Life cycle of Nostoc sphaericum (Nostocales, Cyanoprokaryota) in tropical wetlands

Life cycle as a stable trait in the evaluation of diversity of Nostoc from biofilms in rivers

“…Distinctive characteristics of life cycles in Nostoc have been proposed and discussed in the delimitation of species (Mollenhauer et al, 1994;Potts, 2000;Kondratyeva & Kislova, 2002). Complicated life cycles were described in detail for some strains, such as, for example, N. muscorum (Lazaroff, 1973), N. commune (Robinson & Miller, 1970;Potts, 2000), and field colonies of Nostoc sphaericum (Becerra-Absalón & Tavera, 2009) and Nostoc cordubensis (Prosperi, 1989). Hrouzek et al (2003) studied selected strains isolated from soils, not forming distinct macroscopic colonies and growing mostly in slimy mats, and they resolved three groups of strains, corresponding to N. muscorum, Nostoc edaphicum and N. calcicola, respectively, on the basis of their life cycle.…”

Effect of Nitrogen and Periphyton Extract on the Growth of Nostoc sphaericum in Cultures

“…It was observed that the absence of the water column for 8 months in the EER did not limit this species to sprawl. It seems that akinetes fulfill the function of expansion of the thalli mainly in the dry season [8]. This role of akinetes is probably not unique to the studied species since it has been suggested that akinetes could have appeared early in the evolution as a dispersal response that conferred a significantly selective advantage, which may have been even greater than that of nitrogen fixation [24].…”

“…It seems clear that the amount of nitrogen in the rainforest substrate can be higher than in the tropical deciduous forest. It is remarkable that despite the differences in the way N. sphaericum develops, the life cycle is similar in both locations, including the suppression of the aseriate phase that only occurs in cultures without nitrogen [8]. Filaments in culture enter the aseriate stage as usual in the genus, through cell divisions that occur at various angles and that depart from the transverse plane of the filament [9].…”

“…The above observations do not provide any information about a relationship between the nutrient concentrations, the presence of Cyanoprokaryota that sometimes accompany N. sphaericum and the observed growth difference in the two wetlands. Therefore, using populations of the two ecosystems, we studied the life cycle under laboratory conditions as a first approximation [8] and then expanded the laboratory experiments by testing different combinations of conditions such as nitrogen in the substrate and the presence of other Cyanoprokaryota, which appear to be related to N. sphaericum in the field. The study was based on observations in cultures of ten weeks.…”