Cultures of Phormidium, Plectonema, Lyngbya and Synechococcus (Cyanophyceae) under different conditions: their growth and morphological variability

Phormidium, Plectonema, Lyngbya and Synechococcus strains from freshwater- and marine habitats were incubated in media with different concentrations of seawater, under different light intensities and temperatures, submitted to different desiccation procedures, tested for endolithic growth in shells and grown on two different media solidified with agar. On the basis of the observed differences in halotolerance, cell dimensions and the reaction pattern with regard to the other parameters used, three taxa, existing at about species level, could be recognized within those strains which were identified as Schizothhx calcicola sensu Drouet, Characters as false branching and sheath morphology could not be used for the distinction between these taxa. The results also led to the conclusions that two other strains, which belong to the Drouet species Microcoleus lyngbyaceus, are no ecophenes of each other. The two coccoid Synechococcus strains could be ranked under two different species. The results are discussed with regard to Drouet’s species concept within the Cyanophyceae. It is suggested to determine the genotypic relationships between the strains used, as a verification of the usefulness of the morphological and ecological characters involved in the delimitation of the different taxa recognized.