The diversity of freshwater and inland saline planktic cyanoprokaryote microflora (cyanobacteria, cyanophytes) in Mexico depends on the wide variation of the biotopes in this country. There are no detailed studies, describing the planktic cyanoprokaryotic species from this region. This paper lists 51 planktic morphospecies, which were found in various water bodies in central Mexico during May 1992 and March-September 1993. Four new species (Cyanobacterium lineatum, Cyanotetras aerotopa, Anabaena fallax, Cylindrospermopsis taverae) are described, and important species commented. Various species characteristic for various types of reservoirs (volcanic lakes, lakes and artificial reservoirs with diverse trophic levels, hypertrophic pools, saline coastal lakes) were found. Taxonomic and ecological elaborations of the planktic cyanobacteria of Mexico (from an ecological, geographical as well as sanitary point of view – eutrofication, biomass production, toxicity) are urgently needed.
Two differently coloured strains of the genus Chroococcus were isolated from a cyanobacterial assemblage collected from the stony littoral of a backwater of the Danube River in southern Slovakia. When grown after isolation, both subcultures were similar morphologically and their growth parameters did not differ substantially, but their pigment content (PC: PE and carotenoid ratios), details in their morphology during their life cycles and slime production were different. Identical and different characters of both morphotypes remained stable during cultivation on both agarized and liquid media, even when the cultivation parameters were changed. Both of the subcultures were studied using electron microscopy and almost their complete 16S rRNA genes were sequenced, which showed that in terms of their genetic relationship there was a 96.4% sequence similarity and certain taxonomic interspecific differences between both subcultures were confirmed. The various chromatic modifications recorded in cyanobacteria and their ecological consequences are discussed. The results yielded further data on the changes that occur during the cyanobacterial differentiation processes and their genetic stabilization.