research outputs found
Physodes and the phenolic compounds of brown algae. Composition and significance of physodes in vivo
The evolution of photosynthesis in chromist algae through serial endosymbioses
Chromist algae include diverse photosynthetic organisms of great ecological and social importance. Despite vigorous research efforts, a clear understanding of how various chromists acquired photosynthetic organelles has been complicated by conflicting phylogenetic results, along with an undetermined number and pattern of endosymbioses, and the horizontal movement of genes that accompany them. We apply novel statistical approaches to assess impacts of endosymbiotic gene transfer on three principal chromist groups at the heart of long-standing controversies. Our results provide robust support for acquisitions of photosynthesis through serial endosymbioses, beginning with the adoption of a red alga by cryptophytes, then a cryptophyte by the ancestor of ochrophytes, and finally an ochrophyte by the ancestor of haptophytes. Resolution of how chromist algae are related through endosymbioses provides a framework for unravelling the further reticulate history of red algal-derived plastids, and for clarifying evolutionary processes that gave rise to eukaryotic photosynthetic diversity
Monilochaetes and allied genera of the Glomerellales, and a reconsideration of families in the Microascales
We examined the phylogenetic relationships of two species that mimic
Chaetosphaeria in teleomorph and anamorph morphologies,
Chaetosphaeria tulasneorum with a Cylindrotrichum
anamorph and Australiasca queenslandica with a Dischloridium
anamorph. Four data sets were analysed: a) the internal transcribed spacer
region including ITS1, 5.8S rDNA and ITS2 (ITS), b) nc28S (ncLSU) rDNA, c)
nc18S (ncSSU) rDNA, and d) a combined data set of ncLSU-ncSSU-RPB2 (ribosomal
polymerase B2). The traditional placement of Ch. tulasneorum in the
Microascales based on ncLSU sequences is unsupported and
Australiasca does not belong to the Chaetosphaeriaceae. Both
holomorph species are nested within the Glomerellales. A new genus,
Reticulascus, is introduced for Ch. tulasneorum with
associated Cylindrotrichum anamorph; another species of
Reticulascus and its anamorph in Cylindrotrichum are
described as new. The taxonomic structure of the Glomerellales is
clarified and the name is validly published. As delimited here, it includes
three families, the Glomerellaceae and the newly described
Australiascaceae and Reticulascaceae. Based on ITS and ncLSU
rDNA sequence analyses, we confirm the synonymy of the anamorph genera
Dischloridium with Monilochaetes. Consequently
Dischloridium laeënse, type species of the genus, and three
related species are transferred to the older genus Monilochaetes. The
teleomorph of D. laeënse is described in Australiasca
as a new species. The Plectosphaerellaceae, to which the anamorph
genus Stachylidium is added, is basal to the Glomerellales
in the three-gene phylogeny. Stilbella annulata also belongs to this
family and is newly combined in Acrostalagmus. Phylogenetic analyses
based on ncLSU, ncSSU, and combined ncLSU-ncSSU-RPB2 sequences clarify family
relationships within the Microascales. The family
Ceratocystidaceae is validated as a strongly supported monophyletic
group consisting of Ceratocystis, Cornuvesica,
Thielaviopsis, and the type species of Ambrosiella. The new
family Gondwanamycetaceae, a strongly supported sister clade to the
Ceratocystidaceae, is introduced for the teleomorph genus
Gondwanamyces and its Custingophora anamorphs. Four families
are accepted in the Microascales, namely the
Ceratocystidaceae, Gondwanamycetaceae,
Halosphaeriaceae, and Microascaceae. Because of a suggested
affinity of a Faurelina indica isolate to the Microascales,
the phylogenetic position of the Chadefaudiellaceae is reevaluated.
