Filamentous Cyanobacterium, Anabaena sp. (SEM x5,000) Nonfilamentous cyanobacteria The morphological diversity of the cyanobacteria is considerable. Both unicellular and filamentous forms are known, and considerable variation within these morphological types occurs.Filamentous Cyanobacterium, Anabaena sp. (SEM x5,000) Nonfilamentous cyanobacteria The morphological diversity of the cyanobacteria is considerable. Both unicellular and filamentous forms are known, and considerable variation within these morphological types occurs