Arthrospira Stizenberger ex Gomont

Arthrospira filaments are usually in large, screw-like coils that do not have a mucous sheath. They may be solitary and free-floating plankton or grouped into slimy benthic clumps colored blue- green, olive-green, or reddish-brown. Each trichome is cylindrical, isopolar, and may be long or short. Arthrospira is usually nonmotile, but occasionally glides with a rotating motion. Each
cell has visible cross walls and special pore patterns in the cell wall, including a row of pores circling
the cell. The apical or end cells are rounded or cylindrical and may have calyptras or thickened walls. The thylakoids are arranged radially or in a whirled pattern. A few species have gas vesicles.
Some researchers think Arthrospira should be included within the genus Spirulina. A. maxima and A. fusiformis are also known as Spirulina platensis and are mass cultivated commercially.

Note how changing the focus slightly allows different cellular structures to be viewed on the same specimen.
On the image to the left, note the cross walls
between cells and the thylakoid membranes.
On the image to the right, notice the surface of
the cell and the presence of numerous granules.