Based on the results from a separate ncLSU analysis of the
Dothideomycetes, Faurelina is excluded from the
Microascales and placed in the Pleosporales
Structural Color in Marine Algae
Structural colouration is widespread in the marine environment. Within the large variety of marine organisms, macroalgae represent a diverse group of more than 24,700 species. Some macroalgae have developed complex optical responses using different nanostructures and material compositions. In this review, we describe the mechanisms that are employed to produce structural colour in algae and provide a discussion on the functional relevance by analysing the geographical distribution and ecology in detail. In contrast to what is observed in the animal kingdom, we hypothesise that structural colour in algae predominantly functions for a non-communicative purpose, most likely protection from radiation damage, e.g. by harmful UV light. We suggest that the presence of structural colour in algae is likely influenced by local factors such as radiation intensity and turbidity of the water.Biotechnology and Biological Sciences Research Council (Grant ID: BBSRC David Phillips, 13 BB/K014617/1), European Research Council (Grant ID: ERC-2014-STG H2020 639088), Department of Chemistry, Cambridge (Philip and Patricia Brown Next Generation Fellowship), National Centre of Competence in Research âBio-Inspired Materialsâ, Adolphe Merkle Foundatio
Contribuição ao conhecimento dos algas do gĂȘnero Euglena (Euglenophyceae) no municĂpio do Rio de Janeiro e arredores, Brasil
Mission de recherche au Québec sur les phénomÚnes de marginalité dans les régions périphériques : 11 juin - 3 juillet 1978 : rapport d'activité
«... Enfants de l'aviron, toujours nous aimerons notre Bayonne» : Jean-Pierre Augustin et Alain Garrigou, Le rugby. Essai sur les Associations sportives, le Pouvoir et les Notables
Chadefaud Michel. «... Enfants de l'aviron, toujours nous aimerons notre Bayonne» : Jean-Pierre Augustin et Alain Garrigou, Le rugby. Essai sur les Associations sportives, le Pouvoir et les Notables. In: Revue géographique des Pyrénées et du Sud-Ouest, tome 57, fascicule 2, 1986. Pyrénées. pp. 276-277
Une formule originale de tourisme social : les gĂźtes ruraux
« Les gßtes ruraux individuels » et les « gßtes communaux » se répartissent au sud d'une ligne Bayonne-Besançon. L'étude des gßtes ruraux constitue une sorte de sondage des locations de vacances en milieu rural. D'une rentabilité non immédiate, le gßte rural donne aux agriculteurs une mentalité d'accueil car il facilite, plus que toute autre formule, la rencontre du rural et du citadin. Ce systÚme permet la sauvegarde du pittoresque de nos campagnes. L'ensemble de la clientÚle demeure « moyenne », bien que ce type d'hébergement s'adresse à un éventail social de plus en plus large car il facilite, par excellence, des vacances familiales. Le « gßte de week-end » se développe et se confond alors avec la résidence secondaire louée.Chadefaud Michel. Une formule originale de tourisme social : les gßtes ruraux. In: Revue géographique des Pyrénées et du Sud-Ouest, tome 39, fascicule 3, 1968. pp. 273-297
Autour de la bataille de Kadech : image et texte dans les choix de la « propagande » religieuse et politique de RamsÚs II
Pendant le Nouvel Empire (1580-1085 av. J.-C) lâiconographie de Pharaon Ă©volue Ă la faveur des conquĂȘtes, tant en Nubie quâen Asie. Sous le rĂšgne de RamsĂšs II le roi utilise tous les espaces sacrĂ©s pour mettre en scĂšne ses actions tant par les inscriptions que par les images (bas-relief et statuaire). La bataille de Kadech (en Syrie, 1274 av. J.-C.) contre les Hittites fait lâobjet dâun vaste programme de reprĂ©sentations dans plusieurs citĂ©s. Cinq temples dâĂgypte figurent les variantes qui justifient lâexaltation de la vaillance du roi, mĂ©diateur des divinitĂ©s et protecteur du pays. Lâanalyse de ces images montre dâune part lâenracinement de lâiconographie royale dans des traditions antĂ©rieures Ă RamsĂšs, liĂ©es dĂšs lâAncien Empire Ă la figuration des ennemis vaincus. Dâautre part des innovations insistent sur lâaction de RamsĂšs soutenu par Amon-RĂȘ. La vaillance du roi et lâintervention divine sauvegardent les frontiĂšres de lâempire et assurent la paix Ă la population.Chadefaud Catherine. Autour de la bataille de Kadech : image et texte dans les choix de la « propagande » religieuse et politique de RamsĂšs II. In: Le pouvoir de lâimage. Actes du 132e CongrĂšs national des sociĂ©tĂ©s historiques et scientifiques, « Images et imagerie », Arles, 2007. Paris : Editions du CTHS, 2012. pp. 181-193. (Actes des congrĂšs nationaux des sociĂ©tĂ©s historiques et scientifiques, 132-10
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