EVALUATION OF BLUE-GREEN ALGAE

In the presence of inadequate Precambrian fossil records, the importance of cultural studies has been realised in unravelling the mystery of the evolution of blue-green algae. Realising the importance of mutagenesis in unfolding the genetic variability throwing light on ontogeny, the author has proposed a new hypothesis supporting the retrogressive view for the evolution of prokaryotic algae. The development of heterotrichous, multiseriate filaments with both false and true branching in otherwise uniseriate, unbranched filamentous alga, Anabaena doliolum by the effect of Naja naja venom suggest that a member of Nostocales has given rise to the Stigonematalean characteristics by reverting to the old evolutionary pattern indicating the primitiveness of the order Stigonematales having characteristics like heterotrichy, heterocystous, hormogonia formation, true and false branching and 3-plane of division; retention of one, two or more of these characters might have given rise to different orders, families and genera in separate lines. Blue-green algae and photosynthetic bacteria have been considered to have evolved monophyletically from heterotrophs in the Lower Precambrian and further evolution of blue-green algae might have taken place in diphyletic lines, one giving rise to coccoid forms and other to filamentous forms.