Chaetophora

Abstract: Previously published molecular phylogenetic analyses of the Chaetophorales (Chlorophyceae) suffered from limited taxon sampling (six genera with only a single species per genus). To test the monophyly of species-rich genera, and to analyze the phylogenetic relationships among families and genera in the Chaetophorales, we determined nuclear-encoded SSU rDNA sequences from 30 strains of Chaetophorales, performed phylogenetic analyses using various methods, and screened clades for support by unique molecular synapomorphies in the SSU rRNA secondary structure. The Schizomeridaceae and the weakly supported Aphanochaetaceae were recovered as basal lineages. The derived family Chaetophoraceae diverged into two clades: the "Uronema clade" containing unbranched filaments, and a sister clade designated as "branched Chaetophoraceae" comprising Chaetophora, Stigeoclonium, Draparnaldia, Caespitella, and Fritschiella. Although some terminal clades corresponded to genera described (e.g., Caespitella and Draparnaldia), other clades were in conflict with traditional taxonomic designations. Especially, the genera Stigeoclonium and Chaetophora were shown to be polyphyletic. The globose species Chaetophora elegans was unrelated to lobate Chaetophora spp. (e.g., Chaetophora lobata). Since the original description of Chaetophora referred to a lobate thallus organization, the latter clade represented Chaetophora sensu stricto. In consequence, C. lobata was designated as lectotype of Chaetophora. Two Stigeoclonium species, Stigeoclonium farctum Berthold and Stigeoclonium'Longipilus', diverged independently from the type species of Stigeoclonium, Stigeoclonium tenue (C. Agardh) Kutz. These results indicated that some commonly used taxonomic characters are either homoplasious or plesiomorphic and call for a reevaluation of the systematics of the Chaetophorales using novel morphological and molecular approaches.

Abstract: SUMMARY To elucidate the phylogeny of the Dunaliellales sensu 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 that Oltmannsiellopsis 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. Hafniomonas and Polytomella are 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 that Planophita terrestns Groover et Hof-stetter (Chaetopeltidales) and Chaetophora incras-sata (Hudson) Hazen (Chaetophorales) are distinct lineages in the Chlorophyceae.

Abstract: SUMMARY Two populations of Chaetophora elegans (Roth) C, Agardh and two of Stigeoclonium helveticum Vischer were investigated for microhabitat characteristics and morphological variation in streams of Sao Paulo State, southeastern Brazil. Different patterns of microhabitat distribution were found between species investigated. Populations of C, elegans were distributed under relatively narrow microhabitat conditions (high irradiance, low depth, moderate to high current velocity, rocky substrata and lower values of niche width) and showing little morphometric variation (colony diameter, main axis cell size, and apical branch number), Stigeoclonium helveticum occurred under more diverse microhabitat conditions, revealed by lack of significant difference between sampling units with and without the alga and wider niche width, but also exhibited relatively narrow morphometric variation (plant length, main axis cell and lateral branch cell sizes). The narrow microhabitat conditions and smaller niche width of C. elegans can explain its low abundance (percentage cover) in streams from the area studied as well as in other regions of Sao Paulo State, In contrast, the wider variation of microhabitat conditions and the higher niche widths of S. helveticum suggest that this green alga is able to grow in a high number of stream ecosystems in the region investigated, ranging from undisturbed to highly disturbed habitats. Thus, the results suggest that S. helveticum is a generalist species.

Abstract: The influence of various element deficiencies was tested on 13 strains of Chaetophorales (1 Chaetophora, 2 Draparnaldia, 10 Stigeoclonium) isolated from sites in Belgium, N.E. England and Germany. Judged by the yield in batch culture, the relative response to each deficiency was quite similar in all strains: control > –P > –Fe > –Ca = –S > –Mg > –N. Judged by the extent of hair formation, the relative response was quite different: –P > –N > –Fe = –S > –Ca > –Mg > control. P- and N-limited cultures were the only ones to have typical hairs, and hair development was much greater in the former. It proved possible to maintain continued growth of a culture in a hairy condition by developing a continuous culture technique and using a medium with a high N:P ratio. Five strains were selected for more detailed study. N and P compositions, percentage hairiness and surface phosphatase activity were followed during growth in batch culture in medium leading to P-limitation. Although the maximum P composition r...