Scenedesmus acutus, SEM

Scenedesmus acutus. Coloured scanning electron micrograph (SEM) of Scenedesmus acutus, a flat colony of 4 alga cells. Scenedesmus, a green alga from the Chlorophyceae group, is a small, non-motile, colonial green alga consisting of cells aligned in a flat plate. The colonies most often have two or four cells, but may have 8, 16, or 32 cells. Cells may have additional spines or chitinous bristles. Each cell contains a single parietal, plate-like chloroplast with a pyrenoid (the site of CO2 fixation). The cell walls may be covered in bumps or reticulations. Scenedesmus is a photosynthetic planktonic organism that is important in the aquatic food chain. Magnification: x 3000 when printed at 10cm wide. Specimen collected from Vietnam courtesy of Mike Allen, Plymouth Marine Laboratory.