Culturally Induced Variation in Four Morphologically Diverse Bluegreen Algae

Characters used in taxonomic placement at levels from family to species appeared, disappeared, or varied widely, while others remained constant, in cultures of four disparate species of blue‐green algae (Cyanophyta) under varying conditions of culture. Species of Anabaena and Gloeocapsa displayed fairly stable characteristics. Species of Calothrix and Lyngbya exhibited much greater variability, especially in twisting of filaments, presence or absence of constrictions at the cross walls, abundance of heterocysts, pseudovacuoles, fragmentation of filaments, and change of color. Color change was associated with abrupt p H shift in Lyngbya and could be reversed by adding nitrate. In the putatively nitrogen‐fixing Anabaena , similar change in color with age was not associated with sharp p H shift, nor could it be reversed with nitrate. In general, growth on agar in turbulent conditions and with decreased CO 2 –O 2 exchange was less than that obtainable under other conditions, and media with acid p H were partially or totally inhibitory to growth.