Hi, This is probably species belong to genera Oscillatoria. Are you sure that on the picture is correct scale?

this is in the oscillatoriales-the question is whether it recently was released from a filament (no visible sheath-the trichome would growth this back). The scale bar does seem off!

it looks like a hermogonium of Oscillatoria but looking to the scale the breadth is too high for the genus. If the scale is correct it is certainly not Oscillatoria.

Thanks to everyone. The scale bar is incorrect. There was system maintenance problem. I will see to it. There was no sheath found during observation.

This appears to be a hormogone of one of these two taxa: Planktothrix planctonica or Planktothrix clathrata (the scale shown on this photograph must be rechecked) as described fully in this publication:

Komárek, J. and J. Komárková. 2004. Taxonomic review of the cyanoprokaryotic genera Planktothrix and Planktothricoides. Czech Phycology, Olomouc, 4: 1-18, 2004

However, it would be helpful to know from where it was sampled. Was it free floating in the water column or on the surface of the soil, rock, sediments, whatever? Are more mature, fully developed filaments present in your sample, and if so, are pseudovaculoes present? According to these authors: “ It (Planktothrix) was originally classified into the genus Oscillatoria, because it grows in solitary trichomes without sheaths, heterocytes and akinetes. However, there are gas vesicles gathered in aerotopes (“gas vacuoles”; see, e.g., WALSBY et al. 1983), localized irregularly within the whole cell volume. Also, the planktic type of life is specific. Thus, the genus Planktothrix was separated from Oscillatoria in respect to different ultrastructure, life strategy and phenotypic appearance, and this separation was proved also according to molecular 16S rRNA sequencing (Fig. 1; CASTENHOLZ 2001, GeneBank [NCBI] 2000, RIPPKA & HERDMAN 1992, SUDA et al. 2002). Planktothrix represents now a unique and strictly delimited cluster, well distinguishable also according to morphological characters”.

The photo should be much clearer too, Soma!

This may be a representative of Oscillatoria.

I also agree, this may be a representative of Oscillatoria also common in Sri Lanka in small numbers, Contact Prof. Eugen Rott for further details.

Thank you for all your valuable comments. This will help me a lot.