Polyphasic characterization of eight planktonic Anabaena strains (Cyanobacteria) with reference to the variability of 61 Anabaena populations observed in the field

Abstract

The plasticity of morphological features used for single morphospecies identification was studied under varied experimental conditions (temperature, light, nitrogen, phosphorus) in eight planktonic Anabaena strains. The strains represented all of the morphospecies with coiled trichomes commonly occurring in Central Europe (two strains of A. mendotae & A. sigmoidea complex, two A. lemmermannii strains, two A. flos-aquae strains, and two strains of A. circinalis & A. crassa complex). Significant effects of the growth conditions on vegetative cell dimensions were observed in seven strains, and P concentration was the main influencing factor in most cases (six strains). Significant effect of an environmental factor (P) on akinete morphology was found in only one strain. Experimentally assessed temperature and light growth optima were specific for each strain and were not consistent with the taxonomic affiliation of the strains. Morphologies of the Anabaena strains studied were compared with the field morphologies of 61 Anabaena populations of eight morphospecies observed in the Czech Republic. The range of morphological variability of single strains under the experimental conditions spanned the total variability of the populations of relevant morphospecies observed in the field. Delimitations and proper descriptions of the morphospecies are discussed in the light of partial 16S rRNA gene sequences of the studied strains.