A two-dimensional morphospace for cyanobacteria and microalgae: Morphological diversity,evolutionary relatedness,and size constraints

1. Body metrics are considered as master traits that regulate physiological, behavioural and life history features of planktic cyanobacteria and microalgae. Although the distribution of their morphological traits reflects the various trade-offs and strategies needed for survival in pelagic habitats, previous methods for quantifying phytoplankton body shape do not adequately represent the intricate details of surface variation that are so important for their nutrient- and light-harvesting capabilities. Therefore, here we provide a new framework to quantify and illustrate the morphological diversity of cyanobacteria and microalgae.
2. Essential components of formulae used for surface area (A = Cs × d²) and volume (V = Cv × d³) calculations are provided by the shape-specific surface area and volume constants (Cs, Cv). Cs, the surface shape factor, characterises the coarseness of the object surface, and Cv, the volumetric shape factor, characterises the shape deviation from a sphere. Using these morphologically and biologically relevant variables, we defined a two-dimensional morphological space, in which all three-dimensional objects have well-defined positions.
3. By analysing morphologies of taxa representing various forms in major cyanobacterial and microalgal groups, we demonstrated that these groups show considerable differences in the area occupied within the morphospace and these differences are not affected by evolutionary relatedness. We showed that the ratio of surface and volume constants correlated with organism size, suggesting that the development of basic morphologies is constrained by their linear dimensions.
4. Using surface and volumetric shape factors, we created a two-dimensional Euclidean morphospace in which all three-dimensional objects have a specific position. Positioning uni- and multicellular cyanobacteria and microalgae of various shapes into this morphospace allows their geometrical and ecological limitations to be understood. Because of the close linkage between phytoplankton morphology and ecology, the proposed morphospace may serve as a proxy for an ecospace. Thus, in future the proposed morphospace can be used to visualise current ecological processes such as eutrophication or seasonal succession of phytoplankton.

     

Contributions mycologiques pour la connaissance de la spermatosphère des graines en germination

Summary A list of 26 species of microfungi found on seeds of various plants is presented. A new genus of Hypocreaceous Ascomycete is describedViennotidia, which includes two different species. Moreover, the following species are described as new:Phoma cuscutae, Sclerophomina tritici, Sirophoma petroselini andPyrenochaeta spinaciae.     

Sopra alcuni aspetti morfologici di Candida pulcherrima (Lindner) Windisch

Sommario Gli AA. descriono in uno stipite diC. pulcherrima (Lindner) Windisch degli aspetti ameboidi delle blastospore. Ritengono che questi aspetti più che preludere a processi sporologici, precedano forse la formazione di pseudomicelio; per questo essi aspetti ameboidi non hanno alcun particolare valore sistematico in quanto da ditenersi una fase che occuperebbe un posto intermedio tra quella non filamentosa tipoTorulopsis e quella filamentosa tipoCandida.

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About some morphological appearances ofCandida pulcherrima (Lindner) Windisch

Summary The AA. describe in a strain ofC. pulcherrima (Lindner) Windisch, some amoeboid appearances of blastospores. They think these figures to be, more than the introduction to sporologic processes, the preamble to the formation of pseudomycelium; for this reason these amoeboid figures have no peculiar systematic value, as they are to be considered as a stage likely placed between the non-filamentous one of theTorulopsis type, and the filamentous one of theCandida type.