Biodiversity of epilithic cyanobacteria from freshwater streams of Kakoijana reserve forest, Assam, India.

The biodiversity of epilithic cyanobacteria from one of the unexplored habitats of freshwater streams of Kakoijana reserve forest of Assam, India was estimated. This paper lists a total of 29 species representing 18 genera of 12 families and 4 orders as per recent system of classification. Morphological descriptions, common habitats and distribution pattern were described for each species identified that were represented systematically. Of these 29 species, 11 were unicellular, 9 non-heterocytous filamentous and 9 heterocytous filamentous forms. All the unicellular (Aphanocapsa crassa, A. muscicola, Aphanothece nidulans, A. saxicola, Chlorogloea purpurea, Chroococcus cohaerens, C. minimus, C. minor, Cyanobacterium cedrorum, Cyanocystis versicolor and Gloeocapsopsis crepidinum) and 13 (Calothrix epiphytica, C. scopulorum, Leptolyngbya boryana, L. calotrichoides, L. fragilis, L. notata, Lyngbya arboricola, Nostoc humifusum, N. oryzae, N. punctiforme, Parthasarathiella prolifica, Porphyrosiphon ceylanicus and Scytonema millei) of the remaining 18 species were recorded for the first time as freshwater epiliths. While, 5 species (Hapalosiphon welwitschii, Leptolyngbya tenuis, Oscillatoria pseudogeminata, Phormidium laetevirens, Tolypothrix fragilis) and 8 species (Aphanothece saxicola, Calothrix scopulorum Chlorogloea purpurea, Chroococcus minor, Gloeocapsopsis crepidinum, Leptolyngbya calotrichoides, L. fragilis and L. tenuis) were reported earlier as freshwater-and marine-epilithic forms respectively. All are new records for Assam except 6 species (A. nidulans, H. welwitschii, N. punctiforme, N. oryzae, O. pseudogeminata and P. ceylanicus), while 3 species (C. purpurea, L. boryana and L. calotrichoides) are new records for India. Six nitrogen fixing heterocytous forms such as, C. epiphytica, C. scopulorum, N. humifusum, N. punctiforme, N. oryzae and S. millei, were common to the neighboring paddy fields.