The
cells of Microcystis are small - only a few microns in
diameter - and lack individual mucilage sheaths. The cells are
usually arranged in colonies that are initially spherical but
become irregular or perforated over time. The cells may be grouped
tightly or sparsely within the fine, colorless colonial mucilage.
The colonies are free-floating and may
be
composed of clustered subcolonies. Smaller colonies are microscopic,
while larger colonies
may
be viewed with the naked eye.
The cells are
spherical or hemispherical after dividing. The protoplast is
a pale blue-green, but overall the cells appear dark or brownish
due to the
presence of
gas
vesicles. This feature easily distinguishes Microcystis
from Aphanocapsa
under
light microscopy.
In
culture, cells may exist singly or in irregular clumps.